zlib: check if the stream is destroyed before push

If the stream is destroyed while the transform is still being
applied, push() should not be called, and the internal state
should be cleared.

See: koajs/compress#60

Author: mcollina

lib/zlib.js

@@ -472,6 +472,11 @@ function processCallback() {
     return;
   }
 
+  if (self.destroyed) {
+    this.buffer = null;
+    return;
+  }
+
   var availOutAfter = state[0];
   var availInAfter = state[1];
 

test/parallel/test-zlib-destroy-pipe.js

@@ -0,0 +1,21 @@
+'use strict';
+
+const common = require('../common');
+const zlib = require('zlib');
+const { Writable } = require('stream');
+
+// verify that the zlib transform does not error in case
+// it is destroyed with data still in flight
+
+const ts = zlib.createGzip();
+
+const ws = new Writable({
+  write: common.mustCall((chunk, enc, cb) => {
+    setImmediate(cb);
+    ts.destroy();
+  })
+});
+
+const buf = Buffer.allocUnsafe(1024 * 1024 * 20);
+ts.end(buf);
+ts.pipe(ws);