Invalidate context when CSS changes

tailwindlabs · Feb 25, 2022 · dc7b00a · dc7b00a
1 parent 7a24b3f
commit dc7b00a
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Showing 6 changed files with 151 additions and 9 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Preserve source maps for generated CSS ([#7588](https://github.com/tailwindlabs/tailwindcss/pull/7588))
 - Split box shadows on top-level commas only ([#7479](https://github.com/tailwindlabs/tailwindcss/pull/7479))
 - Use local user CSS cache for `@apply` ([#7524](https://github.com/tailwindlabs/tailwindcss/pull/7524))
+- Invalidate context when main CSS changes ([#7626](https://github.com/tailwindlabs/tailwindcss/pull/7626))
 
 ### Changed
 

diff --git a/src/lib/cacheInvalidation.js b/src/lib/cacheInvalidation.js
@@ -0,0 +1,52 @@
+import crypto from 'crypto'
+import * as sharedState from './sharedState'
+
+/**
+ * Calculate the hash of a string.
+ *
+ * This doesn't need to be cryptographically secure or
+ * anything like that since it's used only to detect
+ * when the CSS changes to invalidate the context.
+ *
+ * This is wrapped in a try/catch because it's really dependent
+ * on how Node itself is build and the environment and OpenSSL
+ * version / build that is installed on the user's machine.
+ *
+ * Based on the environment this can just outright fail.
+ *
+ * See https://github.com/nodejs/node/issues/40455
+ *
+ * @param {string} str
+ */
+function getHash(str) {
+  try {
+    return crypto.createHash('md5').update(str, 'utf-8').digest('binary')
+  } catch (err) {
+    return ''
+  }
+}
+
+/**
+ * Determine if the CSS tree is different from the
+ * previous version for the given `sourcePath`.
+ *
+ * @param {string} sourcePath
+ * @param {import('postcss').Node} root
+ */
+export function hasContentChanged(sourcePath, root) {
+  let css = root.toString()
+
+  // We only care about files with @tailwind directives
+  // Other files use an existing context
+  if (!css.includes('@tailwind')) {
+    return false
+  }
+
+  let existingHash = sharedState.sourceHashMap.get(sourcePath)
+  let rootHash = getHash(css)
+  let didChange = existingHash !== rootHash
+
+  sharedState.sourceHashMap.set(sourcePath, rootHash)
+
+  return didChange
+}
diff --git a/src/lib/setupContextUtils.js b/src/lib/setupContextUtils.js
@@ -20,6 +20,7 @@ import log from '../util/log'
 import negateValue from '../util/negateValue'
 import isValidArbitraryValue from '../util/isValidArbitraryValue'
 import { generateRules } from './generateRules'
+import { hasContentChanged } from './cacheInvalidation.js'
 
 function prefix(context, selector) {
   let prefix = context.tailwindConfig.prefix
@@ -790,6 +791,8 @@ export function createContext(tailwindConfig, changedContent = [], root = postcs
   let resolvedPlugins = resolvePlugins(context, root)
   registerPlugins(resolvedPlugins, context)
 
+  sharedState.contextInvalidationCount++
+
   return context
 }
 
@@ -822,14 +825,16 @@ export function getContext(
     existingContext = context
   }
 
+  let cssDidChange = hasContentChanged(sourcePath, root)
+
   // If there's already a context in the cache and we don't need to
   // reset the context, return the cached context.
   if (existingContext) {
     let contextDependenciesChanged = trackModified(
       [...contextDependencies],
       getFileModifiedMap(existingContext)
     )
-    if (!contextDependenciesChanged) {
+    if (!contextDependenciesChanged && !cssDidChange) {
       return [existingContext, false]
     }
   }

diff --git a/src/lib/sharedState.js b/src/lib/sharedState.js
@@ -5,6 +5,13 @@ export const env = {
 export const contextMap = new Map()
 export const configContextMap = new Map()
 export const contextSourcesMap = new Map()
+/**
+ * A map of source files to their sizes / hashes
+ *
+ * @type {Map<string, string>}
+ */
+export const sourceHashMap = new Map()
+export const contextInvalidationCount = 0
 export const NOT_ON_DEMAND = new String('*')
 
