tests/run-tests.py: Use normal discovery if tests dir passed explicitly.

Scan the --test-dirs argument for the main tests directory being
passed and if so do the same thing as if running from within that
main test directory.

In practice this makes the following (which used to counterintuitively
try and fail to run the .py files in the tests/ directory itself)

 >python micropython/tests/run-tests.py -d micropython/tests

do the same thing as

 >cd micropython/tests
 >python ./run-tests.py

which is logical and convenient.

Signed-off-by: stijn <stijn@ignitron.net>

Author: stinos

tests/run-tests.py

@@ -1222,7 +1222,19 @@ def main():
         if args.platform == "webassembly":
             test_extensions += ("*.js", "*.mjs")
 
-        if args.test_dirs is None:
+        all_test_dirs = []
+        main_tests_dir_in_args = None
+        if args.test_dirs is not None:
+            # Run tests from given directories though if user explicitly passes this directory as argument
+            # still do the normal test discovery to be consistent with running from within this directory.
+            main_tests_dir = os.path.realpath(base_path())
+            for test_dir in args.test_dirs:
+                if os.path.realpath(test_dir) == main_tests_dir:
+                    main_tests_dir_in_args = test_dir
+                else:
+                    all_test_dirs.append(test_dir)
+
+        if args.test_dirs is None or main_tests_dir_in_args is not None:
             test_dirs = (
                 "basics",
                 "micropython",
@@ -1246,13 +1258,18 @@ def main():
                 test_dirs += ("import",)
                 if args.build != "minimal":
                     test_dirs += ("cmdline", "io")
-        else:
-            # run tests from these directories
-            test_dirs = args.test_dirs
+
+            all_test_dirs.extend(
+                test_dir
+                if main_tests_dir_in_args is None
+                else os.path.join(main_tests_dir_in_args, test_dir)
+                for test_dir in test_dirs
+            )
+
         tests = sorted(
             test_file
             for test_files in (
-                glob(os.path.join(dir, ext)) for dir in test_dirs for ext in test_extensions
+                glob(os.path.join(dir, ext)) for dir in all_test_dirs for ext in test_extensions
             )
             for test_file in test_files
         )