mtest: Allow filtering tests by subproject

You could always specify a list of tests to run by passing the names as
arguments to `meson test`. If there were multiple tests with that name (in the
same project or different subprojects), all of them would be run. Now you can:

1. Run all tests with the specified name from a specific subproject: `meson test subprojname:testname`
1. Run all tests defined in a specific subproject: `meson test subprojectname:`

Also forbid ':' in test names. We already forbid this elsewhere, so
should not be a big deal.

3 files changed, 53 insertions, 7 deletions

diff --git a/docs/markdown/snippets/mtest_test_list_subprojects.md b/docs/markdown/snippets/mtest_test_list_subprojects.md
new file mode 100644
index 000000000..a8dbf4c89
--- /dev/null
+++ b/docs/markdown/snippets/mtest_test_list_subprojects.md
@@ -0,0 +1,18 @@
+## `meson test` can now filter tests by subproject
+
+You could always specify a list of tests to run by passing the names as
+arguments to `meson test`. If there were multiple tests with that name (in the
+same project or different subprojects), all of them would be run. Now you can:
+
+1. Run all tests with the specified name from a specific subproject: `meson test subprojname:testname`
+1. Run all tests defined in a specific subproject: `meson test subprojectname:`
+
+As before, these can all be specified multiple times and mixed:
+
+```sh
+# Run:
+# * All tests called 'name1' or 'name2' and
+# * All tests called 'name3' in subproject 'bar' and
+# * All tests in subproject 'foo'
+$ meson test name1 name2 bar:name3 foo:
+```
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index ca1411e4a..be19af359 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -4074,8 +4074,13 @@ This will become a hard error in the future.''' % kwargs['input'], location=self
     def add_test(self, node, args, kwargs, is_base_test):
         if len(args) != 2:
             raise InterpreterException('test expects 2 arguments, {} given'.format(len(args)))
-        if not isinstance(args[0], str):
+        name = args[0]
+        if not isinstance(name, str):
             raise InterpreterException('First argument of test must be a string.')
+        if ':' in name:
+            mlog.deprecation('":" is not allowed in test name "{}", it has been replaced with "_"'.format(name),
+                             location=node)
+            name = name.replace(':', '_')
         exe = args[1]
         if not isinstance(exe, (ExecutableHolder, JarHolder, ExternalProgramHolder)):
             if isinstance(exe, mesonlib.File):
@@ -4120,14 +4125,14 @@ This will become a hard error in the future.''' % kwargs['input'], location=self
         priority = kwargs.get('priority', 0)
         if not isinstance(priority, int):
             raise InterpreterException('Keyword argument priority must be an integer.')
-        t = Test(args[0], prj, suite, exe.held_object, depends, par, cmd_args,
+        t = Test(name, prj, suite, exe.held_object, depends, par, cmd_args,
                  env, should_fail, timeout, workdir, protocol, priority)
         if is_base_test:
             self.build.tests.append(t)
-            mlog.debug('Adding test', mlog.bold(args[0], True))
+            mlog.debug('Adding test', mlog.bold(name, True))
         else:
             self.build.benchmarks.append(t)
-            mlog.debug('Adding benchmark', mlog.bold(args[0], True))
+            mlog.debug('Adding benchmark', mlog.bold(name, True))
 
     @FeatureNewKwargs('install_headers', '0.47.0', ['install_mode'])
     @permittedKwargs(permitted_kwargs['install_headers'])
diff --git a/mesonbuild/mtest.py b/mesonbuild/mtest.py
index caf403922..a5c2dda21 100644
--- a/mesonbuild/mtest.py
+++ b/mesonbuild/mtest.py
@@ -124,7 +124,9 @@ def add_arguments(parser: argparse.ArgumentParser) -> None:
     parser.add_argument('--test-args', default=[], type=split_args,
                         help='Arguments to pass to the specified test(s) or all tests')
     parser.add_argument('args', nargs='*',
-                        help='Optional list of tests to run')
+                        help='Optional list of test names to run. "testname" to run all tests with that name, '
+                        '"subprojname:testname" to specifically run "testname" from "subprojname", '
+                        '"subprojname:" to run all tests defined by "subprojname".')
 
 
 def returncode_to_status(retcode: int) -> str:
@@ -1039,6 +1041,28 @@ class TestHarness:
                 TestHarness.test_in_suites(test, self.options.include_suites)) and not
                 TestHarness.test_in_suites(test, self.options.exclude_suites))
 
+    def tests_from_args(self, tests: T.List[TestSerialisation]) -> T.Generator[TestSerialisation, None, None]:
+        '''
+        Allow specifying test names like "meson test foo1 foo2", where test('foo1', ...)
+
+        Also support specifying the subproject to run tests from like
+        "meson test subproj:" (all tests inside subproj) or "meson test subproj:foo1"
+        to run foo1 inside subproj. Coincidentally also "meson test :foo1" to
+        run all tests with that name across all subprojects, which is
+        identical to "meson test foo1"
+        '''
+        for arg in self.options.args:
+            if ':' in arg:
+                subproj, name = arg.split(':', maxsplit=1)
+            else:
+                subproj, name = '', arg
+            for t in tests:
+                if subproj and t.project_name != subproj:
+                    continue
+                if name and t.name != name:
+                    continue
+                yield t
+
     def get_tests(self) -> T.List[TestSerialisation]:
         if not self.tests:
             print('No tests defined.')
@@ -1052,9 +1076,8 @@ class TestHarness:
         else:
             tests = self.tests
 
-        # allow specifying test names like "meson test foo1 foo2", where test('foo1', ...)
         if self.options.args:
-            tests = [t for t in tests if t.name in self.options.args]
+            tests = list(self.tests_from_args(tests))
 
         if not tests:
             print('No suitable tests defined.')