fix: exclude PR-modified tests from the flaky count

A failure in a test that the pull request itself modified is likely
caused by that change, so counting it as an independent flaky occurrence
overstates the number of affected pull requests.

Compare the failing test against the files the pull request touched and
drop the occurrence when they match. When the file list cannot be
fetched the occurrence is kept, so incomplete information never removes
a genuine failure.

Fixes: #1164
Signed-off-by: Avocado <ujubongbong@gmail.com>

Author: zeexzeex

bin/ncu-ci.js

@@ -460,8 +460,8 @@ class WalkCommand extends CICommand {
     if (this.queue.length === 0) {
       return;
     }
-    const aggregator = new FailureAggregator(cli, this.json);
-    this.json = aggregator.aggregate();
+    const aggregator = new FailureAggregator(cli, this.json, this.request);
+    this.json = await aggregator.aggregate();
     cli.log('');
     cli.separator('Stats');
     cli.log('');
@@ -541,8 +541,8 @@ class DailyCommand extends CICommand {
 
   async aggregate() {
     const { argv, cli } = this;
-    const aggregator = new FailureAggregator(cli, this.json);
-    this.json = aggregator.aggregate();
+    const aggregator = new FailureAggregator(cli, this.json, this.request);
+    this.json = await aggregator.aggregate();
     cli.log('');
     cli.separator('Stats');
     cli.log('');

lib/ci/failure_aggregator.js

@@ -20,14 +20,47 @@ function uniqBy(array, key) {
 }
 
 export class FailureAggregator {
-  constructor(cli, data) {
+  constructor(cli, data, request) {
     this.cli = cli;
+    this.request = request;
     this.health = data[0];
     this.failures = data.slice(1);
     this.aggregates = null;
   }
 
-  aggregate() {
+  /**
+   * Tells whether the pull request that triggered the run also modified the
+   * test that failed. Such a failure is likely caused by the change itself,
+   * so it should not count as an independent flaky occurrence.
+   */
+  async isSelfInflicted(failure) {
+    const { file, source } = failure;
+    if (!file || !this.request) {
+      return false;
+    }
+
+    const pr = parsePRFromURL(source);
+    if (!pr) {
+      return false;
+    }
+
+    const path = `test/${file}.js`;
+    try {
+      for await (const changed of this.request.getPullRequestFiles(pr)) {
+        if (changed.filename === path) {
+          return true;
+        }
+      }
+    } catch {
+      // Not being able to fetch the changed files is not fatal: keep the
+      // occurrence rather than dropping it on incomplete information.
+      this.cli.warn(`Could not determine the files changed by ${source}`);
+    }
+
+    return false;
+  }
+
+  async aggregate() {
     const groupedByReason = Object.groupBy(this.failures, getHighlight);
     const data = [];
     for (const reason of Object.keys(groupedByReason).sort()) {
@@ -37,7 +70,11 @@ export class FailureAggregator {
 
       // If multiple sub builds of one PR are failed by the same reason,
       // we'll only take one of those builds, as that might be a genuine failure
-      const prs = uniqBy(failures, 'source')
+      const candidates = uniqBy(failures, 'source');
+      const selfInflicted = await Promise.all(
+        candidates.map(failure => this.isSelfInflicted(failure)));
+      const prs = candidates
+        .filter((_, index) => !selfInflicted[index])
         .map(({ source, upstream }) => ({ source, upstream, _id: parseJobFromURL(upstream).jobid }))
         .sort((a, b) => a._id - b._id);
       const machines = uniqBy(
@@ -57,9 +94,9 @@ export class FailureAggregator {
   }
 
   formatAsMarkdown() {
-    let { aggregates } = this;
+    const { aggregates } = this;
     if (!aggregates) {
-      aggregates = this.aggregates = this.aggregate();
+      throw new Error('aggregate() must be awaited before formatAsMarkdown()');
     }
 
     const last = parseJobFromURL(this.failures[0].upstream);
@@ -118,9 +155,9 @@ export class FailureAggregator {
   }
 
   display() {
-    let { cli, aggregates } = this;
+    const { cli, aggregates } = this;
     if (!aggregates) {
-      aggregates = this.aggregates = this.aggregate();
+      throw new Error('aggregate() must be awaited before display()');
     }
 
