Add support for custom fetch implementation (#2993)

.github/workflows/ci.yml

@@ -109,9 +109,31 @@ jobs:
       - name: Build
         run: yarn build
 
+  test-js:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        working-directory:
+          - "libs/sdk-js"
+    defaults:
+      run:
+        working-directory: ${{ matrix.working-directory }}
+    steps:
+      - uses: actions/checkout@v3
+      - name: Setup Node.js (LTS)
+        uses: actions/setup-node@v3
+        with:
+          node-version: "20"
+          cache: "yarn"
+          cache-dependency-path: ${{ matrix.working-directory }}/yarn.lock
+      - name: Install dependencies
+        run: yarn install
+      - name: Run tests
+        run: yarn test
+
   ci_success:
     name: "CI Success"
-    needs: [lint, lint-js, test, test-langgraph, test-scheduler-kafka, integration-test]
+    needs: [lint, lint-js, test, test-langgraph, test-scheduler-kafka, integration-test, test-js]
     if: |
       always()
     runs-on: ubuntu-latest

libs/sdk-js/jest.config.js

@@ -0,0 +1,17 @@
+/** @type {import('jest').Config} */
+export default {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  extensionsToTreatAsEsm: ['.ts'],
+  moduleNameMapper: {
+    '^(\\.{1,2}/.*)\\.js$': '$1',
+  },
+  transform: {
+    '^.+\\.tsx?$': [
+      'ts-jest',
+      {
+        useESM: true,
+      },
+    ],
+  },
+};

libs/sdk-js/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@langchain/langgraph-sdk",
-  "version": "0.0.35",
+  "version": "0.0.36",
   "description": "Client library for interacting with the LangGraph API",
   "type": "module",
   "packageManager": "[email protected]",
@@ -9,7 +9,8 @@
     "build": "yarn clean && yarn lc_build --create-entrypoints --pre --tree-shaking",
     "prepublish": "yarn run build",
     "format": "prettier --write src",
-    "lint": "prettier --check src && tsc --noEmit"
+    "lint": "prettier --check src && tsc --noEmit",
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest --testPathIgnorePatterns=\\.int\\.test.ts"
   },
   "main": "index.js",
   "license": "MIT",
@@ -20,12 +21,16 @@
     "uuid": "^9.0.0"
   },
   "devDependencies": {
+    "@jest/globals": "^29.7.0",
     "@langchain/scripts": "^0.1.4",
     "@tsconfig/recommended": "^1.0.2",
+    "@types/jest": "^29.5.12",
     "@types/node": "^20.12.12",
     "@types/uuid": "^9.0.1",
     "concat-md": "^0.5.1",
+    "jest": "^29.7.0",
     "prettier": "^3.2.5",
+    "ts-jest": "^29.1.2",
     "typedoc": "^0.26.1",
     "typedoc-plugin-markdown": "^4.1.0",
     "typescript": "^5.4.5"

libs/sdk-js/src/client.ts

@@ -37,7 +37,7 @@ import {
 } from "./types.js";
 import { mergeSignals } from "./utils/signals.js";
 import { getEnvironmentVariable } from "./utils/env.js";
-
+import { _getFetchImplementation } from "./singletons/fetch.js";
 /**
  * Get the API key from the environment.
  * Precedence:
@@ -164,7 +164,8 @@ class BaseClient {
       signal?: AbortSignal;
     },
   ): Promise<T> {
-    const response = await this.asyncCaller.fetch(
+    const response = await this.asyncCaller.call(
+      _getFetchImplementation(),
       ...this.prepareFetchOptions(path, options),
     );
     if (response.status === 202 || response.status === 204) {
@@ -752,7 +753,8 @@ export class RunsClient extends BaseClient {
 
     const endpoint =
       threadId == null ? `/runs/stream` : `/threads/${threadId}/runs/stream`;
-    const response = await this.asyncCaller.fetch(
+    const response = await this.asyncCaller.call(
+      _getFetchImplementation(),
       ...this.prepareFetchOptions(endpoint, {
         method: "POST",
         json,
@@ -1044,7 +1046,8 @@ export class RunsClient extends BaseClient {
         ? { signal: options }
         : options;
 
