matplotlib · dopplershift · Jul 30, 2019 · Mar 2, 2019 · dopplershift · Jul 30, 2019
diff --git a/doc/api/next_api_changes/2019-03-03-AL.rst b/doc/api/next_api_changes/2019-03-03-AL.rst
@@ -0,0 +1,14 @@
+Deprecations
+````````````
+
+The following methods and attributes of the `MovieWriterRegistry` class are
+deprecated: ``set_dirty``, ``ensure_not_dirty``, ``reset_available_writers``,
+``avail``.
+
+The ``rcsetup.validate_animation_writer_path`` function is deprecated.
+
+`MovieWriterRegistry` now always checks the availability of the writer classes
+before returning them.  If one wishes, for example, to get the first available
+writer, without performing the availability check on subsequent writers, it is
+now possible to iterate over the registry, which will yield the names of the
+available classes.
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -98,13 +98,11 @@ def correct_roundoff(x, dpi, n):
 class MovieWriterRegistry(object):
     '''Registry of available writer classes by human readable name.'''
     def __init__(self):
-        self.avail = dict()
         self._registered = dict()
-        self._dirty = False
 
+    @cbook.deprecated("3.2")
     def set_dirty(self):
         """Sets a flag to re-setup the writers."""
-        self._dirty = True
 
     def register(self, name):
         """Decorator for registering a class under a name.
@@ -115,32 +113,27 @@ def register(self, name):
             class Foo:
                 pass
         """
-        def wrapper(writerClass):
-            self._registered[name] = writerClass
-            if writerClass.isAvailable():
-                self.avail[name] = writerClass
-            return writerClass
+        def wrapper(writer_cls):
+            self._registered[name] = writer_cls
+            return writer_cls
         return wrapper
 
+    @cbook.deprecated("3.2")
     def ensure_not_dirty(self):
         """If dirty, reasks the writers if they are available"""
-        if self._dirty:
-                self.reset_available_writers()
 
+    @cbook.deprecated("3.2")
     def reset_available_writers(self):
         """Reset the available state of all registered writers"""
-        self.avail = {name: writerClass
-                      for name, writerClass in self._registered.items()
-                      if writerClass.isAvailable()}
-        self._dirty = False
 
-    def list(self):
-        '''Get a list of available MovieWriters.'''
-        self.ensure_not_dirty()
-        return list(self.avail)
+    @cbook.deprecated("3.2")
+    @property
+    def avail(self):
+        return {name: self._registered[name] for name in self.list()}
 
     def is_available(self, name):
-        '''Check if given writer is available by name.
+        """
+        Check if given writer is available by name.
 
         Parameters
         ----------
@@ -149,19 +142,28 @@ def is_available(self, name):
         Returns
         -------
         available : bool
-        '''
-        self.ensure_not_dirty()
-        return name in self.avail
-
-    def __getitem__(self, name):
-        self.ensure_not_dirty()
-        if not self.avail:
-            raise RuntimeError("No MovieWriters available!")
+        """
         try:
-            return self.avail[name]
+            cls = self._registered[name]
         except KeyError:
-            raise RuntimeError(
-                'Requested MovieWriter ({}) not available'.format(name))
+            return False
+        return cls.isAvailable()
+
+    def __iter__(self):
+        """Iterate over names of available writer class."""
+        for name in self._registered:
+            if self.is_available(name):
+                yield name
+
+    def list(self):
+        """Get a list of available MovieWriters."""
+        return [*self]
+
+    def __getitem__(self, name):
+        """Get an available writer class from its name."""
+        if self.is_available(name):
+            return self._registered[name]
+        raise RuntimeError(f"Requested MovieWriter ({name}) not available")
 
 
 writers = MovieWriterRegistry()
@@ -1071,22 +1073,21 @@ class to use, such as 'ffmpeg'. If ``None``, defaults to
         # If we have the name of a writer, instantiate an instance of the
         # registered class.
         if isinstance(writer, str):
-            if writer in writers.avail:
+            if writers.is_available(writer):
                 writer = writers[writer](fps, codec, bitrate,
                                          extra_args=extra_args,
                                          metadata=metadata)
             else:
-                if writers.list():
-                    alt_writer = writers[writers.list()[0]]
-                    _log.warning("MovieWriter %s unavailable; trying to use "
-                                 "%s instead.", writer, alt_writer)
-                    writer = alt_writer(
-                        fps, codec, bitrate,
-                        extra_args=extra_args, metadata=metadata)
-                else:
+                alt_writer = next(writers, None)
+                if alt_writer is None:
                     raise ValueError("Cannot save animation: no writers are "
                                      "available. Please install ffmpeg to "
                                      "save animations.")
+                _log.warning("MovieWriter %s unavailable; trying to use %s "
+                             "instead.", writer, alt_writer)
+                writer = alt_writer(
+                    fps, codec, bitrate,
+                    extra_args=extra_args, metadata=metadata)
         _log.info('Animation.save using %s', type(writer))
 
         if 'bbox_inches' in savefig_kwargs:

diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -927,6 +927,7 @@ def validate_hist_bins(s):
                      " a sequence of floats".format(valid_strs))
 
