MAINT: improve error reporting when meson --version fails

mesonpy/__init__.py

@@ -998,13 +998,15 @@ def _get_meson_command(
     # package, however, it may occur that the meson Python package is installed
     # but the corresponding meson command is not available in $PATH. Implement
     # a runtime check to verify that the build environment is setup correcly.
-    required_version = _parse_version_string(version)
     try:
-        meson_version = subprocess.run(cmd + ['--version'], check=False, text=True, capture_output=True).stdout
+        r = subprocess.run(cmd + ['--version'], text=True, capture_output=True)
     except FileNotFoundError as err:
         raise ConfigError(f'meson executable "{meson}" not found') from err
+    if r.returncode != 0:
+        raise ConfigError(f'Could not execute meson: {r.stderr.strip()}')
+    meson_version = r.stdout.strip()
 
-    if _parse_version_string(meson_version) < required_version:
+    if _parse_version_string(meson_version) < _parse_version_string(version):
         raise ConfigError(f'Could not find meson version {version} or newer, found {meson_version}.')
 
     return cmd

tests/test_pep517.py

@@ -2,9 +2,12 @@
 #
 # SPDX-License-Identifier: MIT
 
+import os
+import re
 import shutil
 import subprocess
 import sys
+import textwrap
 
 from typing import List
 
@@ -95,3 +98,48 @@ def test_validate_config_settings_list():
 def test_validate_config_settings_tuple():
     config = mesonpy._validate_config_settings({'setup-args': ('-Done=1', '-Dtwo=2')})
     assert config['setup-args'] == ['-Done=1', '-Dtwo=2']
+
+
+@pytest.mark.parametrize('meson', [None, 'meson'])
+def test_get_meson_command(monkeypatch, meson):
+    # The MESON environment variable affects the meson executable lookup and breaks the test.
+    monkeypatch.delenv('MESON', raising=False)
+    assert mesonpy._get_meson_command(meson) == ['meson']
+
+
+def test_get_meson_command_bad_path(monkeypatch):
+    # The MESON environment variable affects the meson executable lookup and breaks the test.
+    monkeypatch.delenv('MESON', raising=False)
+    with pytest.raises(mesonpy.ConfigError, match=re.escape('meson executable "bad" not found')):
+        mesonpy._get_meson_command('bad')
+
+
+def test_get_meson_command_bad_python_path(monkeypatch):
+    # The MESON environment variable affects the meson executable lookup and breaks the test.
+    monkeypatch.delenv('MESON', raising=False)
+    with pytest.raises(mesonpy.ConfigError, match=re.escape('Could not find the specified meson: "bad-python-path.py"')):
+        mesonpy._get_meson_command('bad-python-path.py')
+
+
+def test_get_meson_command_wrong_version(monkeypatch, tmp_path):
+    # The MESON environment variable affects the meson executable lookup and breaks the test.
+    monkeypatch.delenv('MESON', raising=False)
+    meson = tmp_path / 'meson.py'
+    meson.write_text(textwrap.dedent('''
+        print('0.0.1')
+    '''))
+    with pytest.raises(mesonpy.ConfigError, match=r'Could not find meson version [0-9\.]+ or newer, found 0\.0\.1\.'):
+        mesonpy._get_meson_command(os.fspath(meson))
+
+
+def test_get_meson_command_error(monkeypatch, tmp_path):
+    # The MESON environment variable affects the meson executable lookup and breaks the test.
+    monkeypatch.delenv('MESON', raising=False)
+    meson = tmp_path / 'meson.py'
+    meson.write_text(textwrap.dedent('''
+        import sys
+        print('Just testing', file=sys.stderr)
+        sys.exit(1)
+    '''))
+    with pytest.raises(mesonpy.ConfigError, match=re.escape('Could not execute meson: Just testing')):
+        mesonpy._get_meson_command(os.fspath(meson))