chore: add no-unused-expressions lint rule by simon-id · Pull Request #7007 · DataDog/dd-trace-js

simon-id · 2025-11-27T13:30:08Z

What does this PR do?

Add the eslint rule no-unused-expressions, it prevents stuff like:

function a () {
  if (x) false // forgot the return statement

  blabla()
}

It also allows the use of the void operator, to explicitly allow statements with only side effects.

Motivation

Mistakes have been made in previous PRs that could have been prevented with this rule.

github-actions · 2025-11-27T13:30:27Z

Overall package size

Self size: 4.56 MB
Deduped: 5.4 MB
No deduping: 5.4 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | import-in-the-middle | 2.0.6 | 81.92 kB | 813.08 kB | | dc-polyfill | 0.1.10 | 26.73 kB | 26.73 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

codecov · 2025-11-27T13:30:48Z

Codecov Report

❌ Patch coverage is 46.66667% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.41%. Comparing base (5e2f013) to head (b5bbc7a).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...ckages/datadog-plugin-azure-functions/src/index.js	0.00%	3 Missing ⚠️
packages/datadog-instrumentations/src/couchbase.js	33.33%	2 Missing ⚠️
packages/datadog-instrumentations/src/dns.js	0.00%	1 Missing ⚠️
...ages/datadog-instrumentations/src/elasticsearch.js	0.00%	1 Missing ⚠️
packages/datadog-instrumentations/src/mysql.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7007      +/-   ##
==========================================
+ Coverage   80.40%   80.41%   +0.01%     
==========================================
  Files         732      732              
  Lines       31050    31050              
==========================================
+ Hits        24965    24970       +5     
+ Misses       6085     6080       -5

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pr-commenter · 2025-11-27T13:39:13Z

Benchmarks

Benchmark execution time: 2026-02-04 12:43:58

Comparing candidate commit b5bbc7a in PR branch simon-id-patch-2 with baseline commit 5e2f013 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 226 metrics, 34 unstable metrics.

packages/datadog-instrumentations/src/mariadb.js

eslint.config.mjs

packages/datadog-plugin-azure-functions/src/index.js

packages/datadog-instrumentations/src/mariadb.js

packages/dd-trace/src/remote_config/scheduler.js

packages/datadog-plugin-azure-functions/src/index.js

BridgeAR · 2026-01-22T21:15:18Z

Ping @simon-id

Co-authored-by: Thomas Watson <[email protected]>

packages/datadog-plugin-azure-functions/test/integration-test/eventhubs-test/eventhubs.spec.js

packages/datadog-plugin-mariadb/test/index.spec.js

simon-id

LGTM @BridgeAR care to approve? i can't since i'm author and last comitter. I made a couple commits, PTAL

Azure functions was in some circumstances attaching the span to a parent span instead of acting as a root span by missing a return statement. Mariadb v2 did not track promise errors in all cases. This was detected by adding the no-unused-expressions lint rule. To address confusion, JSDoc was added about childOf being `null` and its meaning. In addition, the azure tests are now using the latest version again, since their library fixed the former support range issue. The void is now allowed as statement to address issues around e.g., `error.stack` access for triggering the stack calculation.

simon-id added the semver-patch label Dec 1, 2025

simon-id changed the title ~~Update eslint.config.mjs~~ chore: add no-unused-expressions lint rule Dec 1, 2025

simon-id self-assigned this Dec 1, 2025

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simon-id marked this pull request as ready for review December 2, 2025 12:41

simon-id requested review from a team as code owners December 2, 2025 12:41

simon-id requested review from khanayan123 and removed request for a team December 2, 2025 12:41

simon-id commented Dec 2, 2025

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BridgeAR reviewed Dec 2, 2025

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rochdev previously approved these changes Dec 2, 2025

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watson reviewed Dec 3, 2025

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simon-id dismissed rochdev’s stale review via 61593c8 December 3, 2025 09:30

bm1549 removed the request for review from khanayan123 December 31, 2025 16:27

simon-id and others added 10 commits February 2, 2026 20:59

Update eslint.config.mjs

b7b23b4

zeui

e3d055e

add void before error.stack

1049a4f

replace short-circuit with optional chaining

e4a7358

add probably missing return

9137c3d

order rule correctly

df9fe8e

disable no-void

243a0c7

fix weird line

86deb5f

Update packages/dd-trace/src/remote_config/scheduler.js

28387e0

Co-authored-by: Thomas Watson <[email protected]>

fixup! add tests, limit eslint rule, add JSDoc

4be72bd

BridgeAR force-pushed the simon-id-patch-2 branch from 61593c8 to 4be72bd Compare February 3, 2026 02:08

BridgeAR added 2 commits February 3, 2026 03:39

fixup! add regression tests and remove outdated comment

0b23e0b

fixup! remove very slow azure test

b510d07

simon-id commented Feb 3, 2026

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packages/datadog-plugin-azure-functions/test/integration-test/eventhubs-test/eventhubs.spec.js Show resolved Hide resolved

simon-id commented Feb 4, 2026

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simon-id added 3 commits February 4, 2026 10:02

Merge branch 'master' into simon-id-patch-2

2cdc8b0

change ternary into if statement

a677d19

try something

b5bbc7a

simon-id commented Feb 4, 2026

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BridgeAR approved these changes Feb 4, 2026

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BridgeAR merged commit 313fe22 into master Feb 4, 2026
788 checks passed

BridgeAR deleted the simon-id-patch-2 branch February 4, 2026 22:09

dd-octo-sts bot mentioned this pull request Feb 5, 2026

v5.85.0 proposal #7399

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chore: add no-unused-expressions lint rule#7007

chore: add no-unused-expressions lint rule#7007
BridgeAR merged 15 commits intomasterfrom
simon-id-patch-2

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