From 18103bcd0c81980eaa2bf647835ba0f10b6c4368 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:23:35 +0100
Subject: [PATCH 01/21] Remove custom_sampling_context

---
 MIGRATION_GUIDE.md                            |  2 ++
 sentry_sdk/api.py                             | 15 +++--------
 .../integrations/opentelemetry/consts.py      |  2 ++
 .../integrations/opentelemetry/sampler.py     | 24 ++++++++----------
 .../integrations/opentelemetry/scope.py       |  4 ++-
 sentry_sdk/tracing.py                         | 25 ++++++++++++++-----
 6 files changed, 39 insertions(+), 33 deletions(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 495bfff75e..620cd7a3c5 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -19,11 +19,13 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - Redis integration: In Redis pipeline spans there is no `span["data"]["redis.commands"]` that contains a dict `{"count": 3, "first_ten": ["cmd1", "cmd2", ...]}` but instead `span["data"]["redis.commands.count"]` (containing `3`) and `span["data"]["redis.commands.first_ten"]` (containing `["cmd1", "cmd2", ...]`).
 - clickhouse-driver integration: The query is now available under the `db.query.text` span attribute (only if `send_default_pii` is `True`).
 - `sentry_sdk.init` now returns `None` instead of a context manager.
+- The sampling context accessible in `traces_sampler` has changed. It now contains all span attributes. The original `sampling_context["transaction_context"]["name"]` and `sampling_context["transaction_context"]["op"]` are now accessible as `sampling_context["sentry_name"]` and `sampling_context["sentry_op"]`, respectively.
 
 ### Removed
 
 - Spans no longer have a `description`. Use `name` instead.
 - Dropped support for Python 3.6.
+- The `custom_sampling_context` parameter of `start_transaction` has been removed.
 - The PyMongo integration no longer sets tags. The data is still accessible via span attributes.
 - The PyMongo integration doesn't set `operation_ids` anymore. The individual IDs (`operation_id`, `request_id`, `session_id`) are now accessible as separate span attributes.
 - `sentry_sdk.metrics` and associated metrics APIs have been removed as Sentry no longer accepts metrics data in this form. See https://sentry.zendesk.com/hc/en-us/articles/26369339769883-Upcoming-API-Changes-to-Metrics
diff --git a/sentry_sdk/api.py b/sentry_sdk/api.py
index 7d06abf660..a44d3f440e 100644
--- a/sentry_sdk/api.py
+++ b/sentry_sdk/api.py
@@ -40,7 +40,6 @@
         ExcInfo,
         MeasurementUnit,
         LogLevelStr,
-        SamplingContext,
     )
     from sentry_sdk.tracing import Span, TransactionKwargs
 
@@ -239,12 +238,8 @@ def flush(
     return get_client().flush(timeout=timeout, callback=callback)
 
 
-def start_span(
-    *,
-    custom_sampling_context=None,
-    **kwargs,  # type: Any
-):
-    # type: (...) -> POTelSpan
+def start_span(**kwargs):
+    # type: (type.Any) -> POTelSpan
     """
     Start and return a span.
 
@@ -257,13 +252,11 @@ def start_span(
     of the `with` block. If not using context managers, call the `finish()`
     method.
     """
-    # TODO: Consider adding type hints to the method signature.
-    return get_current_scope().start_span(custom_sampling_context, **kwargs)
+    return get_current_scope().start_span(**kwargs)
 
 
 def start_transaction(
     transaction=None,  # type: Optional[Transaction]
-    custom_sampling_context=None,  # type: Optional[SamplingContext]
     **kwargs,  # type: Unpack[TransactionKwargs]
 ):
     # type: (...) -> POTelSpan
@@ -295,14 +288,12 @@ def start_transaction(
 
     :param transaction: The transaction to start. If omitted, we create and
         start a new transaction.
-    :param custom_sampling_context: The transaction's custom sampling context.
     :param kwargs: Optional keyword arguments to be passed to the Transaction
         constructor. See :py:class:`sentry_sdk.tracing.Transaction` for
         available arguments.
     """
     return start_span(
         span=transaction,
-        custom_sampling_context=custom_sampling_context,
         **kwargs,
     )
 
diff --git a/sentry_sdk/integrations/opentelemetry/consts.py b/sentry_sdk/integrations/opentelemetry/consts.py
index 6d7c91f3f1..9cf19eb01d 100644
--- a/sentry_sdk/integrations/opentelemetry/consts.py
+++ b/sentry_sdk/integrations/opentelemetry/consts.py
@@ -30,3 +30,5 @@ class SentrySpanAttribute:
     NAME = "sentry.name"
     SOURCE = "sentry.source"
     CONTEXT = "sentry.context"
+    CUSTOM_SAMPLED = "sentry.custom_sampled"
+    PARENT_SAMPLED = "sentry.parent_sampled"
diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index ed8ca36ebd..4420c8b428 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -2,7 +2,6 @@
 from typing import cast
 
 from opentelemetry import trace
-
 from opentelemetry.sdk.trace.sampling import Sampler, SamplingResult, Decision
 from opentelemetry.trace.span import TraceState
 
@@ -12,6 +11,7 @@
 from sentry_sdk.integrations.opentelemetry.consts import (
     TRACESTATE_SAMPLED_KEY,
     TRACESTATE_SAMPLE_RATE_KEY,
+    SentrySpanAttribute,
 )
 
 from typing import TYPE_CHECKING
@@ -118,25 +118,21 @@ def should_sample(
         if not has_tracing_enabled(client.options):
             return dropped_result(parent_span_context, attributes)
 
-        sample_rate = None
+        # Explicit sampled value provided at start_span
+        if attributes.get(SentrySpanAttribute.CUSTOM_SAMPLED) is not None:
+            sample_rate = float(attributes[SentrySpanAttribute.CUSTOM_SAMPLED])
+            return sampled_result(parent_span_context, attributes, sample_rate)
 
-        # Check if sampled=True was passed to start_transaction
-        # TODO-anton: Do we want to keep the start_transaction(sampled=True) thing?
+        sample_rate = None
 
         # Check if there is a traces_sampler
         # Traces_sampler is responsible to check parent sampled to have full transactions.
         has_traces_sampler = callable(client.options.get("traces_sampler"))
         if has_traces_sampler:
-            # TODO-anton: Make proper sampling_context
-            # TODO-neel-potel: Make proper sampling_context
-            sampling_context = {
-                "transaction_context": {
-                    "name": name,
-                },
-                "parent_sampled": get_parent_sampled(parent_span_context, trace_id),
-            }
-
-            sample_rate = client.options["traces_sampler"](sampling_context)
+            attributes[SentrySpanAttribute.PARENT_SAMPLED] = get_parent_sampled(
+                parent_span_context, trace_id
+            )
+            sample_rate = client.options["traces_sampler"](attributes)
 
         else:
             # Check if there is a parent with a sampling decision
diff --git a/sentry_sdk/integrations/opentelemetry/scope.py b/sentry_sdk/integrations/opentelemetry/scope.py
index 0c0087dae1..4274d70296 100644
--- a/sentry_sdk/integrations/opentelemetry/scope.py
+++ b/sentry_sdk/integrations/opentelemetry/scope.py
@@ -123,7 +123,9 @@ def start_transaction(self, custom_sampling_context=None, **kwargs):
 
     def start_span(self, custom_sampling_context=None, **kwargs):
         # type: (Optional[SamplingContext], Any) -> POTelSpan
-        return POTelSpan(**kwargs, scope=self)
+        return POTelSpan(
+            **kwargs, custom_sampling_context=custom_sampling_context, scope=self
+        )
 
