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, 186 insertions, 0 deletions

diff --git a/run_meson_command_tests.py b/run_meson_command_tests.py
new file mode 100755
index 0000000..6efd911
--- /dev/null
+++ b/run_meson_command_tests.py
@@ -0,0 +1,186 @@
+#!/usr/bin/env python3
+
+# Copyright 2018 The Meson development team
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import tempfile
+import unittest
+import subprocess
+from pathlib import Path
+
+from mesonbuild.mesonlib import windows_proof_rmtree, python_command, is_windows
+
+# Find the meson.py adjacent to us
+meson_py = Path(__file__).resolve().parent / 'meson.py'
+if not meson_py.is_file():
+    raise RuntimeError("meson.py not found: test must only run from git")
+
+def get_pypath():
+    import sysconfig
+    pypath = sysconfig.get_path('purelib', vars={'base': ''})
+    # Ensure that / is the path separator and not \, then strip /
+    return Path(pypath).as_posix().strip('/')
+
+def get_pybindir():
+    import sysconfig
+    # 'Scripts' on Windows and 'bin' on other platforms including MSYS
+    return sysconfig.get_path('scripts', vars={'base': ''}).strip('\\/')
+
+class CommandTests(unittest.TestCase):
+    '''
+    Test that running meson in various ways works as expected by checking the
+    value of mesonlib.meson_command that was set during configuration.
+    '''
+
+    def setUp(self):
+        super().setUp()
+        self.orig_env = os.environ.copy()
+        self.orig_dir = os.getcwd()
+        os.environ['MESON_COMMAND_TESTS'] = '1'
+        self.tmpdir = Path(tempfile.mkdtemp()).resolve()
+        self.src_root = Path(__file__).resolve().parent
+        self.testdir = str(self.src_root / 'test cases/common/1 trivial')
+        self.meson_args = ['--backend=ninja']
+
+    def tearDown(self):
+        try:
+            windows_proof_rmtree(str(self.tmpdir))
+        except FileNotFoundError:
+            pass
+        os.environ.clear()
+        os.environ.update(self.orig_env)
+        os.chdir(str(self.orig_dir))
+        super().tearDown()
+
+    def _run(self, command, workdir=None):
+        '''
+        Run a command while printing the stdout and stderr to stdout,
+        and also return a copy of it
+        '''
+        # If this call hangs CI will just abort. It is very hard to distinguish
+        # between CI issue and test bug in that case. Set timeout and fail loud
+        # instead.
+        p = subprocess.run(command, stdout=subprocess.PIPE,
+                           stderr=subprocess.STDOUT, env=os.environ.copy(),
+                           universal_newlines=True, cwd=workdir, timeout=60 * 5)
+        print(p.stdout)
+        if p.returncode != 0:
+            raise subprocess.CalledProcessError(p.returncode, command)
+        return p.stdout
+
+    def assertMesonCommandIs(self, line, cmd):
+        self.assertTrue(line.startswith('meson_command '), msg=line)
+        self.assertEqual(line, 'meson_command is {!r}'.format(cmd))
+
+    def test_meson_uninstalled(self):
+        # This is what the meson command must be for all these cases
+        resolved_meson_command = python_command + [str(self.src_root / 'meson.py')]
+        # Absolute path to meson.py
+        os.chdir('/')
+        builddir = str(self.tmpdir / 'build1')
+        meson_py = str(self.src_root / 'meson.py')
+        meson_setup = [meson_py, 'setup']
+        meson_command = python_command + meson_setup + self.meson_args
+        stdo = self._run(meson_command + [self.testdir, builddir])
+        self.assertMesonCommandIs(stdo.split('\n')[0], resolved_meson_command)
+        # ./meson.py
+        os.chdir(str(self.src_root))
+        builddir = str(self.tmpdir / 'build2')
+        meson_py = './meson.py'
+        meson_setup = [meson_py, 'setup']
+        meson_command = python_command + meson_setup + self.meson_args
+        stdo = self._run(meson_command + [self.testdir, builddir])
+        self.assertMesonCommandIs(stdo.split('\n')[0], resolved_meson_command)
+        # Symlink to meson.py
+        if is_windows():
+            # Symlinks require admin perms
+            return
+        os.chdir(str(self.src_root))
+        builddir = str(self.tmpdir / 'build3')
+        # Create a symlink to meson.py in bindir, and add it to PATH
+        bindir = (self.tmpdir / 'bin')
+        bindir.mkdir()
+        (bindir / 'meson').symlink_to(self.src_root / 'meson.py')
+        os.environ['PATH'] = str(bindir) + os.pathsep + os.environ['PATH']
+        # See if it works!
