Recompile Buster

Mix task that analyzes your xref graph to find modules causing excessive recompilation, and helps you fix them.

Recompile Buster analyzes your Elixir project's xref compile-connected graph to surface the modules whose changes trigger the most transitive recompilation. It ranks files by dependency depth, lets you drill into specific files with --explain, and can fail CI when recompilation hotspots exceed a threshold. Stop waiting for full rebuilds — bust the compile-time coupling.

Installation

Add recompile_buster to your list of dependencies in mix.exs:

def deps do
  [
    {:recompile_buster, "~> 0.1.0", only: [:dev, :test], runtime: false}
  ]
end

Usage

# Show top 20 files causing the most recompilation
mix recompile_buster

# Show top 10 only
mix recompile_buster --limit 10

# Fail CI if more than 200 problematic files
mix recompile_buster --fail-above 200

# Drill into a specific file
mix recompile_buster --explain lib/my_app/accounts/user.ex

Options

Option	Description
`--limit N`	Show top N files (default: 20)
`--fail-above N`	Fail (exit 1) if problematic files exceed N
`--min-transitive-deps N`	Minimum transitive deps to be considered problematic (default: 5)
`--explain FILE`	Show detailed breakdown for a specific file

How it works

Generates two xref graphs: full (all labels) and compile-connected
Builds a reverse graph from compile-connected edges (recompilation impact)
Counts transitive dependencies per file (up to 3 levels deep) from the full graph
Filters to files that are compile dependencies (recompiles > 0)
Ranks by transitive_deps, optionally failing CI if a threshold is exceeded

Understanding the output

The report shows a table with two key metrics per file:

Transitive deps: Number of unique transitive dependencies (up to 3 levels). Higher means more volatile — changes in any of these files can trigger a cascade.
Recompiles: Number of files that recompile when this file changes.

Use --explain to drill into a specific file and see:

(A) Which files recompile when it changes
(B) Its direct dependencies and their own transitive dep counts

Every file in (A) will recompile if any file in (B) changes. To fix this, either break the compile dependency (A) or reduce the transitive deps (B).

License

MIT