Add more explicit types for the default theme (#8780)

* Add more explicit types for the default theme

* Update changelog

* Cleanup

* Cleanup code a bit

* Add special cases for a few keys

* Fix order

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Don’t prefix selectors in arbitrary variants ([#8773](https://github.com/tailwindlabs/tailwindcss/pull/8773))
 - Add support for alpha values in safe list ([#8774](https://github.com/tailwindlabs/tailwindcss/pull/8774))
 - Support default `font-weight`s in font size utilities ([#8763](https://github.com/tailwindlabs/tailwindcss/pull/8763))
+- Add more explicit types for the default theme ([#8780](https://github.com/tailwindlabs/tailwindcss/pull/8780))
 
 ## [3.1.4] - 2022-06-21
 

defaultTheme.d.ts

@@ -1,3 +1,4 @@
 import type { Config } from './types/config'
-declare const theme: Config['theme']
+import { DefaultTheme } from './types/generated/default-theme'
+declare const theme: Config['theme'] & DefaultTheme
 export = theme

scripts/generate-types.js

@@ -1,8 +1,10 @@
 import prettier from 'prettier'
 import { corePlugins } from '../src/corePlugins'
 import colors from '../src/public/colors'
+import defaultTheme from '../src/public/default-theme'
 import fs from 'fs'
 import path from 'path'
+import * as types from './type-utils'
 
 fs.writeFileSync(
   path.join(process.cwd(), 'types', 'generated', 'corePluginList.d.ts'),
@@ -50,3 +52,54 @@ fs.writeFileSync(
     }
   )
 )
+
+const defaultThemeTypes = Object.entries(defaultTheme)
+  .map(([name, value]) => {
+    // Special cases for slightly more accurate types
+    if (name === 'keyframes') {
+      return [name, `Record<${types.forKeys(value)}, Record<string, CSSDeclarationList>>`]
+    }
+
+    if (name === 'fontSize') {
+      return [name, `Record<${types.forKeys(value)}, [string, { lineHeight: string }]>`]
+    }
+
+    // General cases
+    if (typeof value === 'string') {
+      return [name, `string`]
+    }
+
+    if (typeof value === 'function') {
+      return [name, null]
+    }
+
+    if (typeof value === 'object') {
+      if (Object.keys(value).length === 0) {
+        return [name, null]
+      }
+
+      return [name, types.forValue(value)]
+    }
+
+    return [name, `unknown`]
+  })
+  .filter(([, type]) => type !== null)
+  .map(([name, type]) => `${name}: ${type}`)
+  .join('\n')
+
+fs.writeFileSync(
+  path.join(process.cwd(), 'types', 'generated', 'default-theme.d.ts'),
+  prettier.format(
+    `
+    import { Config } from '../../types'
+    type CSSDeclarationList = Record<string, string>
+    export type DefaultTheme = Config['theme'] & { ${defaultThemeTypes} }
+  `,
+    {
+      semi: false,
+      singleQuote: true,
+      printWidth: 100,
+      parser: 'typescript',
+    }
+  )
+)

scripts/type-utils.js

@@ -0,0 +1,27 @@
+export function union(types) {
+  return [...new Set(types)].join(' | ')
+}
+
+export function unionValues(values) {
+  return union(values.map(forValue))
+}
+
+export function forKeys(value) {
+  return union(Object.keys(value).map((key) => `'${key}'`))
+}
+
+export function forValue(value) {
+  if (Array.isArray(value)) {
+    return `(${unionValues(value)})[]`
+  }
+
+  if (typeof value === 'object') {
+    return `Record<${forKeys(value)}, ${unionValues(Object.values(value))}>`
+  }
+
+  if (typeof value === 'string') {
+    return `string`
+  }
+
+  return `any`
+}