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/* eslint-disable @typescript-eslint/no-require-imports */ |
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/** @type {import('postcss-load-config').Config} */ |
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const postcss = require('postcss') |
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const valueParser = require('postcss-value-parser') |
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/* |
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This plugin polyfills @property definitions with regular CSS variables |
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Additionally, it removes `in <colorspace>` after `to left` or `to right` gradient args for older browsers |
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*/ |
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const propertyInjectPlugin = () => { |
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return { |
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postcssPlugin: 'postcss-property-polyfill', |
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Once(root) { |
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const fallbackRules = [] |
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// 1. Collect initial-value props from @property at-rules |
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root.walkAtRules('property', (rule) => { |
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const declarations = {} |
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let varName = null |
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rule.walkDecls((decl) => { |
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if (decl.prop === 'initial-value') { |
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varName = rule.params.trim() |
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declarations[varName] = decl.value |
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} |
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}) |
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if (varName) { |
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fallbackRules.push(`${varName}: ${declarations[varName]};`) |
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} |
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}) |
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// 2. Inject fallback variables if any exist |
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if (fallbackRules.length > 0) { |
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// check for paint() because its browser support aligns with @property at-rule |
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const fallbackCSS = `@supports not (background: paint(something)) { |
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:root { ${fallbackRules.join(' ')} } |
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}` |
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const sourceFile = root.source?.input?.file || root.source?.input?.from |
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const fallbackAst = postcss.parse(fallbackCSS, { from: sourceFile }) |
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// Insert after last @import (or prepend if none found) |
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let lastImportIndex = -1 |
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root.nodes.forEach((node, i) => { |
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if (node.type === 'atrule' && node.name === 'import') { |
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lastImportIndex = i |
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} |
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}) |
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if (lastImportIndex === -1) { |
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root.prepend(fallbackAst) |
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} |
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else { |
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root.insertAfter(root.nodes[lastImportIndex], fallbackAst) |
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} |
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} |
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// 3. Remove `in <colorspace>` after `to left` or `to right`, e.g. "to right in oklab" -> "to right" |
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root.walkDecls((decl) => { |
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if (!decl.value) return |
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decl.value = decl.value.replaceAll(/\bto\s+(left|right)\s+in\s+[\w-]+/g, (_, direction) => { |
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return `to ${direction}` |
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}) |
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}) |
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}, |
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} |
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} |
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propertyInjectPlugin.postcss = true |
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/* |
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This plugin resolves/calculates CSS variables within color-mix() functions so they can be calculated using postcss-color-mix-function |
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Exception: dynamic values like currentColor |
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*/ |
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const colorMixVarResolverPlugin = () => { |
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return { |
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postcssPlugin: 'postcss-color-mix-var-resolver', |
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Once(root) { |
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const cssVariables = {} |
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// 1. Collect all CSS variable definitions from tailwind |
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root.walkRules((rule) => { |
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if (!rule.selectors) return |
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const isRootOrHost = rule.selectors.some( |
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sel => sel.includes(':root') || sel.includes(':host'), |
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) |
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if (isRootOrHost) { |
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// Collect all --var declarations in this rule |
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rule.walkDecls((decl) => { |
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if (decl.prop.startsWith('--')) { |
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cssVariables[decl.prop] = decl.value.trim() |
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} |
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}) |
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} |
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}) |
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// 2. Parse each declaration's value and replace var(...) in color-mix(...) |
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root.walkDecls((decl) => { |
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const originalValue = decl.value |
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if (!originalValue || !originalValue.includes('color-mix(')) return |
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const parsed = valueParser(originalValue) |
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let modified = false |
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parsed.walk((node) => { |
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if (node.type === 'function' && node.value === 'color-mix') { |
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node.nodes.forEach((childNode) => { |
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if (childNode.type === 'function' && childNode.value === 'var' && childNode.nodes.length > 0) { |
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const varName = childNode.nodes[0]?.value |
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if (!varName) return |
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const resolvedVarName = cssVariables[varName] === undefined ? 'black' : cssVariables[varName] // fall back to black if var is undefined |
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// add whitespace because it might just be a part of a color notation e.g. #fff 10% |
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const resolved = `${resolvedVarName} ` || `var(${varName})` |
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childNode.type = 'word' |
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childNode.value = resolved |
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childNode.nodes = [] |
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modified = true |
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} |
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}) |
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} |
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}) |
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if (modified) { |
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const newValue = parsed.toString() |
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decl.value = newValue |
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} |
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}) |
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}, |
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} |
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} |
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colorMixVarResolverPlugin.postcss = true |
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/* |
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This plugin transforms shorthand rotate/scale/translate into their transform[3d] counterparts |
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*/ |
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const transformShortcutPlugin = () => { |
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return { |
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postcssPlugin: 'postcss-transform-shortcut', |
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Once(root) { |
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const defaults = { |
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rotate: [0, 0, 1, '0deg'], |
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scale: [1, 1, 1], |
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translate: [0, 0, 0], |
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} |
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const fallbackAtRule = postcss.atRule({ |
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name: 'supports', |
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params: 'not (translate: 0)', // or e.g. 'not (translate: 1px)' |
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}) |
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root.walkRules((rule) => { |
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let hasTransformShorthand = false |
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const transformFunctions = [] |
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rule.walkDecls((decl) => { |
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if (/^(rotate|scale|translate)$/.test(decl.prop)) { |
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hasTransformShorthand = true |
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const newValues = [...defaults[decl.prop]] |
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// add whitespaces for minified vars |
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const value = decl.value.replaceAll(/\)\s*var\(/g, ') var(') |
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const userValues = postcss.list.space(value) |
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// special case: rotate w/ single angle only |
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if (decl.prop === 'rotate' && userValues.length === 1) { |
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newValues.splice(-1, 1, ...userValues) |
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} |
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else { |
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// for scale/translate, or rotate with multiple params |
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newValues.splice(0, userValues.length, ...userValues) |
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} |
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// e.g. "translate3d(10px,20px,0)" |
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transformFunctions.push(`${decl.prop}3d(${newValues.join(',')})`) |
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} |
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}) |
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// Process rotate/scale/translate in this rule: |
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if (hasTransformShorthand && transformFunctions.length > 0) { |
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const fallbackRule = postcss.rule({ selector: rule.selector }) |
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fallbackRule.append({ |
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prop: 'transform', |
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value: transformFunctions.join(' '), |
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}) |
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fallbackAtRule.append(fallbackRule) |
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} |
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}) |
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if (fallbackAtRule.nodes && fallbackAtRule.nodes.length > 0) { |
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root.append(fallbackAtRule) |
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} |
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}, |
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} |
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} |
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transformShortcutPlugin.postcss = true |
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/** |
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* PostCSS plugin to transform empty fallback values from `var(--foo,)`, |
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* turning them into `var(--foo, )`. Older browsers need this. |
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*/ |
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const addSpaceForEmptyVarFallback = () => { |
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return { |
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postcssPlugin: 'postcss-add-space-for-empty-var-fallback', |
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/** |
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* We do our edits in `OnceExit`, meaning we process each decl after |
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* the AST is fully built and won't get re-visited or re-triggered |
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* in the same pass. |
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*/ |
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OnceExit(root) { |
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root.walkDecls((decl) => { |
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if (!decl.value || !decl.value.includes('var(')) { |
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return |
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} |
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const parsed = valueParser(decl.value) |
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let changed = false |
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parsed.walk((node) => { |
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// Only consider var(...) function calls |
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if (node.type === 'function' && node.value === 'var') { |
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// Look for the `div` node with value "," that separates property & fallback |
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const commaIndex = node.nodes.findIndex( |
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n => n.type === 'div' && n.value === ',', |
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) |
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// If no comma is found, no fallback segment |
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if (commaIndex === -1) return |
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// Gather any fallback text |
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const fallbackNodes = node.nodes.slice(commaIndex + 1) |
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const fallbackText = fallbackNodes.map(n => n.value).join('').trim() |
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// If there's no fallback text => `var(--something,)` => we insert a space |
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if (fallbackText === '') { |
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const commaNode = node.nodes[commaIndex] |
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// If the comma node is literally "," with no space, change it to ", " |
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if (commaNode.value === ',') { |
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commaNode.value = ', ' |
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changed = true |
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} |
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} |
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} |
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}) |
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if (changed) { |
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decl.value = parsed.toString() |
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} |
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}) |
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}, |
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} |
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} |
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addSpaceForEmptyVarFallback.postcss = true |
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const config = { |
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plugins: [ |
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require('@csstools/postcss-cascade-layers'), |
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propertyInjectPlugin(), |
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colorMixVarResolverPlugin(), |
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transformShortcutPlugin(), |
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addSpaceForEmptyVarFallback(), |
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require('postcss-media-minmax'), |
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require('@csstools/postcss-oklab-function'), |
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require('@csstools/postcss-color-mix-function'), |
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require('postcss-nesting'), |
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require('autoprefixer'), |
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], |
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} |
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module.exports = config |
Impressive!