Set the meson command to use when we know what it is

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, 7 insertions, 13 deletions

diff --git a/run_project_tests.py b/run_project_tests.py
index 2669a92..0b77a37 100755
--- a/run_project_tests.py
+++ b/run_project_tests.py
@@ -38,8 +38,7 @@ import time
 import multiprocessing
 from concurrent.futures import ProcessPoolExecutor
 import re
-from run_unittests import get_fake_options, run_configure
-
+from run_tests import get_fake_options, run_configure, get_meson_script
 from run_tests import get_backend_commands, get_backend_args_for_dir, Backend
 from run_tests import ensure_backend_detects_changes
 
@@ -88,12 +87,6 @@ no_meson_log_msg = 'No meson-log.txt found.'
 
 system_compiler = None
 
-meson_command = os.path.join(os.getcwd(), 'meson')
-if not os.path.exists(meson_command):
-    meson_command += '.py'
-    if not os.path.exists(meson_command):
-        raise RuntimeError('Could not find main Meson script to run.')
-
 class StopException(Exception):
     def __init__(self):
         super().__init__('Stopped by user')
@@ -324,7 +317,7 @@ def _run_test(testdir, test_build_dir, install_dir, extra_args, compiler, backen
     if pass_libdir_to_test(testdir):
         gen_args += ['--libdir', 'lib']
     gen_args += [testdir, test_build_dir] + flags + test_args + extra_args
-    (returncode, stdo, stde) = run_configure(meson_command, gen_args)
+    (returncode, stdo, stde) = run_configure(gen_args)
     try:
         logfile = Path(test_build_dir, 'meson-logs', 'meson-log.txt')
         mesonlog = logfile.open(errors='ignore', encoding='utf-8').read()
@@ -417,7 +410,7 @@ def have_d_compiler():
 
 def have_objc_compiler():
     with AutoDeletedDir(tempfile.mkdtemp(prefix='b ', dir='.')) as build_dir:
-        env = environment.Environment(None, build_dir, None, get_fake_options('/'), [])
+        env = environment.Environment(None, build_dir, get_fake_options('/'), [])
         try:
             objc_comp = env.detect_objc_compiler(False)
         except mesonlib.MesonException:
@@ -432,7 +425,7 @@ def have_objc_compiler():
 
 def have_objcpp_compiler():
     with AutoDeletedDir(tempfile.mkdtemp(prefix='b ', dir='.')) as build_dir:
-        env = environment.Environment(None, build_dir, None, get_fake_options('/'), [])
+        env = environment.Environment(None, build_dir, get_fake_options('/'), [])
         try:
             objcpp_comp = env.detect_objcpp_compiler(False)
         except mesonlib.MesonException:
@@ -648,11 +641,12 @@ def check_format():
                 check_file(fullname)
 
 def check_meson_commands_work():
-    global backend, meson_command, compile_commands, test_commands, install_commands
+    global backend, compile_commands, test_commands, install_commands
     testdir = PurePath('test cases', 'common', '1 trivial').as_posix()
+    meson_commands = mesonlib.python_command + [get_meson_script()]
     with AutoDeletedDir(tempfile.mkdtemp(prefix='b ', dir='.')) as build_dir:
         print('Checking that configuring works...')
-        gen_cmd = mesonlib.meson_command + [testdir, build_dir] + backend_flags
+        gen_cmd = meson_commands + [testdir, build_dir] + backend_flags
         pc, o, e = Popen_safe(gen_cmd)
         if pc.returncode != 0:
             raise RuntimeError('Failed to configure {!r}:\n{}\n{}'.format(testdir, e, o))