ci: add required-features entries to Cargo.toml

.github/workflows/ci.yml

@@ -31,6 +31,8 @@ jobs:
         run: nox -s rustfmt
       - name: Check markdown formatting (rumdl)
         run: nox -s rumdl
+      - name: Check `required-features` in Cargo.toml
+        run: nox -s check-test-features
 
   resolve:
     runs-on: ubuntu-latest

Cargo.toml

@@ -229,3 +229,179 @@ bare_urls = "warn"
 
 [lints]
 workspace = true
+
+# Many tests are only relevant on certain feature combinations;
+# CI is marginally more efficient if `required-feature` is specified to avoid
+# building and launching empty test suites.
+
+[[test]]
+name = "test_anyhow"
+required-features = ["anyhow"]
+
+[[test]]
+name = "test_append_to_inittab"
+required-features = ["macros"]
+
+[[test]]
+name = "test_arithmetics"
+required-features = ["macros"]
+
+[[test]]
+name = "test_buffer"
+required-features = ["macros"]
+
+[[test]]
+name = "test_buffer_protocol"
+required-features = ["macros"]
+
+[[test]]
+name = "test_bytes"
+required-features = ["macros"]
+
+[[test]]
+name = "test_class_attributes"
+required-features = ["macros"]
+
+[[test]]
+name = "test_class_basics"
+required-features = ["macros"]
+
+[[test]]
+name = "test_class_comparisons"
+required-features = ["macros"]
+
+[[test]]
+name = "test_class_conversion"
+required-features = ["macros"]
+
+[[test]]
+name = "test_class_formatting"
+required-features = ["macros"]
+
+[[test]]
+name = "test_class_init"
+required-features = ["macros"]
+
+[[test]]
+name = "test_class_new"
+required-features = ["macros"]
+
+[[test]]
+name = "test_compile_error"
+required-features = ["macros"]
+
+[[test]]
+name = "test_coroutine"
+required-features = ["experimental-async"]
+
+[[test]]
+name = "test_declarative_module"
+required-features = ["macros"]
+
+[[test]]
+name = "test_default_impls"
+required-features = ["macros"]
+
+[[test]]
+name = "test_enum"
+required-features = ["macros"]
+
+[[test]]
+name = "test_exceptions"
+required-features = ["macros"]
+
+[[test]]
+name = "test_field_cfg"
+required-features = ["macros"]
+
+[[test]]
+name = "test_frompy_intopy_roundtrip"
+required-features = ["macros"]
+
+[[test]]
+name = "test_frompyobject"
+required-features = ["macros"]
+
+[[test]]
+name = "test_gc"
+required-features = ["macros"]
+
+[[test]]
+name = "test_getter_setter"
+required-features = ["macros"]
+
+[[test]]
+name = "test_inheritance"
+required-features = ["macros"]
+
+[[test]]
+name = "test_intopyobject"
+required-features = ["macros"]
+
+[[test]]
+name = "test_macro_docs"
+required-features = ["macros"]
+
+[[test]]
+name = "test_macros"
+required-features = ["macros"]
+
+[[test]]
+name = "test_mapping"
+required-features = ["macros"]
+
+[[test]]
+name = "test_methods"
+required-features = ["macros"]
+
+[[test]]
+name = "test_module"
+required-features = ["macros"]
+
+[[test]]
+name = "test_multiple_pymethods"
+required-features = ["multiple-pymethods"]
+
+[[test]]
+name = "test_proto_methods"
+required-features = ["macros"]
+
+[[test]]
+name = "test_pyfunction"
+required-features = ["macros"]
+
+[[test]]
+name = "test_pyself"
+required-features = ["macros"]
+
+[[test]]
+name = "test_sequence"
+required-features = ["macros"]
+
+[[test]]
+name = "test_serde"
+required-features = ["serde"]
+
+[[test]]
+name = "test_static_slots"
+required-features = ["macros"]
+
+[[test]]
+name = "test_string"
+required-features = ["macros"]
+
+[[test]]
+name = "test_super"
+required-features = ["macros"]
+
+[[test]]
+name = "test_text_signature"
+required-features = ["macros"]
+
+[[test]]
+name = "test_variable_arguments"
+required-features = ["macros"]
+
+[[test]]
+name = "test_various"
+required-features = ["macros"]

noxfile.py

@@ -980,6 +980,82 @@ def format_ffi_extern(session: nox.Session):
     _format_ffi_extern(session)
 
 
+_INNER_CFG_RE = re.compile(r"^#!\[\s*cfg\s*\((.*)\)\s*\]\s*$")
+_FEATURE_RE = re.compile(r'feature\s*=\s*"([^"]+)"')
+
+
+def _read_inner_cfgs(path: Path) -> List[str]:
+    """Return the bodies of leading `#![cfg(...)]` inner attributes."""
+    cfgs: List[str] = []
+    with path.open("r", encoding="utf-8") as f:
+        for line in f:
+            stripped = line.strip()
+            if stripped == "" or stripped.startswith("//"):
+                continue
+            if not stripped.startswith("#!["):
+                break
+            m = _INNER_CFG_RE.match(stripped)
+            if m:
+                cfgs.append(m.group(1).strip())
+    return cfgs
+
+
+@nox.session(name="check-test-features", venv_backend="none")
+def check_test_features(session: nox.Session) -> None:
+    if toml is None:
+        session.error("requires Python 3.11 or `toml` to be installed")
+
+    expected_tests = {}
+    errors = []
+    for path in sorted((PYO3_DIR / "tests").glob("test_*.rs")):
+        features = set()
+        for body in _read_inner_cfgs(path):
+            feature = _FEATURE_RE.search(body)
+            if not feature:
+                continue
+
+            if feature.group(0) != body:
+                # To keep the this check simple, expect a single simple `cfg` per required feature
+                errors.append(
+                    f'{path}: please use simple `#![cfg(feature = "...")] for feature predicates, got `#![cfg({body})]`'
+                )
+
+            features.add(feature.group(1))
+
+        if features:
+            expected_tests[path.stem] = sorted(features)
+
+    declared_tests = {
+        test["name"]: test
+        for test in toml.loads((PYO3_DIR / "Cargo.toml").read_text()).get("test", [])
+    }
+    all_test_names = sorted(expected_tests.keys() | declared_tests.keys())
+
+    for test in all_test_names:
+        if (expected := expected_tests.get(test)) is None:
+            errors.append(f"Remove [[test]] entry for {test!r} from Cargo.toml")
+            continue
+
+        declared = declared_tests.get(test, {})
+        declared_features = declared.get("required-features", [])
+
+        if set(declared_features) != set(expected):
+            errors.append(
+                f"""- Update Cargo.toml for test {test}:
+
+    [[test]]
+    name = "{test}"
+    required-features = [{", ".join(f'"{f}"' for f in expected)}]
+                """
+            )
+
+    if errors:
+        print("Errors found in test feature predicates:", file=sys.stderr)
+        for error in errors:
+            print("  " + error, file=sys.stderr)
+        session.error()
+
+
 @nox.session(name="address-sanitizer", venv_backend="none")
 def address_sanitizer(session: nox.Session):
     _run_cargo(

tests/test_append_to_inittab.rs

@@ -1,4 +1,5 @@
-#![cfg(all(feature = "macros", not(PyPy)))]
+#![cfg(feature = "macros")]
+#![cfg(not(PyPy))]
 
 use pyo3::prelude::*;