feat: allow worker options via variable

docs/guide/features.md

@@ -657,7 +657,15 @@ const worker = new Worker(new URL('./worker.js', import.meta.url), {
 })
 ```
 
-The worker detection will only work if the `new URL()` constructor is used directly inside the `new Worker()` declaration. Additionally, all options parameters must be static values (i.e. string literals).
+The worker detection will only work if the `new URL()` constructor is used directly inside the `new Worker()` declaration. Additionally, all options parameters must be static values (i.e. string literals), or a variable that is defined before the `new Worker()`, as follows:
+
+```ts
+const workerOptions = { type: 'module' }
+const worker = new Worker(
+  new URL('./worker.js', import.meta.url),
+  workerOptions,
+)
+```
 
 ### Import with Query Suffixes
 

packages/vite/src/node/plugins/workerImportMetaUrl.ts

@@ -34,7 +34,7 @@ function parseWorkerOptions(
     opts = evalValue<WorkerOptions>(rawOpts)
   } catch {
     throw err(
-      'Vite is unable to parse the worker options as the value is not static.' +
+      'Vite is unable to parse the worker options as the value is neither static or variable.' +
         'To ignore this error, please use /* @vite-ignore */ in the worker options.',
       optsStartIndex,
     )
@@ -54,6 +54,37 @@ function parseWorkerOptions(
   return opts
 }
 
+function findVarDefinition(
+  raw: string,
+  clean: string,
+  endIndex: number,
+  varName: string,
+): [string, number] {
+  const workerOptionsVarRE = new RegExp(
+    `(?:var|let|const)\\s*${varName}\\s*=\\s*`,
+    'g',
+  )
+
+  let optsStartIndex: number | null = null
+  while (workerOptionsVarRE.exec(clean)) {
+    if (workerOptionsVarRE.lastIndex >= endIndex) break
+    optsStartIndex = workerOptionsVarRE.lastIndex
+  }
+
+  if (!optsStartIndex) {
+    throw err(
+      'Vite is unable to parse the worker options as the value is neither static or variable. ' +
+        'To ignore this error, please use /* @vite-ignore */ in the worker options.',
+      optsStartIndex,
+    )
+  }
+
+  const optsEndIndex = clean.indexOf('}', optsStartIndex)
+  const workerOptString = raw.substring(optsStartIndex, optsEndIndex + 1)
+
+  return [workerOptString, optsStartIndex]
+}
+
 function getWorkerType(raw: string, clean: string, i: number): WorkerType {
   const commaIndex = clean.indexOf(',', i)
   if (commaIndex === -1) {
@@ -82,7 +113,22 @@ function getWorkerType(raw: string, clean: string, i: number): WorkerType {
     return 'classic'
   }
 
-  const workerOpts = parseWorkerOptions(workerOptString, commaIndex + 1)
+  let workerOpts: WorkerOptions
+
+  // if worker options is a variable, try to find its closest definition
+  const varMatch = cleanWorkerOptString.match(/^\s*(\w+)\s*(?:,\s*)?$/)
+  if (varMatch) {
+    const [workerOptString, workerOptIndex] = findVarDefinition(
+      raw,
+      clean,
+      i,
+      varMatch[1],
+    )
+    workerOpts = parseWorkerOptions(workerOptString, workerOptIndex)
+  } else {
+    workerOpts = parseWorkerOptions(workerOptString, commaIndex + 1)
+  }
+
   if (
     workerOpts.type &&
     (workerOpts.type === 'module' || workerOpts.type === 'classic')

playground/worker/index.html

@@ -99,6 +99,13 @@ <h2 class="format-iife">format iife:</h2>
 </p>
 <code class="worker-import-meta-url-without-extension"></code>
 
+<p>
+  var workerOptions = { type: 'module' } new Worker(new URL('./url-worker.js',
+  import.meta.url), workerOptions)
+  <span class="classname">.worker-import-meta-url-via-variable</span>
+</p>
+<code class="worker-import-meta-url-via-variable"></code>
+
 <p>
   new SharedWorker(new URL('./url-shared-worker.js', import.meta.url), { type:
   'module' })

playground/worker/worker/main-module.js

@@ -135,6 +135,17 @@ wWithoutExt.addEventListener('message', (ev) =>
   text('.worker-import-meta-url-without-extension', JSON.stringify(ev.data)),
 )
 
+const myWorkerOptions = { type: 'module' }
+
+// url import worker via variable
+const wViaVariable = new Worker(
+  new URL('../url-worker', import.meta.url),
+  myWorkerOptions,
+)
+wViaVariable.addEventListener('message', (ev) =>
+  text('.worker-import-meta-url-via-variable', JSON.stringify(ev.data)),
+)
+
 const genWorkerName = () => 'module'
 const w2 = new SharedWorker(
   new URL('../url-shared-worker.js', import.meta.url),