support res.removeListener('drain'), res.once('drain')

Fixes expressjs#152
Fixes expressjs#135

.travis.yml

@@ -12,6 +12,7 @@ node_js:
   - "7.10"
   - "8.11"
   - "9.11"
+  - "10"
 sudo: false
 cache:
   directories:

index.js

@@ -64,6 +64,7 @@ function compression (options) {
 
     var _end = res.end
     var _on = res.on
+    var _removeListener = res.removeListener
     var _write = res.write
 
     // flush
@@ -131,6 +132,32 @@ function compression (options) {
       return this
     }
 
+    res.addListener = res.on
+
+    res.removeListener = function removeListener (type, listener) {
+      if (!listeners || type !== 'drain') {
+        return _removeListener.call(this, type, listener)
+      }
+
+      if (stream) {
+        return stream.removeListener(type, listener)
+      }
+
+      // remove buffered listener
+      for (var i = listeners.length - 1; i >= 0; i--) {
+        if (listeners[i][0] === type && listeners[i][1] === listener) {
+          listeners.splice(i, 1)
+        }
+      }
+
+      return this
+    }
+
+    if (res.off) {
+      // emitter.off was added in Node.js v10+; don't add it to earlier versions
+      res.off = res.removeListener
+    }
+
     function nocompress (msg) {
       debug('no compression: %s', msg)
       addListeners(res, _on, listeners)

test/compression.js

@@ -301,6 +301,185 @@ describe('compression()', function () {
       .expect(200, done)
   })
 
+  it('should support removeListener("drain") after on("drain"); stream present', function (done) {
+    // compression doesn't proxy listenerCount() to the compression stream, so
+    // instead watch for a MaxListenersExceededWarning
+    var hasWarned = false
+    var onWarning = function () {
+      hasWarned = true
+    }
+    process.on('warning', onWarning)
+    var server = createServer({threshold: 0}, function (req, res) {
+      res.setHeader('Content-Type', 'text/plain')
+      var len = bytes('40kb')
+      var buf = Buffer.alloc(len, '.')
+      res.write(buf)
+      for (var times = 0; times < res.getMaxListeners() + 1; times++) {
+        var listener = function () {}
+        res.on('drain', listener)
+        res.removeListener('drain', listener)
+      }
+      res.end()
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .expect(function () {
+        process.removeListener('warning', onWarning)
+        assert.ok(!hasWarned)
+      })
+      .expect(200, done)
+  })
+
+  it('should support removeListener("drain") after addListener("drain")', function (done) {
+    var hasWarned = false
+    var onWarning = function () {
+      hasWarned = true
+    }
+    process.on('warning', onWarning)
+    var server = createServer({threshold: 0}, function (req, res) {
+      res.setHeader('Content-Type', 'text/plain')
+      var len = bytes('40kb')
+      var buf = Buffer.alloc(len, '.')
+      res.write(buf)
+      for (var times = 0; times < res.getMaxListeners() + 1; times++) {
+        var listener = function () {}
+        res.addListener('drain', listener)
+        res.removeListener('drain', listener)
+      }
+      res.end()
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .expect(function () {
+        process.removeListener('warning', onWarning)
+        assert.ok(!hasWarned)
+      })
+      .expect(200, done)
+  })
+
+  it('should support off("drain") after addListener("drain")', function (done) {
+    if (!require('events').EventEmitter.prototype.off) { // off was added in Node.js v10
+      this.skip()
+    }
+    var hasWarned = false
+    var onWarning = function () {
+      hasWarned = true
+    }
+    process.on('warning', onWarning)
+    var server = createServer({threshold: 0}, function (req, res) {
+      res.setHeader('Content-Type', 'text/plain')
+      var len = bytes('40kb')
+      var buf = Buffer.alloc(len, '.')
+      res.write(buf)
+      for (var times = 0; times < res.getMaxListeners() + 1; times++) {
+        var listener = function () {}
+        res.addListener('drain', listener)
+        res.off('drain', listener)
+      }
+      res.end()
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .expect(function () {
+        process.removeListener('warning', onWarning)
+        assert.ok(!hasWarned)
+      })
+      .expect(200, done)
+  })
+
+  it('should support removeListener("drain"); buffered', function (done) {
+    // Variant of above tests for scenario when the listener is buffered (stream
+    // is not yet present).
+    var hasWarned = false
+    var onWarning = function () {
+      hasWarned = true
+    }
+    process.on('warning', onWarning)
+    var server = createServer({threshold: 0}, function (req, res) {
+      res.setHeader('Content-Type', 'text/plain')
+      for (var times = 0; times < res.getMaxListeners() + 1; times++) {
+        var listener = function () {}
+        res.on('drain', listener)
+        res.removeListener('drain', listener)
+      }
+      res.end()
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .expect(function () {
+        process.removeListener('warning', onWarning)
+        assert.ok(!hasWarned)
+      })
+      .expect(200, done)
+  })
+
+  it('should support removeListener("drain"); multiple bindings of same listener, buffered', function (done) {
+    // Variant of above test for scenario when the listener is buffered (stream
+    // is not yet present) and the same listener is added two or more times.
+    var hasWarned = false
+    var onWarning = function () {
+      hasWarned = true
+    }
+    process.on('warning', onWarning)
+    var server = createServer({threshold: 0}, function (req, res) {
+      res.setHeader('Content-Type', 'text/plain')
+      for (var times = 0; times < res.getMaxListeners() + 1; times++) {
+        var listener = function () {}
+        res.on('drain', listener)
+        res.on('drain', listener)
+        res.removeListener('drain', listener)
+      }
+      res.end()
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .expect(function () {
+        process.removeListener('warning', onWarning)
+        assert.ok(!hasWarned)
+      })
+      .expect(200, done)
+  })
+
+  it('should not leak event listeners when res.unpipe() is used (#135)', function (done) {
+    var hasWarned = false
+    var onWarning = function () {
+      hasWarned = true
+    }
+    var server = createServer({threshold: 0}, function (req, res) {
+      var times = 0
+      var int = setInterval(function () {
+        var rs = require('fs').createReadStream('does not exist')
+        rs.on('error', function (e) {
+          rs.unpipe(res)
+        })
+        rs.pipe(res)
+        if (times++ > res.getMaxListeners()) {
+          clearInterval(int)
+          res.end('hello, world')
+        }
+      })
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .expect(function () {
+        process.removeListener('warning', onWarning)
+        assert.ok(!hasWarned)
+      })
+      .expect(200, done)
+  })
+
   describe('threshold', function () {
     it('should not compress responses below the threshold size', function (done) {
       var server = createServer({ threshold: '1kb' }, function (req, res) {
@@ -656,6 +835,13 @@ function createServer (opts, fn) {
         return
       }
 
+      if (typeof res.getMaxListeners !== 'function') {
+        // Added in v0.11.2
+        res.getMaxListeners = function getMaxListeners () {
+          return 10
+        }
+      }
+
       fn(req, res)
     })
   })