Fixed wrong error indentation for subclass in union (pytorch-lightning#17254).

Author: mauvilsa

CHANGELOG.rst

@@ -19,6 +19,8 @@ Fixed
 ^^^^^
 - `str` parameter in subclass incorrectly parsed as dict with implicit `null`
   value (`#262 <https://github.com/omni-us/jsonargparse/issues/262>`__).
+- Wrong error indentation for subclass in union (`pytorch-lightning#17254
+  <https://github.com/Lightning-AI/lightning/issues/17254>`__).
 
 Changed
 ^^^^^^^

jsonargparse/typehints.py

@@ -535,7 +535,8 @@ def raise_unexpected_value(message: str, val: Any = inspect._empty, exception: O
 
 
 def raise_union_unexpected_value(uniontype, val: Any, exceptions: List[Exception]) -> NoReturn:
-    errors = indent_text('- ' + '\n- '.join(map(str, exceptions)))
+    str_exceptions = [indent_text(str(e), first_line=False) for e in exceptions]
+    errors = indent_text('- ' + '\n- '.join(str_exceptions))
     errors = errors.replace(f'. Got value: {val}', '').replace(f' {val} ', ' ')
     subtypes = uniontype.__args__
     raise ValueError(
@@ -770,7 +771,7 @@ def adapt_typehints(
         val = subclass_spec_as_namespace(val, prev_val)
         if not is_subclass_spec(val):
             raise_unexpected_value(
-                f'Not a valid {typehint.__name__}. Got value: {val_input}\n'
+                f'Not a valid subclass of {typehint.__name__}. Got value: {val_input}\n'
                 'Subclass types expect one of:\n'
                 '- a class path (str)\n'
                 '- a dict with class_path entry\n'
@@ -785,8 +786,8 @@ def adapt_typehints(
             val = adapt_class_type(val, serialize, instantiate_classes, sub_add_kwargs, prev_val=prev_val)
         except (ImportError, AttributeError, AssertionError, ArgumentError) as ex:
             class_path = val if isinstance(val, str) else val['class_path']
-            error = indent_text(f'\n- {ex}')
-            raise_unexpected_value(f'Problem with given class_path {class_path!r}:{error}', exception=ex)
+            error = indent_text(str(ex))
+            raise_unexpected_value(f'Problem with given class_path {class_path!r}:\n{error}', exception=ex)
 
     return val
 

jsonargparse/util.py

@@ -333,8 +333,13 @@ def iter_to_set_str(val, sep=','):
     return '{'+sep.join(str(x) for x in val)+'}'
 
 
-def indent_text(text: str) -> str:
-    return textwrap.indent(text, '  ')
+def indent_text(text: str, first_line: bool = True) -> str:
+    if first_line:
+        return textwrap.indent(text, '  ')
+    lines = text.splitlines()
+    if len(lines) == 1:
+        return text
+    return lines[0] + os.linesep + textwrap.indent(os.linesep.join(lines[1:]), '  ')
 
 
 def get_private_kwargs(data, **kwargs):

jsonargparse_tests/test_signatures.py

@@ -1193,7 +1193,7 @@ def __init__(self, val: Optional[Union[int, dict]] = None):
             with redirect_stderr(err), self.assertRaises(SystemExit):
                 parser.parse_args(['--cls=Class', '--cls.init_args.val=abc'])
             expected = textwrap.dedent('''
-            - Parser key "val":
+            Parser key "val":
               Does not validate against any of the Union subtypes
               Subtypes: (<class 'int'>, <class 'dict'>, <class 'NoneType'>)
               Errors:
@@ -1207,6 +1207,34 @@ def __init__(self, val: Optional[Union[int, dict]] = None):
             self.assertIn(expected, err.getvalue())
 
 
+    def test_subclass_in_union_error_message_indentation(self):
+        class Class:
+            def __init__(self, val: int):
+                pass
+
+        with mock_module(Class):
+            parser = ArgumentParser()
+            parser.add_argument('--union', type=Union[str, Class])
+            err = StringIO()
+            with redirect_stderr(err), self.assertRaises(SystemExit):
+                parser.parse_object({'union': [{'class_path': 'Class', 'init_args': {'val': 'x'}}]})
+            expected = textwrap.dedent('''
+            Errors:
+              - Expected a <class 'str'>
+              - Not a valid subclass of Class
+                Subclass types expect one of:
+                - a class path (str)
+                - a dict with class_path entry
+                - a dict without class_path but with init_args entry (class path given previously)
+            Given value type: <class 'list'>
+            Given value: [{'class_path': 'Class', 'init_args': {'val': 'x'}}]
+            ''').strip()
+            expected = textwrap.indent(expected, '  ')
+            expected = '\n'.join(expected.splitlines())
+            obtained = '\n'.join(err.getvalue().splitlines())
+            self.assertIn(expected, obtained)
+
+
 class SignaturesConfigTests(TempDirTestCase):
 
     def test_add_function_arguments_config(self):