Fix: Made bpy.path.ensure_ext compatible with compound extensions.

Extensions such as ".tar.gz" are now also supported. Before this patch,
ensure_ext('demo.tar.gz', '.tar.gz') would return 'demo.tar.tar.gz'.

This results in issues with the `ExportHelper` mix-in class; clicking
an existing file in the file dialogue warns about overwriting it
(highlighting the input box in red), but then saves to a different
file.

Also added a unit test for the new behaviour.

Reviewers: mont29, campbellbarton

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D1498

2 files changed, 47 insertions, 10 deletions

diff --git a/release/scripts/modules/bpy/path.py b/release/scripts/modules/bpy/path.py
index b7d7d9ee694..c31188a49fd 100644
--- a/release/scripts/modules/bpy/path.py
+++ b/release/scripts/modules/bpy/path.py
@@ -283,22 +283,18 @@ def ensure_ext(filepath, ext, case_sensitive=False):
     """
     Return the path with the extension added if it is not already set.
 
-    :arg ext: The extension to check for.
+    :arg ext: The extension to check for, can be a compound extension. Should
+              start with a dot, such as '.blend' or '.tar.gz'.
     :type ext: string
     :arg case_sensitive: Check for matching case when comparing extensions.
     :type case_sensitive: bool
     """
-    fn_base, fn_ext = _os.path.splitext(filepath)
-    if fn_base and fn_ext:
-        if ((case_sensitive and ext == fn_ext) or
-            (ext.lower() == fn_ext.lower())):
 
-            return filepath
-        else:
-            return fn_base + ext
+    if ((case_sensitive and filepath.endswith(ext)) or
+            (not case_sensitive and filepath.lower().endswith(ext.lower()))):
+        return filepath
 
-    else:
-        return filepath + ext
+    return filepath + ext
 
 
 def module_names(path, recursive=False):
diff --git a/tests/python/bl_bpy_path.py b/tests/python/bl_bpy_path.py
new file mode 100644
index 00000000000..5c4ae91a5df
--- /dev/null
+++ b/tests/python/bl_bpy_path.py
@@ -0,0 +1,41 @@
+# Apache License, Version 2.0
+
+# ./blender.bin --background -noaudio --python tests/python/bl_bpy_path.py -- --verbose
+import unittest
+
+
+class TestBpyPath(unittest.TestCase):
+    def test_ensure_ext(self):
+        from bpy.path import ensure_ext
+
+        # Should work with both strings and bytes.
+        self.assertEqual(ensure_ext('demo', '.blend'), 'demo.blend')
+        self.assertEqual(ensure_ext(b'demo', b'.blend'), b'demo.blend')
+
+        # Test different cases.
+        self.assertEqual(ensure_ext('demo.blend', '.blend'), 'demo.blend')
+        self.assertEqual(ensure_ext('demo.BLEND', '.blend'), 'demo.BLEND')
+        self.assertEqual(ensure_ext('demo.blend', '.BLEND'), 'demo.blend')
+
+        # Test empty extensions, compound extensions etc.
+        self.assertEqual(ensure_ext('demo', 'blend'), 'demoblend')
+        self.assertEqual(ensure_ext('demo', ''), 'demo')
+        self.assertEqual(ensure_ext('demo', '.json.gz'), 'demo.json.gz')
+        self.assertEqual(ensure_ext('demo.json.gz', '.json.gz'), 'demo.json.gz')
+        self.assertEqual(ensure_ext('demo.json', '.json.gz'), 'demo.json.json.gz')
+        self.assertEqual(ensure_ext('', ''), '')
+        self.assertEqual(ensure_ext('', '.blend'), '.blend')
+
+        # Test case-sensitive behaviour.
+        self.assertEqual(ensure_ext('demo', '.blend', True), 'demo.blend')
+        self.assertEqual(ensure_ext('demo.BLEND', '.blend', True), 'demo.BLEND.blend')
+        self.assertEqual(ensure_ext('demo', 'Blend', True), 'demoBlend')
+        self.assertEqual(ensure_ext('demoBlend', 'blend', True), 'demoBlendblend')
+        self.assertEqual(ensure_ext('demo', '', True), 'demo')
+
+
+if __name__ == '__main__':
+    import sys
+
+    sys.argv = [__file__] + (sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else [])
+    unittest.main()