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, 1 insertions, 47 deletions

diff --git a/mesonbuild/mesonlib.py b/mesonbuild/mesonlib.py
index fe426c574..15c791840 100644
--- a/mesonbuild/mesonlib.py
+++ b/mesonbuild/mesonlib.py
@@ -38,58 +38,12 @@ except Exception:
 
 from glob import glob
 
-def detect_meson_py_location():
-    c = sys.argv[0]
-    c_dir, c_fname = os.path.split(c)
-
-    # get the absolute path to the <mesontool> folder
-    m_dir = None
-    if os.path.isabs(c):
-        # $ /foo/<mesontool>.py <args>
-        m_dir = c_dir
-    elif c_dir == '':
-        # $ <mesontool> <args> (gets run from /usr/bin/<mesontool>)
-        in_path_exe = shutil.which(c_fname)
-        if in_path_exe:
-            if not os.path.isabs(in_path_exe):
-                m_dir = os.getcwd()
-                c_fname = in_path_exe
-            else:
-                m_dir, c_fname = os.path.split(in_path_exe)
-    else:
-        m_dir = os.path.abspath(c_dir)
-
-    # find meson in m_dir
-    if m_dir is not None:
-        for fname in ['meson', 'meson.py']:
-            m_path = os.path.join(m_dir, fname)
-            if os.path.exists(m_path):
-                return m_path
-
-    # No meson found, which means that either:
-    # a) meson is not installed
-    # b) meson is installed to a non-standard location
-    # c) the script that invoked mesonlib is not the one of meson tools (e.g. run_unittests.py)
-    fname = os.path.normpath(os.path.join(os.path.dirname(__file__), '..', 'meson.py'))
-    if os.path.exists(fname):
-        return fname
-    # If meson is still not found, we might be imported by out-of-source tests
-    # https://github.com/mesonbuild/meson/issues/3015
-    exe = shutil.which('meson')
-    if exe is None:
-        exe = shutil.which('meson.py')
-    if exe is not None:
-        return exe
-    # Give up.
-    raise RuntimeError('Could not determine how to run Meson. Please file a bug with details.')
-
 if os.path.basename(sys.executable) == 'meson.exe':
     # In Windows and using the MSI installed executable.
-    meson_command = [sys.executable]
     python_command = [sys.executable, 'runpython']
 else:
     python_command = [sys.executable]
-    meson_command = python_command + [detect_meson_py_location()]
+meson_command = None
 
 def is_ascii_string(astring):
     try: