initial commit. phase 1 complete

frontend/node_modules/tailwindcss/src/cli/build/watching.js

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+// @ts-check
+
+import chokidar from 'chokidar'
+import fs from 'fs'
+import micromatch from 'micromatch'
+import normalizePath from 'normalize-path'
+import path from 'path'
+
+import { readFileWithRetries } from './utils.js'
+
+/**
+ * The core idea of this watcher is:
+ * 1. Whenever a file is added, changed, or renamed we queue a rebuild
+ * 2. Perform as few rebuilds as possible by batching them together
+ * 3. Coalesce events that happen in quick succession to avoid unnecessary rebuilds
+ * 4. Ensure another rebuild happens _if_ changed while a rebuild is in progress
+ */
+
+/**
+ *
+ * @param {*} args
+ * @param {{ state, rebuild(changedFiles: any[]): Promise<any> }} param1
+ * @returns {{
+ *   fswatcher: import('chokidar').FSWatcher,
+ *   refreshWatchedFiles(): void,
+ * }}
+ */
+export function createWatcher(args, { state, rebuild }) {
+  let shouldPoll = args['--poll']
+  let shouldCoalesceWriteEvents = shouldPoll || process.platform === 'win32'
+
+  // Polling interval in milliseconds
+  // Used only when polling or coalescing add/change events on Windows
+  let pollInterval = 10
+
+  let watcher = chokidar.watch([], {
+    // Force checking for atomic writes in all situations
+    // This causes chokidar to wait up to 100ms for a file to re-added after it's been unlinked
+    // This only works when watching directories though
+    atomic: true,
+
+    usePolling: shouldPoll,
+    interval: shouldPoll ? pollInterval : undefined,
+    ignoreInitial: true,
+    awaitWriteFinish: shouldCoalesceWriteEvents
+      ? {
+          stabilityThreshold: 50,
+          pollInterval: pollInterval,
+        }
+      : false,
+  })
+
+  // A queue of rebuilds, file reads, etc… to run
+  let chain = Promise.resolve()
+
+  /**
+   * A list of files that have been changed since the last rebuild
+   *
+   * @type {{file: string, content: () => Promise<string>, extension: string}[]}
+   */
+  let changedContent = []
+
+  /**
+   * A list of files for which a rebuild has already been queued.
+   * This is used to prevent duplicate rebuilds when multiple events are fired for the same file.
+   * The rebuilt file is cleared from this list when it's associated rebuild has _started_
+   * This is because if the file is changed during a rebuild it won't trigger a new rebuild which it should
+   **/
+  let pendingRebuilds = new Set()
+
+  let _timer
+  let _reject
+
+  /**
+   * Rebuilds the changed files and resolves when the rebuild is
+   * complete regardless of whether it was successful or not
+   */
+  async function rebuildAndContinue() {
+    let changes = changedContent.splice(0)
+
+    // There are no changes to rebuild so we can just do nothing
+    if (changes.length === 0) {
+      return Promise.resolve()
+    }
+
+    // Clear all pending rebuilds for the about-to-be-built files
+    changes.forEach((change) => pendingRebuilds.delete(change.file))
+
+    // Resolve the promise even when the rebuild fails
+    return rebuild(changes).then(
+      () => {},
+      (e) => {
+        console.error(e.toString())
+      }
+    )
+  }
+
+  /**
+   *
+   * @param {*} file
+   * @param {(() => Promise<string>) | null} content
+   * @param {boolean} skipPendingCheck
+   * @returns {Promise<void>}
+   */
+  function recordChangedFile(file, content = null, skipPendingCheck = false) {
+    file = path.resolve(file)
+
+    // Applications like Vim/Neovim fire both rename and change events in succession for atomic writes
+    // In that case rebuild has already been queued by rename, so can be skipped in change
+    if (pendingRebuilds.has(file) && !skipPendingCheck) {
+      return Promise.resolve()
+    }
+
+    // Mark that a rebuild of this file is going to happen
+    // It MUST happen synchronously before the rebuild is queued for this to be effective
+    pendingRebuilds.add(file)
+
+    changedContent.push({
+      file,
