test: add more tests of run_python_file

The tests in test_process run the exception handling in execfile.py, but
only under coverage, so metacov can't see it.  These smaller tests
exercise the code without coverage on top.

Author: nedbat

coverage/execfile.py

@@ -220,8 +220,7 @@ def run(self):
 
             # Call the excepthook.
             try:
-                if hasattr(err, "__traceback__"):
-                    err.__traceback__ = err.__traceback__.tb_next
+                err.__traceback__ = err.__traceback__.tb_next
                 sys.excepthook(typ, err, tb.tb_next)
             except SystemExit:                      # pylint: disable=try-except-raise
                 raise
@@ -231,8 +230,7 @@ def run(self):
                 sys.stderr.write("Error in sys.excepthook:\n")
                 typ2, err2, tb2 = sys.exc_info()
                 err2.__suppress_context__ = True
-                if hasattr(err2, "__traceback__"):
-                    err2.__traceback__ = err2.__traceback__.tb_next
+                err2.__traceback__ = err2.__traceback__.tb_next
                 sys.__excepthook__(typ2, err2, tb2.tb_next)
                 sys.stderr.write("\nOriginal exception was:\n")
                 raise ExceptionDuringRun(typ, err, tb.tb_next) from exc

tests/test_execfile.py

@@ -14,7 +14,7 @@
 import pytest
 
 from coverage import env
-from coverage.exceptions import NoCode, NoSource
+from coverage.exceptions import NoCode, NoSource, ExceptionDuringRun
 from coverage.execfile import run_python_file, run_python_module
 from coverage.files import python_reported_file
 
@@ -102,6 +102,91 @@ def test_directory_without_main(self):
         with pytest.raises(NoSource, match="Can't find '__main__' module in 'without_main'"):
             run_python_file(["without_main"])
 
+    def test_code_throws(self):
+        self.make_file("throw.py", """\
+            class MyException(Exception):
+                pass
+
+            def f1():
+                print("about to raise..")
+                raise MyException("hey!")
+
+            def f2():
+                f1()
+
+            f2()
+            """)
+
+        with pytest.raises(SystemExit) as exc_info:
+            run_python_file(["throw.py"])
+        assert exc_info.value.args == (1,)
+        assert self.stdout() == "about to raise..\n"
+        assert self.stderr() == ""
+
+    def test_code_exits(self):
+        self.make_file("exit.py", """\
+            import sys
+            def f1():
+                print("about to exit..")
+                sys.exit(17)
+
+            def f2():
+                f1()
+
+            f2()
+            """)
+
+        with pytest.raises(SystemExit) as exc_info:
+            run_python_file(["exit.py"])
+        assert exc_info.value.args == (17,)
+        assert self.stdout() == "about to exit..\n"
+        assert self.stderr() == ""
+
+    @pytest.mark.skipif(not env.CPYTHON,
+        reason="non-CPython handles excepthook exits differently, punt for now."
+    )
+    def test_excepthook_exit(self):
+        self.make_file("excepthook_exit.py", """\
+            import sys
+
+            def excepthook(*args):
+                print('in excepthook')
+                sys.exit(0)
+
+            sys.excepthook = excepthook
+
+            raise RuntimeError('Error Outside')
+            """)
+        with pytest.raises(SystemExit):
+            run_python_file(["excepthook_exit.py"])
+        cov_out = self.stdout()
+        assert cov_out == "in excepthook\n"
+
+    @pytest.mark.skipif(env.PYPY, reason="PyPy handles excepthook throws differently.")
+    def test_excepthook_throw(self):
+        self.make_file("excepthook_throw.py", """\
+            import sys
+
+            def excepthook(*args):
+                # Write this message to stderr so that we don't have to deal
+                # with interleaved stdout/stderr comparisons in the assertions
+                # in the test.
+                sys.stderr.write('in excepthook\\n')
+                raise RuntimeError('Error Inside')
+
+            sys.excepthook = excepthook
+
+            raise RuntimeError('Error Outside')
+            """)
+        with pytest.raises(ExceptionDuringRun) as exc_info:
+            run_python_file(["excepthook_throw.py"])
+        # The ExceptionDuringRun exception has the RuntimeError as its argument.
+        assert exc_info.value.args[1].args[0] == "Error Outside"
+        stderr = self.stderr()
+        assert "in excepthook\n" in stderr
+        assert "Error in sys.excepthook:\n" in stderr
+        assert "RuntimeError: Error Inside" in stderr
+
 
 class RunPycFileTest(CoverageTest):
     """Test cases for `run_python_file`."""

tests/test_process.py

@@ -468,8 +468,11 @@ def test_running_missing_file(self):
 
     def test_code_throws(self):
         self.make_file("throw.py", """\
+            class MyException(Exception):
+                pass
+
             def f1():
-                raise Exception("hey!")
+                raise MyException("hey!")
 
             def f2():
                 f1()
@@ -488,9 +491,9 @@ def f2():
 
         # But also make sure that the output is what we expect.
         path = python_reported_file('throw.py')
-        msg = f'File "{re.escape(path)}", line 5,? in f2'
+        msg = f'File "{re.escape(path)}", line 8, in f2'
         assert re.search(msg, out)
-        assert 'raise Exception("hey!")' in out
+        assert 'raise MyException("hey!")' in out
         assert status == 1
 
     def test_code_exits(self):
@@ -1121,7 +1124,7 @@ def excepthook(*args):
         assert cov_st == py_st
         assert cov_st == 0
 
-        assert "in excepthook" in py_out
+        assert py_out == "in excepthook\n"
         assert cov_out == py_out
 
     @pytest.mark.skipif(env.PYPY, reason="PyPy handles excepthook throws differently.")