rust: new target rustdoc

Another rust tool, another rough copy of the code to run clippy.
Apart from the slightly different command lines, the output is in a
directory and test targets are skipped.

Knowing the output directory can be useful, so print that on successful
execution of rustdoc.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 135 insertions, 0 deletions

diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index f698a2b..9ca092c 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -3716,6 +3716,21 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
         elem.add_dep(list(self.all_structured_sources))
         self.add_build(elem)
 
+    def generate_rustdoc(self) -> None:
+        if 'rustdoc' in self.all_outputs or not self.have_language('rust'):
+            return
+
+        cmd = self.environment.get_build_command() + \
+            ['--internal', 'rustdoc', self.environment.build_dir]
+        elem = self.create_phony_target('rustdoc', 'CUSTOM_COMMAND', 'PHONY')
+        elem.add_item('COMMAND', cmd)
+        elem.add_item('pool', 'console')
+        for crate in self.rust_crates.values():
+            if crate.crate_type in {'rlib', 'dylib', 'proc-macro'}:
+                elem.add_dep(crate.target_name)
+        elem.add_dep(list(self.all_structured_sources))
+        self.add_build(elem)
+
     def generate_scanbuild(self) -> None:
         if not environment.detect_scanbuild():
             return
@@ -3789,6 +3804,7 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
         self.generate_clangformat()
         self.generate_clangtidy()
         self.generate_clippy()
+        self.generate_rustdoc()
         self.generate_tags('etags', 'TAGS')
         self.generate_tags('ctags', 'ctags')
         self.generate_tags('cscope', 'cscope')
diff --git a/mesonbuild/scripts/rustdoc.py b/mesonbuild/scripts/rustdoc.py
new file mode 100644
index 0000000..f5f74c4
--- /dev/null
+++ b/mesonbuild/scripts/rustdoc.py
@@ -0,0 +1,101 @@
+# SPDX-License-Identifier: Apache-2.0
+# Copyright 2024 The Meson development team
+
+from __future__ import annotations
+from collections import defaultdict
+import os
+import tempfile
+import typing as T
+
+from .run_tool import run_tool_on_targets, run_with_buffered_output
+from .. import build, mlog
+from ..mesonlib import MachineChoice, PerMachine
+from ..wrap import WrapMode, wrap
+
+if T.TYPE_CHECKING:
+    from ..compilers.rust import RustCompiler
+
+async def run_and_confirm_success(cmdlist: T.List[str], crate: str) -> int:
+    returncode = await run_with_buffered_output(cmdlist)
+    if returncode == 0:
+        print(mlog.green('Generated'), os.path.join('doc', crate))
+    return returncode
+
+class Rustdoc:
+    def __init__(self, build: build.Build, tempdir: str, subprojects: T.Set[str]) -> None:
+        self.tools: PerMachine[T.List[str]] = PerMachine([], [])
+        self.warned: T.DefaultDict[str, bool] = defaultdict(lambda: False)
+        self.tempdir = tempdir
+        self.subprojects = subprojects
+        for machine in MachineChoice:
+            compilers = build.environment.coredata.compilers[machine]
+            if 'rust' in compilers:
+                compiler = T.cast('RustCompiler', compilers['rust'])
+                self.tools[machine] = compiler.get_rust_tool('rustdoc', build.environment)
+
+    def warn_missing_rustdoc(self, machine: str) -> None:
+        if self.warned[machine]:
+            return
+        mlog.warning(f'rustdoc not found for {machine} machine')
+        self.warned[machine] = True
+
+    def __call__(self, target: T.Dict[str, T.Any]) -> T.Iterable[T.Coroutine[None, None, int]]:
+        if target['subproject'] is not None and target['subproject'] not in self.subprojects:
+            return
+
+        for src_block in target['target_sources']:
+            if 'compiler' in src_block and src_block['language'] == 'rust':
+                rustdoc = getattr(self.tools, src_block['machine'])
+                if not rustdoc:
+                    self.warn_missing_rustdoc(src_block['machine'])
+                    continue
+
+                cmdlist = list(rustdoc)
+                prev = None
+                crate_name = None
+                is_test = False
+                for arg in src_block['parameters']:
+                    if prev:
+                        if prev == '--crate-name':
+                            cmdlist.extend((prev, arg))
+                            crate_name = arg
+                        prev = None
+                        continue
+
+                    if arg == '--test':
+                        is_test = True
+                        break
+                    elif arg in {'--crate-name', '--emit', '--out-dir', '-l'}:
+                        prev = arg
+                    elif arg != '-g' and not arg.startswith('-l'):
+                        cmdlist.append(arg)
+
+                if is_test:
+                    # --test has a completely different meaning for rustc and rustdoc;
+                    # when using rust.test(), only the non-test target is documented
+                    continue
+                if crate_name:
+                    cmdlist.extend(src_block['sources'])
+                    # Assume documentation is generated for the developer's use
+                    cmdlist.append('--document-private-items')
+                    cmdlist.append('-o')
+                    cmdlist.append('doc')
+                    yield run_and_confirm_success(cmdlist, crate_name)
+                else:
+                    print(mlog.yellow('Skipping'), target['name'], '(no crate name)')
+
+def get_nonwrap_subprojects(build_data: build.Build) -> T.Set[str]:
+    wrap_resolver = wrap.Resolver(
+        build_data.environment.get_source_dir(),
+        build_data.subproject_dir,
+        wrap_mode=WrapMode.nodownload)
+    return set(sp
+               for sp in build_data.environment.coredata.initialized_subprojects
+               if sp and (sp not in wrap_resolver.wraps or wrap_resolver.wraps[sp].type is None))
+
+def run(args: T.List[str]) -> int:
+    os.chdir(args[0])
+    build_data = build.load(os.getcwd())
+    subproject_list = get_nonwrap_subprojects(build_data)
+    with tempfile.TemporaryDirectory() as d:
+        return run_tool_on_targets(Rustdoc(build_data, d, subproject_list))
diff --git a/unittests/allplatformstests.py b/unittests/allplatformstests.py
index fbb1c91..a189065 100644
--- a/unittests/allplatformstests.py
+++ b/unittests/allplatformstests.py
@@ -4917,6 +4917,24 @@ class AllPlatformTests(BasePlatformTests):
                     self.assertEqual(res[data_type][file], details)
 
     @skip_if_not_language('rust')
+    @unittest.skipIf(not shutil.which('rustdoc'), 'Test requires rustdoc')
+    def test_rustdoc(self) -> None:
+        if self.backend is not Backend.ninja:
+            raise unittest.SkipTest('Rust is only supported with ninja currently')
+        try:
+            with tempfile.TemporaryDirectory() as tmpdir:
+                testdir = os.path.join(tmpdir, 'a')
+                shutil.copytree(os.path.join(self.rust_test_dir, '9 unit tests'),
+                                testdir)
+                self.init(testdir)
+                self.build('rustdoc')
+        except PermissionError:
+            # When run under Windows CI, something (virus scanner?)
+            # holds on to the git files so cleaning up the dir
+            # fails sometimes.
+            pass
+
+    @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: