fix(client): Some mcp server need default env(#393, #196)

src/client/stdio.test.ts

@@ -59,3 +59,33 @@ test("should read messages", async () => {
 
   await client.close();
 });
+
+test("should work with actual node mcp server", async () => {
+  const client = new StdioClientTransport({
+    command: "npx",
+    args: ["-y", "@wrtnlabs/calculator-mcp"],
+  });
+
+  await client.start();
+  await client.close();
+});
+
+test("should work with actual node mcp server and empty env", async () => {
+  const client = new StdioClientTransport({
+    command: "npx",
+    args: ["-y", "@wrtnlabs/calculator-mcp"],
+    env: {},
+  });
+  await client.start();
+  await client.close();
+});
+
+test("should work with actual node mcp server and custom env", async () => {
+  const client = new StdioClientTransport({
+    command: "npx",
+    args: ["-y", "@wrtnlabs/calculator-mcp"],
+    env: {TEST_VAR: "test-value"},
+  });
+  await client.start();
+  await client.close();
+}); 

src/client/stdio.ts

@@ -117,7 +117,11 @@ export class StdioClientTransport implements Transport {
         this._serverParams.command,
         this._serverParams.args ?? [],
         {
-          env: this._serverParams.env ?? getDefaultEnvironment(),
+          // merge default env with server env because mcp server needs some env vars
+          env: {
+            ...getDefaultEnvironment(),
+            ...this._serverParams.env,
+          },
           stdio: ["pipe", "pipe", this._serverParams.stderr ?? "inherit"],
           shell: false,
           signal: this._abortController.signal,