Revert "Avoid unnecessary Buffer allocations in minifyJs."

This reverts commit ff0d85d391.

tools/isobuild/bundler.js

@@ -1354,7 +1354,17 @@ class Target {
       inputHashesByJsFile.set(jsf, file.hash());
 
       if (file.targetPath.startsWith("dynamic/")) {
+        // Dynamic files consist of a single anonymous function
+        // expression, which some minifiers (e.g. UglifyJS) either fail to
+        // parse or mistakenly eliminate as dead code. To avoid these
+        // problems, we temporarily name the function __minifyJs.
+        file._contents = Buffer.concat([
+          MINIFY_RENAMED_FUNCTION,
+          file.contents().slice(MINIFY_PLAIN_FUNCTION.length)
+        ]);
+
         dynamicFiles.push(jsf);
+
       } else {
         staticFiles.push(jsf);
       }
@@ -1382,8 +1392,19 @@ class Target {
 
     function handle(source, dynamic) {
       source._minifiedFiles.forEach(file => {
-        if (typeof file.data === "string") {
-          file.data = Buffer.from(file.data, "utf8");
+        // Remove the function name __minifyJs that was added above.
+        if (typeof file.data === 'string') {
+          file.data = Buffer.from(
+            file.data
+              .replace(/^\s*function\s+__minifyJs\s*\(/,
+                       "function("),
+            "utf8"
+          );
+        } else if (dynamic) {
+          file.data = Buffer.concat([
+            MINIFY_PLAIN_FUNCTION,
+            file.data.slice(MINIFY_RENAMED_FUNCTION.length)
+          ]);
         }
 
         const newFile = new File({

tools/isobuild/linker.js

@@ -685,7 +685,7 @@ _.extend(File.prototype, {
 
   _getClosureHeader() {
     if (this.meteorInstallOptions) {
-      const headerParts = ["function module("];
+      const headerParts = ["function("];
 
       if (this.source.match(/\b__dirname\b/)) {
         headerParts.push("require,exports,module,__filename,__dirname");