python · markshannon · Mar 14, 2021 · Mar 14, 2021 · Mar 14, 2021 · Mar 14, 2021
diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
@@ -837,6 +837,51 @@ def no_code2():
                 self.assertEqual(end, len(code.co_code))
                 self.assertEqual(line, code.co_firstlineno)
 
+    def test_lineno_attribute(self):
+        def load_attr():
+            return (
+                o.
+                a
+            )
+        load_attr_lines = [ 2, 3, 1 ]
+
+        def load_method():
+            return (
+                o.
+                m(
+                    0
+                )
+            )
+        load_method_lines = [ 2, 3, 4, 3, 1 ]
+
+        def store_attr():
+            (
+                o.
+                a
+            ) = (
+                v
+            )
+        store_attr_lines = [ 5, 2, 3 ]
+
+        def aug_store_attr():
+            (
+                o.
+                a
+            ) += (
+                v
+            )
+        aug_store_attr_lines = [ 2, 3, 5, 1, 3 ]
+
+        funcs = [ load_attr, load_method, store_attr, aug_store_attr]
+        func_lines = [ load_attr_lines, load_method_lines,
+                 store_attr_lines, aug_store_attr_lines]
+
+        for func, lines in zip(funcs, func_lines, strict=True):
+            with self.subTest(func=func):
+                code_lines = [ line-func.__code__.co_firstlineno
+                              for (_, _, line) in func.__code__.co_lines() ]
+                self.assertEqual(lines, code_lines)
+
 
     def test_big_dict_literal(self):
         # The compiler has a flushing point in "compiler_dict" that calls compiles

diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-03-14-16-44-50.bpo-39316.Ns3a_F.rst b/Misc/NEWS.d/next/Core and Builtins/2021-03-14-16-44-50.bpo-39316.Ns3a_F.rst
@@ -0,0 +1,3 @@
+Tracing now has correct line numbers for attribute accesses when the
+the attribute is on a different line from the object.
+Improves debugging and profiling for multi-line method chains.
diff --git a/Python/compile.c b/Python/compile.c
@@ -4145,9 +4145,12 @@ maybe_optimize_method_call(struct compiler *c, expr_ty e)
 
     /* Alright, we can optimize the code. */
     VISIT(c, expr, meth->v.Attribute.value);
+    int old_lineno = c->u->u_lineno;
+    c->u->u_lineno = meth->end_lineno;
     ADDOP_NAME(c, LOAD_METHOD, meth->v.Attribute.attr, names);
     VISIT_SEQ(c, expr, e->v.Call.args);
     ADDOP_I(c, CALL_METHOD, asdl_seq_LEN(e->v.Call.args));
+    c->u->u_lineno = old_lineno;
     return 1;
 }
 
@@ -5113,12 +5116,21 @@ compiler_visit_expr1(struct compiler *c, expr_ty e)
         VISIT(c, expr, e->v.Attribute.value);
         switch (e->v.Attribute.ctx) {
         case Load:
+        {
+            int old_lineno = c->u->u_lineno;
+            c->u->u_lineno = e->end_lineno;
             ADDOP_NAME(c, LOAD_ATTR, e->v.Attribute.attr, names);
+            c->u->u_lineno = old_lineno;
             break;
+        }
         case Store:
-            if (forbidden_name(c, e->v.Attribute.attr, e->v.Attribute.ctx))
+            if (forbidden_name(c, e->v.Attribute.attr, e->v.Attribute.ctx)) {
                 return 0;
+            }
+            int old_lineno = c->u->u_lineno;
+            c->u->u_lineno = e->end_lineno;
             ADDOP_NAME(c, STORE_ATTR, e->v.Attribute.attr, names);
+            c->u->u_lineno = old_lineno;
             break;
         case Del:
             ADDOP_NAME(c, DELETE_ATTR, e->v.Attribute.attr, names);
@@ -5182,7 +5194,10 @@ compiler_augassign(struct compiler *c, stmt_ty s)
     case Attribute_kind:
         VISIT(c, expr, e->v.Attribute.value);
         ADDOP(c, DUP_TOP);
+        int old_lineno = c->u->u_lineno;
+        c->u->u_lineno = e->end_lineno;
         ADDOP_NAME(c, LOAD_ATTR, e->v.Attribute.attr, names);
+        c->u->u_lineno = old_lineno;
         break;
     case Subscript_kind:
         VISIT(c, expr, e->v.Subscript.value);
@@ -5211,6 +5226,7 @@ compiler_augassign(struct compiler *c, stmt_ty s)
 
     switch (e->kind) {
     case Attribute_kind:
+        c->u->u_lineno = e->end_lineno;
         ADDOP(c, ROT_TWO);
         ADDOP_NAME(c, STORE_ATTR, e->v.Attribute.attr, names);
         break;

diff --git a/Python/importlib.h b/Python/importlib.h
diff --git a/Python/importlib_external.h b/Python/importlib_external.h