Add --vsenv command line option and active VS only when needed

14 files changed, 150 insertions, 115 deletions

diff --git a/docs/markdown/snippets/vsenv.md b/docs/markdown/snippets/vsenv.md
new file mode 100644
index 0000000..16e9424
--- /dev/null
+++ b/docs/markdown/snippets/vsenv.md
@@ -0,0 +1,14 @@
+## Force Visual Studio environment activation
+
+Since `0.59.0`, meson automatically activates Visual Studio environment on Windows
+for all its subcommands, but only if no other compilers (e.g. `gcc` or `clang`)
+are found, and silently continue if Visual Studio activation fails.
+
+`meson setup --vsenv` command line argument can now be used to force Visual Studio
+activation even when other compilers are found. It also make Meson abort with an
+error message when activation fails. This is especially useful for Github Action
+because their Windows images have gcc in their PATH by default.
+
+`--vsenv` is set by default when using `vs` backend.
+
+Only `setup`, `compile`, `dist` and `devenv` subcommands now activate Visual Studio.
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index a053be6..37f5259 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -49,7 +49,6 @@ from ..mesonlib import get_compiler_for_source, has_path_sep, OptionKey
 from .backends import CleanTrees
 from ..build import GeneratedList, InvalidArguments, ExtractedObjects
 from ..interpreter import Interpreter
-from ..mesonmain import need_setup_vsenv
 
 if T.TYPE_CHECKING:
     from .._typing import ImmutableListProtocol
@@ -513,7 +512,7 @@ class NinjaBackend(backends.Backend):
 
     def generate(self):
         ninja = environment.detect_ninja_command_and_version(log=True)
-        if need_setup_vsenv:
+        if self.build.need_vsenv:
             builddir = Path(self.environment.get_build_dir())
             try:
                 # For prettier printing, reduce to a relative path. If
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 273f457..37c2e02 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -272,6 +272,7 @@ class Build:
             environment.is_cross_build(), {}, {})
         self.devenv: T.List[EnvironmentVariables] = []
         self.modules: T.List[str] = []
+        self.need_vsenv = False
 
     def get_build_targets(self):
         build_targets = OrderedDict()
diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index b82525f..9f2c705 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -1115,6 +1115,16 @@ external dependencies (including libraries) must go to "dependencies".''')
         mlog.log('Project name:', mlog.bold(proj_name))
         mlog.log('Project version:', mlog.bold(self.project_version))
 
+        if not self.is_subproject():
+            # We have to activate VS before adding languages and before calling
+            # self.set_backend() otherwise it wouldn't be able to detect which
+            # vs backend version we need. But after setting default_options in case
+            # the project sets vs backend by default.
+            backend = self.coredata.get_option(OptionKey('backend'))
+            force_vsenv = self.user_defined_options.vsenv or backend.startswith('vs')
+            if mesonlib.setup_vsenv(force_vsenv):
+                self.build.need_vsenv = True
+
         self.add_languages(proj_langs, True, MachineChoice.HOST)
         self.add_languages(proj_langs, False, MachineChoice.BUILD)
 
diff --git a/mesonbuild/mcompile.py b/mesonbuild/mcompile.py
index f586fde..146ea13 100644
--- a/mesonbuild/mcompile.py
+++ b/mesonbuild/mcompile.py
@@ -26,9 +26,10 @@ from pathlib import Path
 from . import mlog
 from . import mesonlib
 from . import coredata
-from .mesonlib import MesonException
+from .mesonlib import MesonException, RealPathAction, setup_vsenv
 from mesonbuild.environment import detect_ninja
 from mesonbuild.coredata import UserArrayOption
+from mesonbuild import build
 
 if T.TYPE_CHECKING:
     import argparse
@@ -286,14 +287,9 @@ def add_arguments(parser: 'argparse.ArgumentParser') -> None:
         action='store_true',
         help='Clean the build directory.'
     )
-    parser.add_argument(
-        '-C',
-        action='store',
-        dest='builddir',
-        type=Path,
-        default='.',
-        help='The directory containing build files to be built.'
-    )
+    parser.add_argument('-C', dest='wd', action=RealPathAction,
+                        help='directory to cd into before running')
+
     parser.add_argument(
         '-j', '--jobs',
         action='store',
@@ -333,8 +329,12 @@ def add_arguments(parser: 'argparse.ArgumentParser') -> None:
     )
 
