Fixed #28050 -- Added template name to TemplateSyntaxError.

django/template/base.py

@@ -199,6 +199,14 @@ class Template:
         except Exception as e:
             if self.engine.debug:
                 e.template_debug = self.get_exception_info(e, e.token)
+            if (
+                isinstance(e, TemplateSyntaxError)
+                and self.origin.name != UNKNOWN_SOURCE
+                and e.args
+            ):
+                raw_message = e.args[0]
+                e.raw_error_message = raw_message
+                e.args = (f"Template: {self.origin.name}, {raw_message}", *e.args[1:])
             raise
 
     def get_exception_info(self, exception, token):

django/views/debug.py

@@ -414,7 +414,9 @@ class ExceptionReporter:
         if self.exc_type:
             c["exception_type"] = self.exc_type.__name__
         if self.exc_value:
-            c["exception_value"] = str(self.exc_value)
+            c["exception_value"] = getattr(
+                self.exc_value, "raw_error_message", self.exc_value
+            )
             if exc_notes := getattr(self.exc_value, "__notes__", None):
                 c["exception_notes"] = "\n" + "\n".join(exc_notes)
         if frames:

tests/template_tests/syntax_tests/test_basic.py

@@ -1,7 +1,8 @@
-from django.template.base import TemplateSyntaxError
+from django.template.base import Origin, Template, TemplateSyntaxError
 from django.template.context import Context
 from django.template.loader_tags import BlockContext, BlockNode
 from django.test import SimpleTestCase
+from django.views.debug import ExceptionReporter
 
 from ..utils import SilentAttrClass, SilentGetItemClass, SomeClass, setup
 
@@ -402,3 +403,29 @@ class BlockContextTests(SimpleTestCase):
             "<BlockContext: blocks=defaultdict(<class 'list'>, "
             "{'content': [<Block Node: content. Contents: []>]})>",
         )
+
+
+class TemplateNameInExceptionTests(SimpleTestCase):
+    template_error_msg = (
+        "Invalid block tag on line 1: 'endfor'. Did you forget to register or "
+        "load this tag?"
+    )
+
+    def test_template_name_in_error_message(self):
+        msg = f"Template: test.html, {self.template_error_msg}"
+        with self.assertRaisesMessage(TemplateSyntaxError, msg):
+            Template("{% endfor %}", origin=Origin("test.html"))
+
+    def test_template_name_not_in_debug_view(self):
+        try:
+            Template("{% endfor %}", origin=Origin("test.html"))
+        except TemplateSyntaxError as e:
+            reporter = ExceptionReporter(None, e.__class__, e, None)
+            traceback_data = reporter.get_traceback_data()
+            self.assertEqual(traceback_data["exception_value"], self.template_error_msg)
+
+    def test_unknown_source_template(self):
+        try:
+            Template("{% endfor %}")
+        except TemplateSyntaxError as e:
+            self.assertEqual(str(e), self.template_error_msg)