+      content: content ?? (() => fs.promises.readFile(file, 'utf8')),
+      extension: path.extname(file).slice(1),
+    })
+
+    if (_timer) {
+      clearTimeout(_timer)
+      _reject()
+    }
+
+    // If a rebuild is already in progress we don't want to start another one until the 10ms timer has expired
+    chain = chain.then(
+      () =>
+        new Promise((resolve, reject) => {
+          _timer = setTimeout(resolve, 10)
+          _reject = reject
+        })
+    )
+
+    // Resolves once this file has been rebuilt (or the rebuild for this file has failed)
+    // This queues as many rebuilds as there are changed files
+    // But those rebuilds happen after some delay
+    // And will immediately resolve if there are no changes
+    chain = chain.then(rebuildAndContinue, rebuildAndContinue)
+
+    return chain
+  }
+
+  watcher.on('change', (file) => recordChangedFile(file))
+  watcher.on('add', (file) => recordChangedFile(file))
+
+  // Restore watching any files that are "removed"
+  // This can happen when a file is pseudo-atomically replaced (a copy is created, overwritten, the old one is unlinked, and the new one is renamed)
+  // TODO: An an optimization we should allow removal when the config changes
+  watcher.on('unlink', (file) => {
+    file = normalizePath(file)
+
+    // Only re-add the file if it's not covered by a dynamic pattern
+    if (!micromatch.some([file], state.contentPatterns.dynamic)) {
+      watcher.add(file)
+    }
+  })
+
+  // Some applications such as Visual Studio (but not VS Code)
+  // will only fire a rename event for atomic writes and not a change event
+  // This is very likely a chokidar bug but it's one we need to work around
+  // We treat this as a change event and rebuild the CSS
+  watcher.on('raw', (evt, filePath, meta) => {
+    if (evt !== 'rename' || filePath === null) {
+      return
+    }
+
+    let watchedPath = meta.watchedPath
+
+    // Watched path might be the file itself
+    // Or the directory it is in
+    filePath = watchedPath.endsWith(filePath) ? watchedPath : path.join(watchedPath, filePath)
+
+    // Skip this event since the files it is for does not match any of the registered content globs
+    if (!micromatch.some([filePath], state.contentPatterns.all)) {
+      return
+    }
+
+    // Skip since we've already queued a rebuild for this file that hasn't happened yet
+    if (pendingRebuilds.has(filePath)) {
+      return
+    }
+
+    // We'll go ahead and add the file to the pending rebuilds list here
+    // It'll be removed when the rebuild starts unless the read fails
+    // which will be taken care of as well
+    pendingRebuilds.add(filePath)
+
+    async function enqueue() {
+      try {
+        // We need to read the file as early as possible outside of the chain
+        // because it may be gone by the time we get to it. doing the read
+        // immediately increases the chance that the file is still there
+        let content = await readFileWithRetries(path.resolve(filePath))
+
+        if (content === undefined) {
+          return
+        }
+
+        // This will push the rebuild onto the chain
+        // We MUST skip the rebuild check here otherwise the rebuild will never happen on Linux
+        // This is because the order of events and timing is different on Linux
+        // @ts-ignore: TypeScript isn't picking up that content is a string here
+        await recordChangedFile(filePath, () => content, true)
+      } catch {
+        // If reading the file fails, it's was probably a deleted temporary file
+        // So we can ignore it and no rebuild is needed
+      }
+    }
+
+    enqueue().then(() => {
+      // If the file read fails we still need to make sure the file isn't stuck in the pending rebuilds list
+      pendingRebuilds.delete(filePath)
+    })
+  })
+
+  return {
+    fswatcher: watcher,
+
+    refreshWatchedFiles() {
+      watcher.add(Array.from(state.contextDependencies))
+      watcher.add(Array.from(state.configBag.dependencies))
+      watcher.add(state.contentPatterns.all)
+    },
+  }
+}