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remove error-inject and fix error handling #1409

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merged 6 commits into from May 16, 2020
Merged

remove error-inject and fix error handling #1409

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45e6659
remove `error-inject` and fix error handling
tinovyatkin Oct 17, 2019
0eef9ff
Merge branch 'master' into remove-error-inject
tinovyatkin Oct 28, 2019
39e5aa9
Merge branch 'master' into remove-error-inject
tinovyatkin Jan 17, 2020
3921003
add failing test
tinovyatkin Apr 30, 2020
f4de618
Merge branch 'master' into remove-error-inject
tinovyatkin May 5, 2020
e85c77a
Merge branch 'master' into remove-error-inject
tinovyatkin May 15, 2020
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12 changes: 6 additions & 6 deletions lib/response.js
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Expand Up @@ -6,7 +6,6 @@
*/

const contentDisposition = require('content-disposition');
const ensureErrorHandler = require('error-inject');
const getType = require('cache-content-type');
const onFinish = require('on-finished');
const escape = require('escape-html');
Expand Down Expand Up @@ -167,12 +166,13 @@ module.exports = {
}

// stream
if ('function' === typeof val.pipe) {
if (val instanceof Stream) {
onFinish(this.res, destroy.bind(null, val));
ensureErrorHandler(val, err => this.ctx.onerror(err));

// overwriting
if (null != original && original !== val) this.remove('Content-Length');
if (original != val) {
val.once('error', err => this.ctx.onerror(err));
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The two implementations seem to be not equal. We should only add error event listener when the stream has no other error event listener, which aim to avoid uncaught exception.

Also IMO koa's code philosophy is to keep code simple, so we don't treat 'one-liner module' as a bad thing.

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In current implementation the check in the error-inject does nothing (as two inline created functions never the same) and just always add .on('error') handler. Do you mean that was desired behaviour?
I'm proposing to remove error-inject here not because it's one line, but because even you (module author) forgot that you are breaking it functionality while refactored to inline function. It just does nothing in current version.

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i don't understand what you mean, can you explain in a test?

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@jonathanong Sorry for my English. I've added a failing test to this PR, it's pretty simple:

it('should add error handler to the stream, but only once', () => {
      const res = response();
      const body = new Stream.PassThrough();
      assert.strictEqual(body.listenerCount('error'), 0);
      res.body = body;
      assert.strictEqual(body.listenerCount('error'), 1);
      res.body = body;
      assert.strictEqual(body.listenerCount('error'), 1);
    });

This fails in Koa master and passing after merging this PR.

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seems like a developer error

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It is, but the most probable explanation here is that by hiding the actual logic in a one-line module even the author of the module forgot the logic on a next refactoring and broke the functionality. That's what this PR is all about - fix the error and bring the logic inside to prevent such a problem in the future.

// overwriting
if (null != original) this.remove('Content-Length');
}

if (setType) this.type = 'bin';
return;
Expand Down
1 change: 0 additions & 1 deletion package.json
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Expand Up @@ -32,7 +32,6 @@
"depd": "^1.1.2",
"destroy": "^1.0.4",
"encodeurl": "^1.0.2",
"error-inject": "^1.0.0",
"escape-html": "^1.0.3",
"fresh": "~0.5.2",
"http-assert": "^1.3.0",
Expand Down
11 changes: 11 additions & 0 deletions test/response/body.js
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Expand Up @@ -4,6 +4,7 @@
const response = require('../helpers/context').response;
const assert = require('assert');
const fs = require('fs');
const Stream = require('stream');

describe('res.body=', () => {
describe('when Content-Type is set', () => {
Expand Down Expand Up @@ -108,6 +109,16 @@ describe('res.body=', () => {
res.body = fs.createReadStream('LICENSE');
assert.equal('application/octet-stream', res.header['content-type']);
});

it('should add error handler to the stream, but only once', () => {
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This test case clearly shows where the problem is, LGTM

const res = response();
const body = new Stream.PassThrough();
assert.strictEqual(body.listenerCount('error'), 0);
res.body = body;
assert.strictEqual(body.listenerCount('error'), 1);
res.body = body;
assert.strictEqual(body.listenerCount('error'), 1);
});
});

describe('when a buffer is given', () => {
Expand Down