c-ext: correctly define fully qualified type names to zstandard.*

indygreg · indygreg · commit 51a277a795db · 2025-09-14T11:40:53.000-07:00
These have been wrong for years. I'm honestly a bit surprised that nothing complains about the mismatch: this thing is easy enough to validate at module import time by the interpreter or via analysis of all types post import via some linter. I guess strong typing has never been Python's strength. Closes #248.
diff --git a/c-ext/bufferutil.c b/c-ext/bufferutil.c
@@ -259,7 +259,7 @@ PyType_Slot ZstdBufferWithSegmentsSlots[] = {
 };
 
 PyType_Spec ZstdBufferWithSegmentsSpec = {
-    "zstd.BufferWithSegments",
+    "zstandard.backend_c.BufferWithSegments",
     sizeof(ZstdBufferWithSegments),
     0,
     Py_TPFLAGS_DEFAULT,
@@ -290,7 +290,7 @@ PyType_Slot ZstdBufferSegmentsSlots[] = {
 };
 
 PyType_Spec ZstdBufferSegmentsSpec = {
-    "zstd.BufferSegments",
+    "zstandard.backend_c.BufferSegments",
     sizeof(ZstdBufferSegments),
     0,
     Py_TPFLAGS_DEFAULT,
@@ -350,7 +350,7 @@ PyType_Slot ZstdBufferSegmentSlots[] = {
 };
 
 PyType_Spec ZstdBufferSegmentSpec = {
-    "zstd.BufferSegment",
+    "zstandard.backend_c.BufferSegment",
     sizeof(ZstdBufferSegment),
     0,
     Py_TPFLAGS_DEFAULT,
@@ -518,7 +518,7 @@ PyType_Slot ZstdBufferWithSegmentsCollectionSlots[] = {
 };
 
 PyType_Spec ZstdBufferWithSegmentsCollectionSpec = {
-    "zstd.BufferWithSegmentsCollection",
+    "zstandard.backend_c.BufferWithSegmentsCollection",
     sizeof(ZstdBufferWithSegmentsCollection),
     0,
     Py_TPFLAGS_DEFAULT,
diff --git a/c-ext/compressionchunker.c b/c-ext/compressionchunker.c
@@ -144,7 +144,7 @@ PyType_Slot ZstdCompressionChunkerIteratorSlots[] = {
 };
 
 PyType_Spec ZstdCompressionChunkerIteratorSpec = {
-    "zstd.ZstdCompressionChunkerIterator",
+    "zstandard.backend_c.ZstdCompressionChunkerIterator",
     sizeof(ZstdCompressionChunkerIterator),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
@@ -286,7 +286,7 @@ PyType_Slot ZstdCompressionChunkerSlots[] = {
 };
 
 PyType_Spec ZstdCompressionChunkerSpec = {
-    "zstd.ZstdCompressionChunkerType",
+    "zstandard.backend_c.ZstdCompressionChunkerType",
     sizeof(ZstdCompressionChunker),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/compressiondict.c b/c-ext/compressiondict.c
@@ -326,7 +326,7 @@ PyType_Slot ZstdCompressionDictSlots[] = {
 };
 
 PyType_Spec ZstdCompressionDictSpec = {
-    "zstd.ZstdCompressionDict",
+    "zstandard.backend_c.ZstdCompressionDict",
     sizeof(ZstdCompressionDict),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/compressionparams.c b/c-ext/compressionparams.c
@@ -479,7 +479,7 @@ PyType_Slot ZstdCompressionParametersSlots[] = {
 };
 
 PyType_Spec ZstdCompressionParametersSpec = {
-    "zstd.ZstdCompressionParameters",
+    "zstandard.backend_c.ZstdCompressionParameters",
     sizeof(ZstdCompressionParametersObject),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/compressionreader.c b/c-ext/compressionreader.c
@@ -788,7 +788,7 @@ PyType_Slot ZstdCompressionReaderSlots[] = {
 };
 
 PyType_Spec ZstdCompressionReaderSpec = {
-    "zstd.ZstdCompressionReader",
+    "zstandard.backend_c.ZstdCompressionReader",
     sizeof(ZstdCompressionReader),
     0,
     Py_TPFLAGS_DEFAULT,
diff --git a/c-ext/compressionwriter.c b/c-ext/compressionwriter.c
@@ -330,7 +330,7 @@ PyType_Slot ZstdCompressionWriterSlots[] = {
 };
 
 PyType_Spec ZstdCompressionWriterSpec = {
-    "zstd.ZstdCompressionWriter",
+    "zstandard.backend_c.ZstdCompressionWriter",
     sizeof(ZstdCompressionWriter),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/compressobj.c b/c-ext/compressobj.c
@@ -202,7 +202,7 @@ PyType_Slot ZstdCompressionObjSlots[] = {
 };
 
