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stream: try to wait for flush to complete before 'finish'
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Due to compat reasons Transform streams don't always wait
for flush to complete before finishing the stream.

Try to wait when possible, i.e. when the user does not
override _final.

Fixes: #34274

PR-URL: #34314
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
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ronag committed Jul 15, 2020
1 parent e44855d commit a65218f
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Showing 3 changed files with 49 additions and 2 deletions.
22 changes: 20 additions & 2 deletions lib/_stream_transform.js
Original file line number Diff line number Diff line change
Expand Up @@ -106,24 +106,42 @@ function Transform(options) {
this.on('prefinish', prefinish);
}

function prefinish() {
function final(cb) {
if (typeof this._flush === 'function' && !this.destroyed) {
this._flush((er, data) => {
if (er) {
this.destroy(er);
if (cb) {
cb(er);
} else {
this.destroy(er);
}
return;
}

if (data != null) {
this.push(data);
}
this.push(null);
if (cb) {
cb();
}
});
} else {
this.push(null);
if (cb) {
cb();
}
}
}

function prefinish() {
if (this._final !== final) {
final.call(this);
}
}

Transform.prototype._final = final;

Transform.prototype._transform = function(chunk, encoding, callback) {
throw new ERR_METHOD_NOT_IMPLEMENTED('_transform()');
};
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5 changes: 5 additions & 0 deletions lib/zlib.js
Original file line number Diff line number Diff line change
Expand Up @@ -323,6 +323,11 @@ ZlibBase.prototype._flush = function(callback) {
this._transform(Buffer.alloc(0), '', callback);
};

// Force Transform compat behavior.
ZlibBase.prototype._final = function(callback) {
callback();
};

// If a flush is scheduled while another flush is still pending, a way to figure
// out which one is the "stronger" flush is needed.
// This is currently only used to figure out which flush flag to use for the
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24 changes: 24 additions & 0 deletions test/parallel/test-stream-pipeline.js
Original file line number Diff line number Diff line change
Expand Up @@ -1231,3 +1231,27 @@ const net = require('net');
assert.strictEqual(res, 'helloworld');
}));
}

{
let flushed = false;
const makeStream = () =>
new Transform({
transform: (chunk, enc, cb) => cb(null, chunk),
flush: (cb) =>
setTimeout(() => {
flushed = true;
cb(null);
}, 1),
});

const input = new Readable();
input.push(null);

pipeline(
input,
makeStream(),
common.mustCall(() => {
assert.strictEqual(flushed, true);
}),
);
}

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