+        meson_py = 'meson'
+        meson_setup = [meson_py, 'setup']
+        meson_command = meson_setup + self.meson_args
+        stdo = self._run(meson_command + [self.testdir, builddir])
+        self.assertMesonCommandIs(stdo.split('\n')[0], resolved_meson_command)
+
+    def test_meson_installed(self):
+        # Install meson
+        prefix = self.tmpdir / 'prefix'
+        pylibdir = prefix / get_pypath()
+        bindir = prefix / get_pybindir()
+        pylibdir.mkdir(parents=True)
+        os.environ['PYTHONPATH'] = str(pylibdir)
+        os.environ['PATH'] = str(bindir) + os.pathsep + os.environ['PATH']
+        self._run(python_command + ['setup.py', 'install', '--prefix', str(prefix)])
+        self.assertTrue(pylibdir.is_dir())
+        self.assertTrue(bindir.is_dir())
+        # Run `meson`
+        os.chdir('/')
+        if is_windows():
+            resolved_meson_command = python_command + [str(bindir / 'meson.py')]
+        else:
+            resolved_meson_command = python_command + [str(bindir / 'meson')]
+            # The python configuration on appveyor does not register .py as
+            # a valid extension, so we cannot run `meson` on Windows.
+            builddir = str(self.tmpdir / 'build1')
+            meson_setup = ['meson', 'setup']
+            meson_command = meson_setup + self.meson_args
+            stdo = self._run(meson_command + [self.testdir, builddir])
+            self.assertMesonCommandIs(stdo.split('\n')[0], resolved_meson_command)
+        # Run `/path/to/meson`
+        builddir = str(self.tmpdir / 'build2')
+        if is_windows():
+            # Cannot run .py directly because of the appveyor configuration,
+            # and the script is named meson.py, not meson
+            meson_setup = python_command + [str(bindir / 'meson.py'), 'setup']
+        else:
+            meson_setup = [str(bindir / 'meson'), 'setup']
+        meson_command = meson_setup + self.meson_args
+        stdo = self._run(meson_command + [self.testdir, builddir])
+        self.assertMesonCommandIs(stdo.split('\n')[0], resolved_meson_command)
+        # Run `python3 -m mesonbuild.mesonmain`
+        resolved_meson_command = python_command + ['-m', 'mesonbuild.mesonmain']
+        builddir = str(self.tmpdir / 'build3')
+        meson_setup = ['-m', 'mesonbuild.mesonmain', 'setup']
+        meson_command = python_command + meson_setup + self.meson_args
+        stdo = self._run(meson_command + [self.testdir, builddir])
+        self.assertMesonCommandIs(stdo.split('\n')[0], resolved_meson_command)
+        if is_windows():
+            # Next part requires a shell
+            return
+        # `meson` is a wrapper to `meson.real`
+        resolved_meson_command = python_command + [str(bindir / 'meson.real')]
+        builddir = str(self.tmpdir / 'build4')
+        (bindir / 'meson').rename(bindir / 'meson.real')
+        wrapper = (bindir / 'meson')
+        with open(wrapper, 'w') as f:
+            f.write('#!/bin/sh\n\nmeson.real "$@"')
+        wrapper.chmod(0o755)
+        meson_setup = [str(wrapper), 'setup']
+        meson_command = meson_setup + self.meson_args
+        stdo = self._run(meson_command + [self.testdir, builddir])
+        self.assertMesonCommandIs(stdo.split('\n')[0], resolved_meson_command)
+
+    def test_meson_exe_windows(self):
+        raise unittest.SkipTest('NOT IMPLEMENTED')
+
+if __name__ == '__main__':
+    unittest.main(buffer=True)