add msgspec 0.18.4 (#4265)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

docs/project/changelog.md

@@ -51,6 +51,8 @@ myst:
 
 - Added `zengl` version 1.16.0 {pr}`4208`
 
+- Added `msgspec` version 0.18.4 {pr}`4265`
+
 ### Load time & size optimizations
 
 - {{ Performance }} Do not use `importlib.metadata` when identifying installed packages,

packages/msgspec/meta.yaml

@@ -0,0 +1,13 @@
+package:
+  name: msgspec
+  version: 0.18.4
+  top-level:
+    - msgspec
+source:
+  sha256: cb62030bd6b1a00b01a2fcb09735016011696304e6b1d3321e58022548268d3e
+  url: https://files.pythonhosted.org/packages/f2/5f/d202be1baac094064d3c4d2bd926b5ff83002fe411410b225d0c88f8c5ba/msgspec-0.18.4.tar.gz
+about:
+  home: https://jcristharif.com/msgspec
+  PyPI: https://pypi.org/project/msgspec
+  summary: A fast serialization and validation library, with builtin support for JSON, MessagePack, YAML, and TOML.
+  license: BSD-3-Clause

packages/msgspec/test_msgspec.py

@@ -0,0 +1,28 @@
+from pytest_pyodide import run_in_pyodide
+
+
+@run_in_pyodide(packages=["msgspec"])
+def test_msgspec(selenium_standalone):
+    import msgspec
+    import pytest
+
+    class User(msgspec.Struct):
+        """A new type describing a User"""
+
+        name: str
+        groups: set[str] = set()
+        email: str | None = None
+
+    alice = User("alice", groups={"admin", "engineering"})
+    msg = msgspec.json.encode(alice)
+
+    # set order is undefined
+    assert msg in [
+        b'{"name":"alice","groups":["admin","engineering"],"email":null}',
+        b'{"name":"alice","groups":["engineering","admin"],"email":null}',
+    ]
+
+    msgspec.json.decode(msg, type=User)
+
+    with pytest.raises(msgspec.ValidationError, match=r"str.*int.*\$\.groups\[0\]"):
+        msgspec.json.decode(b'{"name":"bob","groups":[123]}', type=User)