mtest: fix rebuilding all before running tests

If an explicit list of targets is passed on the CLI, then that is passed
to rebuild_deps. If not, we pass every loaded test to rebuild_deps
instead. This means we cannot distinguish between "trying to run all
tests" and "trying to run specific tests". We then load all the deps for
all tests, and try to build them all as explicit arguments to the
underlying ninja.

This is usually papered over by people running `ninja test`, which
depends on "all" anyway as a prerequisite for invoking the underlying
`meson test --no-rebuild --print-errorlogs`, however, instead running
`meson setup builddir && meson test -C builddir` with under-specified
test deps would actually build a handful of deps and not anything else,
then fail.

Instead, pass no tests to rebuild_deps, so that we iterate over nothing
and add no explicit targets. Hence, meson rebuilds the default "all"
rule.

mesonbuild/mtest.py

@@ -1666,9 +1666,10 @@ def doit(self) -> int:
             raise RuntimeError('Test harness object can only be used once.')
         self.is_run = True
         tests = self.get_tests()
+        rebuild_only_tests = tests if self.options.args else []
         if not tests:
             return 0
-        if not self.options.no_rebuild and not rebuild_deps(self.options.wd, tests):
+        if not self.options.no_rebuild and not rebuild_deps(self.options.wd, rebuild_only_tests):
             # We return 125 here in case the build failed.
             # The reason is that exit code 125 tells `git bisect run` that the current
             # commit should be skipped.  Thus users can directly use `meson test` to

test cases/unit/106 underspecified mtest/main.c

@@ -0,0 +1 @@
+int main(void) { return 0 ; }

test cases/unit/106 underspecified mtest/meson.build

@@ -0,0 +1,8 @@
+project('underspecified deps', 'c')
+
+runner = find_program('runner.py')
+exe1 = executable('main1', 'main.c')
+exe2 = executable('main2', 'main.c')
+
+test('runner-with-exedep', runner, args: exe1)
+test('runner-without-dep', runner, args: exe2.full_path())

test cases/unit/106 underspecified mtest/runner.py

@@ -0,0 +1,5 @@
+#!/usr/bin/env python3
+
+import sys, subprocess
+
+subprocess.run(sys.argv[1:], check=True)

unittests/platformagnostictests.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import os
+import subprocess
 import tempfile
 from unittest import skipIf
 
@@ -83,3 +84,12 @@ def test_debug_function_outputs_to_meson_log(self):
         mesonlog = os.path.join(self.builddir, 'meson-logs/meson-log.txt')
         with open(mesonlog, mode='r', encoding='utf-8') as file:
             self.assertIn(log_msg, file.read())
+
+    def test_mtest_rebuild_deps(self):
+        testdir = os.path.join(self.unit_test_dir, '106 underspecified mtest')
+        self.init(testdir)
+
+        self._run(self.mtest_command)
+        self.clean()
+
+        self._run(self.mtest_command + ['runner-with-exedep'])