 
 _INITIAL_CURRENT_SCOPE = PotelScope(ty=ScopeType.CURRENT)
diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index c2bd5734c5..868a47144f 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -41,6 +41,8 @@
 
     from typing_extensions import TypedDict, Unpack
 
+    from opentelemetry.utils import types as OTelSpanAttributes
+
     P = ParamSpec("P")
     R = TypeVar("R")
 
@@ -683,9 +685,9 @@ def get_trace_context(self):
             rv["status"] = self.status
 
         if self.containing_transaction:
-            rv[
-                "dynamic_sampling_context"
-            ] = self.containing_transaction.get_baggage().dynamic_sampling_context()
+            rv["dynamic_sampling_context"] = (
+                self.containing_transaction.get_baggage().dynamic_sampling_context()
+            )
 
         data = {}
 
@@ -1200,10 +1202,12 @@ def __init__(
         op=None,  # type: Optional[str]
         description=None,  # type: Optional[str]
         status=None,  # type: Optional[str]
+        sampled=None,  # type: Optional[bool]
         start_timestamp=None,  # type: Optional[Union[datetime, float]]
         origin=None,  # type: Optional[str]
         name=None,  # type: Optional[str]
         source=TRANSACTION_SOURCE_CUSTOM,  # type: str
+        attributes=None,  # type: OTelSpanAttributes
         otel_span=None,  # type: Optional[OtelSpan]
         **_,  # type: dict[str, object]
     ):
@@ -1218,6 +1222,7 @@ def __init__(
         if otel_span is not None:
             self._otel_span = otel_span
         else:
+            from sentry_sdk.integrations.opentelemetry.consts import SentrySpanAttribute
             from sentry_sdk.integrations.opentelemetry.utils import (
                 convert_to_otel_timestamp,
             )
@@ -1227,12 +1232,20 @@ def __init__(
                 start_timestamp = convert_to_otel_timestamp(start_timestamp)
 
             span_name = name or description or op or ""
-            self._otel_span = tracer.start_span(span_name, start_time=start_timestamp)
+
+            # Prepopulate some attrs to be accessible in traces_sampler
+            attributes = attributes or {}
+            attributes[SentrySpanAttribute.NAME] = span_name
+            attributes[SentrySpanAttribute.OP] = op
+            if sampled is not None:
+                attributes[SentrySpanAttribute.CUSTOM_SAMPLED] = sampled
+
+            self._otel_span = tracer.start_span(
+                span_name, start_time=start_timestamp, attributes=attributes
+            )
 
             self.origin = origin or DEFAULT_SPAN_ORIGIN
-            self.op = op
             self.description = description
-            self.name = span_name
             self.source = source
 
             if status is not None:

From 68402fff97e3f7b77aa07c58b45ae784200df912 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:24:18 +0100
Subject: [PATCH 02/21] confusing wording

---
 MIGRATION_GUIDE.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 620cd7a3c5..b7c9db0241 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -19,7 +19,7 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - Redis integration: In Redis pipeline spans there is no `span["data"]["redis.commands"]` that contains a dict `{"count": 3, "first_ten": ["cmd1", "cmd2", ...]}` but instead `span["data"]["redis.commands.count"]` (containing `3`) and `span["data"]["redis.commands.first_ten"]` (containing `["cmd1", "cmd2", ...]`).
 - clickhouse-driver integration: The query is now available under the `db.query.text` span attribute (only if `send_default_pii` is `True`).
 - `sentry_sdk.init` now returns `None` instead of a context manager.
-- The sampling context accessible in `traces_sampler` has changed. It now contains all span attributes. The original `sampling_context["transaction_context"]["name"]` and `sampling_context["transaction_context"]["op"]` are now accessible as `sampling_context["sentry_name"]` and `sampling_context["sentry_op"]`, respectively.
+- The sampling context accessible in `traces_sampler` has changed. The original `sampling_context["transaction_context"]["name"]` and `sampling_context["transaction_context"]["op"]` are now accessible as `sampling_context["sentry_name"]` and `sampling_context["sentry_op"]`, respectively.
 
 ### Removed
 

From fa5d0ba76c57fde8d1498d2b2dc1ae1c674867a8 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:38:47 +0100
Subject: [PATCH 03/21] keep old format (why not)

---
 MIGRATION_GUIDE.md                               |  1 -
 sentry_sdk/integrations/opentelemetry/consts.py  |  2 --
 sentry_sdk/integrations/opentelemetry/sampler.py | 12 ++++++++----
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index b7c9db0241..1c6daa0e29 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -19,7 +19,6 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - Redis integration: In Redis pipeline spans there is no `span["data"]["redis.commands"]` that contains a dict `{"count": 3, "first_ten": ["cmd1", "cmd2", ...]}` but instead `span["data"]["redis.commands.count"]` (containing `3`) and `span["data"]["redis.commands.first_ten"]` (containing `["cmd1", "cmd2", ...]`).
 - clickhouse-driver integration: The query is now available under the `db.query.text` span attribute (only if `send_default_pii` is `True`).
 - `sentry_sdk.init` now returns `None` instead of a context manager.
-- The sampling context accessible in `traces_sampler` has changed. The original `sampling_context["transaction_context"]["name"]` and `sampling_context["transaction_context"]["op"]` are now accessible as `sampling_context["sentry_name"]` and `sampling_context["sentry_op"]`, respectively.
 
 ### Removed
 
diff --git a/sentry_sdk/integrations/opentelemetry/consts.py b/sentry_sdk/integrations/opentelemetry/consts.py
index 9cf19eb01d..6d7c91f3f1 100644
--- a/sentry_sdk/integrations/opentelemetry/consts.py
+++ b/sentry_sdk/integrations/opentelemetry/consts.py
@@ -30,5 +30,3 @@ class SentrySpanAttribute:
     NAME = "sentry.name"
     SOURCE = "sentry.source"
     CONTEXT = "sentry.context"
-    CUSTOM_SAMPLED = "sentry.custom_sampled"
-    PARENT_SAMPLED = "sentry.parent_sampled"
diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 4420c8b428..d9bd777ef7 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -129,10 +129,14 @@ def should_sample(
         # Traces_sampler is responsible to check parent sampled to have full transactions.
         has_traces_sampler = callable(client.options.get("traces_sampler"))
         if has_traces_sampler:
-            attributes[SentrySpanAttribute.PARENT_SAMPLED] = get_parent_sampled(
-                parent_span_context, trace_id
-            )
-            sample_rate = client.options["traces_sampler"](attributes)
+            sampling_context = {
+                "transaction_context": {
+                    "name": name,
+                    "op": attributes.get("op"),
+                },
+                "parent_sampled": get_parent_sampled(parent_span_context, trace_id),
+            }
+            sample_rate = client.options["traces_sampler"](sampling_context)
 
         else:
             # Check if there is a parent with a sampling decision

From 5df9ccc6336a513e11cdeb14c6339297c116eb0f Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:40:36 +0100
Subject: [PATCH 04/21] .

---
 sentry_sdk/integrations/opentelemetry/consts.py  | 1 +
 sentry_sdk/integrations/opentelemetry/sampler.py | 2 +-
 sentry_sdk/tracing.py                            | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/sentry_sdk/integrations/opentelemetry/consts.py b/sentry_sdk/integrations/opentelemetry/consts.py
index 6d7c91f3f1..197e85cc8b 100644
--- a/sentry_sdk/integrations/opentelemetry/consts.py
+++ b/sentry_sdk/integrations/opentelemetry/consts.py
@@ -30,3 +30,4 @@ class SentrySpanAttribute:
     NAME = "sentry.name"
     SOURCE = "sentry.source"
     CONTEXT = "sentry.context"
+    CUSTOM_SAMPLED = "sentry.custom_sampled"
diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index d9bd777ef7..2308ffafc1 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -132,7 +132,7 @@ def should_sample(
             sampling_context = {
                 "transaction_context": {
                     "name": name,
-                    "op": attributes.get("op"),
+                    "op": attributes.get(SentrySpanAttribute.OP),
                 },
                 "parent_sampled": get_parent_sampled(parent_span_context, trace_id),
             }
diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index 868a47144f..94715591b6 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -1235,7 +1235,6 @@ def __init__(
 
             # Prepopulate some attrs to be accessible in traces_sampler
             attributes = attributes or {}
-            attributes[SentrySpanAttribute.NAME] = span_name
             attributes[SentrySpanAttribute.OP] = op
             if sampled is not None:
                 attributes[SentrySpanAttribute.CUSTOM_SAMPLED] = sampled
@@ -1244,6 +1243,7 @@ def __init__(
                 span_name, start_time=start_timestamp, attributes=attributes
             )
 
+            self.name = name
             self.origin = origin or DEFAULT_SPAN_ORIGIN
             self.description = description
             self.source = source

From 472ab5c23690fc7ae6cbd3c658654b36c8b31e1e Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:41:37 +0100
Subject: [PATCH 05/21] add attrs

---
 sentry_sdk/integrations/opentelemetry/sampler.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 2308ffafc1..055abaef4d 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -136,6 +136,7 @@ def should_sample(
                 },
                 "parent_sampled": get_parent_sampled(parent_span_context, trace_id),
             }
+            sampling_context.update(attributes)
             sample_rate = client.options["traces_sampler"](sampling_context)
 
         else:

From f893f12a2deee3f5d6af89a767b92bb1d5a767e1 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:42:31 +0100
Subject: [PATCH 06/21] .

---
 sentry_sdk/tracing.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index 94715591b6..1e712af161 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -1233,7 +1233,7 @@ def __init__(
 
             span_name = name or description or op or ""
 
-            # Prepopulate some attrs to be accessible in traces_sampler
+            # Prepopulate some attrs so that they're accessible in traces_sampler
             attributes = attributes or {}
             attributes[SentrySpanAttribute.OP] = op
             if sampled is not None:

From fff9f163cb4d94e9930d50530d2f5752f0aaae97 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:48:16 +0100
Subject: [PATCH 07/21] .

---
 sentry_sdk/integrations/opentelemetry/scope.py | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/sentry_sdk/integrations/opentelemetry/scope.py b/sentry_sdk/integrations/opentelemetry/scope.py
index 4274d70296..82828d61de 100644
--- a/sentry_sdk/integrations/opentelemetry/scope.py
+++ b/sentry_sdk/integrations/opentelemetry/scope.py
@@ -24,7 +24,6 @@
     from typing import Tuple, Optional, Generator, Dict, Any
     from typing_extensions import Unpack
 
-    from sentry_sdk._types import SamplingContext
     from sentry_sdk.tracing import TransactionKwargs
 
 
@@ -112,20 +111,18 @@ def _incoming_otel_span_context(self):
 
         return span_context
 
-    def start_transaction(self, custom_sampling_context=None, **kwargs):
-        # type: (Optional[SamplingContext], Unpack[TransactionKwargs]) -> POTelSpan
+    def start_transaction(self, **kwargs):
+        # type: (Unpack[TransactionKwargs]) -> POTelSpan
         """
         .. deprecated:: 3.0.0
             This function is deprecated and will be removed in a future release.
             Use :py:meth:`sentry_sdk.start_span` instead.
         """
-        return self.start_span(custom_sampling_context=custom_sampling_context)
+        return self.start_span(**kwargs)
 
-    def start_span(self, custom_sampling_context=None, **kwargs):
-        # type: (Optional[SamplingContext], Any) -> POTelSpan
-        return POTelSpan(
-            **kwargs, custom_sampling_context=custom_sampling_context, scope=self
-        )
+    def start_span(self, **kwargs):
+        # type: (Any) -> POTelSpan
+        return POTelSpan(**kwargs, scope=self)
 
 
 _INITIAL_CURRENT_SCOPE = PotelScope(ty=ScopeType.CURRENT)

From ce815e8ccee4d5940258b754bc13e16b432adf2f Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 7 Nov 2024 12:51:06 +0100
Subject: [PATCH 08/21] more removals

---
 sentry_sdk/scope.py            |  8 +-------
 tests/tracing/test_sampling.py | 13 -------------
 2 files changed, 1 insertion(+), 20 deletions(-)

diff --git a/sentry_sdk/scope.py b/sentry_sdk/scope.py
index 983b38bf2c..2a6700b178 100644
--- a/sentry_sdk/scope.py
+++ b/sentry_sdk/scope.py
@@ -946,9 +946,7 @@ def add_breadcrumb(self, crumb=None, hint=None, **kwargs):
         while len(self._breadcrumbs) > max_breadcrumbs:
             self._breadcrumbs.popleft()
 
-    def start_transaction(
-        self, transaction=None, custom_sampling_context=None, **kwargs
-    ):
+    def start_transaction(self, transaction=None, **kwargs):
         # type: (Optional[Transaction], Optional[SamplingContext], Unpack[TransactionKwargs]) -> Union[Transaction, NoOpSpan]
         """
         Start and return a transaction.
@@ -974,7 +972,6 @@ def start_transaction(
 
         :param transaction: The transaction to start. If omitted, we create and
             start a new transaction.
-        :param custom_sampling_context: The transaction's custom sampling context.
         :param kwargs: Optional keyword arguments to be passed to the Transaction
             constructor. See :py:class:`sentry_sdk.tracing.Transaction` for
             available arguments.
@@ -985,8 +982,6 @@ def start_transaction(
 
         try_autostart_continuous_profiler()
 
-        custom_sampling_context = custom_sampling_context or {}
-
         # if we haven't been given a transaction, make one
         transaction = Transaction(**kwargs)
 
@@ -996,7 +991,6 @@ def start_transaction(
             "transaction_context": transaction.to_json(),
             "parent_sampled": transaction.parent_sampled,
         }
-        sampling_context.update(custom_sampling_context)
         transaction._set_initial_sampling_decision(sampling_context=sampling_context)
 
         if transaction.sampled:
diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index 2e6ed0dab3..23cadf254c 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -211,19 +211,6 @@ def test_passes_parent_sampling_decision_in_sampling_context(
     assert sampling_context["parent_sampled"]._mock_wraps is parent_sampling_decision
 
