gh-105724: Add location information to assert errors (GH-105935)

Lib/test/test_compile.py

@@ -1315,18 +1315,18 @@ def test_multiline_assert(self):
         snippet = textwrap.dedent("""\
             assert (a > 0 and
                     bb > 0 and
-                    ccc == 4), "error msg"
+                    ccc == 1000000), "error msg"
             """)
         compiled_code, _ = self.check_positions_against_ast(snippet)
         self.assertOpcodeSourcePositionIs(compiled_code, 'LOAD_ASSERTION_ERROR',
-            line=1, end_line=3, column=0, end_column=30, occurrence=1)
+            line=1, end_line=3, column=0, end_column=36, occurrence=1)
         #  The "error msg":
         self.assertOpcodeSourcePositionIs(compiled_code, 'LOAD_CONST',
-            line=3, end_line=3, column=19, end_column=30, occurrence=4)
+            line=3, end_line=3, column=25, end_column=36, occurrence=4)
         self.assertOpcodeSourcePositionIs(compiled_code, 'CALL',
-            line=1, end_line=3, column=0, end_column=30, occurrence=1)
+            line=1, end_line=3, column=0, end_column=36, occurrence=1)
         self.assertOpcodeSourcePositionIs(compiled_code, 'RAISE_VARARGS',
-            line=1, end_line=3, column=0, end_column=30, occurrence=1)
+            line=1, end_line=3, column=8, end_column=22, occurrence=1)
 
     def test_multiline_generator_expression(self):
         snippet = textwrap.dedent("""\

Lib/test/test_exceptions.py

@@ -1931,6 +1931,123 @@ def test_copy_pickle(self):
                 self.assertEqual(exc.name, orig.name)
                 self.assertEqual(exc.path, orig.path)
 
+
+class AssertionErrorTests(unittest.TestCase):
+    def tearDown(self):
+        unlink(TESTFN)
+
+    def write_source(self, source):
+        with open(TESTFN, 'w') as testfile:
+            testfile.write(dedent(source))
+        _rc, _out, err = script_helper.assert_python_failure('-Wd', '-X', 'utf8', TESTFN)
+        return err.decode('utf-8').splitlines()
+
+    def test_assertion_error_location(self):
+        cases = [
+            ('assert None',
+                [
+                    '    assert None',
+                    '           ^^^^',
+                    'AssertionError',
+                ],
+            ),
+            ('assert 0',
+                [
+                    '    assert 0',
+                    '           ^',
+                    'AssertionError',
+                ],
+            ),
+            ('assert 1 > 2',
+                [
+                    '    assert 1 > 2',
+                    '           ^^^^^',
+                    'AssertionError',
+                ],
+            ),
+            ('assert 1 > 2 and 3 > 2',
+                [
+                    '    assert 1 > 2 and 3 > 2',
+                    '           ^^^^^^^^^^^^^^^',
+                    'AssertionError',
+                ],
+            ),
+            ('assert 1 > 2, "message"',
+                [
+                    '    assert 1 > 2, "message"',
+                    '           ^^^^^',
+                    'AssertionError: message',
+                ],
+            ),
+
+            # Multiline:
+            ("""
+             assert (
+                 1 > 2)
+             """,
+                [
+                    '    1 > 2)',
+                    '    ^^^^^',
+                    'AssertionError',
+                ],
+            ),
+            ("""
+             assert (
+                 1 > 2), "Message"
+             """,
+                [
+                    '    1 > 2), "Message"',
+                    '    ^^^^^',
+                    'AssertionError: Message',
+                ],
+            ),
+            ("""
+             assert (
+                 1 > 2), \\
+                 "Message"
+             """,
+                [
+                    '    1 > 2), \\',
+                    '    ^^^^^',
+                    'AssertionError: Message',
+                ],
+            ),
+        ]
+        for source, expected in cases:
+            with self.subTest(source):
+                result = self.write_source(source)
+                self.assertEqual(result[-3:], expected)
+
+    def test_multiline_not_highlighted(self):
+        cases = [
+            ("""
+             assert (
+                 1 > 2
+             )
+             """,
+                [
+                    '    1 > 2',
+                    'AssertionError',
+                ],
+            ),
+            ("""
+             assert (
+                 1 < 2 and
+                 3 > 4
+             )
+             """,
+                [
+                    '    1 < 2 and',
+                    'AssertionError',
+                ],
+            ),
+        ]
+        for source, expected in cases:
+            with self.subTest(source):
+                result = self.write_source(source)
+                self.assertEqual(result[-2:], expected)
+
+
 class SyntaxErrorTests(unittest.TestCase):
     def test_range_of_offsets(self):
         cases = [

Misc/NEWS.d/next/Core and Builtins/2023-06-20-10-53-17.gh-issue-105724.d23L4M.rst

@@ -0,0 +1 @@
+Improve ``assert`` error messages by providing exact error range.

Python/compile.c

@@ -3952,7 +3952,7 @@ compiler_assert(struct compiler *c, stmt_ty s)
         VISIT(c, expr, s->v.Assert.msg);
         ADDOP_I(c, LOC(s), CALL, 0);
     }
-    ADDOP_I(c, LOC(s), RAISE_VARARGS, 1);
+    ADDOP_I(c, LOC(s->v.Assert.test), RAISE_VARARGS, 1);
 
     USE_LABEL(c, end);
     return SUCCESS;