 def run(options: 'argparse.Namespace') -> int:
-    bdir = options.builddir  # type: Path
-    validate_builddir(bdir.resolve())
+    bdir = Path(options.wd)
+    buildfile = bdir / 'meson-private' / 'build.dat'
+    if not buildfile.is_file():
+        raise MesonException(f'Directory {options.wd!r} does not seem to be a Meson build directory.')
+    b = build.load(options.wd)
+    setup_vsenv(b.need_vsenv)
 
     cmd = []    # type: T.List[str]
     env = None  # type: T.Optional[T.Dict[str, str]]
diff --git a/mesonbuild/mdevenv.py b/mesonbuild/mdevenv.py
index c304cbb..eb05020 100644
--- a/mesonbuild/mdevenv.py
+++ b/mesonbuild/mdevenv.py
@@ -4,7 +4,7 @@ import tempfile
 
 from pathlib import Path
 from . import build
-from .mesonlib import MesonException, RealPathAction, is_windows
+from .mesonlib import MesonException, RealPathAction, is_windows, setup_vsenv
 
 import typing as T
 
@@ -41,6 +41,7 @@ def run(options: argparse.Namespace) -> int:
     if not buildfile.is_file():
         raise MesonException(f'Directory {options.wd!r} does not seem to be a Meson build directory.')
     b = build.load(options.wd)
+    setup_vsenv(b.need_vsenv)
 
     devenv = get_env(b, options.wd)
 
diff --git a/mesonbuild/mdist.py b/mesonbuild/mdist.py
index 43bc66f..d5db4fb 100644
--- a/mesonbuild/mdist.py
+++ b/mesonbuild/mdist.py
@@ -26,7 +26,7 @@ from glob import glob
 from pathlib import Path
 from mesonbuild.environment import detect_ninja
 from mesonbuild.mesonlib import (MesonException, RealPathAction, quiet_git,
-                                 windows_proof_rmtree)
+                                 windows_proof_rmtree, setup_vsenv)
 from mesonbuild.wrap import wrap
 from mesonbuild import mlog, build
 from .scripts.meson_exe import run_exe
@@ -281,6 +281,7 @@ def run(options):
     if not buildfile.is_file():
         raise MesonException(f'Directory {options.wd!r} does not seem to be a Meson build directory.')
     b = build.load(options.wd)
+    setup_vsenv(b.need_vsenv)
     # This import must be load delayed, otherwise it will get the default
     # value of None.
     from mesonbuild.mesonlib import get_meson_command
diff --git a/mesonbuild/mesonlib/__init__.py b/mesonbuild/mesonlib/__init__.py
index 5b646b5..5b2e82d 100644
--- a/mesonbuild/mesonlib/__init__.py
+++ b/mesonbuild/mesonlib/__init__.py
@@ -19,6 +19,7 @@
 import os
 