 
-def test_passes_custom_samling_context_from_start_transaction_to_traces_sampler(
-    sentry_init, DictionaryContaining  # noqa: N803
-):
-    traces_sampler = mock.Mock()
-    sentry_init(traces_sampler=traces_sampler)
-
-    start_transaction(custom_sampling_context={"dogs": "yes", "cats": "maybe"})
-
-    traces_sampler.assert_any_call(
-        DictionaryContaining({"dogs": "yes", "cats": "maybe"})
-    )
-
-
 def test_sample_rate_affects_errors(sentry_init, capture_events):
     sentry_init(sample_rate=0)
     events = capture_events()

From 747ecc6ca113fbf2d3b5488732c649c7c1dcdccc Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 09:45:19 +0100
Subject: [PATCH 09/21] more readme

---
 MIGRATION_GUIDE.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 1c6daa0e29..64a21f17b6 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -19,12 +19,13 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - Redis integration: In Redis pipeline spans there is no `span["data"]["redis.commands"]` that contains a dict `{"count": 3, "first_ten": ["cmd1", "cmd2", ...]}` but instead `span["data"]["redis.commands.count"]` (containing `3`) and `span["data"]["redis.commands.first_ten"]` (containing `["cmd1", "cmd2", ...]`).
 - clickhouse-driver integration: The query is now available under the `db.query.text` span attribute (only if `send_default_pii` is `True`).
 - `sentry_sdk.init` now returns `None` instead of a context manager.
+- The `sampling_context` argument of `traces_sampler` now additionally contains all span attributes known at span start.
 
 ### Removed
 
 - Spans no longer have a `description`. Use `name` instead.
 - Dropped support for Python 3.6.
-- The `custom_sampling_context` parameter of `start_transaction` has been removed.
+- The `custom_sampling_context` parameter of `start_transaction` has been removed. Use `attributes` instead to set key-value pairs of data that should be accessible in the traces sampler.
 - The PyMongo integration no longer sets tags. The data is still accessible via span attributes.
 - The PyMongo integration doesn't set `operation_ids` anymore. The individual IDs (`operation_id`, `request_id`, `session_id`) are now accessible as separate span attributes.
 - `sentry_sdk.metrics` and associated metrics APIs have been removed as Sentry no longer accepts metrics data in this form. See https://sentry.zendesk.com/hc/en-us/articles/26369339769883-Upcoming-API-Changes-to-Metrics

From 7ae6745076486ce851ce3375b75aa49869f7993a Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 09:49:19 +0100
Subject: [PATCH 10/21] more info

---
 MIGRATION_GUIDE.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 64a21f17b6..0095cafab7 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -25,7 +25,7 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 
 - Spans no longer have a `description`. Use `name` instead.
 - Dropped support for Python 3.6.
-- The `custom_sampling_context` parameter of `start_transaction` has been removed. Use `attributes` instead to set key-value pairs of data that should be accessible in the traces sampler.
+- The `custom_sampling_context` parameter of `start_transaction` has been removed. Use `attributes` instead to set key-value pairs of data that should be accessible in the traces sampler. Note that span attributes need to conform to the [OpenTelemetry specification](https://opentelemetry.io/docs/concepts/signals/traces/#attributes), meaning only certain types can be set as values.
 - The PyMongo integration no longer sets tags. The data is still accessible via span attributes.
 - The PyMongo integration doesn't set `operation_ids` anymore. The individual IDs (`operation_id`, `request_id`, `session_id`) are now accessible as separate span attributes.
 - `sentry_sdk.metrics` and associated metrics APIs have been removed as Sentry no longer accepts metrics data in this form. See https://sentry.zendesk.com/hc/en-us/articles/26369339769883-Upcoming-API-Changes-to-Metrics

From 09d247ec3a1ffe1a96533efd1ba8014645513f5c Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 09:50:34 +0100
Subject: [PATCH 11/21] comment

---
 sentry_sdk/integrations/opentelemetry/consts.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sentry_sdk/integrations/opentelemetry/consts.py b/sentry_sdk/integrations/opentelemetry/consts.py
index 197e85cc8b..1585e8d893 100644
--- a/sentry_sdk/integrations/opentelemetry/consts.py
+++ b/sentry_sdk/integrations/opentelemetry/consts.py
@@ -30,4 +30,4 @@ class SentrySpanAttribute:
     NAME = "sentry.name"
     SOURCE = "sentry.source"
     CONTEXT = "sentry.context"
-    CUSTOM_SAMPLED = "sentry.custom_sampled"
+    CUSTOM_SAMPLED = "sentry.custom_sampled"  # used for saving start_span(sampled=X)

From 1aeeb68d7d3a00de82ea2dd60181eb8fd61d6ac2 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 09:53:05 +0100
Subject: [PATCH 12/21] small change

---
 sentry_sdk/tracing.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index 348e0c20ba..70744d2d71 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -1257,9 +1257,9 @@ def __init__(
                     span_name, start_time=start_timestamp, attributes=attributes
                 )
 
-                self.name = name
                 self.origin = origin or DEFAULT_SPAN_ORIGIN
                 self.description = description
+                self.name = span_name
                 self.source = source
 
                 if status is not None:

From 786bb9ea3ad3a8987734097c93e4854019bf09e7 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 10:33:36 +0100
Subject: [PATCH 13/21] .

---
 tests/tracing/test_sampling.py | 95 +++++++++++++++++++---------------
 1 file changed, 52 insertions(+), 43 deletions(-)

diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index 23cadf254c..60daa50222 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -5,7 +5,7 @@
 import pytest
 
 import sentry_sdk
-from sentry_sdk import start_span, start_transaction, capture_exception
+from sentry_sdk import start_span, capture_exception
 from sentry_sdk.tracing import Transaction
 from sentry_sdk.utils import logger
 
@@ -13,7 +13,7 @@
 def test_sampling_decided_only_for_transactions(sentry_init, capture_events):
     sentry_init(traces_sample_rate=0.5)
 
-    with start_transaction(name="hi") as transaction:
+    with start_span(name="hi") as transaction:
         assert transaction.sampled is not None
 
         with start_span() as span:
@@ -24,16 +24,14 @@ def test_sampling_decided_only_for_transactions(sentry_init, capture_events):
 
 
 @pytest.mark.parametrize("sampled", [True, False])
-def test_nested_transaction_sampling_override(sentry_init, sampled):
+def test_nested_span_sampling_override(sentry_init, sampled):
     sentry_init(traces_sample_rate=1.0)
 
-    with start_transaction(name="outer", sampled=sampled) as outer_transaction:
-        assert outer_transaction.sampled is sampled
-        with start_transaction(
-            name="inner", sampled=(not sampled)
-        ) as inner_transaction:
-            assert inner_transaction.sampled is not sampled
-        assert outer_transaction.sampled is sampled
+    with start_span(name="outer", sampled=sampled) as outer_span:
+        assert outer_span.sampled is sampled
+        with start_span(name="inner", sampled=(not sampled)) as inner_span:
+            assert inner_span.sampled is not sampled
+        assert outer_span.sampled is sampled
 
 
 def test_no_double_sampling(sentry_init, capture_events):
@@ -42,19 +40,19 @@ def test_no_double_sampling(sentry_init, capture_events):
     sentry_init(traces_sample_rate=1.0, sample_rate=0.0)
     events = capture_events()
 
