Add a test for the --vsenv meson setup option

The tests and the unittests both unconditionally call setup_vsenv()
because all tests are run using the backend commands directly: ninja,
msbuild, etc.

There's no way to undo this vs env setup, so the only way to test that
--vsenv works is by:

1. Removing all paths in PATH that provide ninja
2. Changing setup_vsenv(force=True) to forcibly set-up a new vsenv
   when MESON_FORCE_VSENV_FOR_UNITTEST is set
3. Mock-patching build_command, test_command, install_command to use
   `meson` instead of `ninja`
4. Asserting that 'Activating VS' is in the output for all commands
5. Ensure that compilation works because ninja is picked up from the
   vs env.

I manually checked that this test actually does fail when the previous
commit is reverted.

3 files changed, 44 insertions, 4 deletions

diff --git a/unittests/baseplatformtests.py b/unittests/baseplatformtests.py
index 2f8064e..cfc78ce 100644
--- a/unittests/baseplatformtests.py
+++ b/unittests/baseplatformtests.py
@@ -249,10 +249,10 @@ class BasePlatformTests(TestCase):
 
     def run_tests(self, *, inprocess=False, override_envvars=None):
         if not inprocess:
-            self._run(self.test_command, workdir=self.builddir, override_envvars=override_envvars)
+            return self._run(self.test_command, workdir=self.builddir, override_envvars=override_envvars)
         else:
             with mock.patch.dict(os.environ, override_envvars):
-                run_mtest_inprocess(['-C', self.builddir])
+                return run_mtest_inprocess(['-C', self.builddir])[1]
 
     def install(self, *, use_destdir=True, override_envvars=None):
         if self.backend is not Backend.ninja:
@@ -263,7 +263,7 @@ class BasePlatformTests(TestCase):
                 override_envvars = destdir
             else:
                 override_envvars.update(destdir)
-        self._run(self.install_command, workdir=self.builddir, override_envvars=override_envvars)
+        return self._run(self.install_command, workdir=self.builddir, override_envvars=override_envvars)
 
     def uninstall(self, *, override_envvars=None):
         self._run(self.uninstall_command, workdir=self.builddir, override_envvars=override_envvars)
diff --git a/unittests/helpers.py b/unittests/helpers.py
index b759dba..bf06bdc 100644
--- a/unittests/helpers.py
+++ b/unittests/helpers.py
@@ -5,11 +5,13 @@ import unittest
 import functools
 import re
 import typing as T
+from pathlib import Path
 from contextlib import contextmanager
 
 from mesonbuild.compilers import detect_c_compiler, compiler_from_language
 from mesonbuild.mesonlib import (
-    MachineChoice, is_osx, is_cygwin, EnvironmentException, OptionKey, MachineChoice
+    MachineChoice, is_osx, is_cygwin, EnvironmentException, OptionKey, MachineChoice,
+    OrderedSet
 )
 from run_tests import get_fake_env
 
@@ -170,3 +172,15 @@ def get_rpath(fname: str) -> T.Optional[str]:
     # don't check for, so clear those
     final = ':'.join([e for e in raw.split(':') if not e.startswith('/nix')])
     return final
+
+def get_path_without_cmd(cmd: str, path: str) -> str:
+    pathsep = os.pathsep
+    paths = OrderedSet([Path(p).resolve() for p in path.split(pathsep)])
+    while True:
+        full_path = shutil.which(cmd, path=path)
+        if full_path is None:
+            break
+        dirname = Path(full_path).resolve().parent
+        paths.discard(dirname)
+        path = pathsep.join([str(p) for p in paths])
+    return path
diff --git a/unittests/windowstests.py b/unittests/windowstests.py
index bd75c74..d3ad932 100644
--- a/unittests/windowstests.py
+++ b/unittests/windowstests.py
@@ -373,3 +373,29 @@ class WindowsTests(BasePlatformTests):
             raise SkipTest('Not using MSVC')
         self.init(testdir, extra_args=['-Dtest-failure=true'])
         self.assertRaises(subprocess.CalledProcessError, self.build)
+
+    @unittest.skipIf(is_cygwin(), "Needs visual studio")
+    def test_vsenv_option(self):
+        if self.backend is not Backend.ninja:
+            raise SkipTest('Only ninja backend is valid for test')
+        env = os.environ.copy()
+        env['MESON_FORCE_VSENV_FOR_UNITTEST'] = '1'
+        # Remove ninja from PATH to ensure that the one provided by Visual
+        # Studio is picked, as a regression test for
+        # https://github.com/mesonbuild/meson/issues/9774
+        env['PATH'] = get_path_without_cmd('ninja', env['PATH'])
+        testdir = os.path.join(self.common_test_dir, '1 trivial')
+        out = self.init(testdir, extra_args=['--vsenv'], override_envvars=env)
+        self.assertIn('Activating VS', out)
+        self.assertRegex(out, 'Visual Studio environment is needed to run Ninja')
+        # All these directly call ninja with the full path, so we need to patch
+        # it out to use meson subcommands
+        with mock.patch.object(self, 'build_command', self.meson_command + ['compile']):
+            out = self.build(override_envvars=env)
+            self.assertIn('Activating VS', out)
+        with mock.patch.object(self, 'test_command', self.meson_command + ['test']):
+            out = self.run_tests(override_envvars=env)
+            self.assertIn('Activating VS', out)
+        with mock.patch.object(self, 'install_command', self.meson_command + ['install']):
+            out = self.install(override_envvars=env)
+            self.assertIn('Activating VS', out)