Extract isJsonRpcPayload method to rpc-spec

.changeset/bright-snakes-search.md

@@ -0,0 +1,5 @@
+---
+'@solana/rpc-spec': patch
+---
+
+Add new `isJsonRpcPayload` helper method

packages/rpc-spec/README.md

@@ -135,3 +135,20 @@ A config object with the following properties:
 
 -   `requestTransformer<T>(request: RpcRequest<T>): RpcRequest`: An optional function that transforms the `RpcRequest` before it is sent to the JSON RPC server.
 -   `responseTransformer<T>(response: RpcResponse, request: RpcRequest): RpcResponse<T>`: An optional function that transforms the `RpcResponse` before it is returned to the caller.
+
+### `isJsonRpcPayload(payload)`
+
+A helper function that returns `true` if the given payload is a JSON RPC v2 payload. This means, the payload is an object such that:
+
+-   It has a `jsonrpc` property with a value of `'2.0'`.
+-   It has a `method` property that is a string.
+-   It has a `params` property of any type.
+
+```ts
+import { isJsonRpcPayload } from '@solana/rpc-spec';
+
+if (isJsonRpcPayload(payload)) {
+    const payloadMethod: string = payload.method;
+    const payloadParams: unknown = payload.params;
+}
+```

packages/rpc-spec/src/__tests__/rpc-transport-test.ts

@@ -0,0 +1,29 @@
+import { isJsonRpcPayload } from '../rpc-transport';
+
+describe('isJsonRpcPayload', () => {
+    it('recognizes JSON RPC payloads', () => {
+        expect(isJsonRpcPayload({ jsonrpc: '2.0', method: 'getFoo', params: [123] })).toBe(true);
+    });
+    it('returns false if the payload is not an object', () => {
+        expect(isJsonRpcPayload(undefined)).toBe(false);
+        expect(isJsonRpcPayload(null)).toBe(false);
+        expect(isJsonRpcPayload(true)).toBe(false);
+        expect(isJsonRpcPayload(false)).toBe(false);
+        expect(isJsonRpcPayload([])).toBe(false);
+        expect(isJsonRpcPayload('o hai')).toBe(false);
+        expect(isJsonRpcPayload(123)).toBe(false);
+        expect(isJsonRpcPayload(123n)).toBe(false);
+    });
+    it('returns false if the payload is an empty object', () => {
+        expect(isJsonRpcPayload({})).toBe(false);
+    });
+    it('returns false if the payload is not a JSON RPC v2', () => {
+        expect(isJsonRpcPayload({ jsonrpc: '42.0', method: 'getFoo', params: [123] })).toBe(false);
+    });
+    it('returns false if the method name is missing', () => {
+        expect(isJsonRpcPayload({ jsonrpc: '2.0', params: [123] })).toBe(false);
+    });
+    it('returns false if the parameters are missing', () => {
+        expect(isJsonRpcPayload({ jsonrpc: '2.0', method: 'getFoo' })).toBe(false);
+    });
+});

packages/rpc-spec/src/__typetests__/rpc-transport-typetest.ts

@@ -0,0 +1,9 @@
+import { isJsonRpcPayload } from '../rpc-transport';
+
+{
+    // [isJsonRpcPayload]: It narrows the type of the payload to a JSON RPC payload.
+    const payload = {} as unknown;
+    if (isJsonRpcPayload(payload)) {
+        payload satisfies { jsonrpc: '2.0'; method: string; params: unknown };
+    }
+}

packages/rpc-spec/src/rpc-transport.ts

@@ -8,3 +8,20 @@ type RpcTransportRequest = Readonly<{
 export type RpcTransport = {
     <TResponse>(request: RpcTransportRequest): Promise<RpcResponse<TResponse>>;
 };
+
+export function isJsonRpcPayload(payload: unknown): payload is Readonly<{
+    jsonrpc: '2.0';
+    method: string;
+    params: unknown;
+}> {
+    if (payload == null || typeof payload !== 'object' || Array.isArray(payload)) {
+        return false;
+    }
+    return (
+        'jsonrpc' in payload &&
+        payload.jsonrpc === '2.0' &&
+        'method' in payload &&
+        typeof payload.method === 'string' &&
+        'params' in payload
+    );
+}

packages/rpc/src/rpc-request-deduplication.ts

@@ -1,17 +1,5 @@
 import fastStableStringify from '@solana/fast-stable-stringify';
-
-function isJsonRpcPayload(payload: unknown): payload is Readonly<{ method: string; params: unknown }> {
-    if (payload == null || typeof payload !== 'object' || Array.isArray(payload)) {
-        return false;
-    }
-    return (
-        'jsonrpc' in payload &&
-        payload.jsonrpc === '2.0' &&
-        'method' in payload &&
-        typeof payload.method === 'string' &&
-        'params' in payload
-    );
-}
+import { isJsonRpcPayload } from '@solana/rpc-spec';
 
 export function getSolanaRpcPayloadDeduplicationKey(payload: unknown): string | undefined {
     return isJsonRpcPayload(payload) ? fastStableStringify([payload.method, payload.params]) : undefined;