pythongh-109162: Refactor Regrtest.action_run_tests()

Refator Regrtest class:

* Rename finalize() finalize_tests().
* Pass tracer to run_test() and finalize_tests(). Remove Regrtest.tracer.
* run_test() does less things: move code to its caller.

Lib/test/libregrtest/main.py

@@ -111,9 +111,6 @@ def __init__(self, ns: Namespace):
         # used by --slow
         self.test_times = []
 
-        # used by --coverage, trace.Trace instance
-        self.tracer = None
-
         # used to display the progress bar "[ 3/100]"
         self.start_time = time.perf_counter()
         self.test_count_text = ''
@@ -443,28 +440,18 @@ def display_result(self):
             print(count(len(self.run_no_tests), "test"), "run no tests:")
             printlist(self.run_no_tests)
 
-    def run_test(self, test_index, test_name, previous_test, save_modules):
-        text = test_name
-        if previous_test:
-            text = '%s -- %s' % (text, previous_test)
-        self.display_progress(test_index, text)
-
-        if self.tracer:
+    def run_test(self, test_name: str, runtests: RunTests, tracer):
+        if tracer is not None:
             # If we're tracing code coverage, then we don't exit with status
             # if on a false return value from main.
-            cmd = ('result = runtest(self.ns, test_name); '
-                   'self.accumulate_result(result)')
+            cmd = ('result = runtest(self.ns, test_name)')
             ns = dict(locals())
-            self.tracer.runctx(cmd, globals=globals(), locals=ns)
+            tracer.runctx(cmd, globals=globals(), locals=ns)
             result = ns['result']
         else:
             result = runtest(self.ns, test_name)
-            self.accumulate_result(result)
 
-        # Unload the newly imported modules (best effort finalization)
-        for module in sys.modules.keys():
-            if module not in save_modules and module.startswith("test."):
-                support.unload(module)
+        self.accumulate_result(result)
 
         return result
 
@@ -477,7 +464,9 @@ def run_tests_sequentially(self, runtests):
 
         if coverage:
             import trace
-            self.tracer = trace.Trace(trace=False, count=True)
+            tracer = trace.Trace(trace=False, count=True)
+        else:
+            tracer = None
 
         save_modules = sys.modules.keys()
 
@@ -491,8 +480,17 @@ def run_tests_sequentially(self, runtests):
         for test_index, test_name in enumerate(tests_iter, 1):
             start_time = time.perf_counter()
 
-            result = self.run_test(test_index, test_name,
-                                   previous_test, save_modules)
+            text = test_name
+            if previous_test:
+                text = '%s -- %s' % (text, previous_test)
+            self.display_progress(test_index, text)
+
+            result = self.run_test(test_name, runtests, tracer)
+
+            # Unload the newly imported modules (best effort finalization)
+            for module in sys.modules.keys():
+                if module not in save_modules and module.startswith("test."):
+                    support.unload(module)
 
             if result.must_stop(fail_fast, fail_env_changed):
                 break
@@ -508,6 +506,8 @@ def run_tests_sequentially(self, runtests):
         if previous_test:
             print(previous_test)
 
+        return tracer
+
     def display_header(self):
         # Print basic platform information
         print("==", platform.python_implementation(), *sys.version.split())
@@ -604,45 +604,28 @@ def set_tests(self, runtests: RunTests):
             self.test_count_text = '/{}'.format(len(self.tests))
             self.test_count_width = len(self.test_count_text) - 1
 
-    def run_tests(self):
-        # For a partial run, we do not need to clutter the output.
-        if (self.want_header
-            or not(self.ns.pgo or self.ns.quiet or self.ns.single
-                   or self.tests or self.ns.args)):
-            self.display_header()
-
-        if self.ns.huntrleaks:
-            warmup, repetitions, _ = self.ns.huntrleaks
-            if warmup < 3:
-                msg = ("WARNING: Running tests with --huntrleaks/-R and less than "
-                        "3 warmup repetitions can give false positives!")
-                print(msg, file=sys.stdout, flush=True)
-
-        if self.randomize:
-            print("Using random seed", self.random_seed)
-
-        tests = self.selected
-        runtests = RunTests(tuple(tests), forever=self.forever)
+    def run_tests(self, runtests: RunTests):
         self.first_runtests = runtests
         self.set_tests(runtests)
         if self.ns.use_mp:
             self._run_tests_mp(runtests)
+            tracer = None
         else:
-            self.run_tests_sequentially(runtests)
-        return runtests
+            tracer = self.run_tests_sequentially(runtests)
+        return tracer
 
-    def finalize(self):
+    def finalize_tests(self, tracer):
         if self.next_single_filename:
             if self.next_single_test:
                 with open(self.next_single_filename, 'w') as fp:
                     fp.write(self.next_single_test + '\n')
             else:
                 os.unlink(self.next_single_filename)
 
-        if self.tracer:
-            r = self.tracer.results()
-            r.write_results(show_missing=True, summary=True,
-                            coverdir=self.ns.coverdir)
+        if tracer is not None:
+            results = tracer.results()
+            results.write_results(show_missing=True, summary=True,
+                                  coverdir=self.ns.coverdir)
 
         if self.ns.runleaks:
             os.system("leaks %d" % os.getpid())
@@ -858,15 +841,32 @@ def get_exitcode(self):
         return exitcode
 
     def action_run_tests(self):
-        runtests = self.run_tests()
+        if self.ns.huntrleaks:
+            warmup, repetitions, _ = self.ns.huntrleaks
+            if warmup < 3:
+                msg = ("WARNING: Running tests with --huntrleaks/-R and less than "
+                        "3 warmup repetitions can give false positives!")
+                print(msg, file=sys.stdout, flush=True)
+
+        # For a partial run, we do not need to clutter the output.
+        if (self.want_header
+            or not(self.ns.pgo or self.ns.quiet or self.ns.single
+                   or self.tests or self.ns.args)):
+            self.display_header()
+
+        if self.randomize:
+            print("Using random seed", self.random_seed)
+
+        runtests = RunTests(tuple(self.selected), forever=self.forever)
+        tracer = self.run_tests(runtests)
         self.display_result()
 
         need_rerun = self.need_rerun
         if self.ns.rerun and need_rerun:
             self.rerun_failed_tests(need_rerun, runtests)
 
         self.display_summary()
-        self.finalize()
+        self.finalize_tests(tracer)
 
     def _main(self):
         if self.is_worker():