-    with start_transaction(name="/"):
+    with start_span(name="/"):
         pass
 
     assert len(events) == 1
 
 
 @pytest.mark.parametrize("sampling_decision", [True, False])
-def test_get_transaction_and_span_from_scope_regardless_of_sampling_decision(
+def test_get_span_from_scope_regardless_of_sampling_decision(
     sentry_init, sampling_decision
 ):
     sentry_init(traces_sample_rate=1.0)
 
-    with start_transaction(name="/", sampled=sampling_decision):
+    with start_span(name="/", sampled=sampling_decision):
         with start_span(op="child-span"):
             with start_span(op="child-child-span"):
                 scope = sentry_sdk.get_current_scope()
@@ -74,8 +72,8 @@ def test_uses_traces_sample_rate_correctly(
     sentry_init(traces_sample_rate=traces_sample_rate)
 
     with mock.patch.object(random, "random", return_value=0.5):
-        transaction = start_transaction(name="dogpark")
-        assert transaction.sampled is expected_decision
+        span = start_span(name="dogpark")
+        assert span.sampled is expected_decision
 
 
 @pytest.mark.parametrize(
@@ -90,8 +88,8 @@ def test_uses_traces_sampler_return_value_correctly(
     sentry_init(traces_sampler=mock.Mock(return_value=traces_sampler_return_value))
 
     with mock.patch.object(random, "random", return_value=0.5):
-        transaction = start_transaction(name="dogpark")
-        assert transaction.sampled is expected_decision
+        span = start_span(name="dogpark")
+        assert span.sampled is expected_decision
 
 
 @pytest.mark.parametrize("traces_sampler_return_value", [True, False])
@@ -100,19 +98,19 @@ def test_tolerates_traces_sampler_returning_a_boolean(
 ):
     sentry_init(traces_sampler=mock.Mock(return_value=traces_sampler_return_value))
 
-    transaction = start_transaction(name="dogpark")
-    assert transaction.sampled is traces_sampler_return_value
+    span = start_span(name="dogpark")
+    assert span.sampled is traces_sampler_return_value
 
 
 @pytest.mark.parametrize("sampling_decision", [True, False])
-def test_only_captures_transaction_when_sampled_is_true(
+def test_only_captures_span_when_sampled_is_true(
     sentry_init, sampling_decision, capture_events
 ):
     sentry_init(traces_sampler=mock.Mock(return_value=sampling_decision))
     events = capture_events()
 
-    transaction = start_transaction(name="dogpark")
-    transaction.finish()
+    span = start_span(name="dogpark")
+    span.finish()
 
     assert len(events) == (1 if sampling_decision else 0)
 
@@ -133,9 +131,9 @@ def test_prefers_traces_sampler_to_traces_sample_rate(
         traces_sampler=traces_sampler,
     )
 
-    transaction = start_transaction(name="dogpark")
+    span = start_span(name="dogpark")
     assert traces_sampler.called is True
-    assert transaction.sampled is traces_sampler_return_value
+    assert span.sampled is traces_sampler_return_value
 
 
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
@@ -147,10 +145,8 @@ def test_ignores_inherited_sample_decision_when_traces_sampler_defined(
     traces_sampler = mock.Mock(return_value=not parent_sampling_decision)
     sentry_init(traces_sampler=traces_sampler)
 
-    transaction = start_transaction(
-        name="dogpark", parent_sampled=parent_sampling_decision
-    )
-    assert transaction.sampled is not parent_sampling_decision
+    span = start_span(name="dogpark", parent_sampled=parent_sampling_decision)
+    assert span.sampled is not parent_sampling_decision
 
 
 @pytest.mark.parametrize("explicit_decision", [True, False])
@@ -162,8 +158,8 @@ def test_traces_sampler_doesnt_overwrite_explicitly_passed_sampling_decision(
     traces_sampler = mock.Mock(return_value=not explicit_decision)
     sentry_init(traces_sampler=traces_sampler)
 
-    transaction = start_transaction(name="dogpark", sampled=explicit_decision)
-    assert transaction.sampled is explicit_decision
+    span = start_span(name="dogpark", sampled=explicit_decision)
+    assert span.sampled is explicit_decision
 
 
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
@@ -177,10 +173,8 @@ def test_inherits_parent_sampling_decision_when_traces_sampler_undefined(
     mock_random_value = 0.25 if parent_sampling_decision is False else 0.75
 
     with mock.patch.object(random, "random", return_value=mock_random_value):
-        transaction = start_transaction(
-            name="dogpark", parent_sampled=parent_sampling_decision
-        )
-        assert transaction.sampled is parent_sampling_decision
+        span = start_span(name="dogpark", parent_sampled=parent_sampling_decision)
+        assert span.sampled is parent_sampling_decision
 
 
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
@@ -195,11 +189,13 @@ def test_passes_parent_sampling_decision_in_sampling_context(
         )
     )
 
+    # XXX
+
     transaction = Transaction.continue_from_headers(
         headers={"sentry-trace": sentry_trace_header}, name="dogpark"
     )
     spy = mock.Mock(wraps=transaction)
-    start_transaction(transaction=spy)
+    start_span(span=spy)
 
     # there's only one call (so index at 0) and kwargs are always last in a call
     # tuple (so index at -1)
@@ -223,6 +219,19 @@ def test_sample_rate_affects_errors(sentry_init, capture_events):
     assert len(events) == 0
 
 
+def test_passes_custom_attributes_from_start_span_to_traces_sampler(
+    sentry_init, DictionaryContaining  # noqa: N803
+):
+    traces_sampler = mock.Mock()
+    sentry_init(traces_sampler=traces_sampler)
+
+    start_span(attributes={"dogs": "yes", "cats": "maybe"})
+
+    traces_sampler.assert_any_call(
+        DictionaryContaining({"dogs": "yes", "cats": "maybe"})
+    )
+
+
 @pytest.mark.parametrize(
     "traces_sampler_return_value",
     [
@@ -243,9 +252,9 @@ def test_warns_and_sets_sampled_to_false_on_invalid_traces_sampler_return_value(
     sentry_init(traces_sampler=mock.Mock(return_value=traces_sampler_return_value))
 
     with mock.patch.object(logger, "warning", mock.Mock()):
-        transaction = start_transaction(name="dogpark")
+        span = start_span(name="dogpark")
         logger.warning.assert_any_call(StringContaining("Given sample rate is invalid"))
-        assert transaction.sampled is False
+        assert span.sampled is False
 
 
 @pytest.mark.parametrize(
@@ -270,9 +279,9 @@ def test_records_lost_event_only_if_traces_sample_rate_enabled(
     sentry_init(traces_sample_rate=traces_sample_rate)
     record_lost_event_calls = capture_record_lost_event_calls()
 
-    transaction = start_transaction(name="dogpark")
-    assert transaction.sampled is sampled_output
-    transaction.finish()
+    span = start_span(name="dogpark")
+    assert span.sampled is sampled_output
+    span.finish()
 
     # Use Counter because order of calls does not matter
     assert Counter(record_lost_event_calls) == Counter(expected_record_lost_event_calls)
@@ -300,9 +309,9 @@ def test_records_lost_event_only_if_traces_sampler_enabled(
     sentry_init(traces_sampler=traces_sampler)
     record_lost_event_calls = capture_record_lost_event_calls()
 
-    transaction = start_transaction(name="dogpark")
-    assert transaction.sampled is sampled_output
-    transaction.finish()
+    span = start_span(name="dogpark")
+    assert span.sampled is sampled_output
+    span.finish()
 
     # Use Counter because order of calls does not matter
     assert Counter(record_lost_event_calls) == Counter(expected_record_lost_event_calls)

From 80427c6d4a304466c73b5897a1fcd0c74091dcd6 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 11:09:55 +0100
Subject: [PATCH 14/21] dont do everything in this pr

---
 tests/tracing/test_sampling.py | 108 +++++++++++++++++----------------
 1 file changed, 56 insertions(+), 52 deletions(-)

diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index 60daa50222..70baacc951 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -5,7 +5,7 @@
 import pytest
 
 import sentry_sdk
-from sentry_sdk import start_span, capture_exception
+from sentry_sdk import start_span, start_transaction, capture_exception
 from sentry_sdk.tracing import Transaction
 from sentry_sdk.utils import logger
 
@@ -13,7 +13,7 @@
 def test_sampling_decided_only_for_transactions(sentry_init, capture_events):
     sentry_init(traces_sample_rate=0.5)
 
-    with start_span(name="hi") as transaction:
+    with start_transaction(name="hi") as transaction:
         assert transaction.sampled is not None
 
         with start_span() as span:
@@ -24,14 +24,16 @@ def test_sampling_decided_only_for_transactions(sentry_init, capture_events):
 
 
 @pytest.mark.parametrize("sampled", [True, False])
-def test_nested_span_sampling_override(sentry_init, sampled):
+def test_nested_transaction_sampling_override(sentry_init, sampled):
     sentry_init(traces_sample_rate=1.0)
 
-    with start_span(name="outer", sampled=sampled) as outer_span:
-        assert outer_span.sampled is sampled
-        with start_span(name="inner", sampled=(not sampled)) as inner_span:
-            assert inner_span.sampled is not sampled
-        assert outer_span.sampled is sampled
+    with start_transaction(name="outer", sampled=sampled) as outer_transaction:
+        assert outer_transaction.sampled is sampled
+        with start_transaction(
+            name="inner", sampled=(not sampled)
+        ) as inner_transaction:
+            assert inner_transaction.sampled is not sampled
+        assert outer_transaction.sampled is sampled
 
 
 def test_no_double_sampling(sentry_init, capture_events):
@@ -40,19 +42,19 @@ def test_no_double_sampling(sentry_init, capture_events):
     sentry_init(traces_sample_rate=1.0, sample_rate=0.0)
     events = capture_events()
 
-    with start_span(name="/"):
+    with start_transaction(name="/"):
         pass
 
     assert len(events) == 1
 
 
 @pytest.mark.parametrize("sampling_decision", [True, False])
-def test_get_span_from_scope_regardless_of_sampling_decision(
+def test_get_transaction_and_span_from_scope_regardless_of_sampling_decision(
     sentry_init, sampling_decision
 ):
     sentry_init(traces_sample_rate=1.0)
 
-    with start_span(name="/", sampled=sampling_decision):
+    with start_transaction(name="/", sampled=sampling_decision):
         with start_span(op="child-span"):
             with start_span(op="child-child-span"):
                 scope = sentry_sdk.get_current_scope()
@@ -72,8 +74,8 @@ def test_uses_traces_sample_rate_correctly(
     sentry_init(traces_sample_rate=traces_sample_rate)
 
     with mock.patch.object(random, "random", return_value=0.5):
-        span = start_span(name="dogpark")
-        assert span.sampled is expected_decision
+        transaction = start_transaction(name="dogpark")
+        assert transaction.sampled is expected_decision
 
 
 @pytest.mark.parametrize(
@@ -88,8 +90,8 @@ def test_uses_traces_sampler_return_value_correctly(
     sentry_init(traces_sampler=mock.Mock(return_value=traces_sampler_return_value))
 
     with mock.patch.object(random, "random", return_value=0.5):
-        span = start_span(name="dogpark")
-        assert span.sampled is expected_decision
+        transaction = start_transaction(name="dogpark")
+        assert transaction.sampled is expected_decision
 
 
 @pytest.mark.parametrize("traces_sampler_return_value", [True, False])
@@ -98,19 +100,19 @@ def test_tolerates_traces_sampler_returning_a_boolean(
 ):
     sentry_init(traces_sampler=mock.Mock(return_value=traces_sampler_return_value))
 
-    span = start_span(name="dogpark")
-    assert span.sampled is traces_sampler_return_value
+    transaction = start_transaction(name="dogpark")
+    assert transaction.sampled is traces_sampler_return_value
 
 
 @pytest.mark.parametrize("sampling_decision", [True, False])
-def test_only_captures_span_when_sampled_is_true(
+def test_only_captures_transaction_when_sampled_is_true(
     sentry_init, sampling_decision, capture_events
 ):
     sentry_init(traces_sampler=mock.Mock(return_value=sampling_decision))
     events = capture_events()
 
-    span = start_span(name="dogpark")
-    span.finish()
+    transaction = start_transaction(name="dogpark")
+    transaction.finish()
 
     assert len(events) == (1 if sampling_decision else 0)
 
@@ -131,9 +133,9 @@ def test_prefers_traces_sampler_to_traces_sample_rate(
         traces_sampler=traces_sampler,
     )
 
-    span = start_span(name="dogpark")
+    transaction = start_transaction(name="dogpark")
     assert traces_sampler.called is True
-    assert span.sampled is traces_sampler_return_value
+    assert transaction.sampled is traces_sampler_return_value
 
 
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
@@ -145,8 +147,10 @@ def test_ignores_inherited_sample_decision_when_traces_sampler_defined(
     traces_sampler = mock.Mock(return_value=not parent_sampling_decision)
     sentry_init(traces_sampler=traces_sampler)
 
-    span = start_span(name="dogpark", parent_sampled=parent_sampling_decision)
-    assert span.sampled is not parent_sampling_decision
+    transaction = start_transaction(
+        name="dogpark", parent_sampled=parent_sampling_decision
+    )
+    assert transaction.sampled is not parent_sampling_decision
 
 
 @pytest.mark.parametrize("explicit_decision", [True, False])
@@ -158,8 +162,8 @@ def test_traces_sampler_doesnt_overwrite_explicitly_passed_sampling_decision(
     traces_sampler = mock.Mock(return_value=not explicit_decision)
     sentry_init(traces_sampler=traces_sampler)
 
-    span = start_span(name="dogpark", sampled=explicit_decision)
-    assert span.sampled is explicit_decision
+    transaction = start_transaction(name="dogpark", sampled=explicit_decision)
+    assert transaction.sampled is explicit_decision
 
 
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
@@ -173,8 +177,10 @@ def test_inherits_parent_sampling_decision_when_traces_sampler_undefined(
     mock_random_value = 0.25 if parent_sampling_decision is False else 0.75
 
     with mock.patch.object(random, "random", return_value=mock_random_value):
-        span = start_span(name="dogpark", parent_sampled=parent_sampling_decision)
-        assert span.sampled is parent_sampling_decision
+        transaction = start_transaction(
+            name="dogpark", parent_sampled=parent_sampling_decision
+        )
+        assert transaction.sampled is parent_sampling_decision
 
 
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
@@ -189,13 +195,11 @@ def test_passes_parent_sampling_decision_in_sampling_context(
         )
     )
 
-    # XXX
-
     transaction = Transaction.continue_from_headers(
         headers={"sentry-trace": sentry_trace_header}, name="dogpark"
     )
     spy = mock.Mock(wraps=transaction)
-    start_span(span=spy)
+    start_transaction(transaction=spy)
 
     # there's only one call (so index at 0) and kwargs are always last in a call
     # tuple (so index at -1)
@@ -207,6 +211,19 @@ def test_passes_parent_sampling_decision_in_sampling_context(
     assert sampling_context["parent_sampled"]._mock_wraps is parent_sampling_decision
 
 
+def test_passes_attributes_from_start_span_to_traces_sampler(
+    sentry_init, DictionaryContaining  # noqa: N803
+):
+    traces_sampler = mock.Mock()
+    sentry_init(traces_sampler=traces_sampler)
+
+    start_transaction(attributes={"dogs": "yes", "cats": "maybe"})
+
+    traces_sampler.assert_any_call(
+        DictionaryContaining({"dogs": "yes", "cats": "maybe"})
+    )
+
+
 def test_sample_rate_affects_errors(sentry_init, capture_events):
     sentry_init(sample_rate=0)
     events = capture_events()
@@ -219,19 +236,6 @@ def test_sample_rate_affects_errors(sentry_init, capture_events):
     assert len(events) == 0
 
 
-def test_passes_custom_attributes_from_start_span_to_traces_sampler(
-    sentry_init, DictionaryContaining  # noqa: N803
-):
-    traces_sampler = mock.Mock()
-    sentry_init(traces_sampler=traces_sampler)
-
-    start_span(attributes={"dogs": "yes", "cats": "maybe"})
-
-    traces_sampler.assert_any_call(
-        DictionaryContaining({"dogs": "yes", "cats": "maybe"})
-    )
-
-
 @pytest.mark.parametrize(
     "traces_sampler_return_value",
     [
@@ -252,9 +256,9 @@ def test_warns_and_sets_sampled_to_false_on_invalid_traces_sampler_return_value(
     sentry_init(traces_sampler=mock.Mock(return_value=traces_sampler_return_value))
 
     with mock.patch.object(logger, "warning", mock.Mock()):
-        span = start_span(name="dogpark")
+        transaction = start_transaction(name="dogpark")
         logger.warning.assert_any_call(StringContaining("Given sample rate is invalid"))
-        assert span.sampled is False
+        assert transaction.sampled is False
 
 
 @pytest.mark.parametrize(
@@ -279,9 +283,9 @@ def test_records_lost_event_only_if_traces_sample_rate_enabled(
     sentry_init(traces_sample_rate=traces_sample_rate)
     record_lost_event_calls = capture_record_lost_event_calls()
 
-    span = start_span(name="dogpark")
-    assert span.sampled is sampled_output
-    span.finish()
+    transaction = start_transaction(name="dogpark")
+    assert transaction.sampled is sampled_output
+    transaction.finish()
 
     # Use Counter because order of calls does not matter
     assert Counter(record_lost_event_calls) == Counter(expected_record_lost_event_calls)
@@ -309,9 +313,9 @@ def test_records_lost_event_only_if_traces_sampler_enabled(
     sentry_init(traces_sampler=traces_sampler)
     record_lost_event_calls = capture_record_lost_event_calls()
 
-    span = start_span(name="dogpark")
-    assert span.sampled is sampled_output
-    span.finish()
+    transaction = start_transaction(name="dogpark")
+    assert transaction.sampled is sampled_output
+    transaction.finish()
 
     # Use Counter because order of calls does not matter
     assert Counter(record_lost_event_calls) == Counter(expected_record_lost_event_calls)

From 2acef08640fd3f15e0b429f423de3ea754cfa339 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 13:00:36 +0100
Subject: [PATCH 15/21] get rid of none attributes

---
 sentry_sdk/integrations/opentelemetry/sampler.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 055abaef4d..bb9d8cf377 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -114,6 +114,8 @@ def should_sample(
 
         parent_span_context = trace.get_current_span(parent_context).get_span_context()
 
+        attributes = attributes or {}
+
         # No tracing enabled, thus no sampling
         if not has_tracing_enabled(client.options):
             return dropped_result(parent_span_context, attributes)

From eb2df70b988c52fda9362181f0a965e1caffac4b Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 13:05:41 +0100
Subject: [PATCH 16/21] dropped result too

---
 sentry_sdk/integrations/opentelemetry/sampler.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index bb9d8cf377..79e2ec7d8f 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -123,7 +123,10 @@ def should_sample(
         # Explicit sampled value provided at start_span
         if attributes.get(SentrySpanAttribute.CUSTOM_SAMPLED) is not None:
             sample_rate = float(attributes[SentrySpanAttribute.CUSTOM_SAMPLED])
-            return sampled_result(parent_span_context, attributes, sample_rate)
+            if sample_rate > 0:
+                return sampled_result(parent_span_context, attributes, sample_rate)
+            else:
+                return dropped_result(parent_span_context, attributes)
 
         sample_rate = None
 

From 2cee3737a4ef7108ae653bcc04c5d90ad38e3cc2 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 13:32:39 +0100
Subject: [PATCH 17/21] Replace custom_sampling_context with attributes in ASGI

---
 MIGRATION_GUIDE.md              |  1 +
 sentry_sdk/integrations/asgi.py | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 0095cafab7..8913550ae8 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -20,6 +20,7 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - clickhouse-driver integration: The query is now available under the `db.query.text` span attribute (only if `send_default_pii` is `True`).
 - `sentry_sdk.init` now returns `None` instead of a context manager.
 - The `sampling_context` argument of `traces_sampler` now additionally contains all span attributes known at span start.
+- The `sampling_context` argument of `traces_sampler` doesn't contain the `asgi_scope` object anymore for ASGI frameworks. Instead, the individual properties, if available, are accessible as `asgi_scope.endpoint`, `asgi_scope.path`, `asgi_scope.root_path`, `asgi_scope.route`, `asgi_scope.scheme`, `asgi_scope.server` and `asgi_scope.type`.
 
