Flutter Design System

You are working on a Flutter design system package - a design_system/ package at the monorepo root, depended on by every app.

When argument is "setup" or empty

Scaffold the complete design system package structure:

Package Structure

design_system/
├── pubspec.yaml
└── lib/
    ├── design_system.dart              ← Barrel export file
    └── src/
        ├── tokens/
        │   ├── ds_colors.dart          ← All brand colors
        │   ├── ds_typography.dart      ← TextStyle definitions
        │   ├── ds_spacing.dart         ← Spacing constants
        │   ├── ds_radius.dart          ← Border radius constants
        │   └── ds_shadows.dart         ← BoxShadow constants
        ├── theme/
        │   └── ds_theme.dart           ← ThemeData factory
        └── components/
            ├── buttons/
            │   └── ds_button.dart
            ├── inputs/
            │   └── ds_text_field.dart
            └── typography/
                └── ds_text.dart

Design Tokens Pattern (mapped from Figma tokens)

ds_colors.dart:

abstract final class DSColors {
  // Neutral
  static const Color neutral0   = Color(0xFFFFFFFF);
  static const Color neutral100 = Color(0xFFF5F5F5);
  static const Color neutral200 = Color(0xFFE5E5E5);
  static const Color neutral500 = Color(0xFF737373);
  static const Color neutral900 = Color(0xFF181D27);

  // Brand / Primary
  static const Color brandPrimary   = Color(0xFF7839EE);
  static const Color brandSecondary = Color(0xFF5B21B6);

  // Semantic
  static const Color success = Color(0xFF16A34A);
  static const Color warning = Color(0xFFF59E0B);
  static const Color error   = Color(0xFFDC2626);
  static const Color info    = Color(0xFF2563EB);

  // Text (semantic aliases)
  static const Color textPrimary   = neutral900;
  static const Color textSecondary = neutral500;
  static const Color textInverse   = neutral0;
}

ds_spacing.dart:

abstract final class DSSpacing {
  static const double xs  = 4.0;
  static const double sm  = 8.0;
  static const double md  = 12.0;
  static const double lg  = 16.0;
  static const double xl  = 24.0;
  static const double xxl = 32.0;
  static const double xxxl = 48.0;
}

ds_radius.dart:

abstract final class DSRadius {
  static const double xs  = 4.0;
  static const double sm  = 6.0;
  static const double md  = 8.0;
  static const double lg  = 12.0;
  static const double xl  = 16.0;
  static const double full = 999.0;

  static BorderRadius get xsBorderRadius => BorderRadius.circular(xs);
  static BorderRadius get smBorderRadius => BorderRadius.circular(sm);
  static BorderRadius get mdBorderRadius => BorderRadius.circular(md);
  static BorderRadius get lgBorderRadius => BorderRadius.circular(lg);
}

ds_typography.dart:

import 'package:flutter/material.dart';
import '../tokens/ds_colors.dart';

abstract final class DSTypography {
  static const String _fontFamily = 'Roboto';

  // Headings
  static const TextStyle headingH4 = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 28,
    fontWeight: FontWeight.w700,
    color: DSColors.textPrimary,
    height: 1.25,
  );

  static const TextStyle headingH5 = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 22,
    fontWeight: FontWeight.w600,
    color: DSColors.textPrimary,
    height: 1.3,
  );

  static const TextStyle headingH6 = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 18,
    fontWeight: FontWeight.w600,
    color: DSColors.textPrimary,
    height: 1.4,
  );

  // Body
  static const TextStyle body16Regular = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 16,
    fontWeight: FontWeight.w400,
    color: DSColors.textPrimary,
    height: 1.5,
  );

  static const TextStyle body14Regular = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 14,
    fontWeight: FontWeight.w400,
    color: DSColors.textPrimary,
    height: 1.5,
  );

  static const TextStyle body14Medium = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 14,
    fontWeight: FontWeight.w500,
    color: DSColors.textPrimary,
    height: 1.5,
  );

  static const TextStyle body12Regular = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 12,
    fontWeight: FontWeight.w400,
    color: DSColors.textSecondary,
    height: 1.5,
  );

  // Labels / Captions
  static const TextStyle label = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 12,
    fontWeight: FontWeight.w600,
    letterSpacing: 0.4,
    color: DSColors.textSecondary,
  );

  static const TextStyle caption = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 11,
    fontWeight: FontWeight.w400,
    color: DSColors.textSecondary,
  );

  // Price (domain-specific)
  static const TextStyle price = TextStyle(
    fontFamily: _fontFamily,
    fontSize: 16,
    fontWeight: FontWeight.w700,
    color: DSColors.brandPrimary,
  );
}

ds_theme.dart:

import 'package:flutter/material.dart';
import '../tokens/ds_colors.dart';
import '../tokens/ds_typography.dart';
import '../tokens/ds_radius.dart';

class DSTheme {
  static ThemeData light() => ThemeData(
    useMaterial3: true,
    fontFamily: 'Roboto',
    colorScheme: ColorScheme.fromSeed(
      seedColor: DSColors.brandPrimary,
      brightness: Brightness.light,
    ),
    textTheme: const TextTheme(
      headlineMedium: DSTypography.headingH5,
      titleLarge:     DSTypography.headingH6,
      bodyLarge:      DSTypography.body16Regular,
      bodyMedium:     DSTypography.body14Regular,
      bodySmall:      DSTypography.body12Regular,
      labelSmall:     DSTypography.label,
    ),
    filledButtonTheme: FilledButtonThemeData(
      style: FilledButton.styleFrom(
        backgroundColor: DSColors.brandPrimary,
        foregroundColor: DSColors.neutral0,
        shape: RoundedRectangleBorder(
          borderRadius: DSRadius.mdBorderRadius,
        ),
        minimumSize: const Size(double.infinity, 48),
      ),
    ),
    inputDecorationTheme: InputDecorationTheme(
      border: OutlineInputBorder(borderRadius: DSRadius.mdBorderRadius),
      contentPadding: const EdgeInsets.symmetric(
        horizontal: 16,
        vertical: 12,
      ),
    ),
  );
}

Barrel file (lib/design_system.dart):

export 'src/tokens/ds_colors.dart';
export 'src/tokens/ds_typography.dart';
export 'src/tokens/ds_spacing.dart';
export 'src/tokens/ds_radius.dart';
export 'src/tokens/ds_shadows.dart';
export 'src/theme/ds_theme.dart';
export 'src/components/buttons/ds_button.dart';
export 'src/components/inputs/ds_text_field.dart';
export 'src/components/typography/ds_text.dart';

When argument is a component name

Create a new component in the appropriate components/ subfolder.

Component pattern (e.g., DSButton):

import 'package:flutter/material.dart';
import '../../tokens/ds_colors.dart';
import '../../tokens/ds_spacing.dart';
import '../../tokens/ds_radius.dart';

enum DSButtonVariant { filled, outlined, ghost }

class DSButton extends StatelessWidget {
  final String label;
  final VoidCallback? onPressed;
  final DSButtonVariant variant;
  final bool isLoading;
  final IconData? icon;

  const DSButton({
    super.key,
    required this.label,
    required this.onPressed,
    this.variant = DSButtonVariant.filled,
    this.isLoading = false,
    this.icon,
  });

  @override
  Widget build(BuildContext context) {
    final child = isLoading
        ? const SizedBox(
            width: 20,
            height: 20,
            child: CircularProgressIndicator(strokeWidth: 2),
          )
        : Row(
            mainAxisSize: MainAxisSize.min,
            children: [
              if (icon != null) ...[
                Icon(icon, size: 18),
                const SizedBox(width: DSSpacing.sm),
              ],
              Text(label),
            ],
          );

    return switch (variant) {
      DSButtonVariant.filled => FilledButton(
          onPressed: isLoading ? null : onPressed,
          child: child,
        ),
      DSButtonVariant.outlined => OutlinedButton(
          onPressed: isLoading ? null : onPressed,
          child: child,
        ),
      DSButtonVariant.ghost => TextButton(
          onPressed: isLoading ? null : onPressed,
          child: child,
        ),
    };
  }
}

Instructions

1. Read the existing design_system/ package first if it exists
2. Never duplicate tokens that already exist — extend or update them
3. All token classes use abstract final class (cannot instantiate)
4. All token values are static const
5. Component names are prefixed with DS (e.g., DSButton, DSTextField)
6. Export every new public symbol from the barrel file
7. Add the design_system dependency to any package that needs it in its pubspec.yaml
8. Do NOT use flutter_screenutil in the design system package itself — keep it framework-agnostic