Improve sanity import test messaging. (#26782)

test/runner/importer.py

@@ -23,7 +23,8 @@ def main():
             message = str(ex)
             results = list(reversed(traceback.extract_tb(exc_tb)))
             source = None
-            line = None
+            line = 0
+            offset = 0
 
             for result in results:
                 if result[0].startswith(base_dir):
@@ -32,11 +33,24 @@ def main():
                     break
 
             if not source:
+                # If none of our source files are found in the traceback, report the file we were testing.
+                # I haven't been able to come up with a test case that encounters this issue yet.
                 source = path
-                line = 0
                 message += ' (in %s:%d)' % (results[-1][0], results[-1][1])
-
-            error = '%s:%d:0: %s: %s' % (source, line, exc_type.__name__, message)
+            elif isinstance(ex, SyntaxError):
+                if ex.filename.endswith(path):  # pylint: disable=locally-disabled, no-member
+                    # A SyntaxError in the source we're importing will have the correct path, line and offset.
+                    # However, the traceback will report the path to this importer.py script instead.
+                    # We'll use the details from the SyntaxError in this case, as it's more accurate.
+                    source = path
+                    line = ex.lineno  # pylint: disable=locally-disabled, no-member
+                    offset = ex.offset  # pylint: disable=locally-disabled, no-member
+                    message = str(ex)
+
+                    # Hack to remove the filename and line number from the message, if present.
+                    message = message.replace(' (%s, line %d)' % (os.path.basename(path), line), '')
+
+            error = '%s:%d:%d: %s: %s' % (source, line, offset, exc_type.__name__, message)
 
             if error not in messages:
                 messages.add(error)