デザインシステムの計画

A design system is a collection of reusable components, design tokens, guidelines, and documentation that enables teams to build consistent user interfaces efficiently. In a Tailwind context, the design system includes the token configuration in tailwind.config.js, a library of styled components, written conventions, and documentation tooling so the whole team uses the system rather than reinventing solutions.

Before writing any code, define the scope of your design system. Answer three questions: Which products does it serve? (one app, multiple apps, third-party consumers). Which component categories does it cover? (typography, forms, layout primitives, complex patterns). Who maintains it? (dedicated team, distributed contributors). Scope drives every subsequent decision about complexity and governance.

Design tokens are the atomic values the system is built from. Plan a two-tier taxonomy: primitive tokens are raw values (like blue-500: #3b82f6), and semantic tokens are purpose-driven references (like color.primary: blue-500). Semantic tokens are what components consume; primitive tokens are what semantic tokens reference. This indirection enables theme switching without touching components.

Pick your documentation approach early because it shapes how you write components. Common options: Storybook for interactive component sandboxes and visual regression testing, Docusaurus for written documentation with code samples, or a custom Next.js documentation site using your own design system (eating your own dog food). Each has trade-offs in setup cost and maintenance burden.

List every component your products need and prioritize them by frequency of use and impact on consistency. Buttons appear everywhere — build them first. DataTables are used rarely and complex — defer until later iterations. A simple spreadsheet with columns for component name, priority (high/medium/low), and status (planned/in-progress/done) is sufficient to track the build-out.

Decide on your accessibility target level before building any components. WCAG 2.1 AA is the standard most organizations target. Document which ARIA patterns each component type must implement: buttons need type attributes, modals need focus trapping, dropdowns need role='listbox', etc. Including accessibility in the planning phase costs far less than retrofitting it later.

Establish naming conventions before writing a single component. Choose a style for component names (PascalCase), variant prop names (variant: primary | secondary | danger), and size prop names (size: sm | md | lg). Document this in your contributing guide so all contributors produce predictable, discoverable APIs without needing code review for naming disagreements.

Lay out the repository structure before coding. A typical design system package contains a src/components/ directory (one subfolder per component), a src/tokens/ directory, a src/index.ts barrel export, and a tailwind.config.js. Storybook stories live alongside their components in ComponentName.stories.tsx files for proximity.

A design system without governance degrades into inconsistency. Define a contribution process: how engineers propose new components (RFC document or issue template), who reviews them (design system team + one other designer), and what the acceptance criteria are (WCAG AA, TypeScript types, Storybook story, unit test). Write this in a CONTRIBUTING.md at the package root.

Version the design system using Semantic Versioning: patch for bug fixes, minor for new components or additive changes, major for breaking changes to existing APIs. Publish a machine-readable changelog with each release. Establish a policy for how long deprecated APIs are supported before removal — typically two major versions — so consumers have time to migrate without being stranded.

Keep design tokens synchronized between your Figma files and the code. Tools like Style Dictionary or Tokens Studio can export Figma design tokens directly to a JSON format that populates the Tailwind config. This single source of truth prevents the classic scenario where designers update colors in Figma but the code still uses old hex values weeks later.

Test your understanding of Tailwind CSS Mastery concepts from this lesson.

In this lesson you learned: defining system scope including products, component inventory, and maintainership, planning a two-tier token taxonomy with primitive and semantic tokens, and establishing governance with contribution processes, versioning policy, and design-to-code token synchronization. Next up we implement the token and config layer.