 from .universal import *
+from .vsenv import setup_vsenv
 
 # Here we import either the posix implementations, the windows implementations,
 # or a generic no-op implementation
diff --git a/mesonbuild/mesonlib/vsenv.py b/mesonbuild/mesonlib/vsenv.py
new file mode 100644
index 0000000..1966634
--- /dev/null
+++ b/mesonbuild/mesonlib/vsenv.py
@@ -0,0 +1,100 @@
+import os
+import subprocess
+import json
+import pathlib
+import shutil
+import tempfile
+
+from .. import mlog
+from .universal import MesonException, is_windows
+
+
+bat_template = '''@ECHO OFF
+
+call "{}"
+
+ECHO {}
+SET
+'''
+
+# If on Windows and VS is installed but not set up in the environment,
+# set it to be runnable. In this way Meson can be directly invoked
+# from any shell, VS Code etc.
+def _setup_vsenv(force: bool) -> bool:
+    if not is_windows():
+        return False
+    if os.environ.get('OSTYPE') == 'cygwin':
+        return False
+    if 'Visual Studio' in os.environ['PATH']:
+        return False
+    # VSINSTALL is set when running setvars from a Visual Studio installation
+    # Tested with Visual Studio 2012 and 2017
+    if 'VSINSTALLDIR' in os.environ:
+        return False
+    # Check explicitly for cl when on Windows
+    if shutil.which('cl.exe'):
+        return False
+    if not force:
+        if shutil.which('cc'):
+            return False
+        if shutil.which('gcc'):
+            return False
+        if shutil.which('clang'):
+            return False
+        if shutil.which('clang-cl'):
+            return False
+
+    root = os.environ.get("ProgramFiles(x86)") or os.environ.get("ProgramFiles")
+    bat_locator_bin = pathlib.Path(root, 'Microsoft Visual Studio/Installer/vswhere.exe')
+    if not bat_locator_bin.exists():
+        raise MesonException(f'Could not find {bat_locator_bin}')
+    bat_json = subprocess.check_output(
+        [
+            str(bat_locator_bin),
+            '-latest',
+            '-prerelease',
+            '-requiresAny',
+            '-requires', 'Microsoft.VisualStudio.Component.VC.Tools.x86.x64',
+            '-products', '*',
+            '-utf8',
+            '-format',
+            'json'
+        ]
+    )
+    bat_info = json.loads(bat_json)
+    if not bat_info:
+        # VS installer instelled but not VS itself maybe?
+        raise MesonException(f'Could not parse vswhere.exe output')
+    bat_root = pathlib.Path(bat_info[0]['installationPath'])
+    bat_path = bat_root / 'VC/Auxiliary/Build/vcvars64.bat'
+    if not bat_path.exists():
+        raise MesonException(f'Could not find {bat_path}')
+
+    mlog.log('Activating VS', bat_info[0]['catalog']['productDisplayVersion'])
+    bat_separator = '---SPLIT---'
+    bat_contents = bat_template.format(bat_path, bat_separator)
+    bat_file = tempfile.NamedTemporaryFile('w', suffix='.bat', encoding='utf-8')
+    bat_file.write(bat_contents)
+    bat_file.flush()
+    bat_output = subprocess.check_output(str(bat_file), universal_newlines=True)
+    bat_lines = bat_output.split('\n')
+    bat_separator_seen = False
+    for bat_line in bat_lines:
+        if bat_line == bat_separator:
+            bat_separator_seen = True
+            continue
+        if not bat_separator_seen:
+            continue
+        if not bat_line:
+            continue
+        k, v = bat_line.split('=', 1)
+        os.environ[k] = v
+    return True
+
+def setup_vsenv(force: bool = False):
+    try:
+        _setup_vsenv(force)
+    except MesonException:
+        if force:
+            raise
+        mlog.warning('Failed to activate VS environment:', str(e))
diff --git a/mesonbuild/mesonmain.py b/mesonbuild/mesonmain.py
index 5d84b37..a60f914 100644
--- a/mesonbuild/mesonmain.py
+++ b/mesonbuild/mesonmain.py
@@ -31,96 +31,6 @@ from .mesonlib import MesonException
 from .environment import detect_msys2_arch
 from .wrap import wraptool
 
-need_setup_vsenv = False
-
-bat_template = '''@ECHO OFF
-
-call "{}"
-
-ECHO {}
-SET
-'''
-
-# If on Windows and VS is installed but not set up in the environment,
-# set it to be runnable. In this way Meson can be directly invoked
-# from any shell, VS Code etc.
-def setup_vsenv() -> None:
-    import subprocess, json, pathlib
-    if not mesonlib.is_windows():
-        return
-    bat_placeholder = 'nananananananananananananananana'
-    # If an existing build tool chain exists in PATH -> do nothing.
-    if shutil.which('cc'):
-        return
-    if shutil.which('gcc'):
-        return
-    if shutil.which('clang'):
-        return
-    if shutil.which('clang-cl'):
-        return
-    if os.environ.get('OSTYPE', bat_placeholder) == 'cygwin':
-        return
-    if 'Visual Studio' in os.environ['PATH']:
-        return
-    # VSINSTALL is set when running setvars from a Visual Studio installation
-    # Tested with Visual Studio 2012 and 2017
-    if 'VSINSTALLDIR' in os.environ:
-        return
-    # Check explicitly for cl when on Windows
-    if shutil.which('cl.exe'):
-        return
-
-    root = os.environ.get("ProgramFiles(x86)") or os.environ.get("ProgramFiles")
-    bat_locator_bin = pathlib.Path(root, 'Microsoft Visual Studio/Installer/vswhere.exe')
-    if not bat_locator_bin.exists():
-        return
-    bat_json = subprocess.check_output(
-        [
-            str(bat_locator_bin),
-            '-latest',
-            '-prerelease',
-            '-requiresAny',
-            '-requires', 'Microsoft.VisualStudio.Component.VC.Tools.x86.x64',
-            '-products', '*',
-            '-utf8',
-            '-format',
-            'json'
-        ]
-    )
-    bat_info = json.loads(bat_json)
-    if not bat_info:
-        # VS installer instelled but not VS itself maybe?
-        return
-    print('Activating VS', bat_info[0]['catalog']['productDisplayVersion'])
-    bat_root = pathlib.Path(bat_info[0]['installationPath'])
-    bat_path = bat_root / 'VC/Auxiliary/Build/vcvars64.bat'
-    if not bat_path.exists():
-        return
-
-    bat_file = pathlib.Path.home() / 'vsdetect.bat'
-
-    bat_separator = '---SPLIT---'
-    bat_contents = bat_template.format(bat_path, bat_separator)
-    bat_file.write_text(bat_contents, encoding='utf-8')
-    try:
-        bat_output = subprocess.check_output(str(bat_file), universal_newlines=True)
-    finally:
-        bat_file.unlink()
-    bat_lines = bat_output.split('\n')
-    bat_separator_seen = False
-    for bat_line in bat_lines:
-        if bat_line == bat_separator:
-            bat_separator_seen = True
-            continue
-        if not bat_separator_seen:
-            continue
-        if not bat_line:
-            continue
-        k, v = bat_line.split('=', 1)
-        os.environ[k] = v
-    global need_setup_vsenv
-    need_setup_vsenv = True
-
 
