Add transform and extract APIs (#4469)

* add `transform` and `extract` APIs

* make svelte transform part of the transformer stuff

src/jit/lib/expandTailwindAtRules.js

@@ -1,5 +1,3 @@
-import fs from 'fs'
-import path from 'path'
 import * as sharedState from './sharedState'
 import { generateRules } from './generateRules'
 import bigSign from '../../util/bigSign'
@@ -11,38 +9,63 @@ let contentMatchCache = sharedState.contentMatchCache
 const BROAD_MATCH_GLOBAL_REGEXP = /[^<>"'`\s]*[^<>"'`\s:]/g
 const INNER_MATCH_GLOBAL_REGEXP = /[^<>"'`\s.(){}[\]#=%]*[^<>"'`\s.(){}[\]#=%:]/g
 
-function getDefaultExtractor(fileExtension) {
-  return function (content) {
-    if (fileExtension === 'svelte') {
-      content = content.replace(/(?:^|\s)class:/g, ' ')
-    }
+const builtInExtractors = {
+  DEFAULT: (content) => {
     let broadMatches = content.match(BROAD_MATCH_GLOBAL_REGEXP) || []
     let innerMatches = content.match(INNER_MATCH_GLOBAL_REGEXP) || []
 
     return [...broadMatches, ...innerMatches]
-  }
+  },
+}
+
+const builtInTransformers = {
+  DEFAULT: (content) => content,
+  svelte: (content) => content.replace(/(?:^|\s)class:/g, ' '),
 }
 
 function getExtractor(tailwindConfig, fileExtension) {
-  const purgeOptions = tailwindConfig && tailwindConfig.purge && tailwindConfig.purge.options
+  let extractors = (tailwindConfig && tailwindConfig.purge && tailwindConfig.purge.extract) || {}
+  const purgeOptions =
+    (tailwindConfig && tailwindConfig.purge && tailwindConfig.purge.options) || {}
 
-  if (!fileExtension) {
-    return (purgeOptions && purgeOptions.defaultExtractor) || getDefaultExtractor()
+  if (typeof extractors === 'function') {
+    extractors = {
+      DEFAULT: extractors,
+    }
   }
-
-  if (!purgeOptions) {
-    return getDefaultExtractor(fileExtension)
+  if (purgeOptions.defaultExtractor) {
+    extractors.DEFAULT = purgeOptions.defaultExtractor
+  }
+  for (let { extensions, extractor } of purgeOptions.extractors || []) {
+    for (let extension of extensions) {
+      extractors[extension] = extractor
+    }
   }
 
-  const fileSpecificExtractor = (purgeOptions.extractors || []).find((extractor) =>
-    extractor.extensions.includes(fileExtension)
+  return (
+    extractors[fileExtension] ||
+    extractors.DEFAULT ||
+    builtInExtractors[fileExtension] ||
+    builtInExtractors.DEFAULT
   )
+}
 
-  if (fileSpecificExtractor) {
-    return fileSpecificExtractor.extractor
+function getTransformer(tailwindConfig, fileExtension) {
+  let transformers =
+    (tailwindConfig && tailwindConfig.purge && tailwindConfig.purge.transform) || {}
+
+  if (typeof transformers === 'function') {
+    transformers = {
+      DEFAULT: transformers,
+    }
   }
 
-  return purgeOptions.defaultExtractor || getDefaultExtractor(fileExtension)
+  return (
+    transformers[fileExtension] ||
+    transformers.DEFAULT ||
+    builtInTransformers[fileExtension] ||
+    builtInTransformers.DEFAULT
+  )
 }
 
 // Scans template contents for possible classes. This is a hot path on initial build but
@@ -141,8 +164,9 @@ export default function expandTailwindAtRules(context) {
     env.DEBUG && console.time('Reading changed files')
 
     for (let { content, extension } of context.changedContent) {
+      let transformer = getTransformer(context.tailwindConfig, extension)
       let extractor = getExtractor(context.tailwindConfig, extension)
-      getClassCandidates(content, extractor, contentMatchCache, candidates, seen)
+      getClassCandidates(transformer(content), extractor, contentMatchCache, candidates, seen)
     }
 
     // ---

src/lib/purgeUnusedStyles.js

@@ -34,6 +34,18 @@ export function tailwindExtractor(content) {
   return broadMatches.concat(broadMatchesWithoutTrailingSlash).concat(innerMatches)
 }
 
+function getTransformer(config, fileExtension) {
+  let transformers = (config.purge && config.purge.transform) || {}
+
+  if (typeof transformers === 'function') {
+    transformers = {
+      DEFAULT: transformers,
+    }
+  }
+
+  return transformers[fileExtension] || transformers.DEFAULT || ((content) => content)
+}
+
 export default function purgeUnusedUtilities(config, configChanged, resolvedConfigPath) {
   const purgeEnabled = _.get(
     config,
@@ -58,7 +70,50 @@ export default function purgeUnusedUtilities(config, configChanged, resolvedConf
     return removeTailwindMarkers
   }
 
