mesonbuild: Add mcompile command

This is tested working with both msbuild and ninja/samu. Since our xcode
support is pretty much broken I didn't bother.

Fixes #6670

5 files changed, 163 insertions, 2 deletions

diff --git a/.github/workflows/lint_mypy.yml b/.github/workflows/lint_mypy.yml
index 8f6d917..7c83714 100644
--- a/.github/workflows/lint_mypy.yml
+++ b/.github/workflows/lint_mypy.yml
@@ -30,4 +30,4 @@ jobs:
       with:
         python-version: '3.x'
     - run: python -m pip install mypy
-    - run: mypy --follow-imports=skip mesonbuild/interpreterbase.py mesonbuild/mtest.py mesonbuild/minit.py mesonbuild/mintro.py mesonbuild/mparser.py mesonbuild/msetup.py mesonbuild/ast mesonbuild/wrap tools/ mesonbuild/modules/fs.py mesonbuild/dependencies/boost.py mesonbuild/dependencies/mpi.py mesonbuild/dependencies/hdf5.py mesonbuild/compilers/mixins/intel.py mesonbuild/mlog.py
+    - run: mypy --follow-imports=skip mesonbuild/interpreterbase.py mesonbuild/mtest.py mesonbuild/minit.py mesonbuild/mintro.py mesonbuild/mparser.py mesonbuild/msetup.py mesonbuild/ast mesonbuild/wrap tools/ mesonbuild/modules/fs.py mesonbuild/dependencies/boost.py mesonbuild/dependencies/mpi.py mesonbuild/dependencies/hdf5.py mesonbuild/compilers/mixins/intel.py mesonbuild/mlog.py mesonbuild/mcompile.py
diff --git a/docs/markdown/snippets/meson_compile_command.md b/docs/markdown/snippets/meson_compile_command.md
new file mode 100644
index 0000000..e029ff8
--- /dev/null
+++ b/docs/markdown/snippets/meson_compile_command.md
@@ -0,0 +1,21 @@
+## Backend agnostic compile command
+
+A new `meson compile` command has been added to support backend agnostic
+compilation. It accepts two arguments, `-j` and `-l`, which are used if
+possible (`-l` does nothing with msbuild). A `-j` or `-l` value < 1 lets the
+backend decide how many threads to use. For msbuild this means `-m`, for
+ninja it means passing no arguments.
+
+```console
+meson builddir --backend vs
+meson compile -C builddir -j0  # this is the same as `msbuild builddir/my.sln -m`
+```
+
+```console
+meson builddir
+meson compile -C builddir -j3  # this is the same as `ninja -C builddir -j3`
+```
+
+Additionally `meson compile` provides a `--clean` switch to clean the project.
+
+A complete list of arguments is always documented via `meson compile --help`
diff --git a/mesonbuild/mcompile.py b/mesonbuild/mcompile.py
new file mode 100644
index 0000000..372c853
--- /dev/null
+++ b/mesonbuild/mcompile.py
@@ -0,0 +1,123 @@
+# Copyright 2020 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Entrypoint script for backend agnostic compile."""
+
+import os
+import pathlib
+import shutil
+import sys
+import typing as T
+
+from . import mlog
+from . import mesonlib
+from .mesonlib import MesonException
+
+if T.TYPE_CHECKING:
+    import argparse
+
+
+def add_arguments(parser: 'argparse.ArgumentParser') -> None:
+    """Add compile specific arguments."""
+    parser.add_argument(
+        '-j', '--jobs',
+        action='store',
+        default=0,
+        type=int,
+        help='The number of worker jobs to run (if supported). If the value is less than 1 the build program will guess.'
+    )
+    parser.add_argument(
+        '-l', '--load-average',
+        action='store',
+        default=0,
+        type=int,
+        help='The system load average to try to maintain (if supported)'
+    )
+    parser.add_argument(
+        '--clean',
+        action='store_true',
+        help='Clean the build directory.'
+    )
+    parser.add_argument(
+        '-C',
+        action='store',
+        dest='builddir',
+        type=pathlib.Path,
+        required=True,
+        default='.',
+        help='The directory containing build files to be built.'
+    )
+
+
+def run(options: 'argparse.Namespace') -> int:
+    bdir = options.builddir  # type: pathlib.Path
+    if not bdir.exists():
+        raise MesonException('Path to builddir {} does not exist!'.format(str(bdir.resolve())))
+    if not bdir.is_dir():
+        raise MesonException('builddir path should be a directory.')
+
+    cmd = []  # type: T.List[str]
+    runner = None  # type T.Optional[str]
+    slns = list(bdir.glob('*.sln'))
+
+    if (bdir / 'build.ninja').exists():
+        runner = os.environ.get('NINJA')
+        if not runner:
+            if shutil.which('ninja'):
+                runner = 'ninja'
+            elif shutil.which('samu'):
+                runner = 'samu'
+
+        if runner is None:
+            raise MesonException('Cannot find either ninja or samu.')
+
+        cmd = [runner, '-C', bdir.as_posix()]
+
+        # If the value is set to < 1 then don't set anything, which let's
+        # ninja/samu decide what to do.
+        if options.jobs > 0:
+            cmd.extend(['-j', str(options.jobs)])
+        if options.load_average > 0:
+            cmd.extend(['-l', str(options.load_average)])
+        if options.clean:
+            cmd.append('clean')
+
+    # TODO: with python 3.8 this could be `elif slns := bdir.glob('*.sln'):`
+    elif slns:
+        assert len(slns) == 1, 'More than one solution in a project?'
+
+        sln = slns[0]
+        cmd = ['msbuild', str(sln.resolve())]
+
+        # In msbuild `-m` with no number means "detect cpus", the default is `-m1`
+        if options.jobs > 0:
+            cmd.append('-m{}'.format(options.jobs))
+        else:
+            cmd.append('-m')
+
+        if options.load_average:
+            mlog.warning('Msbuild does not have a load-average switch, ignoring.')
+        if options.clean:
+            cmd.extend(['/t:Clean'])
+
+    # TODO: xcode?
+    else:
+        raise MesonException(
+            'Could not find any runner or backend for directory {}'.format(bdir.resolve().as_posix()))
+
+    mlog.log('Found runner:', runner)
+
+    p, *_ = mesonlib.Popen_safe(cmd, stdout=sys.stdout.buffer, stderr=sys.stderr.buffer)
+
+    return p.returncode
diff --git a/mesonbuild/mesonmain.py b/mesonbuild/mesonmain.py
index 6ec9682..b6b11df 100644
--- a/mesonbuild/mesonmain.py
+++ b/mesonbuild/mesonmain.py
@@ -22,7 +22,7 @@ import shutil
 
