Consider 'samu' when looking for ninja command

samu prints a different message when the build is a no-op, so make
assertBuildIsNoop consider that as well.

Also, if compile_commands.json cannot be found, just skip the test. This
seems reasonable since meson just produces a warning if `ninja -t compdb`
fails.

Finally, only capture stdout in run_meson_command_tests.py, since the
backend may print messages the tests don't recognize to stderr.

Fixes #3405.

mesonbuild/environment.py

@@ -120,7 +120,7 @@ def find_coverage_tools():
     return gcovr_exe, gcovr_new_rootdir, lcov_exe, genhtml_exe
 
 def detect_ninja(version='1.5', log=False):
-    for n in ['ninja', 'ninja-build']:
+    for n in ['ninja', 'ninja-build', 'samu']:
         try:
             p, found = Popen_safe([n, '--version'])[0:2]
         except (FileNotFoundError, PermissionError):

run_meson_command_tests.py

@@ -63,15 +63,14 @@ class CommandTests(unittest.TestCase):
 
     def _run(self, command, workdir=None):
         '''
-        Run a command while printing the stdout and stderr to stdout,
+        Run a command while printing the stdout, and also return a copy of it
-        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(),
+                           env=os.environ.copy(), universal_newlines=True,
-                           universal_newlines=True, cwd=workdir, timeout=60 * 5)
+                           cwd=workdir, timeout=60 * 5)
         print(p.stdout)
         if p.returncode != 0:
             raise subprocess.CalledProcessError(p.returncode, command)

run_unittests.py

@@ -921,11 +921,11 @@ class BasePlatformTests(unittest.TestCase):
         # Misc stuff
         self.orig_env = os.environ.copy()
         if self.backend is Backend.ninja:
-            self.no_rebuild_stdout = 'ninja: no work to do.'
+            self.no_rebuild_stdout = ['ninja: no work to do.', 'samu: nothing to do']
         else:
             # VS doesn't have a stable output when no changes are done
             # XCode backend is untested with unit tests, help welcome!
-            self.no_rebuild_stdout = 'UNKNOWN BACKEND {!r}'.format(self.backend.name)
+            self.no_rebuild_stdout = ['UNKNOWN BACKEND {!r}'.format(self.backend.name)]
 
         self.builddirs = []
         self.new_builddir()
@@ -1076,8 +1076,11 @@ class BasePlatformTests(unittest.TestCase):
     def get_compdb(self):
         if self.backend is not Backend.ninja:
             raise unittest.SkipTest('Compiler db not available with {} backend'.format(self.backend.name))
+        try:
             with open(os.path.join(self.builddir, 'compile_commands.json')) as ifile:
                 contents = json.load(ifile)
+        except FileNotFoundError:
+            raise unittest.SkipTest('Compiler db not found')
         # If Ninja is using .rsp files, generate them, read their contents, and
         # replace it as the command for all compile commands in the parsed json.
         if len(contents) > 0 and contents[0]['command'].endswith('.rsp'):
@@ -1131,7 +1134,7 @@ class BasePlatformTests(unittest.TestCase):
     def assertBuildIsNoop(self):
         ret = self.build()
         if self.backend is Backend.ninja:
-            self.assertEqual(ret.split('\n')[-2], self.no_rebuild_stdout)
+            self.assertIn(ret.split('\n')[-2], self.no_rebuild_stdout)
         elif self.backend is Backend.vs:
             # Ensure that some target said that no rebuild was done
             self.assertIn('CustomBuild:\n  All outputs are up-to-date.', ret)