     for (const type of Object.keys(aggregates)) {

test/unit/failure_aggregator.test.js

@@ -0,0 +1,122 @@
+import assert from 'node:assert';
+import { describe, it } from 'node:test';
+
+import { FailureAggregator } from '../../lib/ci/failure_aggregator.js';
+
+const health = { type: 'health' };
+
+/**
+ * Builds a JS test failure as produced by the CI parsers, where `file` is the
+ * test name reported by the runner and `source` is the pull request that
+ * triggered the run.
+ */
+function failure(prid, file, jobid) {
+  return {
+    type: 'JS_TEST_FAILURE',
+    reason: `not ok 1 ${file}\n  ---\n  severity: fail\n`,
+    highlight: 0,
+    file,
+    source: `https://github.com/nodejs/node/pull/${prid}/`,
+    upstream: `https://ci.nodejs.org/job/node-test-pull-request/${jobid}/`,
+    builtOn: `test-machine-${jobid}`,
+    url: `https://ci.nodejs.org/job/node-test-commit/${jobid}/console`
+  };
+}
+
+/**
+ * Stubs the parts of the request client the aggregator relies on. `changed`
+ * maps a pull request number to the files it modified.
+ */
+function requestStub(changed) {
+  return {
+    async * getPullRequestFiles({ prid }) {
+      for (const filename of changed[prid] ?? []) {
+        yield { filename };
+      }
+    }
+  };
+}
+
+const cli = { warn() {} };
+
+describe('FailureAggregator', () => {
+  it('should not count a failure in a test the pull request modified', async() => {
+    const request = requestStub({
+      65113: ['lib/fs.js'],
+      65233: ['test/ffi/test-ffi-fast-buffer.js']
+    });
+
+    const aggregator = new FailureAggregator(cli, [
+      health,
+      failure(65113, 'ffi/test-ffi-fast-buffer', 75793),
+      failure(65233, 'ffi/test-ffi-fast-buffer', 75799)
+    ], request);
+
+    const aggregates = await aggregator.aggregate();
+    const [entry] = aggregates.JS_TEST_FAILURE;
+
+    assert.strictEqual(entry.prs.length, 1);
+    assert.strictEqual(
+      entry.prs[0].source,
+      'https://github.com/nodejs/node/pull/65113/'
+    );
+  });
+
+  it('should keep failures in tests the pull request left alone', async() => {
+    const request = requestStub({
+      65113: ['lib/fs.js'],
+      65233: ['src/ffi/fast.cc']
+    });
+
+    const aggregator = new FailureAggregator(cli, [
+      health,
+      failure(65113, 'ffi/test-ffi-fast-buffer', 75793),
+      failure(65233, 'ffi/test-ffi-fast-buffer', 75799)
+    ], request);
+
+    const aggregates = await aggregator.aggregate();
+    const [entry] = aggregates.JS_TEST_FAILURE;
+
+    assert.strictEqual(entry.prs.length, 2);
+  });
+
+  it('should keep the occurrence when the changed files cannot be fetched', async() => {
+    const request = {
+      getPullRequestFiles() {
+        throw new Error('network is down');
+      }
+    };
+
+    const aggregator = new FailureAggregator(cli, [
+      health,
+      failure(65233, 'ffi/test-ffi-fast-buffer', 75799)
+    ], request);
+
+    const aggregates = await aggregator.aggregate();
+    const [entry] = aggregates.JS_TEST_FAILURE;
+
+    assert.strictEqual(entry.prs.length, 1);
+  });
+
+  it('should leave failures without a test file untouched', async() => {
+    const request = requestStub({ 65233: ['test/ffi/test-ffi-fast-buffer.js'] });
+
+    const buildFailure = {
+      type: 'BUILD_FAILURE',
+      reason: 'fatal: could not read Username',
+      highlight: 0,
+      source: 'https://github.com/nodejs/node/pull/65233/',
+      upstream: 'https://ci.nodejs.org/job/node-test-pull-request/75799/',
+      builtOn: 'test-machine',
+      url: 'https://ci.nodejs.org/job/node-test-commit/75799/console'
+    };
+
+    const aggregator = new FailureAggregator(
+      cli, [health, buildFailure], request);
+
+    const aggregates = await aggregator.aggregate();
+    const [entry] = aggregates.BUILD_FAILURE;
+
+    assert.strictEqual(entry.prs.length, 1);
+  });
+});