Add _zstd stdlib module backing compression.zstd

- Implement ZstdDict, ZstdCompressor, and ZstdDecompressor on top of the zstd-safe crate - Wire the module into stdlib_module_defs (gated off Android/wasm32) - Mark test_zstd_multithread_compress as expected failure when libzstd lacks multi-threading support
JamesClarke7283 · May 23, 2026 · May 23, 2026 · May 23, 2026 · May 23, 2026 · May 23, 2026
commit 9e5c27f71ce30ad22558875c1fda75d82054017a
diff --git a/Cargo.toml b/Cargo.toml
@@ -323,6 +323,8 @@ x509-cert = "0.3.0"
 x509-parser = "0.18"
 xml = "1.3"
 writeable = "0.6"
+zstd = { version = "0.13", default-features = false, features = ["zdict_builder"] }
+zstd-safe = { version = "7", default-features = false, features = ["zdict_builder"] }
 
 # Lints
 

diff --git a/Lib/test/test_zstd.py b/Lib/test/test_zstd.py
@@ -321,8 +321,11 @@ def test_unknown_compression_parameter(self):
         with self.assertRaisesRegex(ValueError, pattern):
             ZstdCompressor(options=option)
 
-    @unittest.skipIf(not SUPPORT_MULTITHREADING,
-                     "zstd build doesn't support multi-threaded compression")
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailureIf(
+        not SUPPORT_MULTITHREADING,
+        "TODO: RUSTPYTHON; libzstd built without multi-threaded compression support",
+    )
     def test_zstd_multithread_compress(self):
         size = 40*_1M
         b = THIS_FILE_BYTES * (size // len(THIS_FILE_BYTES))

diff --git a/crates/stdlib/Cargo.toml b/crates/stdlib/Cargo.toml
@@ -121,6 +121,8 @@ pkcs8 = { workspace = true, features = ["encryption", "pkcs5", "pem"], optional
 libsqlite3-sys = { workspace = true, features = ["bundled"], optional = true }
 xz = { workspace = true }
 xz-sys = { workspace = true }
+zstd = { workspace = true }
+zstd-safe = { workspace = true }
 
 [target.'cfg(windows)'.dependencies]
 paste = { workspace = true }

diff --git a/crates/stdlib/src/lib.rs b/crates/stdlib/src/lib.rs
@@ -27,6 +27,9 @@ mod lzma;
 
 mod zlib;
 
+#[cfg(not(any(target_os = "android", target_arch = "wasm32")))]
+mod zstd;
+
 mod blake2;
 mod hashlib;
 mod md5;
@@ -279,5 +282,7 @@ pub fn stdlib_module_defs(ctx: &Context) -> Vec<&'static builtins::PyModuleDef>
         ))]
         uuid::module_def(ctx),
         zlib::module_def(ctx),
+        #[cfg(not(any(target_os = "android", target_arch = "wasm32")))]
+        zstd::module_def(ctx),
     ]
 }