add some basic validation

packages/hono-helpers/src/helpers/openapi.ts

@@ -33,9 +33,44 @@ function addIntegerExamples(node: unknown): void {
 	for (const value of Object.values(obj)) addIntegerExamples(value)
 }
 
+/**
+ * hono-openapi registers a `validator('form', …)` body under `multipart/form-data` ONLY,
+ * and there is no way to ask it for another media type: its media selection reads
+ * `options?.media ?? target === 'json' ? 'application/json' : 'multipart/form-data'`,
+ * which by JS precedence is `((options?.media ?? target) === 'json') ? … : …` — so the
+ * `media` option can never produce anything else.
+ *
+ * That leaves the spec claiming a validated route accepts only multipart, when the real
+ * callers (the Rec Room client and the website) post `application/x-www-form-urlencoded`
+ * and Hono's `parseBody()` reads both. So the urlencoded variant is mirrored back in.
+ *
+ * Safe because nothing here documents a genuinely multipart-only body — there are no file
+ * uploads on these workers, and hand-written form bodies already declare both types. If
+ * one is ever added, it will need to opt out of this.
+ */
+function mirrorFormBodies(node: unknown): void {
+	if (Array.isArray(node)) {
+		for (const item of node) mirrorFormBodies(item)
+		return
+	}
+	if (node === null || typeof node !== 'object') return
+
+	const obj = node as Record<string, unknown>
+	const content = obj.content
+	if (content !== null && typeof content === 'object') {
+		const media = content as Record<string, unknown>
+		const multipart = media['multipart/form-data']
+		if (multipart !== undefined && media['application/x-www-form-urlencoded'] === undefined) {
+			media['application/x-www-form-urlencoded'] = multipart
+		}
+	}
+	for (const value of Object.values(obj)) mirrorFormBodies(value)
+}
+
 /**
  * Wrap `openAPIRouteHandler(...)` so the generated document gets example values for its
- * integer fields. Purely cosmetic — nothing about the documented shapes changes.
+ * integer fields, and so a validated form body documents both content types it really
+ * accepts. Nothing about the runtime behaviour changes — this only corrects the document.
  *
  * ```ts
  * app.get('/openapi.json', describeRoute({ hide: true }), withCleanSpec(openAPIRouteHandler(app, { ... })))
@@ -47,6 +82,7 @@ export function withCleanSpec(handler: Handler | MiddlewareHandler): Handler {
 		if (!(res instanceof Response)) return res as never
 		const spec: unknown = await res.json()
 		addIntegerExamples(spec)
+		mirrorFormBodies(spec)
 		return c.json(spec as Record<string, unknown>)
 	}
 }