⚡🧠️ diff-coverage

Diff-cover, supercharged in Rust 🦀. Get instant, actionable coverage insights at ⚡ blazing speed ⚡ with a 🧠️ tiny memory footprint 🧠️. Built for modern CI and massive repos, it turns slow coverage checks into fast, reliable feedback you can trust.

Usage

diff-coverage coverage.xml --diff-file diff.diff

# Multiple coverage inputs (repeat or comma‑separated)
diff-coverage coverage1.xml coverage2.xml --diff-file diff.diff

# Multiple coverage inputs in a directory
diff-coverage ./coverage/ --diff-file diff.diff

# Fail the build if diff coverage drops below a threshold
diff-coverage ./coverage/ coverage.xml --diff-file diff.diff --fail-under 80

# Output to CI formats
diff-coverage coverage.xml --diff-file diff.diff --output gitlab=diff-cover.json
diff-coverage coverage.xml --diff-file diff.diff --output json=diff-cover.json --output summary

Options

• --diff-file : diff to analyze
• --fail-under : minimum acceptable diff coverage
• --missing-coverage : how to handle files missing from coverage (uncovered or ignore, default: ignore)
• --output <FORMAT=PATH>: output target(s), repeatable or comma‑separated Formats: cli, summary, gitlab, json (note: cli and summary don’t take a path)
• -h, --help: show help
• -V, --version: show version

Performance highlights

Benchmark 1

• Git diff file: 40MB size and 1,808,684 lines long
• Coverage file: 46MB size and 1,115,971 lines long

Metric	Rust	Python	Improvement (Python / Rust)
Mean wall time	2.47s	108.23s	43.90×
Max wall time	3.66s	109.74s	29.98×
Mean peak RSS	22.66 MB	640.37 MB	28.26×
Max peak RSS	22.84 MB	640.66 MB	28.05×

Benchmark 2

• Git diff file: 40MB size and 1,808,684 lines long
• 50 coverage files: each 620KB size and 24,116 lines long

Metric	Rust	Python	Improvement (Python / Rust)
Mean wall time	2.10s	227.24s	108.24×
Max wall time	4.11s	240.35s	58.48×
Mean peak RSS	22.69 MB	494.35 MB	21.78×
Max peak RSS	22.84 MB	494.64 MB	21.65×

Peak RSS shown in MB (kB ÷ 1024).
Full benchmark results

Installation

Prebuilt binaries

Download the prebuilt archives from the GitHub Releases page.

Cargo install

cargo install diff-coverage

Docker

docker run --rm -v "$PWD":/work -w /work <dockerhub-user>/diff-coverage:latest \
  coverage.xml --diff-file diff.diff

Build

cargo build

Run

cargo run

Test

cargo test

Release (GitHub Actions)

Push a version tag and GitHub Actions will run tests and attach executables to the GitHub Release:

git tag v0.1.0
git push origin v0.1.0

Download the prebuilt archives from the GitHub Releases page.