gh-106368: Argument clinic: add tests for more failure paths

Lib/test/test_clinic.py

@@ -45,6 +45,7 @@ def _expect_failure(tc, parser, code, errmsg, *, filename=None, lineno=None):
         tc.assertEqual(cm.exception.filename, filename)
     if lineno is not None:
         tc.assertEqual(cm.exception.lineno, lineno)
+    return cm.exception
 
 
 class ClinicWholeFileTest(TestCase):
@@ -222,6 +223,15 @@ def test_directive_output_print(self):
             last_line.startswith("/*[clinic end generated code: output=")
         )
 
+    def test_directive_wrong_arg_number(self):
+        raw = dedent("""
+            /*[clinic input]
+            preserve foo bar baz eggs spam ham mushrooms
+            [clinic start generated code]*/
+        """)
+        err = "takes 1 positional argument but 8 were given"
+        self.expect_failure(raw, err)
+
     def test_unknown_destination_command(self):
         raw = """
             /*[clinic input]
@@ -600,6 +610,31 @@ def test_directive_output_invalid_command(self):
         self.expect_failure(block, err, lineno=2)
 
 
+class ParseFileUnitTest(TestCase):
+    def expect_parsing_failure(
+        self, *, filename, expected_error, verify=True, output=None
+    ):
+        errmsg = re.escape(dedent(expected_error).strip())
+        with self.assertRaisesRegex(clinic.ClinicError, errmsg):
+            clinic.parse_file(filename)
+
+    def test_parse_file_no_extension(self) -> None:
+        self.expect_parsing_failure(
+            filename="foo",
+            expected_error="Can't extract file type for file 'foo'"
+        )
+
+    def test_parse_file_strange_extension(self) -> None:
+        filenames_to_errors = {
+            "foo.rs": "Can't identify file type for file 'foo.rs'",
+            "foo.hs": "Can't identify file type for file 'foo.hs'",
+            "foo.js": "Can't identify file type for file 'foo.js'",
+        }
+        for filename, errmsg in filenames_to_errors.items():
+            with self.subTest(filename=filename):
+                self.expect_parsing_failure(filename=filename, expected_error=errmsg)
+
+
 class ClinicGroupPermuterTest(TestCase):
     def _test(self, l, m, r, output):
         computed = clinic.permute_optional_groups(l, m, r)
@@ -794,8 +829,8 @@ def parse_function(self, text, signatures_in_block=2, function_index=1):
         return s[function_index]
 
     def expect_failure(self, block, err, *, filename=None, lineno=None):
-        _expect_failure(self, self.parse_function, block, err,
-                        filename=filename, lineno=lineno)
+        return _expect_failure(self, self.parse_function, block, err,
+                               filename=filename, lineno=lineno)
 
     def checkDocstring(self, fn, expected):
         self.assertTrue(hasattr(fn, "docstring"))
@@ -877,6 +912,41 @@ def test_param_default_expr_named_constant(self):
         """
         self.expect_failure(block, err, lineno=2)
 
+    def test_param_with_bizarre_default_fails_correctly(self):
+        template = """
+            module os
+            os.access
+                follow_symlinks: int = {default}
+        """
+        err = "Unsupported expression as default value"
+        for bad_default_value in (
+            "{1, 2, 3}",
+            "3 if bool() else 4",
+            "[x for x in range(42)]"
+        ):
+            with self.subTest(bad_default=bad_default_value):
+                block = template.format(default=bad_default_value)
+                self.expect_failure(block, err, lineno=2)
+
+    def test_unspecified_not_allowed_as_default_value(self):
+        block = """
+            module os
+            os.access
+                follow_symlinks: int(c_default='MAXSIZE') = unspecified
+        """
+        err = "'unspecified' is not a legal default value!"
+        exc = self.expect_failure(block, err, lineno=2)
+        self.assertNotIn('Malformed expression given as default value', str(exc))
+
+    def test_malformed_expression_as_default_value(self):
+        block = """
+            module os
+            os.access
+                follow_symlinks: int(c_default='MAXSIZE') = 1/0
+        """
+        err = "Malformed expression given as default value"
+        self.expect_failure(block, err, lineno=2)
+
     def test_param_default_expr_binop(self):
         err = (
             "When you specify an expression ('a + b') as your default value, "
@@ -1041,6 +1111,28 @@ def test_c_name(self):
         """)
         self.assertEqual("os_stat_fn", function.c_basename)
 
+    def test_base_invalid_syntax(self):
+        block = """
+            module os
+            os.stat
+                invalid syntax: int = 42
+        """
+        err = dedent(r"""
+            Function 'stat' has an invalid parameter declaration:
+            \s+'invalid syntax: int = 42'
+        """).strip()
+        with self.assertRaisesRegex(clinic.ClinicError, err):
+            self.parse_function(block)
+
+    def test_param_default_invalid_syntax(self):
+        block = """
+            module os
+            os.stat
+                x: int = invalid syntax
+        """
+        err = r"Syntax error: 'x = invalid syntax\n'"
+        self.expect_failure(block, err, lineno=2)
+
     def test_cloning_nonexistent_function_correctly_fails(self):
         block = """
             cloned = fooooooooooooooooo
@@ -1414,18 +1506,6 @@ def test_parameters_required_after_star(self):
             with self.subTest(block=block):
                 self.expect_failure(block, err)
 
-    def test_parameters_required_after_depr_star(self):
-        dataset = (
-            "module foo\nfoo.bar\n  * [from 3.14]",
-            "module foo\nfoo.bar\n  * [from 3.14]\nDocstring here.",
-            "module foo\nfoo.bar\n  this: int\n  * [from 3.14]",
-            "module foo\nfoo.bar\n  this: int\n  * [from 3.14]\nDocstring.",
-        )
-        err = "Function 'foo.bar' specifies '* [from 3.14]' without any parameters afterwards."
-        for block in dataset:
-            with self.subTest(block=block):
-                self.expect_failure(block, err)
-
     def test_depr_star_invalid_format_1(self):
         block = """
             module foo

Tools/clinic/clinic.py

@@ -5207,13 +5207,14 @@ def bad_node(self, node: ast.AST) -> None:
                     # but at least make an attempt at ensuring it's a valid expression.
                     try:
                         value = eval(default)
-                        if value is unspecified:
-                            fail("'unspecified' is not a legal default value!")
                     except NameError:
                         pass # probably a named constant
                     except Exception as e:
                         fail("Malformed expression given as default value "
                              f"{default!r} caused {e!r}")
+                    else:
+                        if value is unspecified:
+                            fail("'unspecified' is not a legal default value!")
                 if bad:
                     fail(f"Unsupported expression as default value: {default!r}")