build, win: vcbuild improvements

Removes extra erroor messages when Python is not installed. Removes
"vswhere not found" message when no VS2017 installation is found.
Adds support for DEBUG_HELPER to vcbuild.bat.

Fixes: #16864

PR-URL: #17015
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

tools/msvs/find_python.cmd

@@ -1,4 +1,5 @@
 @IF NOT DEFINED DEBUG_HELPER @ECHO OFF
+echo Looking for Python 2.x
 SETLOCAL
 :: If python.exe is in %Path%, just validate
 FOR /F "delims=" %%a IN ('where python 2^> NUL') DO (
@@ -14,18 +15,18 @@ FOR %%K IN ( "HKCU\Software", "HKLM\SOFTWARE", "HKLM\Software\Wow6432Node") DO (
  :: If validate returns 0 just jump to the end
  IF NOT ERRORLEVEL 1 GOTO :validate
 )
-EXIT /B 1
+goto :no-python
 
 :: Helper subroutine to handle quotes in %1
 :find-main-branch
 SET main_key="%~1\Python\PythonCore"
-REG QUERY %main_key% /s | findstr "2." | findstr InstallPath > NUL 2> NUL
+REG QUERY %main_key% /s 2> NUL | findstr "2." | findstr InstallPath > NUL 2> NUL
 IF NOT ERRORLEVEL 1 CALL :find-key %main_key%
 EXIT /B
 
 :: Query registry sub-tree for InstallPath
 :find-key
-FOR /F "delims=" %%a IN ('REG QUERY %1 /s ^| findstr "2." ^| findstr InstallPath') DO IF NOT ERRORLEVEL 1 CALL :find-path %%a
+FOR /F "delims=" %%a IN ('REG QUERY %1 /s 2> NUL ^| findstr "2." ^| findstr InstallPath') DO IF NOT ERRORLEVEL 1 CALL :find-path %%a
 EXIT /B
 
 :: Parse the value of %1 as the path for python.exe
@@ -39,13 +40,20 @@ EXIT /B 1
 
 :: Check if %p% holds a path to a real python2 executable
 :validate
-IF NOT EXIST "%p%python.exe" EXIT /B 1
+IF NOT EXIST "%p%python.exe" goto :no-python
 :: Check if %p% is python2
 "%p%python.exe" -V 2>&1 | findstr /R "^Python.2.*" > NUL
-IF ERRORLEVEL 1 EXIT /B %ERRORLEVEL%
+IF ERRORLEVEL 1 goto :no-python2
 :: We can wrap it up
 ENDLOCAL & SET pt=%p%& SET need_path_ext=%need_path%
 SET VCBUILD_PYTHON_LOCATION=%pt%python.exe
 IF %need_path_ext%==1 SET Path=%Path%;%pt%
 SET need_path_ext=
-EXIT /B %ERRORLEVEL%
+EXIT /B %ERRORLEVEL%
+
+:no-python2
+echo Python found in %p%, but it is not v2.x.
+exit /B 1
+:no-python
+echo Could not find Python.
+exit /B 1

tools/msvs/vswhere_usability_wrapper.cmd

@@ -28,5 +28,4 @@ for /f "usebackq tokens=*" %%i in (`vswhere %VSWHERE_ARGS%`) do (
 
 :no-vswhere
 endlocal
-echo could not find "vswhere"
 exit /B 1

vcbuild.bat

@@ -1,4 +1,4 @@
-@echo off
+@if not defined DEBUG_HELPER @ECHO OFF
 
 cd %~dp0
 
@@ -170,7 +170,7 @@ if "%target%"=="Clean" rmdir /S /Q %~dp0deps\icu
 :no-depsicu
 
 call tools\msvs\find_python.cmd
-if errorlevel 1 echo Could not find python2 & goto :exit
+if errorlevel 1 goto :exit
 
 call :getnodeversion || exit /b 1