Skip to content
Find underused colors, overused magical numbers and the largest classes in any Flutter project.
Branch: master
Clone or download

Latest commit

Fetching latest commit…
Cannot retrieve the latest commit at this time.


Type Name Latest commit message Commit time
Failed to load latest commit information.

Flutter Resource Ranker

It is easy to overuse colors, write magical numbers or long classes. This project has a script to help you detect these. This was inspired by a tweet from Emma Vanbrabant, where she ranked Android color resources. Seeing the usefulness, I decided replicating and expanding for Flutter. It can do the following:


What it can do

Detect color usage (either Color(...) or Color primary = ...):

  • See frequency of hardcoded colors. Consider using a variable for better maintainability and multi-theme support.
  • Detect colors used in few places. When Chrome was redesigned, the team discovered it had 95 shades of grey. They managed to reduce to 8. Material Design Theme supports 12 categories of color. Try to keep it simple(r).
  • See how detected colors contrast with black or white. It follows WACG recommendations and is useful to see if a heavily used color doesn't have enough contrast with black or white.

Detect class size (counts the number of ; inside each class):

  • Inspired by Detekt LongMethod. Useful to see who are the largest classes and if there is any that is an outlier (i.e. has many more lines of code than others).
  • In the future, this script could be configured for use in a CI system to fail/reject a commit or pull request that has a huge class.

Detect magical numbers (finds every number different than [-1,0,1,2] without a ; or , nearby):

  • Inspired by Detekt MagicNumber. Detect numbers that are not attributed to a variable or method call (as long as there is a , after the number). The script can be customised to be more or less strict.

Getting Started

The script was written in Kotlin and depends on JVM (for File access). If you need to install Kotlin for command line access, check here (brew install kotlin).

The script only scans .dart files.

$ ./resourceranker.kts <project directory> [OPTIONS]
$ kotlinc -script resourceranker.kts <project directory> [OPTIONS]

color       How many colors you are using and how many times
contrast    How many colors and how they compare to black and white
num         How many magical numbers you are using and how many times
class       How many lines each class has.
help        Show this text.
<int>       Max limit. If 0, shows all elements. Default is 10.

$ ./resourceranker.kts documents/project color 10
$ ./resourceranker.kts ../ class 0
$ ./resourceranker.kts ../../ contrast 5
$ ./resourceranker.kts ./ num
$ ./resourceranker.kts desktop class color 0


Issue Tracking

Found a bug? Have an idea for an improvement? Would you like to add to CI or convert to other language? Feel free to add an issue.


Copyright 2020 Bernardo Ferrari.

Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

You can’t perform that action at this time.