mtest: Fix test selection implementation

Omitting test()'s `suite` kwarg used to default to `test.suite==['']`
because of how stringlistify() works. That had inconsistent behavior
with `suite: []` which makes `test.suite==[]`. That changed when porting
to typed_kwarg (#8855), which made the default `test.suite==[]`.

Change `suite: []`, and missing kwarg, back to `test.suite==['']` which
was the original intention. It has impact on `meson test --suite`
selection, an empty `test.suite` list means that test is never going to
be selected when `--suite` is used, even when we want all tests from a
given subproject.

It was also unclear what `--suite foo` means. Is `foo` a suite or a
project name? It can now be either, it selects all tests from project
`foo` as well as all tests from any project in suite `foo`.

1 files changed, 16 insertions, 23 deletions

diff --git a/mesonbuild/mtest.py b/mesonbuild/mtest.py
index c0a22a248..337b70747 100644
--- a/mesonbuild/mtest.py
+++ b/mesonbuild/mtest.py
@@ -1939,29 +1939,22 @@ class TestHarness:
             for prjst in test.suite:
                 (prj, st) = TestHarness.split_suite_string(prjst)
 
-                # the SUITE can be passed as
-                #     suite_name
-                # or
-                #     project_name:suite_name
-                # so we need to select only the test belonging to project_name
-
-                # this if handle the first case (i.e., SUITE == suite_name)
-
-                # in this way we can run tests belonging to different
-                # (sub)projects which share the same suite_name
-                if not st_match and st == prj_match:
-                    return True
-
-                # these two conditions are needed to handle the second option
-                # i.e., SUITE == project_name:suite_name
-
-                # in this way we select the only the tests of
-                # project_name with suite_name
-                if prj_match and prj != prj_match:
-                    continue
-                if st_match and st != st_match:
-                    continue
-                return True
+                # The SUITE can be passed as
+                # - `name` - We select tests belonging to (sub)project OR suite
+                #   with the given name.
+                # - `:suite_name` - We select tests belonging to any (sub)projects
+                #   and in suite_name.
+                # - `project_name:suite_name` - We select tests belonging
+                #   to project_name and in suite_name.
+                if not st_match:
+                    if prj_match in {prj, st}:
+                        return True
+                elif not prj_match:
+                    if st == st_match:
+                        return True
+                else:
+                    if prj == prj_match and st == st_match:
+                        return True
         return False
 
     def test_suitable(self, test: TestSerialisation) -> bool: