Write custom transform file for design tokens from Figma in Style Dictionary for Flutter - flutter

Question

I have barebone Flutter 2.5 project and Figma design tokens which were exported via Figma Tokens.
Those design tokens look like this:
project\style_dictionary\properties\tokens.json
{
"borderWidth": {
"100": {
"value": "1.5",
"type": "borderWidth"
}
},
"opacity": {
"basic": {
"100": {
"value": "0.04",
"type": "opacity"
}
}
},
"colors": {
"basic": {
"red": {
"50": {
"value": "#ffebee",
"type": "color"
}
}
}
}
}
and Style Dictionary config which looks like this
project\style_dictionary\config.json
{
"source": [
"properties/*.json"
],
"platforms": {
"flutter": {
"transformGroup": "flutter",
"buildPath": "../lib/unique_file/",
"files": [
{
"destination": "style_dictionary.dart",
"format": "flutter/class.dart",
"className": "StyleDictionary"
}
]
},
"flutter-separate": {
"transformGroup": "flutter-separate",
"buildPath": "../lib/unique_file/",
"files": [
{
"destination": "style_dictionary_color.dart",
"format": "flutter/class.dart",
"className": "StyleDictionaryColor",
"type": "color",
"filter": {
"attributes": {
"category": "colors"
}
}
}
]
}
}
}
Running style-dictionary build in CMD in style_dictionary will generate next file
project\lib\unique_file\style_dictionary_color.dart
import 'dart:ui';
class StyleDictionaryColor {
StyleDictionaryColor._();
static const basicRed50 = #ffebee;
}
But in should be like that at the end
project\lib\unique_file\style_dictionary_color.dart
import 'dart:ui';
class StyleDictionaryColor {
StyleDictionaryColor._();
static const basicRed50 = Color(0xFFFFEBEE);
}
Question:
How and where can I create Style Dictionary transforms file to create right dart file with Color type of the static variable?
I cannot modify exported design tokens.

Answer 1

Create a project\build.js as a custom Transforms file. Logic of creation was used from default Flutter color transforms and Documentation
const StyleDictionary = require('style-dictionary')
const baseConfig = require('./style_dictionary/config.json')
const Color = require('tinycolor2')
StyleDictionary.registerTransform({
name: 'colors/hex8flutter',
type: 'value',
matcher: prop => {
return prop.attributes.category === 'colors'
},
transformer: prop => {
var str = Color(prop.value).toHex8().toUpperCase();
return `Color(0x${str.slice(6)}${str.slice(0, 6)})`;
},
})
const StyleDictionaryExtended = StyleDictionary.extend(baseConfig)
StyleDictionaryExtended.buildAllPlatforms()
Modify project\style_dictionary\config.json so it can be executed from project directory and include new transforms - "transformColorsToColor" together with other transforms from Flutter
{
"source": [
"style_dictionary/properties/*.json"
],
"platforms": {
"flutter": {
"transforms": ["attribute/cti", "name/cti/camel", "color/hex8flutter", "size/flutter/remToDouble", "content/flutter/literal", "asset/flutter/literal", "font/flutter/literal", "colors/hex8flutter"],
"buildPath": "lib/unique_file/",
"files": [
{
"destination": "style_dictionary.dart",
"format": "flutter/class.dart",
"className": "StyleDictionary"
}
]
},
"flutter-separate": {
"transforms": ["attribute/cti", "name/ti/camel", "color/hex8flutter", "size/flutter/remToDouble", "content/flutter/literal", "asset/flutter/literal", "font/flutter/literal", "colors/hex8flutter"],
"buildPath": "lib/unique_file/",
"files": [
{
"destination": "style_dictionary_color.dart",
"format": "flutter/class.dart",
"className": "StyleDictionaryColor",
"type": "color",
"filter": {
"attributes": {
"category": "colors"
}
}
}
]
}
}
}
Run npm init with all default answers
Run npm install --save tinycolor2
Run node build.js