Fix compression speed gains

docs/changelog.rst

@@ -2,6 +2,14 @@
 Changelog
 =========
 
+Unreleased
+----------
+
+* Fix compression speed gains for the thread pool when running Django’s ``collectstatic``.
+  The thread pool had no effect due to use of a generator for the results, a refactoring introduced when reviewing the initial PR.
+
+  Thanks to Petr Přikryl for the investigation and fix in `PR #616 <https://github.com/evansd/whitenoise/pull/616>`__.
+
 6.8.1 (2024-10-28)
 ------------------
 

src/whitenoise/compress.py

@@ -79,25 +79,24 @@ def should_compress(self, filename):
     def log(self, message):
         pass
 
-    def _lazy_compress(self, path):
+    def compress(self, path):
+        filenames = []
         with open(path, "rb") as f:
             stat_result = os.fstat(f.fileno())
             data = f.read()
         size = len(data)
         if self.use_brotli:
             compressed = self.compress_brotli(data)
             if self.is_compressed_effectively("Brotli", path, size, compressed):
-                yield self.write_data(path, compressed, ".br", stat_result)
+                filenames.append(self.write_data(path, compressed, ".br", stat_result))
             else:
                 # If Brotli compression wasn't effective gzip won't be either
-                return
+                return filenames
         if self.use_gzip:
             compressed = self.compress_gzip(data)
             if self.is_compressed_effectively("Gzip", path, size, compressed):
-                yield self.write_data(path, compressed, ".gz", stat_result)
-
-    def compress(self, path):
-        return list(self._lazy_compress(path))
+                filenames.append(self.write_data(path, compressed, ".gz", stat_result))
+        return filenames
 
     @staticmethod
     def compress_gzip(data):

src/whitenoise/storage.py

@@ -35,11 +35,13 @@ def post_process(
         self.compressor = self.create_compressor(extensions=extensions, quiet=True)
 
         def _compress_path(path: str) -> Generator[tuple[str, str, bool]]:
+            compressed: list[tuple[str, str, bool]] = []
             full_path = self.path(path)
             prefix_len = len(full_path) - len(path)
             for compressed_path in self.compressor.compress(full_path):
                 compressed_name = compressed_path[prefix_len:]
-                yield (path, compressed_name, True)
+                compressed.append((path, compressed_name, True))
+            return compressed
 
         with ThreadPoolExecutor() as executor:
             futures = (
@@ -142,12 +144,14 @@ def compress_files(self, paths):
         extensions = getattr(settings, "WHITENOISE_SKIP_COMPRESS_EXTENSIONS", None)
         self.compressor = self.create_compressor(extensions=extensions, quiet=True)
 
-        def _compress_path(path: str) -> Generator[tuple[str, str]]:
+        def _compress_path(path: str) -> list[tuple[str, str]]:
+            compressed: list[tuple[str, str]] = []
             full_path = self.path(path)
             prefix_len = len(full_path) - len(path)
             for compressed_path in self.compressor.compress(full_path):
                 compressed_name = compressed_path[prefix_len:]
-                yield (path, compressed_name)
+                compressed.append((path, compressed_name))
+            return compressed
 
         with ThreadPoolExecutor() as executor:
             futures = (