REN

Flutter Feature Gravity Analyzer

REN measures the performance weight of each feature in your Flutter project by detecting costly AST patterns — reporting a gravity score per feature, without running the app, without Firebase, without manual instrumentation.

Installation

dart pub global activate ren

Usage

# Analyze the current project
ren

# Analyze a specific path
ren --project ./my_app

# Custom feature root
ren --project ./my_app --features lib/ui/screens

# Exclude generated or internal paths
ren --project ./my_app --exclude lib/generated,lib/_tools

# JSON output for CI/CD
ren --format json > ren-report.json

# Fail pipeline if any feature reaches HIGH or above
ren --fail-on high

How it works

ren scans your project's Dart source files using the analyzer package, visits the AST of each file, and detects patterns known to cause performance issues in Flutter apps. Each pattern carries a weight, and the total weight per feature is normalized to a 0–100 gravity score.

If no feature root is found (lib/features/, lib/modules/), ren falls back to treating lib/ as a single feature — so it always produces output regardless of your project structure.

Detected patterns

Category	Pattern	Weight
GPU	`BackdropFilter`	40
GPU	`saveLayer`	45
GPU	`ShaderMask`	35
GPU	`ImageFiltered`	35
GPU	`ClipPath`	25
GPU	`Opacity`	25
GPU	`CustomPaint`	20
GPU	`ColorFiltered`	20
Lists	`ListView`	30
Lists	`GridView`	30
Lists	`SingleChildScrollView`	20
Lists	`Wrap`	15
Images	`Image.network`	25
Images	`NetworkImage`	25
Images	`FadeInImage`	15
Rebuilds	`MediaQuery.of`	20
Rebuilds	`RepaintBoundary`	15
Memory leaks	`Timer`	20
Memory leaks	`Timer.periodic`	30
Memory leaks	`StreamController`	25
Memory leaks	`StreamSubscription`	25
Lifecycle	`setState in dispose`	60
Lifecycle	`setState in build`	50
Lifecycle	`setState in initState`	35

Gravity levels

Score	Level
0–20	🟢 LOW
21–45	🟡 MEDIUM
46–70	🟠 HIGH
71–100	🔴 CRITICAL

CI/CD

- name: Ren — Feature Gravity
  run: |
    dart pub global activate ren
    ren --format json > ren-report.json
    ren --fail-on high

License

Apache 2.0 — see LICENSE.

REN