Added logic for creation of the baseline images

SidharthBansal · SidharthBansal · commit 25eb8c5baf79 · 2020-06-30T16:39:50.000+05:30
diff --git a/lib/matplotlib/testing/decorators.py b/lib/matplotlib/testing/decorators.py
@@ -6,6 +6,7 @@
 from pathlib import Path
 import shutil
 import string
+import subprocess
 import sys
 import unittest
 import warnings
@@ -486,7 +487,7 @@ def _image_directories(func):
         try:
             import matplotlib_baseline_images
         except:
-            raise ImportError("Not able to import matplotlib_baseline_images")
+            generate_matplotlib_baseline_images_from_previous_commit()
         baseline_dir = (Path(matplotlib_baseline_images.__file__).parent /
                             module_path.stem)
     elif func.__module__.startswith("mpl_toolkits."):
@@ -504,3 +505,23 @@ def _image_directories(func):
     result_dir = Path().resolve() / "result_images" / module_path.stem
     result_dir.mkdir(parents=True, exist_ok=True)
     return baseline_dir, result_dir
+
+
+def generate_matplotlib_baseline_images_from_previous_commit():
+    # Check if current repository is a git repository
+    subprocess.call(['git', '-C', '.' , 'status'],
+                            stderr=subprocess.STDOUT,
+                            stdout = open(os.devnull,
+                                            'w')) == 0
+    # Check that git is installed.
+    subprocess.call(shutil.which('git'),
+                    stderr=subprocess.STDOUT,
+                    stdout = open(os.devnull,
+                                'w')) == 0
+    # Create virtual env in tmpdir.
+    subprocess.run([sys.executable, "-mvenv", tmpenv])
+    subprocess.run(["git", "clone", "<current repo>", "<tmpenv/...>"])
+    ... git checkout HEAD~
+    ... python -mpytest ...
+    # -> this will generate result_images in that temporary directory
+    # -> copy it and cache it.
