Watch .prettierignore for cache invalidation (#3943)

When users modify .prettierignore, the extension may use stale ignore
data because Prettier caches file info. This adds a file system watcher
for .prettierignore that clears the cache on change, create, or delete
events, similar to how other config files are already watched.

Fixes #3942

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: ntotten

CHANGELOG.md

@@ -6,6 +6,8 @@ All notable changes to the "prettier-vscode" extension will be documented in thi
 
 ## [Unreleased]
 
+- Watch `.prettierignore` for changes to invalidate cache (#3942)
+
 ## [12.2.0]
 
 - Fixed `source.fixAll.prettier` code action running even when `editor.defaultFormatter` was set to a different extension (#3908). The code action now respects the user's formatter choice and only runs when Prettier is the default formatter or when `source.fixAll.prettier` is explicitly enabled.

src/PrettierEditService.ts

@@ -159,6 +159,13 @@ export default class PrettierEditService implements Disposable {
       watcher.onDidDelete(this.prettierConfigChanged);
     }
 
+    // Watch .prettierignore for changes to invalidate ignore cache
+    const prettierIgnoreWatcher =
+      workspace.createFileSystemWatcher("**/.prettierignore");
+    prettierIgnoreWatcher.onDidChange(this.prettierConfigChanged);
+    prettierIgnoreWatcher.onDidCreate(this.prettierConfigChanged);
+    prettierIgnoreWatcher.onDidDelete(this.prettierConfigChanged);
+
     const textEditorChange = window.onDidChangeActiveTextEditor(
       this.handleActiveTextEditorChangedSync,
     );
@@ -169,6 +176,7 @@ export default class PrettierEditService implements Disposable {
       packageWatcher,
       configurationWatcher,
       ...prettierConfigWatchers,
+      prettierIgnoreWatcher,
       textEditorChange,
     ];
   }