-    const response = await this.asyncCaller.fetch(
+    const response = await this.asyncCaller.call(
+      _getFetchImplementation(),
       ...this.prepareFetchOptions(`/threads/${threadId}/runs/${runId}/stream`, {
         method: "GET",
         timeoutMs: null,

libs/sdk-js/src/index.ts

@@ -17,5 +17,6 @@ export type {
   Checkpoint,
   Interrupt,
 } from "./schema.js";
+export { overrideFetchImplementation } from "./singletons/fetch.js";
 
 export type { OnConflictBehavior, Command } from "./types.js";

libs/sdk-js/src/singletons/fetch.ts

@@ -0,0 +1,29 @@
+// Wrap the default fetch call due to issues with illegal invocations
+// in some environments:
+// https://stackoverflow.com/questions/69876859/why-does-bind-fix-failed-to-execute-fetch-on-window-illegal-invocation-err
+// @ts-expect-error Broad typing to support a range of fetch implementations
+const DEFAULT_FETCH_IMPLEMENTATION = (...args: any[]) => fetch(...args);
+
+const LANGSMITH_FETCH_IMPLEMENTATION_KEY = Symbol.for(
+  "lg:fetch_implementation",
+);
+
+/**
+ * Overrides the fetch implementation used for LangSmith calls.
+ * You should use this if you need to use an implementation of fetch
+ * other than the default global (e.g. for dealing with proxies).
+ * @param fetch The new fetch function to use.
+ */
+export const overrideFetchImplementation = (fetch: (...args: any[]) => any) => {
+  (globalThis as any)[LANGSMITH_FETCH_IMPLEMENTATION_KEY] = fetch;
+};
+
+/**
+ * @internal
+ */
+export const _getFetchImplementation: () => (...args: any[]) => any = () => {
+  return (
+    (globalThis as any)[LANGSMITH_FETCH_IMPLEMENTATION_KEY] ??
+    DEFAULT_FETCH_IMPLEMENTATION
+  );
+};

libs/sdk-js/src/tests/fetch.test.ts

@@ -0,0 +1,74 @@
+/* eslint-disable no-process-env */
+/* eslint-disable @typescript-eslint/no-explicit-any */
+import { jest } from "@jest/globals";
+import { Client } from "../client.js";
+import { overrideFetchImplementation } from "../singletons/fetch.js";
+
+describe.each([[""], ["mocked"]])("Client uses %s fetch", (description) => {
+  let globalFetchMock: jest.Mock;
+  let overriddenFetch: jest.Mock;
+  let expectedFetchMock: jest.Mock;
+  let unexpectedFetchMock: jest.Mock;
+
+  beforeEach(() => {
+    globalFetchMock = jest.fn(() =>
+      Promise.resolve({
+        ok: true,
+        json: () =>
+          Promise.resolve({
+            batch_ingest_config: {
+              use_multipart_endpoint: true,
+            },
+          }),
+        text: () => Promise.resolve(""),
+      }),
+    );
+    overriddenFetch = jest.fn(() =>
+      Promise.resolve({
+        ok: true,
+        json: () =>
+          Promise.resolve({
+            batch_ingest_config: {
+              use_multipart_endpoint: true,
+            },
+          }),
+        text: () => Promise.resolve(""),
+      }),
+    );
+    expectedFetchMock =
+      description === "mocked" ? overriddenFetch : globalFetchMock;
+    unexpectedFetchMock =
+      description === "mocked" ? globalFetchMock : overriddenFetch;
+
+    if (description === "mocked") {
+      overrideFetchImplementation(overriddenFetch);
+    } else {
+      overrideFetchImplementation(globalFetchMock);
+    }
+    // Mock global fetch
+    (globalThis as any).fetch = globalFetchMock;
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  describe("createRuns", () => {
+    it("should create an example with the given input and generation", async () => {
+      const client = new Client({ apiKey: "test-api-key" });
+
+      const thread = await client.threads.create();
+      expect(expectedFetchMock).toHaveBeenCalledTimes(1);
+      expect(unexpectedFetchMock).not.toHaveBeenCalled();
+
+      jest.clearAllMocks(); // Clear all mocks before the next operation
+
+      // Then clear & run the function
+      await client.runs.create(thread.thread_id, "somegraph", {
+        input: { foo: "bar" },
+      });
+      expect(expectedFetchMock).toHaveBeenCalledTimes(1);
+      expect(unexpectedFetchMock).not.toHaveBeenCalled();
+    });
+  });
+});