feat: add handling for Emscripten wheels tags per PEP 783 (#804)

* Add handling for Emscripten wheels tags per PEP 783

These are the changes to packaging specified in PEP 783.

PEP 783 is now accepted per dstufft
https://discuss.python.org/t/pep-783-emscripten-packaging/86862/104

* Apply suggestions from code review

Co-authored-by: Agriya Khetarpal <74401230+agriyakhetarpal@users.noreply.github.com>

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
Co-authored-by: Agriya Khetarpal <74401230+agriyakhetarpal@users.noreply.github.com>

Author: 3 people

src/packaging/tags.py

@@ -718,6 +718,13 @@ def _linux_platforms(is_32bit: bool = _32_BIT_INTERPRETER) -> Iterator[str]:
         yield f"linux_{arch}"
 
 
+def _emscripten_platforms() -> Iterator[str]:
+    pyemscripten_abi_version = sysconfig.get_config_var("PYEMSCRIPTEN_ABI_VERSION")
+    if pyemscripten_abi_version:
+        yield f"pyemscripten_{pyemscripten_abi_version}_wasm32"
+    yield from _generic_platforms()
+
+
 def _generic_platforms() -> Iterator[str]:
     yield _normalize_string(sysconfig.get_platform())
 
@@ -734,6 +741,8 @@ def platform_tags() -> Iterator[str]:
         return android_platforms()
     elif platform.system() == "Linux":
         return _linux_platforms()
+    elif platform.system() == "Emscripten":
+        return _emscripten_platforms()
     else:
         return _generic_platforms()
 

tests/test_tags.py

@@ -1751,6 +1751,59 @@ def test_cpython_first_none_any_tag(self, monkeypatch: pytest.MonkeyPatch) -> No
         interpreter = f"cp{tags.interpreter_version()}"
         assert tag == tags.Tag(interpreter, "none", "any")
 
+    def test_emscripten(
+        self,
+        mock_interpreter_name: Callable[[str], bool],
+        monkeypatch: pytest.MonkeyPatch,
+    ) -> None:
+        expected_interpreter = "cp" + tags._version_nodot(sys.version_info[:2])
+        if mock_interpreter_name("CPython"):
+            monkeypatch.setattr(
+                tags, "_cpython_abis", lambda _1, _2: [expected_interpreter]
+            )
+        config = {
+            "Py_GIL_DISABLED": 0,
+        }
+
+        monkeypatch.setattr(sysconfig, "get_config_var", config.get)
+        monkeypatch.setattr(platform, "system", lambda: "Emscripten")
+        monkeypatch.setattr(
+            sysconfig, "get_platform", lambda: "emscripten-5.0.3-wasm32"
+        )
+        assert list(tags.platform_tags()) == ["emscripten_5_0_3_wasm32"]
+        result = list(tags.sys_tags())
+        assert result[0] == tags.Tag(
+            expected_interpreter, expected_interpreter, "emscripten_5_0_3_wasm32"
+        )
+
+    def test_pyemscripten(
+        self,
+        mock_interpreter_name: Callable[[str], bool],
+        monkeypatch: pytest.MonkeyPatch,
+    ) -> None:
+        expected_interpreter = "cp" + tags._version_nodot(sys.version_info[:2])
+        config = {
+            "PYEMSCRIPTEN_ABI_VERSION": "2026_0",
+        }
+
+        monkeypatch.setattr(sysconfig, "get_config_var", config.get)
+        if mock_interpreter_name("CPython"):
+            monkeypatch.setattr(
+                tags, "_cpython_abis", lambda _1, _2: [expected_interpreter]
+            )
+        monkeypatch.setattr(platform, "system", lambda: "Emscripten")
+        monkeypatch.setattr(
+            sysconfig, "get_platform", lambda: "emscripten-5.0.3-wasm32"
+        )
+        assert list(tags.platform_tags()) == [
+            "pyemscripten_2026_0_wasm32",
+            "emscripten_5_0_3_wasm32",
+        ]
+        result = list(tags.sys_tags())
+        assert result[0] == tags.Tag(
+            expected_interpreter, expected_interpreter, "pyemscripten_2026_0_wasm32"
+        )
+
 
 class TestBitness:
     def teardown_method(self) -> None: