Changeset

Signed-off-by: Sora Morimoto <[email protected]>

Author: smorimoto

.changeset/loud-dancers-shake.md

@@ -0,0 +1,19 @@
+---
+"swagger-typescript-api": patch
+---
+
+Fix handling of FormData inputs in Fetch HTTP client
+
+Previously, when users passed a `FormData` object directly to the Fetch
+client's `multipart/form-data` formatter, it would incorrectly attempt to use
+`Object.keys()` on the FormData instance, which returns an empty array. This
+caused the FormData to be processed incorrectly.
+
+The fix adds a type check to return FormData instances unchanged, allowing
+users to have full control over FormData construction when needed whilst
+maintaining backwards compatibility for object inputs. This aligns the Fetch
+client behaviour with the existing Axios client implementation.
+
+This resolves issues where users needed to send multipart requests with
+multiple entries for the same key, which is only possible with direct FormData
+manipulation.