 PyType_Spec ZstdCompressionObjSpec = {
-    "zstd.ZstdCompressionObj",
+    "zstandard.backend_c.ZstdCompressionObj",
     sizeof(ZstdCompressionObj),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/compressor.c b/c-ext/compressor.c
@@ -1537,7 +1537,7 @@ PyType_Slot ZstdCompressorSlots[] = {
 };
 
 PyType_Spec ZstdCompressorSpec = {
-    "zstd.ZstdCompressor",
+    "zstandard.backend_c.ZstdCompressor",
     sizeof(ZstdCompressor),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/compressoriterator.c b/c-ext/compressoriterator.c
@@ -194,7 +194,7 @@ PyType_Slot ZstdCompressorIteratorSlots[] = {
 };
 
 PyType_Spec ZstdCompressorIteratorSpec = {
-    "zstd.ZstdCompressorIterator",
+    "zstandard.backend_c.ZstdCompressorIterator",
     sizeof(ZstdCompressorIterator),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/constants.c b/c-ext/constants.c
@@ -25,7 +25,7 @@ void constants_module_init(PyObject *mod) {
     version = PyUnicode_FromString(PYTHON_ZSTANDARD_VERSION);
     PyModule_AddObject(mod, "__version__", version);
 
-    ZstdError = PyErr_NewException("zstd.ZstdError", NULL, NULL);
+    ZstdError = PyErr_NewException("zstandard.backend_c.ZstdError", NULL, NULL);
     PyModule_AddObject(mod, "ZstdError", ZstdError);
 
     PyModule_AddIntConstant(mod, "FLUSH_BLOCK", 0);
diff --git a/c-ext/decompressionreader.c b/c-ext/decompressionreader.c
@@ -756,7 +756,7 @@ PyType_Slot ZstdDecompressionReaderSlots[] = {
 };
 
 PyType_Spec ZstdDecompressionReaderSpec = {
-    "zstd.ZstdDecompressionReader",
+    "zstandard.backend_c.ZstdDecompressionReader",
     sizeof(ZstdDecompressionReader),
     0,
     Py_TPFLAGS_DEFAULT,
diff --git a/c-ext/decompressionwriter.c b/c-ext/decompressionwriter.c
@@ -251,7 +251,7 @@ PyType_Slot ZstdDecompressionWriterSlots[] = {
 };
 
 PyType_Spec ZstdDecompressionWriterSpec = {
-    "zstd.ZstdDecompressionWriter",
+    "zstandard.backend_c.ZstdDecompressionWriter",
     sizeof(ZstdDecompressionWriter),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/decompressobj.c b/c-ext/decompressobj.c
@@ -190,7 +190,7 @@ PyType_Slot ZstdDecompressionObjSlots[] = {
 };
 
 PyType_Spec ZstdDecompressionObjSpec = {
-    "zstd.ZstdDecompressionObj",
+    "zstandard.backend_c.ZstdDecompressionObj",
     sizeof(ZstdDecompressionObj),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/decompressor.c b/c-ext/decompressor.c
@@ -1743,7 +1743,7 @@ PyType_Slot ZstdDecompressorSlots[] = {
 };
 
 PyType_Spec ZstdDecompressorSpec = {
-    "zstd.ZstdDecompressor",
+    "zstandard.backend_c.ZstdDecompressor",
     sizeof(ZstdDecompressor),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/decompressoriterator.c b/c-ext/decompressoriterator.c
@@ -210,7 +210,7 @@ PyType_Slot ZstdDecompressorIteratorSlots[] = {
 };
 
 PyType_Spec ZstdDecompressorIteratorSpec = {
-    "zstd.ZstdDecompressorIterator",
+    "zstandard.backend_c.ZstdDecompressorIterator",
     sizeof(ZstdDecompressorIterator),
     0,
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
diff --git a/c-ext/frameparams.c b/c-ext/frameparams.c
@@ -78,7 +78,7 @@ PyType_Slot FrameParametersSlots[] = {
 };
 
 PyType_Spec FrameParametersSpec = {
-    "zstd.FrameParameters",
+    "zstandard.backend_c.FrameParameters",
     sizeof(FrameParametersObject),
     0,
     Py_TPFLAGS_DEFAULT,
diff --git a/docs/news.rst b/docs/news.rst
@@ -55,6 +55,13 @@ Version History
   legacy distutils ``Version`` classes.
 * Relax run-time libzstd version checking in C extension from exactly 1.5.7
   to >=1.5.6. (#254, #267)
+* C extension types now (correctly) declare their fully qualified type names
+  as ``zstandard.backend_c.*`` versus ``zstd.*`` before. The names have been
+  subtly broken for years. We believe the only practical exposure to this change
+  is via pickling (possibly encountered when using the ``multiprocessing`` or
+  ``concurrent.futures`` packages), which would fail to pickle types like
+  ``ZstdError`` before since the fully qualified type name referenced an
+  incorrect and likely missing package (``zstd``). (#248)
 
 0.24.0 (released 2025-08-17)
 ============================
