feat: use target webworker

Fixes #477. We want to
configure webpack to emit only webworker compatible code.

src/commands/build/wranglerjs/bundle.rs

@@ -38,16 +38,14 @@ impl Bundle {
         }
 
         let mut script_file = File::create(self.script_path())?;
-        let mut script = create_prologue();
-        script += &wranglerjs_output.script;
 
         if let Some(encoded_wasm) = &wranglerjs_output.wasm {
             let wasm = decode(encoded_wasm).expect("could not decode Wasm in base64");
             let mut wasm_file = File::create(self.wasm_path())?;
             wasm_file.write_all(&wasm)?;
         }
 
-        script_file.write_all(script.as_bytes())?;
+        script_file.write_all(wranglerjs_output.script.as_bytes())?;
 
         Ok(())
     }
@@ -81,15 +79,6 @@ impl Bundle {
     }
 }
 
-// We inject some code at the top-level of the Worker; called {prologue}.
-// This aims to provide additional support, for instance providing {window}.
-pub fn create_prologue() -> String {
-    r#"
-        const window = this;
-    "#
-    .to_string()
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

tests/build.rs

@@ -171,6 +171,49 @@ fn it_builds_with_webpack_wast() {
     cleanup(fixture);
 }
 
+#[test]
+fn it_fails_with_webpack_target_web() {
+    let fixture = "webpack_target_web";
+    create_temporary_copy(fixture);
+
+    webpack_config(
+        fixture,
+        r#"{
+          entry: "./index.js",
+          target: "node",
+        }"#,
+    );
+    settings! {fixture, r#"
+        type = "webpack"
+    "#};
+
+    build_fails_with(
+        fixture,
+        "Building a Cloudflare Worker with target \"node\" is not supported",
+    );
+    cleanup(fixture);
+}
+
+#[test]
+fn it_builds_with_webpack_target_webworker() {
+    let fixture = "webpack_target_webworker";
+    create_temporary_copy(fixture);
+
+    webpack_config(
+        fixture,
+        r#"{
+          entry: "./index.js",
+          target: "webworker",
+        }"#,
+    );
+    settings! {fixture, r#"
+        type = "webpack"
+    "#};
+
+    build(fixture);
+    cleanup(fixture);
+}
+
 fn cleanup(fixture: &str) {
     let path = fixture_path(fixture);
     assert!(path.exists(), format!("{:?} does not exist", path));
@@ -236,3 +279,16 @@ fn create_temporary_copy(fixture: &str) {
     options.overwrite = true;
     copy(src, dest, &options).unwrap();
 }
+
+// TODO: remove once https://github.com/cloudflare/wrangler/pull/489 is merged
+pub fn webpack_config(fixture: &str, config: &str) {
+    let file_path = fixture_path(fixture).join("webpack.config.js");
+    let mut file = File::create(file_path).unwrap();
+    let content = format!(
+        r#"
+                 module.exports = {};
+             "#,
+        config
+    );
+    file.write_all(content.as_bytes()).unwrap();
+}

wranglerjs/index.js

@@ -44,6 +44,16 @@ function filterByExtension(ext) {
     );
   }
 
+  if (config.target !== undefined && config.target !== "webworker") {
+    throw error(
+      "Building a Cloudflare Worker with target " +
+        JSON.stringify(config.target) +
+        " is not supported. Wrangler will set webworker by default, please remove " +
+        "the `target` key in your webpack configuration."
+    );
+  }
+  config.target = "webworker";
+
   const compiler = webpack(config);
   const fullConfig = compiler.options;