Initial release.

test/go/doubleselect.js

@@ -0,0 +1,77 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test the situation in which two cases of a select can
+// both end up running. See http://codereview.appspot.com/180068.
+
+'use strict'
+
+const Channel = require('../../lib')
+
+it(`doubleselect`, async function () {
+  this.timeout(10 * 1000)
+  const iterations = 100000 // number of iterations
+
+  // sender sends a counter to one of four different channels. If two cases both
+  // end up running in the same iteration, the same value will be sent to two
+  // different channels.
+  const sender = async (n, c1, c2, c3, c4) => {
+    for (let i = 0; i < n; i++) {
+      await Channel.select(c1.push(i), c2.push(i), c3.push(i), c4.push(i))
+    }
+
+    c1.close()
+    c2.close()
+    c3.close()
+    c4.close()
+  }
+
+  // mux receives the values from sender and forwards them onto another channel.
+  // It would be simpler to just have sender's four cases all be the same
+  // channel, but this doesn't actually trigger the bug.
+  const mux = async (output, input, done) => {
+    await input.forEach(async (value) => {
+      await output.push(value)
+    })
+
+    await done.push(true)
+  }
+
+  // recver gets a steam of values from the four mux's and checks for
+  // duplicates.
+  const recver = (input) => {
+    const seen = new Map()
+
+    input.forEach((v) => {
+      if (seen.has(v)) {
+        throw new Error(`got duplicate value: ${v}`)
+      }
+
+      seen.set(v, true)
+    })
+  }
+
+  const c1 = Channel()
+  const c2 = Channel()
+  const c3 = Channel()
+  const c4 = Channel()
+  const done = Channel()
+  const cmux = Channel()
+  sender(iterations, c1, c2, c3, c4)
+  mux(cmux, c1, done)
+  mux(cmux, c2, done)
+  mux(cmux, c3, done)
+  mux(cmux, c4, done)
+
+  // We keep the recver because it might catch more bugs in the future.
+  // However, the result of the bug linked to at the top is that we'll
+  // end up panicking with: "throw: bad g->status in ready".
+  recver(cmux)
+
+  await done.shift()
+  await done.shift()
+  await done.shift()
+  await done.shift()
+  cmux.close()
+})