Add VPYTHON_BYPASS support for vpython on Windows

At Postman, we use a custom build of Electron which is built using a set
of tools that are managed by us. Till now, we were using the
VPYTHON_BYPASS environment variable to use our own managed version of
Python on macOS but unfortunately, on Windows, depot_tools doesn't
respect the value of this variable, so this change adds support for that
on Windows too.
Signed-off-by: Darshan Sen <raisinten@gmail.com>
Change-Id: I63da0495463ace87d34c3c6fad1c03dee108d14b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3525642Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

vpython.bat

@@ -5,5 +5,49 @@
 
 :: See revert instructions in cipd_manifest.txt
 
+:: Note: we set EnableDelayedExpansion so we can perform string manipulations
+:: in our arguments parsing loop. This only works on Windows XP+.
+setlocal EnableDelayedExpansion
+
+if "%VPYTHON_BYPASS%"=="manually managed python not supported by chrome operations" (
+  set "arguments="
+  set "ignore="
+  set "stop="
+  for %%x in (%*) do (
+    set "arg=%%x"
+
+    if defined stop (
+      set "arguments=!arguments! %%~x"
+    ) else (
+      if "!arg!"=="--" (
+        set "stop=1"
+      ) else (
+        :: These tools all do something vpython related and quit
+        if "!arg:~0,13!"=="-vpython-tool" (
+          goto :END
+        )
+
+        :: Delete any vpython specific flag
+        if "!arg:~0,8!"=="-vpython" (
+          set "ignore=1"
+        ) else (
+          if defined ignore (
+            set "ignore="
+          ) else (
+            set "arguments=!arguments! %%~x"
+          )
+        )
+      )
+    )
+  )
+
+  call "python" !arguments!
+  if errorlevel 1 goto :END
+)
+
 call "%~dp0\cipd_bin_setup.bat" > nul 2>&1
 "%~dp0\.cipd_bin\vpython.exe" -vpython-interpreter "%~dp0\python.bat" %*
+
+:END
+endlocal
+exit /b %ERRORLEVEL%

vpython3.bat

@@ -3,6 +3,46 @@
 :: Use of this source code is governed by a BSD-style license that can be
 :: found in the LICENSE file.
 
+:: Note: we set EnableDelayedExpansion so we can perform string manipulations
+:: in our arguments parsing loop. This only works on Windows XP+.
+setlocal EnableDelayedExpansion
+
+if "%VPYTHON_BYPASS%"=="manually managed python not supported by chrome operations" (
+  set "arguments="
+  set "ignore="
+  set "stop="
+  for %%x in (%*) do (
+    set "arg=%%x"
+
+    if defined stop (
+      set "arguments=!arguments! %%~x"
+    ) else (
+      if "!arg!"=="--" (
+        set "stop=1"
+      ) else (
+        :: These tools all do something vpython related and quit
+        if "!arg:~0,13!"=="-vpython-tool" (
+          goto :END
+        )
+
+        :: Delete any vpython specific flag
+        if "!arg:~0,8!"=="-vpython" (
+          set "ignore=1"
+        ) else (
+          if defined ignore (
+            set "ignore="
+          ) else (
+            set "arguments=!arguments! %%~x"
+          )
+        )
+      )
+    )
+  )
+
+  call "python3" !arguments!
+  if errorlevel 1 goto :END
+)
+
 :: TODO(crbug.com/1003139): Remove.
 :: Add Python 3 to PATH to work around crbug.com/1003139.
 for /f %%i in (%~dp0python3_bin_reldir.txt) do set PYTHON3_BIN_RELDIR=%%i
@@ -10,3 +50,7 @@ set PATH=%~dp0%PYTHON3_BIN_RELDIR%;%~dp0%PYTHON3_BIN_RELDIR%\Scripts;%~dp0%PYTHO
 
 call "%~dp0\cipd_bin_setup.bat" > nul 2>&1
 "%~dp0\.cipd_bin\vpython3.exe" -vpython-interpreter "%~dp0\%PYTHON3_BIN_RELDIR%\python3.exe" %*
+
+:END
+endlocal
+exit /b %ERRORLEVEL%