 export function resolveDebug(debug) {

diff --git a/tests/context-reuse.test.html b/tests/context-reuse.test.html
@@ -7,5 +7,7 @@
     <title>Title</title>
     <link rel="stylesheet" href="./tailwind.css" />
   </head>
-  <body></body>
+  <body>
+    <div class="only:custom-utility"></div>
+  </body>
 </html>
diff --git a/tests/context-reuse.test.js b/tests/context-reuse.test.js
@@ -7,7 +7,9 @@ const configPath = path.resolve(__dirname, './context-reuse.tailwind.config.js')
 const { css } = require('./util/run.js')
 
 function run(input, config = {}, from = null) {
-  from = from || path.resolve(__filename)
+  let { currentTestName } = expect.getState()
+
+  from = `${path.resolve(__filename)}?test=${currentTestName}&${from}`
 
   return postcss(tailwind(config)).process(input, { from })
 }
@@ -26,16 +28,14 @@ afterEach(async () => {
 })
 
 it('re-uses the context across multiple files with the same config', async () => {
-  let from = path.resolve(__filename)
-
   let results = [
-    await run(`@tailwind utilities;`, configPath, `${from}?id=1`),
+    await run(`@tailwind utilities;`, configPath, `id=1`),
 
     // Using @apply directives should still re-use the context
     // They depend on the config but do not the other way around
-    await run(`body { @apply bg-blue-400; }`, configPath, `${from}?id=2`),
-    await run(`body { @apply text-red-400; }`, configPath, `${from}?id=3`),
-    await run(`body { @apply mb-4; }`, configPath, `${from}?id=4`),
+    await run(`body { @apply bg-blue-400; }`, configPath, `id=2`),
+    await run(`body { @apply text-red-400; }`, configPath, `id=3`),
+    await run(`body { @apply mb-4; }`, configPath, `id=4`),
   ]
 
   let dependencies = results.map((result) => {
@@ -85,3 +85,78 @@ it('re-uses the context across multiple files with the same config', async () =>
   // And none of this should have resulted in multiple contexts being created
   expect(sharedState.contextSourcesMap.size).toBe(1)
 })
+
+it('updates layers when any CSS containing @tailwind directives changes', async () => {
+  let result
+
+  // Compile the initial version once
+  let input = css`
+    @tailwind utilities;
+    @layer utilities {
+      .custom-utility {
+        color: orange;
+      }
+    }
+  `
+
+  result = await run(input, configPath, `id=1`)
+
+  expect(result.css).toMatchFormattedCss(css`
+    .only\:custom-utility:only-child {
+      color: orange;
+    }
+  `)
+
+  // Save the file with a change
+  input = css`
+    @tailwind utilities;
+    @layer utilities {
+      .custom-utility {
+        color: blue;
+      }
+    }
+  `
+
+  result = await run(input, configPath, `id=1`)
+
+  expect(result.css).toMatchFormattedCss(css`
+    .only\:custom-utility:only-child {
+      color: blue;
+    }
+  `)
+})
+
+it('invalidates the context when any CSS containing @tailwind directives changes', async () => {
+  sharedState.contextInvalidationCount = 0
+  sharedState.sourceHashMap.clear()
+
+  // Save the file a handful of times with no changes
+  // This builds the context at most once
+  for (let n = 0; n < 5; n++) {
+    await run(`@tailwind utilities;`, configPath, `id=1`)
+  }
+
+  expect(sharedState.contextInvalidationCount).toBe(1)
+
+  // Save the file twice with a change
+  // This should rebuild the context again but only once
+  await run(`@tailwind utilities; .foo {}`, configPath, `id=1`)
+  await run(`@tailwind utilities; .foo {}`, configPath, `id=1`)
+
+  expect(sharedState.contextInvalidationCount).toBe(2)
+
+  // Save the file twice with a content but not length change
+  // This should rebuild the context two more times
+  await run(`@tailwind utilities; .bar {}`, configPath, `id=1`)
+  await run(`@tailwind utilities; .baz {}`, configPath, `id=1`)
+
+  expect(sharedState.contextInvalidationCount).toBe(4)
+
+  // Save a file with a change that does not affect the context
+  // No invalidation should occur
+  await run(`.foo { @apply mb-1; }`, configPath, `id=2`)
+  await run(`.foo { @apply mb-1; }`, configPath, `id=2`)
+  await run(`.foo { @apply mb-1; }`, configPath, `id=2`)
+
+  expect(sharedState.contextInvalidationCount).toBe(4)
+})