Merge pull request #44 from surma/new-url-plain-filename

Add support for plain filenames in `new URL`

README.md

@@ -37,22 +37,28 @@ export default {
 
 ### Auto bundling
 
-In your project's code:
+In your project's code use a module-relative path via `new URL` to include a Worker:
 
 ```js
-const worker = new Worker("./worker.js", { type: "module" });
+const worker = new Worker(new URL("worker.js", import.meta.url), {
+  type: "module"
+});
 ```
 
 This will just work.
 
-If required, the plugin also supports explicitly module-relative paths:
+If required, the plugin also supports plain literal paths:
 
 ```js
-const worker = new Worker(new URL("./worker.js", import.meta.url), {
-  type: "module"
-});
+const worker = new Worker("./worker.js", { type: "module" });
 ```
 
+However, those are less portable: in Rollup they would result in module-relative
+path, but if used directly in the browser, they'll be relative to the document
+URL instead.
+
+Hence, they're deprecated and `new URL` pattern is encouraged instead for portability.
+
 ### Importing workers as URLs
 
 If your worker constructor doesn't match `workerRegexp` (see options below), you might find it easier to import the worker as a URL. In your project's code:

index.js

@@ -147,11 +147,28 @@ This will become a hard error in the future.`,
           workerFile = workerFile.slice(1, -1);
 
           if (!/^\.{1,2}\//.test(workerFile)) {
-            this.warn(
-              `Paths passed to the Worker constructor must be relative to the current file, i.e. start with ./ or ../ (just like dynamic import!). Ignoring "${workerFile}".`,
-              matchIndex
-            );
-            continue;
+            let isError = false;
+            if (directWorkerFile) {
+              // If direct worker file, it must be in `./something` form.
+              isError = true;
+            } else {
+              // If `new URL(...)` it can be in `new URL('something', import.meta.url)` form too,
+              // so just check it's not absolute.
+              if (/^(\/|https?:)/.test(workerFile)) {
+                isError = true;
+              } else {
+                // If it does turn out to be `new URL('something', import.meta.url)` form,
+                // prepend `./` so that it becomes valid module specifier.
+                workerFile = `./${workerFile}`;
+              }
+            }
+            if (isError) {
+              this.warn(
+                `Paths passed to the Worker constructor must be relative to the current file, i.e. start with ./ or ../ (just like dynamic import!). Ignoring "${workerFile}".`,
+                matchIndex
+              );
+              continue;
+            }
           }
 
           workerIdPromise = this.resolve(workerFile, id).then(res => res.id);

tests/fixtures/url-import-meta-worker/entry.js

@@ -12,7 +12,7 @@
  */
 
 // The type module should get removed for AMD format!
-const w = new Worker(new URL("./worker.js", import.meta.url), {
+const w = new Worker(new URL("worker.js", import.meta.url), {
   type: "module"
 });
 w.addEventListener("message", ev => {