Stop requiring vcvarsall.bat before build_mozc.py

With this commit 'vcvarsall.bat' (and its variant) are no longer
requires to be executed before running 'build_mozc.py', like
'build_qt.py' has never required 'vcvarsall.bat' (and its variant) [1].

'--vcvarsall_path' option, which is available in 'build_qt.py' [2],
is also available to explicitly specify a custom path of vcvarsall.bat
as follows.

  build_mozc.py --vcvarsall_path=C:\VS\VC\Auxiliary\Build\vcvarsall.bat

Overall this commit should make our build instructions simpler and
easier to keep maintaining.

Closes #923.

#codehealth

 [1]: baf4188
 [2]: c777896

PiperOrigin-RevId: 629293616

Author: yukawa

.github/workflows/windows.yaml

@@ -59,14 +59,12 @@ jobs:
         shell: cmd
         working-directory: .\src
         run: |
-          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsamd64_x86.bat"
           python build_mozc.py gyp
 
       - name: build package
         shell: cmd
         working-directory: .\src
         run: |
-          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsamd64_x86.bat"
           python build_mozc.py build -c Release package
 
       - name: upload Mozc64.msi
@@ -110,14 +108,12 @@ jobs:
         shell: cmd
         working-directory: .\src
         run: |
-          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsamd64_x86.bat"
           python build_mozc.py gyp --noqt --msvs_version=2022
 
       - name: runtests
         shell: cmd
         working-directory: .\src
         run: |
-          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsamd64_x86.bat"
           python build_mozc.py runtests -c Debug
 
   # actions/cache works without this job, but having this would increase the likelihood of cache hit

docs/build_mozc_in_windows.md

@@ -14,9 +14,6 @@ git clone https://github.com/google/mozc.git
 cd mozc\src
 
 python build_tools/update_deps.py
-
-"C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsamd64_x86.bat"
-
 python build_tools/build_qt.py --release --confirm_license
 python build_mozc.py gyp
 python build_mozc.py build -c Release package
@@ -76,15 +73,6 @@ You can skip this step if you would like to manually download these libraries.
 
 ## Build
 
-### Setup Build system
-
-If you have not set up the build system in your command prompt, you might need
-to execute the setup command like this.
-
-```
-"C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsamd64_x86.bat"
-```
-
 ### Build Qt
 
 ```

src/build_mozc.py

@@ -62,6 +62,7 @@
 from build_tools.util import RemoveFile
 from build_tools.util import RunOrDie
 from build_tools.util import RunOrDieError
+from build_tools.vs_util import get_vs_env_vars
 
 SRC_DIR = '.'
 OSS_SRC_DIR = '.'
@@ -252,6 +253,8 @@ def ParseGypOptions(args):
     parser.add_option('--msvs_version', dest='msvs_version',
                       default='2022',
                       help='Version of the Visual Studio.')
+    parser.add_option('--vcvarsall_path', help='Path of vcvarsall.bat',
+                      default=None)
 
   if IsWindows() or IsMac():
     parser.add_option('--qtdir', dest='qtdir',
@@ -373,6 +376,15 @@ def UpdateEnvironmentFilesForWindows(out_dir):
 
 def GypMain(options, unused_args):
   """The main function for the 'gyp' command."""
+  if IsWindows():
+    # GYP captures environment variables while running so setting them up as if
+    # the developer manually executed 'vcvarsall.bat' command. Otherwise we end
+    # up having to explain how to do that for both cmd.exe and PowerShell.
+    # See https://github.com/google/mozc/pull/923
+    env_vars = get_vs_env_vars('x64', options.vcvarsall_path)
+    for (key, value) in env_vars.items():
+      os.environ[key] = value
+
   # Generate a version definition file.
   logging.info('Generating version definition file...')
   template_path = '%s/%s' % (OSS_SRC_DIR, options.version_file)
@@ -863,11 +875,6 @@ def main():
   command = sys.argv[1]
   args = sys.argv[2:]
 
-  if IsWindows() and (not os.environ.get('VCToolsRedistDir', '')):
-    print('VCToolsRedistDir is not defined.')
-    print('Please use Developer Command Prompt or run vcvarsamd64_x86.bat')
-    return 1
-
   if command == 'gyp':
     (cmd_opts, cmd_args) = ParseGypOptions(args)
     GypMain(cmd_opts, cmd_args)