compilers/rust: Add support for clippy

Clippy is a compiler wrapper for rust that provides an extra layer of
linting. It's quite popular, but unfortunately doesn't provide the
output of the compiler that it's wrapping in it's output, so we don't
detect that clippy is rustc. This small patch adds a new compiler class
(that is the Rustc class with a different id) and the necessary logic to
detect that clippy is in fact rustc)

Fixes: #8767

8 files changed, 59 insertions, 12 deletions

diff --git a/docs/markdown/snippets/rust-clippy-driver-support.md b/docs/markdown/snippets/rust-clippy-driver-support.md
new file mode 100644
index 0000000..c486473
--- /dev/null
+++ b/docs/markdown/snippets/rust-clippy-driver-support.md
@@ -0,0 +1,6 @@
+## Support for clippy-driver as a rustc wrapper
+
+Clippy is a popular linting tool for Rust, and is invoked in place of rustc as a
+wrapper. Unfortunately it doesn't proxy rustc's output, so we need to have a
+small wrapper around it so that Meson can correctly detect the underlying rustc,
+but still display clippy
diff --git a/mesonbuild/compilers/__init__.py b/mesonbuild/compilers/__init__.py
index 8c5275c..98b0b5f 100644
--- a/mesonbuild/compilers/__init__.py
+++ b/mesonbuild/compilers/__init__.py
@@ -112,6 +112,7 @@ __all__ = [
     'PGICPPCompiler',
     'PGIFortranCompiler',
     'RustCompiler',
+    'ClippyRustCompiler',
     'CcrxCCompiler',
     'CcrxCPPCompiler',
     'Xc16CCompiler',
@@ -241,7 +242,7 @@ from .objcpp import (
     ClangObjCPPCompiler,
     GnuObjCPPCompiler,
 )
-from .rust import RustCompiler
+from .rust import RustCompiler, ClippyRustCompiler
 from .swift import SwiftCompiler
 from .vala import ValaCompiler
 from .mixins.visualstudio import VisualStudioLikeCompiler
diff --git a/mesonbuild/compilers/detect.py b/mesonbuild/compilers/detect.py
index 6426380..52ad7f3 100644
--- a/mesonbuild/compilers/detect.py
+++ b/mesonbuild/compilers/detect.py
@@ -124,7 +124,7 @@ from .objcpp import (
     GnuObjCPPCompiler,
 )
 from .cython import CythonCompiler
-from .rust import RustCompiler
+from .rust import RustCompiler, ClippyRustCompiler
 from .swift import SwiftCompiler
 from .vala import ValaCompiler
 from .mixins.visualstudio import VisualStudioLikeCompiler
@@ -952,6 +952,13 @@ def detect_rust_compiler(env: 'Environment', for_machine: MachineChoice) -> Rust
             continue
 
         version = search_version(out)
+        cls: T.Type[RustCompiler] = RustCompiler
+
+        # Clippy is a wrapper around rustc, but it doesn't have rustc in it's
+        # output. We can otherwise treat it as rustc.
+        if 'clippy' in out:
+            out = 'rustc'
+            cls = ClippyRustCompiler
 
         if 'rustc' in out:
             # On Linux and mac rustc will invoke gcc (clang for mac
@@ -976,7 +983,7 @@ def detect_rust_compiler(env: 'Environment', for_machine: MachineChoice) -> Rust
                 extra_args: T.Dict[str, T.Union[str, bool]] = {}
                 always_args: T.List[str] = []
                 if is_link_exe:
-                    compiler.extend(RustCompiler.use_linker_args(cc.linker.exelist[0]))
+                    compiler.extend(cls.use_linker_args(cc.linker.exelist[0]))
                     extra_args['direct'] = True
                     extra_args['machine'] = cc.linker.machine
                 else:
@@ -984,7 +991,7 @@ def detect_rust_compiler(env: 'Environment', for_machine: MachineChoice) -> Rust
                     if 'ccache' in exelist[0]:
                         del exelist[0]
                     c = exelist.pop(0)
-                    compiler.extend(RustCompiler.use_linker_args(c))
+                    compiler.extend(cls.use_linker_args(c))
 
                     # Also ensure that we pass any extra arguments to the linker
                     for l in exelist:
@@ -1002,12 +1009,12 @@ def detect_rust_compiler(env: 'Environment', for_machine: MachineChoice) -> Rust
                                                 **extra_args) # type: ignore
             elif 'link' in override[0]:
                 linker = guess_win_linker(env,
-                    override, RustCompiler, for_machine, use_linker_prefix=False)
+                    override, cls, for_machine, use_linker_prefix=False)
                 # rustc takes linker arguments without a prefix, and
                 # inserts the correct prefix itself.
                 assert isinstance(linker, VisualStudioLikeLinkerMixin)
                 linker.direct = True
-                compiler.extend(RustCompiler.use_linker_args(linker.exelist[0]))
+                compiler.extend(cls.use_linker_args(linker.exelist[0]))
             else:
                 # On linux and macos rust will invoke the c compiler for
                 # linking, on windows it will use lld-link or link.exe.
@@ -1019,10 +1026,10 @@ def detect_rust_compiler(env: 'Environment', for_machine: MachineChoice) -> Rust
                 # Of course, we're not going to use any of that, we just
                 # need it to get the proper arguments to pass to rustc
                 c = linker.exelist[1] if linker.exelist[0].endswith('ccache') else linker.exelist[0]
-                compiler.extend(RustCompiler.use_linker_args(c))
+                compiler.extend(cls.use_linker_args(c))
 
