watch: re-run worker when its dependencies change

Author: SudhansuBandha

lib/internal/watch_mode/files_watcher.js

@@ -17,7 +17,7 @@ const { TIMEOUT_MAX } = require('internal/timers');
 
 const EventEmitter = require('events');
 const { addAbortListener } = require('internal/events/abort_listener');
-const { watch } = require('fs');
+const { watch, readFileSync } = require('fs');
 const { fileURLToPath } = require('internal/url');
 const { resolve, dirname, sep } = require('path');
 const { setTimeout, clearTimeout } = require('timers');
@@ -166,6 +166,29 @@ class FilesWatcher extends EventEmitter {
     }
   }
 
+  #parseWorkerImports(workerFile) {
+    try {
+      const content = readFileSync(workerFile, 'utf8');
+      const imports = [];
+      // Match: import x from 'path', import('path'), require('path')
+      const importRegex =  /(?:import\s+(?:.*?\s+from\s+)?['"`]([^'"`]+)['"`]|import\(\s*['"`]([^'"`]+)['"`]\s*\)|require\(\s*['"`]([^'"`]+)['"`]\s*\))/g;
+      let match;
+      while ((match = importRegex.exec(content)) !== null) {
+        const importPath = match[1] || match[2] || match[3];
+        if (importPath && !importPath.startsWith('node:') && !StringPrototypeStartsWith(importPath, '.')) {
+          // Skip Node.js built-ins and only process relative paths
+          continue;
+        }
+        if (importPath) {
+          imports.push(importPath);
+        }
+      }
+      return imports;
+    } catch (err) {
+      return [];
+    }
+  }
+
   watchChildProcessModules(child, key = null) {
     if (this.#passthroughIPC) {
       this.#setupIPC(child);
@@ -180,7 +203,17 @@ class FilesWatcher extends EventEmitter {
           ArrayPrototypeForEach(message['watch:import'], (file) => this.filterFile(fileURLToPath(file), key));
         }
         if (ArrayIsArray(message['watch:worker'])) {
-           ArrayPrototypeForEach(message['watch:worker'], (file) => this.filterFile(file, key));
+          ArrayPrototypeForEach(message['watch:worker'], (workerFile) => {
+            // Add worker file itself
+            this.filterFile(workerFile, key);
+            
+            // Parse and watch worker dependencies
+            const imports = this.#parseWorkerImports(workerFile);
+            ArrayPrototypeForEach(imports, (importPath) => {
+              const resolvedPath = resolve(dirname(workerFile), importPath);
+              this.filterFile(resolvedPath, key);
+            });
+          });
         }
       } catch {
         // Failed watching file. ignore