-  const { defaultExtractor, ...purgeOptions } = config.purge.options || {}
+  const extractors = config.purge.extract || {}
+  const transformers = config.purge.transform || {}
+  let { defaultExtractor: originalDefaultExtractor, ...purgeOptions } = config.purge.options || {}
+
+  if (!originalDefaultExtractor) {
+    originalDefaultExtractor =
+      typeof extractors === 'function' ? extractors : extractors.DEFAULT || tailwindExtractor
+  }
+
+  const defaultExtractor = (content) => {
+    const preserved = originalDefaultExtractor(content)
+
+    if (_.get(config, 'purge.preserveHtmlElements', true)) {
+      preserved.push(...htmlTags)
+    }
+
+    return preserved
+  }
+
+  // If `extractors` is a function then we don't have any file-specific extractors,
+  // only a default one.
+  let fileSpecificExtractors = typeof extractors === 'function' ? {} : extractors
+
+  // PurgeCSS doesn't support "transformers," so we implement those using extractors.
+  // If we have a custom transformer for an extension, but not a matching extractor,
+  // then we need to create an extractor that we can augment later.
+  if (typeof transformers !== 'function') {
+    for (let [extension] of Object.entries(transformers)) {
+      if (!fileSpecificExtractors[extension]) {
+        fileSpecificExtractors[extension] = defaultExtractor
+      }
+    }
+  }
+
+  // Augment file-specific extractors by running the transformer before we extract classes.
+  fileSpecificExtractors = Object.entries(fileSpecificExtractors).map(([extension, extractor]) => {
+    return {
+      extensions: [extension],
+      extractor: (content) => {
+        const transformer = getTransformer(config, extension)
+        return extractor(transformer(content))
+      },
+    }
+  })
 
   return postcss([
     function (css) {
@@ -106,15 +161,10 @@ export default function purgeUnusedUtilities(config, configChanged, resolvedConf
     removeTailwindMarkers,
     purgecss({
       defaultExtractor: (content) => {
-        const extractor = defaultExtractor || tailwindExtractor
-        const preserved = [...extractor(content)]
-
-        if (_.get(config, 'purge.preserveHtmlElements', true)) {
-          preserved.push(...htmlTags)
-        }
-
-        return preserved
+        const transformer = getTransformer(config)
+        return defaultExtractor(transformer(content))
       },
+      extractors: fileSpecificExtractors,
       ...purgeOptions,
       content: (Array.isArray(config.purge)
         ? config.purge

tests/jit/custom-extractors.test.js

@@ -65,3 +65,58 @@ test('extractors array', () => {
     expect(result.css).toMatchFormattedCss(expected)
   })
 })
+
+test('extract function', () => {
+  let config = {
+    mode: 'jit',
+    purge: {
+      content: [path.resolve(__dirname, './custom-extractors.test.html')],
+      extract: customExtractor,
+    },
+    corePlugins: { preflight: false },
+    theme: {},
+    plugins: [],
+  }
+
+  return run(css, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(expected)
+  })
+})
+
+test('extract.DEFAULT', () => {
+  let config = {
+    mode: 'jit',
+    purge: {
+      content: [path.resolve(__dirname, './custom-extractors.test.html')],
+      extract: {
+        DEFAULT: customExtractor,
+      },
+    },
+    corePlugins: { preflight: false },
+    theme: {},
+    plugins: [],
+  }
+
+  return run(css, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(expected)
+  })
+})
+
+test('extract.{extension}', () => {
+  let config = {
+    purge: {
+      content: [path.resolve(__dirname, './custom-extractors.test.html')],
+      extract: {
+        html: customExtractor,
+      },
+    },
+    mode: 'jit',
+    corePlugins: { preflight: false },
+    theme: {},
+    plugins: [],
+  }
+
+  return run(css, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(expected)
+  })
+})

tests/jit/custom-transformers.test.js

@@ -0,0 +1,93 @@
+import postcss from 'postcss'
+import path from 'path'
+
+function run(input, config = {}) {
+  jest.resetModules()
+  const tailwind = require('../../src/jit/index.js').default
+  return postcss(tailwind(config)).process(input, {
+    from: path.resolve(__filename),
+  })
+}
+
+function customTransformer(content) {
+  return content.replace(/uppercase/g, 'lowercase')
+}
+
+const css = `
+  @tailwind base;
+  @tailwind components;
+  @tailwind utilities;
+`
+
+test('transform function', () => {
+  let config = {
+    mode: 'jit',
+    purge: {
+      content: [{ raw: '<div class="uppercase"></div>' }],
+      transform: customTransformer,
+    },
+    corePlugins: { preflight: false, borderColor: false, ringWidth: false, boxShadow: false },
+    theme: {},
+    plugins: [],
+  }
+
+  return run(css, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(`
+      .lowercase {
+        text-transform: lowercase;
+      }
+    `)
+  })
+})
+
+test('transform.DEFAULT', () => {
+  let config = {
+    mode: 'jit',
+    purge: {
+      content: [{ raw: '<div class="uppercase"></div>' }],
+      transform: {
+        DEFAULT: customTransformer,
+      },
+    },
+    corePlugins: { preflight: false, borderColor: false, ringWidth: false, boxShadow: false },
+    theme: {},
+    plugins: [],
+  }
+
+  return run(css, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(`
+      .lowercase {
+        text-transform: lowercase;
+      }
+    `)
+  })
+})
+
+test('transform.{extension}', () => {
+  let config = {
+    mode: 'jit',
+    purge: {
+      content: [
+        { raw: '<div class="uppercase"></div>', extension: 'html' },
+        { raw: '<div class="uppercase"></div>', extension: 'php' },
+      ],
+      transform: {
+        html: customTransformer,
+      },
+    },
+    corePlugins: { preflight: false, borderColor: false, ringWidth: false, boxShadow: false },
+    theme: {},
+    plugins: [],
+  }
+
+  return run(css, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(`
+      .uppercase {
+        text-transform: uppercase;
+      }
+      .lowercase {
+        text-transform: lowercase;
+      }
+    `)
+  })
+})