fix stdin hang

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@metabase/cli",
-  "version": "0.1.11",
+  "version": "0.1.12",
   "description": "Metabase CLI",
   "license": "AGPL-3.0",
   "repository": {

src/runtime/input.test.ts

@@ -10,9 +10,13 @@ import { readInput } from "./input";
 
 interface MockStdin {
   isTTY: boolean;
+  pause: () => void;
+  unref: () => void;
   [Symbol.asyncIterator]: () => AsyncIterator<string>;
 }
 
+const noop = (): void => {};
+
 const originalStdin = process.stdin;
 
 function setStdin(replacement: MockStdin | NodeJS.ReadStream): void {
@@ -26,6 +30,8 @@ function setStdin(replacement: MockStdin | NodeJS.ReadStream): void {
 function tty(): MockStdin {
   return {
     isTTY: true,
+    pause: noop,
+    unref: noop,
     [Symbol.asyncIterator]() {
       return Readable.from([])[Symbol.asyncIterator]();
     },
@@ -35,12 +41,29 @@ function tty(): MockStdin {
 function piped(content: string): MockStdin {
   return {
     isTTY: false,
+    pause: noop,
+    unref: noop,
     [Symbol.asyncIterator]() {
       return Readable.from([content])[Symbol.asyncIterator]();
     },
   };
 }
 
+function idlePipe(): MockStdin {
+  return {
+    isTTY: false,
+    pause: noop,
+    unref: noop,
+    [Symbol.asyncIterator]() {
+      return {
+        next() {
+          return new Promise<IteratorResult<string>>(() => {});
+        },
+      };
+    },
+  };
+}
+
 describe("readInput precedence", () => {
   let tempDir: string;
   let filePath: string;
@@ -115,6 +138,22 @@ describe("readInput precedence", () => {
     expect(result).toBe("from-positional");
   });
 
+  it("times out an idle non-TTY stdin instead of hanging, then falls through to positional", async () => {
+    setStdin(idlePipe());
+    const result = await readInput({ positional: "from-positional" });
+    expect(result).toBe("from-positional");
+  });
+
+  it("times out an idle non-TTY stdin and throws the required-input error", async () => {
+    setStdin(idlePipe());
+    const error = await readInput({}).catch((caught: unknown) => caught);
+    expect(error).toBeInstanceOf(ConfigError);
+    assert(error instanceof ConfigError, "expected ConfigError");
+    expect(error.message).toBe(
+      "input required: provide one of --body, --file, stdin, or a positional argument",
+    );
+  });
+
   it("throws ConfigError listing all sources when required and all empty", async () => {
     const error = await readInput({}).catch((caught: unknown) => caught);
     expect(error).toBeInstanceOf(ConfigError);

src/runtime/input.ts

@@ -1,4 +1,5 @@
 import { readFile } from "node:fs/promises";
+import { setTimeout as delay } from "node:timers/promises";
 
 import { ConfigError, isNotFoundError } from "../core/errors";
 
@@ -25,7 +26,7 @@ export async function readInput(sources: InputSources): Promise<string> {
   }
 
   if (!process.stdin.isTTY) {
-    const piped = await readStdin();
+    const piped = await readPipedStdin();
     if (piped) {
       return piped;
     }
@@ -44,7 +45,7 @@ export async function readInput(sources: InputSources): Promise<string> {
 
 async function readFileSource(path: string): Promise<string> {
   if (path === "-") {
-    return await readStdin();
+    return await drainStdin();
   }
   try {
     return await readFile(path, "utf8");
@@ -56,10 +57,43 @@ async function readFileSource(path: string): Promise<string> {
   }
 }
 
-async function readStdin(): Promise<string> {
+async function drainStdin(): Promise<string> {
   let data = "";
   for await (const chunk of process.stdin) {
     data += chunk;
   }
   return data;
 }
+
+const STDIN_FIRST_CHUNK_TIMEOUT_MS = 500;
+const STDIN_IDLE = Symbol("stdin-idle");
+
+// A non-TTY stdin we were never asked to read may be an inherited pipe that holds
+// the fd open without ever sending data or EOF — draining it blocks forever. So we
+// race only the first chunk against a deadline: nothing in time means release stdin
+// and report no input; once a chunk arrives we drain in full, so a large or slow
+// body is never truncated. Explicit stdin (`--file -`) skips this and blocks — there
+// the caller has promised data.
+async function readPipedStdin(): Promise<string | null> {
+  const iterator = process.stdin[Symbol.asyncIterator]();
+  const controller = new AbortController();
+  const idle = delay(STDIN_FIRST_CHUNK_TIMEOUT_MS, STDIN_IDLE, {
+    signal: controller.signal,
+  }).catch(() => STDIN_IDLE);
+
+  const first = await Promise.race([iterator.next(), idle]);
+  if (typeof first === "symbol") {
+    process.stdin.pause();
+    process.stdin.unref();
+    return null;
+  }
+  controller.abort();
+
+  let data = "";
+  let chunk = first;
+  while (chunk.done !== true) {
+    data += chunk.value;
+    chunk = await iterator.next();
+  }
+  return data;
+}