Set the meson command to use when we know what it isnirbheek/rework-meson-script-handling

Instead of using fragile guessing to figure out how to invoke meson,
set the value when meson is run. Also rework how we pass of
meson_script_launcher to regenchecker.py -- it wasn't even being used

With this change, we only need to guess the meson path when running
the tests, and in that case:

1. If MESON_EXE is set in the env, we know how to run meson
   for project tests.
2. MESON_EXE is not set, which means we run the configure in-process
   for project tests and need to guess what meson to run, so either
   - meson.py is found next to run_tests.py, or
   - meson, meson.py, or meson.exe is in PATH

Otherwise, you can invoke meson in the following ways:

1. meson is installed, and mesonbuild is available in PYTHONPATH:
   - meson, meson.py, meson.exe from PATH
   - python3 -m mesonbuild.mesonmain
   - python3 /path/to/meson.py
   - meson is a shell wrapper to meson.real
2. meson is not installed, and is run from git:
   - Absolute path to meson.py
   - Relative path to meson.py
   - Symlink to meson.py

All these are tested in test_meson_commands.py, except meson.exe since
that involves building the meson msi and installing it.

1 files changed, 2 insertions, 4 deletions

diff --git a/mesonbuild/scripts/regen_checker.py b/mesonbuild/scripts/regen_checker.py
index a9b00c7b4..80d9242b4 100644
--- a/mesonbuild/scripts/regen_checker.py
+++ b/mesonbuild/scripts/regen_checker.py
@@ -14,7 +14,6 @@
 
 import sys, os
 import pickle, subprocess
-from mesonbuild.mesonlib import meson_command
 
 # This could also be used for XCode.
 
@@ -32,7 +31,7 @@ def need_regen(regeninfo, regen_timestamp):
     Vs2010Backend.touch_regen_timestamp(regeninfo.build_dir)
     return False
 
-def regen(regeninfo, mesonscript, backend):
+def regen(regeninfo, meson_command, backend):
     cmd = meson_command + ['--internal',
                            'regenerate',
                            regeninfo.build_dir,
@@ -48,11 +47,10 @@ def run(args):
         regeninfo = pickle.load(f)
     with open(coredata, 'rb') as f:
         coredata = pickle.load(f)
-    mesonscript = coredata.meson_script_launcher
     backend = coredata.get_builtin_option('backend')
     regen_timestamp = os.stat(dumpfile).st_mtime
     if need_regen(regeninfo, regen_timestamp):
-        regen(regeninfo, mesonscript, backend)
+        regen(regeninfo, coredata.meson_command, backend)
     sys.exit(0)
 
 if __name__ == '__main__':