Fix plugin RPCs with schema transforms (#8550)

* fix(plugins): parse RPC values once at the receiver

Sending parsed values caused transforms to run again on incompatible schema outputs. Keep the wire values in schema-input form and parse only where consumed.

* fix(plugins): let omitted RPC inputs reach schema defaults

* fix(plugins): accept omitted RPC outputs for client defaults

packages/plugin/src/client/host.test.ts

@@ -24,17 +24,23 @@ describe("plugin RPC contracts", () => {
     expectTypeOf<RpcOutput<typeof contract>>().toEqualTypeOf<{ value: number }>();
   });
 
-  it("validates input before invoking the daemon", async () => {
-    let invocations = 0;
-    const invoke = async () => {
-      invocations += 1;
-      return { value: 2 };
+  it("sends input unchanged for the plugin to parse", async () => {
+    let parses = 0;
+    const transformed = defineRpc({
+      name: "transformed",
+      input: z.string().transform((text) => {
+        parses += 1;
+        return Number(text);
+      }),
+      output: z.number(),
+    });
+    const invoke = async (_method: string, input: unknown) => {
+      expect(input).toBe("2");
+      expect(parses).toBe(0);
+      return transformed.input.parseAsync(input);
     };
-
-    await expect(callPluginRpc(contract, invoke, { value: "wrong" })).rejects.toBeInstanceOf(
-      z.ZodError,
-    );
-    expect(invocations).toBe(0);
+    await expect(callPluginRpc(transformed, invoke, "2")).resolves.toBe(2);
+    expect(parses).toBe(1);
   });
 
   it("validates output before resolving", async () => {

packages/plugin/src/rpc.ts

@@ -39,8 +39,7 @@ export async function callPluginRpc<InputSchema extends ZodType, OutputSchema ex
   invoke: (method: string, input: unknown) => Promise<unknown>,
   input: PluginWireInput<ZodInput<InputSchema>>,
 ): Promise<ZodOutput<OutputSchema>> {
-  const parsedInput = await contract.input.parseAsync(input);
-  const output = await invoke(contract.name, parsedInput);
+  const output = await invoke(contract.name, input);
   return contract.output.parseAsync(output);
 }