From 93d83f880a206b3d8206832bf1ff80e9c40d1072 Mon Sep 17 00:00:00 2001
From: Ben Ellis <ben.ellis@softweyr.co.uk>
Date: Wed, 21 Jun 2023 23:53:38 +0100
Subject: [PATCH] Added format_exception to recursive calls of transform_error.
 [#389] (#390)

---
 HISTORY.md      |  2 ++
 src/cattrs/v.py |  4 ++--
 tests/test_v.py | 19 +++++++++++++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/HISTORY.md b/HISTORY.md
index 4e9d5770..0abeb2aa 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -2,6 +2,8 @@
 
 ## 23.2.0 (UNRELEASED)
 
+- Fix `format_exception` parameter working for recursive calls to `transform_error`
+  ([#389](https://github.com/python-attrs/cattrs/issues/389)
 - Use [PDM](https://pdm.fming.dev/latest/) instead of Poetry.
 - _cattrs_ is now linted with [Ruff](https://beta.ruff.rs/docs/).
 - Fix TypedDicts with periods in their field names.
diff --git a/src/cattrs/v.py b/src/cattrs/v.py
index f3c36481..963f8536 100644
--- a/src/cattrs/v.py
+++ b/src/cattrs/v.py
@@ -89,7 +89,7 @@ def transform_error(
         for exc, note in with_notes:
             p = f"{path}[{note.index!r}]"
             if isinstance(exc, (ClassValidationError, IterableValidationError)):
-                errors.extend(transform_error(exc, p))
+                errors.extend(transform_error(exc, p, format_exception))
             else:
                 errors.append(f"{format_exception(exc, note.type)} @ {p}")
         for exc in without:
@@ -99,7 +99,7 @@ def transform_error(
         for exc, note in with_notes:
             p = f"{path}.{note.name}"
             if isinstance(exc, (ClassValidationError, IterableValidationError)):
-                errors.extend(transform_error(exc, p))
+                errors.extend(transform_error(exc, p, format_exception))
             else:
                 errors.append(f"{format_exception(exc, note.type)} @ {p}")
         for exc in without:
diff --git a/tests/test_v.py b/tests/test_v.py
index 6bfac63a..88c063f8 100644
--- a/tests/test_v.py
+++ b/tests/test_v.py
@@ -227,6 +227,25 @@ class C:
         ]
 
 
+def test_custom_error_fn_nested(c: Converter) -> None:
+    def my_format(exc, type):
+        if isinstance(exc, TypeError):
+            return "Must be correct type"
+        return format_exception(exc, type)
+
+    @define
+    class C:
+        a: Dict[str, int]
+
+    try:
+        c.structure({"a": {"a": "str", "b": 1, "c": None}}, C)
+    except Exception as exc:
+        assert transform_error(exc, format_exception=my_format) == [
+            "invalid value for type, expected int @ $.a['a']",
+            "Must be correct type @ $.a['c']",
+        ]
+
+
 def test_typeddict_attribute_errors(c: Converter) -> None:
     """TypedDict errors are correctly generated."""