fix watchers never being cleaned up

Previously, there was an issue, where a slow compilation could cause the
watchers to build up and never be cleaned. This would result in both
excessive logging and the compilation time increasing exponentially.

This fix is a naive patch, simply locking if there is a build in
progress, and unlocking when it completes.

Author: Gazler

packages/@tailwindcss-cli/src/commands/build/index.ts

@@ -237,16 +237,21 @@ export async function handle(args: Result<ReturnType<typeof options>>) {
 
   let [compiler, scanner] = await handleError(() => createCompiler(input, I))
 
+  let lock = false
+
   // Watch for changes
   if (args['--watch']) {
     let cleanupWatchers = await createWatchers(
       watchDirectories(scanner),
       async function handle(files) {
         try {
+          if (lock) return
           // If the only change happened to the output file, then we don't want to
           // trigger a rebuild because that will result in an infinite loop.
           if (files.length === 1 && files[0] === args['--output']) return
 
+          lock = true
+
           using I = new Instrumentation()
           DEBUG && I.start('[@tailwindcss/cli] (watcher)')
 
@@ -362,6 +367,7 @@ export async function handle(args: Result<ReturnType<typeof options>>) {
             eprintln(err.toString())
           }
         }
+        lock = false
       },
     )