 from . import mesonlib
 from . import mlog
-from . import mconf, mdist, minit, minstall, mintro, msetup, mtest, rewriter, msubprojects, munstable_coredata
+from . import mconf, mdist, minit, minstall, mintro, msetup, mtest, rewriter, msubprojects, munstable_coredata, mcompile
 from .mesonlib import MesonException
 from .environment import detect_msys2_arch
 from .wrap import wraptool
@@ -62,6 +62,8 @@ class CommandLineParser:
                          help_msg='Print help of a subcommand')
         self.add_command('rewrite', lambda parser: rewriter.add_arguments(parser, self.formatter), rewriter.run,
                          help_msg='Modify the project definition')
+        self.add_command('compile', mcompile.add_arguments, mcompile.run,
+                         help_msg='Build the project')
 
         # Hidden commands
         self.add_command('runpython', self.add_runpython_arguments, self.run_runpython_command,
diff --git a/run_unittests.py b/run_unittests.py
index 3f5c87e..b9dcd41 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -4412,6 +4412,21 @@ recommended as it is not supported on some platforms''')
         else:
             self.assertEqual(expected_lines, out_lines)
 
+    def test_meson_compile(self):
+        """Test the meson compile command."""
+        prog = 'trivialprog'
+        if is_windows():
+            prog = '{}.exe'.format(prog)
+
+        testdir = os.path.join(self.common_test_dir, '1 trivial')
+        self.init(testdir)
+        self._run([*self.meson_command, 'compile', '-C', self.builddir])
+        # If compile worked then we should get a program
+        self.assertPathExists(os.path.join(self.builddir, prog))
+
+        self._run([*self.meson_command, 'compile', '-C', self.builddir, '--clean'])
+        self.assertPathDoesNotExist(os.path.join(self.builddir, prog))
+
 
 class FailureTests(BasePlatformTests):
     '''