 ### Removed
 
diff --git a/sentry_sdk/integrations/asgi.py b/sentry_sdk/integrations/asgi.py
index f67c47ef02..73801ed102 100644
--- a/sentry_sdk/integrations/asgi.py
+++ b/sentry_sdk/integrations/asgi.py
@@ -209,7 +209,7 @@ async def _run_app(self, scope, receive, send, asgi_version):
                                 name=transaction_name,
                                 source=transaction_source,
                                 origin=self.span_origin,
-                                custom_sampling_context={"asgi_scope": scope},
+                                attributes=_prepopulate_attributes(scope),
                             )
                             if should_trace
                             else nullcontext()
@@ -324,3 +324,16 @@ def _get_transaction_name_and_source(self, transaction_style, asgi_scope):
             return name, source
 
         return name, source
+
+
+def _prepopulate_attributes(scope):
+    # type: (Any) -> dict[str, Any]
+    """Unpack asgi_scope into serializable attributes."""
+    scope = scope or {}
+
+    attributes = {}
+    for attr in ("endpoint", "path", "root_path", "route", "scheme", "server", "type"):
+        if scope.get(attr):
+            attributes[f"asgi_scope.{attr}"] = scope[attr]
+
+    return attributes

From f6fb9a91c704dae255fbb38fe61a0ec131362fe0 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 14:37:13 +0100
Subject: [PATCH 18/21] add source too

---
 .../integrations/opentelemetry/sampler.py       |  1 +
 sentry_sdk/tracing.py                           |  2 +-
 tests/integrations/asgi/test_asgi.py            | 17 +++++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 79e2ec7d8f..3aaa563bd8 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -138,6 +138,7 @@ def should_sample(
                 "transaction_context": {
                     "name": name,
                     "op": attributes.get(SentrySpanAttribute.OP),
+                    "source": attributes.get(SentrySpanAttribute.SOURCE),
                 },
                 "parent_sampled": get_parent_sampled(parent_span_context, trace_id),
             }
diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index 70744d2d71..0764e7c481 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -1250,6 +1250,7 @@ def __init__(
                 # Prepopulate some attrs so that they're accessible in traces_sampler
                 attributes = attributes or {}
                 attributes[SentrySpanAttribute.OP] = op
+                attributes[SentrySpanAttribute.SOURCE] = source
                 if sampled is not None:
                     attributes[SentrySpanAttribute.CUSTOM_SAMPLED] = sampled
 
@@ -1260,7 +1261,6 @@ def __init__(
                 self.origin = origin or DEFAULT_SPAN_ORIGIN
                 self.description = description
                 self.name = span_name
-                self.source = source
 
                 if status is not None:
                     self.set_status(status)
diff --git a/tests/integrations/asgi/test_asgi.py b/tests/integrations/asgi/test_asgi.py
index e0a3900a38..fb97c385a0 100644
--- a/tests/integrations/asgi/test_asgi.py
+++ b/tests/integrations/asgi/test_asgi.py
@@ -721,3 +721,20 @@ async def test_custom_transaction_name(
     assert transaction_event["type"] == "transaction"
     assert transaction_event["transaction"] == "foobar"
     assert transaction_event["transaction_info"] == {"source": "custom"}
+
+
+@pytest.mark.asyncio
+async def test_asgi_scope_in_traces_sampler(sentry_init, asgi3_app):
+    def dummy_traces_sampler(sampling_context):
+        assert sampling_context["asgi_scope.path"] == "/test"
+        assert sampling_context["asgi_scope.scheme"] == "http"
+
+    sentry_init(
+        traces_sampler=dummy_traces_sampler,
+        traces_sample_rate=1.0,
+    )
+
+    app = SentryAsgiMiddleware(asgi3_app)
+
+    async with TestClient(app) as client:
+        await client.get("/test")

From 4002f38e1383409c553c9e041179708e3c0a8726 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 15:45:27 +0100
Subject: [PATCH 19/21] fix starlette tests

---
 tests/integrations/starlette/test_starlette.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tests/integrations/starlette/test_starlette.py b/tests/integrations/starlette/test_starlette.py
index 22ed10b7cb..c436b0b51a 100644
--- a/tests/integrations/starlette/test_starlette.py
+++ b/tests/integrations/starlette/test_starlette.py
@@ -1066,7 +1066,11 @@ def dummy_traces_sampler(sampling_context):
 
     sentry_init(
         auto_enabling_integrations=False,  # Make sure that httpx integration is not added, because it adds tracing information to the starlette test clients request.
-        integrations=[StarletteIntegration(transaction_style=transaction_style)],
+        integrations=[
+            StarletteIntegration(
+                transaction_style=transaction_style, middleware_spans=False
+            )
+        ],
         traces_sampler=dummy_traces_sampler,
         traces_sample_rate=1.0,
     )

From dbc8ba2eb79b404837fdec04683ee9e39a6a19c3 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Tue, 12 Nov 2024 15:46:50 +0100
Subject: [PATCH 20/21] fix fastapi

---
 tests/integrations/fastapi/test_fastapi.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tests/integrations/fastapi/test_fastapi.py b/tests/integrations/fastapi/test_fastapi.py
index 97aea06344..1dc180863a 100644
--- a/tests/integrations/fastapi/test_fastapi.py
+++ b/tests/integrations/fastapi/test_fastapi.py
@@ -458,7 +458,11 @@ def dummy_traces_sampler(sampling_context):
 
     sentry_init(
         auto_enabling_integrations=False,  # Make sure that httpx integration is not added, because it adds tracing information to the starlette test clients request.
-        integrations=[StarletteIntegration(transaction_style=transaction_style)],
+        integrations=[
+            StarletteIntegration(
+                transaction_style=transaction_style, middleware_spans=False
+            )
+        ],
         traces_sampler=dummy_traces_sampler,
         traces_sample_rate=1.0,
     )

From 52f918a997a0e77452e3ee1c0e822f60cbb347c8 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 12:40:09 +0100
Subject: [PATCH 21/21] remove middleware spans toggle

---
 tests/integrations/fastapi/test_fastapi.py     | 6 +-----
 tests/integrations/starlette/test_starlette.py | 6 +-----
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/tests/integrations/fastapi/test_fastapi.py b/tests/integrations/fastapi/test_fastapi.py
index 1dc180863a..97aea06344 100644
--- a/tests/integrations/fastapi/test_fastapi.py
+++ b/tests/integrations/fastapi/test_fastapi.py
@@ -458,11 +458,7 @@ def dummy_traces_sampler(sampling_context):
 
     sentry_init(
         auto_enabling_integrations=False,  # Make sure that httpx integration is not added, because it adds tracing information to the starlette test clients request.
-        integrations=[
-            StarletteIntegration(
-                transaction_style=transaction_style, middleware_spans=False
-            )
-        ],
+        integrations=[StarletteIntegration(transaction_style=transaction_style)],
         traces_sampler=dummy_traces_sampler,
         traces_sample_rate=1.0,
     )
diff --git a/tests/integrations/starlette/test_starlette.py b/tests/integrations/starlette/test_starlette.py
index c436b0b51a..22ed10b7cb 100644
--- a/tests/integrations/starlette/test_starlette.py
+++ b/tests/integrations/starlette/test_starlette.py
@@ -1066,11 +1066,7 @@ def dummy_traces_sampler(sampling_context):
 
     sentry_init(
         auto_enabling_integrations=False,  # Make sure that httpx integration is not added, because it adds tracing information to the starlette test clients request.
-        integrations=[
-            StarletteIntegration(
-                transaction_style=transaction_style, middleware_spans=False
-            )
-        ],
+        integrations=[StarletteIntegration(transaction_style=transaction_style)],
         traces_sampler=dummy_traces_sampler,
         traces_sample_rate=1.0,
     )