Error out when someone tries to use msys/python to run Mesonnirbheek/document-msys-installation-steps

This mistake seems to be a very common hiccup for people trying to use
Meson with MSYS2 on Windows from git or with pip.

msys/python uses POSIX paths with '/' as the root instead of a drive
like `C:/`, and also does not identify the platform as Windows.

This means that configure checks will be wrong, and many build tools
will be unable to parse the paths that are returned by functions in
Python such as shutil.which.

Closes https://github.com/mesonbuild/meson/issues/3653

1 files changed, 10 insertions, 0 deletions

diff --git a/mesonbuild/mesonmain.py b/mesonbuild/mesonmain.py
index c03ef9ba9..67d5a6c7d 100644
--- a/mesonbuild/mesonmain.py
+++ b/mesonbuild/mesonmain.py
@@ -23,6 +23,7 @@ from . import build
 from . import mconf, mintro, mtest, rewriter, minit
 from . import mlog, coredata
 from .mesonlib import MesonException
+from .environment import detect_msys2_arch
 from .wrap import WrapMode, wraptool
 
 default_warning = '1'
@@ -287,6 +288,15 @@ def run(original_args, mainfile):
         print('You have python %s.' % sys.version)
         print('Please update your environment')
         return 1
+    # https://github.com/mesonbuild/meson/issues/3653
+    if sys.platform.lower() == 'msys':
+        mlog.error('This python3 seems to be msys/python on MSYS2 Windows, which is known to have path semantics incompatible with Meson')
+        msys2_arch = detect_msys2_arch()
+        if msys2_arch:
+            mlog.error('Please install and use mingw-w64-i686-python3 and/or mingw-w64-x86_64-python3 with Pacman')
+        else:
+            mlog.error('Please download and use Python from www.python.org')
+        return 2
     # Set the meson command that will be used to run scripts and so on
     set_meson_command(mainfile)
     args = original_args[:]