 # Note: when adding arguments, please also add them to the completion
 # scripts in $MESONSRC/data/shell-completions/
@@ -316,7 +226,6 @@ def run(original_args, mainfile):
     return CommandLineParser().run(args)
 
 def main():
-    setup_vsenv()
     # Always resolve the command path so Ninja can find it for regen, tests, etc.
     if 'meson.exe' in sys.executable:
         assert os.path.isabs(sys.executable)
diff --git a/mesonbuild/msetup.py b/mesonbuild/msetup.py
index a7d28dd..7f2f7ed 100644
--- a/mesonbuild/msetup.py
+++ b/mesonbuild/msetup.py
@@ -50,6 +50,10 @@ def add_arguments(parser: argparse.ArgumentParser) -> None:
                         default=[],
                         action='append',
                         help='File describing cross compilation environment.')
+    parser.add_argument('--vsenv', action='store_true',
+                        help='Setup Visual Studio environment even when other compilers are found, ' +
+                             'abort if Visual Studio is not found. This option has no effect on other ' +
+                             'platforms than Windows. Defaults to True when using "vs" backend.')
     parser.add_argument('-v', '--version', action='version',
                         version=coredata.version)
     parser.add_argument('--profile-self', action='store_true', dest='profile',
diff --git a/run_project_tests.py b/run_project_tests.py
index 0619bdf..176a938 100755
--- a/run_project_tests.py
+++ b/run_project_tests.py
@@ -48,10 +48,9 @@ from mesonbuild import mlog
 from mesonbuild import mtest
 from mesonbuild.compilers import compiler_from_language, detect_objc_compiler, detect_objcpp_compiler
 from mesonbuild.build import ConfigurationData
-from mesonbuild.mesonlib import MachineChoice, Popen_safe, TemporaryDirectoryWinProof
+from mesonbuild.mesonlib import MachineChoice, Popen_safe, TemporaryDirectoryWinProof, setup_vsenv
 from mesonbuild.mlog import blue, bold, cyan, green, red, yellow, normal_green
 from mesonbuild.coredata import backendlist, version as meson_version
-from mesonbuild.mesonmain import setup_vsenv
 from mesonbuild.modules.python import PythonExternalProgram
 from run_tests import get_fake_options, run_configure, get_meson_script
 from run_tests import get_backend_commands, get_backend_args_for_dir, Backend
diff --git a/run_tests.py b/run_tests.py
index 90641ad..b6f8884 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -42,7 +42,7 @@ from mesonbuild import mtest
 from mesonbuild import mlog
 from mesonbuild.environment import Environment, detect_ninja
 from mesonbuild.coredata import backendlist, version as meson_version
-from mesonbuild.mesonlib import OptionKey
+from mesonbuild.mesonlib import OptionKey, setup_vsenv
 
 NINJA_1_9_OR_NEWER = False
 NINJA_CMD = None
@@ -382,6 +382,6 @@ def main():
     return returncode
 
 if __name__ == '__main__':
-    mesonmain.setup_vsenv()
+    setup_vsenv()
     print('Meson build system', meson_version, 'Project and Unit Tests')
     raise SystemExit(main())
diff --git a/run_unittests.py b/run_unittests.py
index f438daa..bc20b22 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -33,14 +33,10 @@ import mesonbuild.environment
 import mesonbuild.mesonlib
 import mesonbuild.coredata
 import mesonbuild.modules.gnome
-from mesonbuild.mesonlib import (
-    python_command
-)
+from mesonbuild.mesonlib import python_command, setup_vsenv
 import mesonbuild.dependencies.base
 import mesonbuild.modules.pkgconfig
 
-from mesonbuild.mesonmain import setup_vsenv
-
 from unittests.allplatformstests import AllPlatformTests
 from unittests.darwintests import DarwinTests
 from unittests.failuretests import FailureTests