 
+@cbook.deprecated("3.2")
 def validate_animation_writer_path(p):
     # Make sure it's a string and then figure out if the animations
     # are already loaded and reset the writers (which will validate
@@ -1454,15 +1455,15 @@ def _validate_linestyle(ls):
     # Additional arguments for HTML writer
     'animation.html_args':    [[], validate_stringlist],
     # Path to ffmpeg binary. If just binary name, subprocess uses $PATH.
-    'animation.ffmpeg_path':  ['ffmpeg', validate_animation_writer_path],
+    'animation.ffmpeg_path':  ['ffmpeg', validate_string],
     # Additional arguments for ffmpeg movie writer (using pipes)
     'animation.ffmpeg_args':   [[], validate_stringlist],
     # Path to AVConv binary. If just binary name, subprocess uses $PATH.
-    'animation.avconv_path':   ['avconv', validate_animation_writer_path],
+    'animation.avconv_path':   ['avconv', validate_string],
     # Additional arguments for avconv movie writer (using pipes)
     'animation.avconv_args':   [[], validate_stringlist],
      # Path to convert binary. If just binary name, subprocess uses $PATH.
-    'animation.convert_path':  ['convert', validate_animation_writer_path],
+    'animation.convert_path':  ['convert', validate_string],
      # Additional arguments for convert movie writer (using pipes)
     'animation.convert_args':  [[], validate_stringlist],
 

diff --git a/lib/matplotlib/tests/test_animation.py b/lib/matplotlib/tests/test_animation.py
@@ -187,27 +187,14 @@ def test_no_length_frames():
 
 
 def test_movie_writer_registry():
-    ffmpeg_path = mpl.rcParams['animation.ffmpeg_path']
-    # Not sure about the first state as there could be some writer
-    # which set rcparams
-    # assert not animation.writers._dirty
     assert len(animation.writers._registered) > 0
-    animation.writers.list()  # resets dirty state
-    assert not animation.writers._dirty
     mpl.rcParams['animation.ffmpeg_path'] = "not_available_ever_xxxx"
-    assert animation.writers._dirty
-    animation.writers.list()  # resets
-    assert not animation.writers._dirty
     assert not animation.writers.is_available("ffmpeg")
     # something which is guaranteed to be available in path
     # and exits immediately
     bin = "true" if sys.platform != 'win32' else "where"
     mpl.rcParams['animation.ffmpeg_path'] = bin
-    assert animation.writers._dirty
-    animation.writers.list()  # resets
-    assert not animation.writers._dirty
     assert animation.writers.is_available("ffmpeg")
-    mpl.rcParams['animation.ffmpeg_path'] = ffmpeg_path
 
 
 @pytest.mark.skipif(
@@ -248,18 +235,14 @@ def test_failing_ffmpeg(tmpdir, monkeypatch):
     succeeds when called with no arguments (so that it gets registered by
     `isAvailable`), but fails otherwise, and add it to the $PATH.
     """
-    try:
-        with tmpdir.as_cwd():
-            monkeypatch.setenv("PATH", ".:" + os.environ["PATH"])
-            exe_path = Path(str(tmpdir), "ffmpeg")
-            exe_path.write_text("#!/bin/sh\n"
-                                "[[ $@ -eq 0 ]]\n")
-            os.chmod(str(exe_path), 0o755)
-            animation.writers.reset_available_writers()
-            with pytest.raises(subprocess.CalledProcessError):
-                make_animation().save("test.mpeg")
-    finally:
-        animation.writers.reset_available_writers()
+    with tmpdir.as_cwd():
+        monkeypatch.setenv("PATH", ".:" + os.environ["PATH"])
+        exe_path = Path(str(tmpdir), "ffmpeg")
+        exe_path.write_text("#!/bin/sh\n"
+                            "[[ $@ -eq 0 ]]\n")
+        os.chmod(str(exe_path), 0o755)
+        with pytest.raises(subprocess.CalledProcessError):
+            make_animation().save("test.mpeg")
 
 
 @pytest.mark.parametrize("cache_frame_data, weakref_assertion_fn", [