cargo: convert proc_macro to crate_type in Library dataclass.

Do not look anymore at proc_macro after init, keeping crate_type as the
sole source of truth about the desired crate types.

3 files changed, 29 insertions, 3 deletions

diff --git a/mesonbuild/cargo/interpreter.py b/mesonbuild/cargo/interpreter.py
index 52c4816f8..fe0a2a591 100644
--- a/mesonbuild/cargo/interpreter.py
+++ b/mesonbuild/cargo/interpreter.py
@@ -597,7 +597,7 @@ class Interpreter:
         depname = _dependency_name(pkg.manifest.package.name, pkg.manifest.package.api, depname_suffix)
 
         lib: mparser.BaseNode
-        if pkg.manifest.lib.proc_macro or crate_type == 'proc-macro':
+        if crate_type == 'proc-macro':
             lib = build.method('proc_macro', build.identifier('rust'), posargs, kwargs)
         else:
             if crate_type in {'lib', 'rlib', 'staticlib'}:
diff --git a/mesonbuild/cargo/manifest.py b/mesonbuild/cargo/manifest.py
index 304ae7526..ad9c9943e 100644
--- a/mesonbuild/cargo/manifest.py
+++ b/mesonbuild/cargo/manifest.py
@@ -347,13 +347,14 @@ class Library(BuildTarget):
     @classmethod
     def from_raw(cls, raw: raw.LibTarget, pkg: Package) -> Self:
         name = raw.get('name', fixup_meson_varname(pkg.name))
+        # If proc_macro is True, it takes precedence and sets crate_type to proc-macro
         proc_macro = raw.get('proc-macro', False)
-        crate_type = 'proc-macro' if proc_macro else 'lib'
         return _raw_to_dataclass(raw, cls, f'Library entry {name}',
                                  name=DefaultValue(name),
                                  path=DefaultValue('src/lib.rs'),
                                  edition=DefaultValue(pkg.edition),
-                                 crate_type=DefaultValue([crate_type]))
+                                 crate_type=ConvertValue(lambda x: ['proc-macro'] if proc_macro else x,
+                                                         ['lib']))
 
 
 @dataclasses.dataclass
diff --git a/unittests/cargotests.py b/unittests/cargotests.py
index 22d77b35f..e9e779c1e 100644
--- a/unittests/cargotests.py
+++ b/unittests/cargotests.py
@@ -280,6 +280,18 @@ class CargoTomlTest(unittest.TestCase):
         ]
     ''')
 
+    CARGO_TOML_3 = textwrap.dedent('''\
+        [package]
+        name = "bits"
+        edition = "2021"
+        rust-version = "1.70"
+        version = "0.1.0"
+
+        [lib]
+        proc-macro = true
+        crate-type = ["lib"] # ignored
+    ''')
+
     CARGO_TOML_WS = textwrap.dedent('''\
         [workspace]
         resolver = "2"
@@ -406,6 +418,19 @@ class CargoTomlTest(unittest.TestCase):
         self.assertEqual(manifest.dev_dependencies['gir-format-check'].meson_version, ['>= 0.1', '< 0.2'])
         self.assertEqual(manifest.dev_dependencies['gir-format-check'].api, '0.1')
 
+    def test_cargo_toml_proc_macro(self) -> None:
+        with tempfile.TemporaryDirectory() as tmpdir:
+            fname = os.path.join(tmpdir, 'Cargo.toml')
+            with open(fname, 'w', encoding='utf-8') as f:
+                f.write(self.CARGO_TOML_3)
+            manifest_toml = load_toml(fname)
+            manifest = Manifest.from_raw(manifest_toml, 'Cargo.toml')
+
+        self.assertEqual(manifest.lib.name, 'bits')
+        self.assertEqual(manifest.lib.crate_type, ['proc-macro'])
+        self.assertEqual(manifest.lib.path, 'src/lib.rs')
+        self.assertEqual(manifest.lib.proc_macro, True)
+
     def test_cargo_toml_targets(self) -> None:
         with tempfile.TemporaryDirectory() as tmpdir:
             fname = os.path.join(tmpdir, 'Cargo.toml')