fix: close zero-length take streams immediately

index.js

@@ -41,6 +41,11 @@ export function takeStream(count) {
 
   let taken = 0;
   return new TransformStream({
+    start(controller) {
+      if (count === 0) {
+        controller.terminate();
+      }
+    },
     transform(chunk, controller) {
       if (taken < count) {
         taken += 1;

readme.md

@@ -44,6 +44,8 @@ Returns a `TransformStream` that only passes chunks where `function_` returns `t
 
 ### takeStream(count)
 
+A count of zero closes the readable side immediately, without waiting for upstream data.
+
 Returns a `TransformStream` that passes only the first `count` chunks then terminates.
 
 ### batchStream(size)

regression.test.js

@@ -0,0 +1,20 @@
+import test from "ava";
+import { takeStream } from "./index.js";
+
+test("takeStream(0) closes without waiting for an upstream chunk", async (t) => {
+  const transform = takeStream(0);
+  const reader = transform.readable.getReader();
+  let timeout;
+  try {
+    const result = await Promise.race([
+      reader.read(),
+      new Promise((resolve) => {
+        timeout = setTimeout(() => resolve("still pending"), 100);
+      }),
+    ]);
+    t.deepEqual(result, { done: true, value: undefined });
+  } finally {
+    clearTimeout(timeout);
+    await reader.cancel();
+  }
+});