Fallow - Dead Code Analysis

Version updated for https://github.com/fallow-rs/fallow to version v1.7.0.

  • This action is used across all versions by 1 repositories.

Action Type

This is a Composite action.

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Action Summary

This GitHub Action, fallow, is a Rust-based codebase analyzer designed to optimize TypeScript and JavaScript projects by detecting unused code, circular dependencies, duplicate code, and high-complexity functions. It automates tasks like identifying dead files, unused exports, and unresolved imports, while offering significantly faster performance compared to similar tools. By streamlining code analysis and improving maintainability, it helps developers identify inefficiencies and reduce technical debt.

Release notes

Hotspot analysis

New fallow health --hotspots command identifies the riskiest files in your codebase by combining git churn with complexity data. The files that are both complex and frequently changing are where bugs hide — now fallow surfaces them automatically.

fallow health --hotspots                # Default: 6 months, min 3 commits
fallow health --hotspots --since 3m     # Last 3 months
fallow health --hotspots --top 10       # Top 10 riskiest files
fallow health --hotspots --format json  # Machine-readable for CI/dashboards

How it works

  • Score: normalized_churn × normalized_complexity × 100 (0-100, higher = riskier)
  • Churn: Recency-weighted commit count with exponential decay (half-life 90 days) — recent changes matter more
  • Trend detection: Each file labeled as accelerating (getting worse), stable, or cooling (improving)
  • Fan-in: Shown as “blast radius” column — how many files depend on this hotspot
  • --since: Accepts durations (6m, 90d, 1y, 2w) and ISO dates (2025-06-01)
  • --min-commits: Filter out low-activity files (default: 3)

Output

Clean two-line format with color-coded scores and trend symbols:

● Hotspots (12 files, since 6 months)

  78.3 ▲  src/components/Dashboard.tsx
          15 commits    892 churn  0.28 density    8 fan-in  ▲ accelerating

  64.1 ▲  src/services/api/client.ts
          11 commits    540 churn  0.19 density   12 fan-in  ▲ accelerating

  42.7 ─  src/utils/validation.ts
           8 commits    310 churn  0.14 density    6 fan-in  ─ stable

Also in this release

  • File health scores (--file-scores) now use the same two-line format for consistency
  • MCP server check_health tool supports hotspots, since, and min_commits parameters
  • Shallow clone detection with warning when git history may be incomplete

Fixes

  • MCP tests on Windows: skip /bin/sh-dependent tests on non-Unix platforms
  • Typo checker false positive and Windows path separator in list tests

Full Changelog: https://github.com/fallow-rs/fallow/compare/v1.6.1...v1.7.0