Deno lint failures (deno lint) in CI

By Daniel Zoghalchali·Latchkey

deno lint applies its built-in rules and exits non-zero when any file violates one. In CI this fails the job and prints the rule name, file, and line for each finding.

What this error means

The lint step fails with "error: Found N problems" and lists each finding with a rule name such as no-unused-vars or require-await.

error[no-unused-vars]: `x` is never used
 --> /home/runner/work/app/app/src/main.ts:2:7
  |
2 | const x = 1;
  |       ^
Found 1 problem

Common causes

Code violates a built-in lint rule

An unused variable, missing await, or other rule violation is flagged and fails the gate.

Lint config differs from local

Rules enabled or excluded in deno.json differ from what you ran locally, so CI reports findings you did not see.

How to fix it

Fix or scope the violations

1. Read each rule and location in the output.
2. Fix the code, or configure lint rules/excludes in deno.json intentionally.
3. Re-run deno lint to confirm it passes.

deno lint

Keep lint config in deno.json

Declare enabled rules and excluded files so local and CI lint identically.

{
  "lint": {
    "rules": { "tags": ["recommended"] },
    "exclude": ["dist/"]
  }
}

How to prevent it

• Run deno lint locally before pushing.
• Keep lint rules and excludes in deno.json under version control.
• Address findings rather than disabling rules broadly.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation