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, 27 insertions, 7 deletions

diff --git a/mesonbuild/mesonmain.py b/mesonbuild/mesonmain.py
index 4a977a1..c03ef9b 100644
--- a/mesonbuild/mesonmain.py
+++ b/mesonbuild/mesonmain.py
@@ -73,9 +73,8 @@ def filter_builtin_options(args, original_args):
 
 class MesonApp:
 
-    def __init__(self, dir1, dir2, script_launcher, handshake, options, original_cmd_line_args):
+    def __init__(self, dir1, dir2, handshake, options, original_cmd_line_args):
         (self.source_dir, self.build_dir) = self.validate_dirs(dir1, dir2, handshake)
-        self.meson_script_launcher = script_launcher
         self.options = options
         self.original_cmd_line_args = original_cmd_line_args
 
@@ -129,7 +128,7 @@ class MesonApp:
             env.coredata.pkgconf_envvar = curvar
 
     def generate(self):
-        env = environment.Environment(self.source_dir, self.build_dir, self.meson_script_launcher, self.options, self.original_cmd_line_args)
+        env = environment.Environment(self.source_dir, self.build_dir, self.options, self.original_cmd_line_args)
         mlog.initialize(env.get_log_dir())
         with mesonlib.BuildDirLock(self.build_dir):
             self._generate(env)
@@ -269,12 +268,27 @@ def run_script_command(args):
         raise MesonException('Unknown internal command {}.'.format(cmdname))
     return cmdfunc(cmdargs)
 
-def run(original_args, mainfile=None):
+def set_meson_command(mainfile):
+    if mainfile.endswith('.exe'):
+        mesonlib.meson_command = [mainfile]
+    elif os.path.isabs(mainfile) and mainfile.endswith('mesonmain.py'):
+        # Can't actually run meson with an absolute path to mesonmain.py, it must be run as -m mesonbuild.mesonmain
+        mesonlib.meson_command = mesonlib.python_command + ['-m', 'mesonbuild.mesonmain']
+    else:
+        mesonlib.meson_command = mesonlib.python_command + [mainfile]
+    # This won't go into the log file because it's not initialized yet, and we
+    # need this value for unit tests.
+    if 'MESON_COMMAND_TESTS' in os.environ:
+        mlog.log('meson_command is {!r}'.format(mesonlib.meson_command))
+
+def run(original_args, mainfile):
     if sys.version_info < (3, 5):
         print('Meson works correctly only with python 3.5+.')
         print('You have python %s.' % sys.version)
         print('Please update your environment')
         return 1
+    # Set the meson command that will be used to run scripts and so on
+    set_meson_command(mainfile)
     args = original_args[:]
     if len(args) > 0:
         # First check if we want to run a subcommand.
@@ -352,9 +366,7 @@ def run(original_args, mainfile=None):
         else:
             dir2 = '.'
     try:
-        if mainfile is None:
-            raise AssertionError('I iz broken. Sorry.')
-        app = MesonApp(dir1, dir2, mainfile, handshake, options, original_args)
+        app = MesonApp(dir1, dir2, handshake, options, original_args)
     except Exception as e:
         # Log directory does not exist, so just print
         # to stdout.
@@ -382,3 +394,11 @@ def run(original_args, mainfile=None):
         mlog.shutdown()
 
     return 0
+
+def main():
+    # Always resolve the command path so Ninja can find it for regen, tests, etc.
+    launcher = os.path.realpath(sys.argv[0])
+    return run(sys.argv[1:], launcher)
+
+if __name__ == '__main__':
+    sys.exit(main())