-            env.coredata.add_lang_args(RustCompiler.language, RustCompiler, for_machine, env)
-            return RustCompiler(
+            env.coredata.add_lang_args(cls.language, cls, for_machine, env)
+            return cls(
                 compiler, version, for_machine, is_cross, info, exe_wrap,
                 linker=linker)
 
diff --git a/mesonbuild/compilers/rust.py b/mesonbuild/compilers/rust.py
index 2337ceb..9423b2d 100644
--- a/mesonbuild/compilers/rust.py
+++ b/mesonbuild/compilers/rust.py
@@ -196,3 +196,20 @@ class RustCompiler(Compiler):
         # Rustc currently has no way to toggle this, it's controlled by whether
         # pic is on by rustc
         return []
+
+
+class ClippyRustCompiler(RustCompiler):
+
+    """Clippy is a linter that wraps Rustc.
+
+    This just provides us a different id
+    """
+
+    def __init__(self, exelist: T.List[str], version: str, for_machine: MachineChoice,
+                 is_cross: bool, info: 'MachineInfo',
+                 exe_wrapper: T.Optional['ExternalProgram'] = None,
+                 full_version: T.Optional[str] = None,
+                 linker: T.Optional['DynamicLinker'] = None):
+        super().__init__(exelist, version, for_machine, is_cross, info,
+                         exe_wrapper, full_version, linker)
+        self.id = 'clippy-driver rustc'
diff --git a/test cases/rust/1 basic/clippy.toml b/test cases/rust/1 basic/clippy.toml
new file mode 100644
index 0000000..e9ac31b
--- /dev/null
+++ b/test cases/rust/1 basic/clippy.toml
@@ -0,0 +1 @@
+blacklisted-names = ["foo"]
diff --git a/test cases/rust/1 basic/prog.rs b/test cases/rust/1 basic/prog.rs
index b171a80..f1b3d30 100644
--- a/test cases/rust/1 basic/prog.rs
+++ b/test cases/rust/1 basic/prog.rs
@@ -1,3 +1,4 @@
 fn main() {
-    println!("rust compiler is working");
+    let foo = "rust compiler is working";
+    println!("{}", foo);
 }
diff --git a/unittests/allplatformstests.py b/unittests/allplatformstests.py
index 7afa989..93a2e49 100644
--- a/unittests/allplatformstests.py
+++ b/unittests/allplatformstests.py
@@ -4034,3 +4034,16 @@ class AllPlatformTests(BasePlatformTests):
             for file, details in files.items():
                 with self.subTest(key='{}.{}'.format(data_type, file)):
                     self.assertEqual(res[data_type][file], details)
+
+    @skip_if_not_language('rust')
+    @unittest.skipIf(not shutil.which('clippy-driver'), 'Test requires clippy-driver')
+    def test_rust_clippy(self) -> None:
+        if self.backend is not Backend.ninja:
+            raise unittest.SkipTest('Rust is only supported with ninja currently')
+        # Wehn clippy is used, we should get an exception since a variable named
+        # "foo" is used, but is on our denylist
+        testdir = os.path.join(self.rust_test_dir, '1 basic')
+        self.init(testdir, extra_args=['--werror'], override_envvars={'RUSTC': 'clippy-driver'})
+        with self.assertRaises(subprocess.CalledProcessError) as cm:
+            self.build()
+        self.assertIn('error: use of a blacklisted/placeholder name `foo`', cm.exception.stdout)
diff --git a/unittests/baseplatformtests.py b/unittests/baseplatformtests.py
index 3492785..9371395 100644
--- a/unittests/baseplatformtests.py
+++ b/unittests/baseplatformtests.py
@@ -69,6 +69,7 @@ class BasePlatformTests(TestCase):
             self.uninstall_command = get_backend_commands(self.backend)
         # Test directories
         self.common_test_dir = os.path.join(src_root, 'test cases/common')
+        self.rust_test_dir = os.path.join(src_root, 'test cases/rust')
         self.vala_test_dir = os.path.join(src_root, 'test cases/vala')
         self.framework_test_dir = os.path.join(src_root, 'test cases/frameworks')
         self.unit_test_dir = os.path.join(src_root, 'test cases/unit')
@@ -135,7 +136,7 @@ class BasePlatformTests(TestCase):
         os.environ.update(self.orig_env)
         super().tearDown()
 
-    def _run(self, command, *, workdir=None, override_envvars=None):
+    def _run(self, command, *, workdir=None, override_envvars: T.Optional[T.Mapping[str, str]] = None):
         '''
         Run a command while printing the stdout and stderr to stdout,
         and also return a copy of it
@@ -164,7 +165,7 @@ class BasePlatformTests(TestCase):
              extra_args=None,
              default_args=True,
              inprocess=False,
-             override_envvars=None,
+             override_envvars: T.Optional[T.Mapping[str, str]] = None,
              workdir=None,
              allow_fail: bool = False) -> str:
         """Call `meson setup`