fix(openapi): read ~standard.jsonSchema via cast, not by widening StandardSchemaV1 (#3)

Adding `jsonSchema?` to the vendored `StandardSchemaV1.Props` diverged it from
`@standard-schema/spec` and perturbed generic type inference in consumers — an
endpoint's body type could collapse to `undefined` when the definer is used
behind a generic wrapper. Revert the spec type to its original shape and read
`~standard.jsonSchema` through a local cast in the generator instead.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: isaacwasserman

packages/better-call/src/openapi.ts

@@ -120,6 +120,17 @@ const BODY_METHODS = new Set<string>(["POST", "PUT", "PATCH", "DELETE"]);
 
 const PATH_PARAM_REGEX = /:([A-Za-z0-9_]+)/g;
 
+/**
+ * The optional JSON Schema conversion exposed on `~standard.jsonSchema` per the
+ * StandardJSONSchemaV1 proposal (https://standardschema.dev/json-schema). Read
+ * via a local cast rather than by widening {@link StandardSchemaV1} itself —
+ * modifying the vendored spec type perturbs generic inference in consumers.
+ */
+interface JSONSchemaConverter {
+	input?: (options?: { target?: string }) => Record<string, any>;
+	output?: (options?: { target?: string }) => Record<string, any>;
+}
+
 /**
  * Convert a Standard Schema to a JSON Schema object using the library-agnostic
  * StandardJSONSchemaV1 interface (`schema["~standard"].jsonSchema`), natively
@@ -132,7 +143,10 @@ function toJsonSchema(
 	schema: StandardSchemaV1 | undefined,
 	io: "input" | "output",
 ): Record<string, any> | undefined {
-	const converter = schema?.["~standard"]?.jsonSchema;
+	const std = schema?.["~standard"] as
+		| { jsonSchema?: JSONSchemaConverter }
+		| undefined;
+	const converter = std?.jsonSchema;
 	if (!converter) return undefined;
 	try {
 		const fn = io === "input" ? converter.input : converter.output;

packages/better-call/src/standard-schema.ts

@@ -17,35 +17,6 @@ export declare namespace StandardSchemaV1 {
 		) => Result<Output> | Promise<Result<Output>>;
 		/** Inferred types associated with the schema. */
 		readonly types?: Types<Input, Output> | undefined;
-		/**
-		 * Optional JSON Schema conversion, per the StandardJSONSchemaV1 proposal
-		 * (https://standardschema.dev/json-schema). Natively implemented by Zod
-		 * (>= 4.2), ArkType (>= 2.1.28), and others. Consumed by the OpenAPI
-		 * generator to describe request bodies and query parameters in a
-		 * library-agnostic way.
-		 */
-		readonly jsonSchema?: JSONSchemaConverter | undefined;
-	}
-
-	/** Options accepted by the JSON Schema conversion methods. */
-	export interface JSONSchemaOptions {
-		/**
-		 * Target JSON Schema dialect. OpenAPI 3.1 aligns with `"draft-2020-12"`.
-		 */
-		readonly target?:
-			| "draft-2020-12"
-			| "draft-07"
-			| "openapi-3.0"
-			| (string & {});
-		readonly [key: string]: unknown;
-	}
-
-	/** The JSON Schema conversion interface exposed on `~standard.jsonSchema`. */
-	export interface JSONSchemaConverter {
-		/** JSON Schema describing accepted input values. */
-		readonly input?: (options?: JSONSchemaOptions) => Record<string, unknown>;
-		/** JSON Schema describing produced output values. */
-		readonly output?: (options?: JSONSchemaOptions) => Record<string, unknown>;
 	}
 
 	/** The result interface of the validate function. */