Merge pull request #122 from asottile/custom-display-name

add a custom display name for loading from a file

Author: asottile

cfgv.py

@@ -392,12 +392,15 @@ def load_from_filename(
         schema,
         load_strategy,
         exc_tp=ValidationError,
+        *,
+        display_filename=None,
 ):
+    display_filename = display_filename or filename
     with reraise_as(exc_tp):
         if not os.path.isfile(filename):
-            raise ValidationError(f'{filename} is not a file')
+            raise ValidationError(f'{display_filename} is not a file')
 
-        with validate_context(f'File {filename}'):
+        with validate_context(f'File {display_filename}'):
             try:
                 with open(filename, encoding='utf-8') as f:
                     contents = f.read()

tests/cfgv_test.py

@@ -36,11 +36,12 @@
 
 
 def _assert_exception_trace(e, trace):
-    inner = e
-    for ctx in trace[:-1]:
-        assert inner.ctx == ctx
-        inner = inner.error_msg
-    assert inner.error_msg == trace[-1]
+    parts = []
+    while e.ctx is not None:
+        parts.append(e.ctx)
+        e = e.error_msg
+    parts.append(e.error_msg)
+    assert tuple(parts) == trace
 
 
 def test_ValidationError_simple_str():
@@ -582,6 +583,35 @@ def test_load_from_filename_applies_defaults(tmpdir):
     assert ret == {'key': False}
 
 
+def test_load_from_filename_custom_display_no_file(tmp_path):
+    with pytest.raises(ValidationError) as excinfo:
+        load_from_filename(
+            tmp_path.joinpath('cfg.json'),
+            map_required,
+            json.loads,
+            display_filename='cfg.json',
+        )
+    _assert_exception_trace(excinfo.value.args[0], ('cfg.json is not a file',))
+
+
+def test_load_from_filename_custom_display_error(tmp_path):
+    f = tmp_path.joinpath('cfg.json')
+    f.write_text('{}')
+    with pytest.raises(ValidationError) as excinfo:
+        load_from_filename(
+            f,
+            map_required,
+            json.loads,
+            display_filename='cfg.json',
+        )
+    expected = (
+        'File cfg.json',
+        'At foo(key=MISSING)',
+        'Missing required key: key',
+    )
+    _assert_exception_trace(excinfo.value.args[0], expected)
+
+
 conditional_recurse = Map(
     'Map', None,