How to Fail CI on Code Duplication

Add a duplicated_lines_density condition to the Sonar gate, or run jscpd standalone with a max threshold that exits non-zero.

For a Sonar-based flow, set a duplicated lines density condition. For a standalone check, run jscpd with --threshold so the command fails the job when duplication is too high.

Standalone jscpd

jobs:
  duplication:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npx jscpd src --threshold 3 --reporters console --min-tokens 50

Sonar gate condition

# In the quality gate on New Code:
#   Duplicated Lines (%) is greater than 3.0  -> gate fails
sonar.cpd.exclusions=**/generated/**,**/*.pb.go

Gotchas

• jscpd exits 1 only when --threshold is set and exceeded; without it the run always passes.
• Tune --min-tokens so small idiomatic blocks are not flagged as duplicates.

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