drop undefined default parameter in IIFE. Closes #1366

terser · Apr 17, 2023 · 0ddf63a · 0ddf63a
1 parent 31753d0
commit 0ddf63a
Show file tree

Hide file tree

Showing 2 changed files with 28 additions and 8 deletions.
diff --git a/lib/compress/index.js b/lib/compress/index.js
@@ -2782,13 +2782,20 @@ def_optimize(AST_DefaultAssign, function(self, compressor) {
 
     // `[x = undefined] = foo` ---> `[x] = foo`
     // `(arg = undefined) => ...` ---> `(arg) => ...` (unless `keep_fargs`)
-    if (
-        evaluateRight === undefined &&
-        (compressor.parent() instanceof AST_Lambda
-            ? compressor.option("keep_fargs") === false
-            : true)
-    ) {
-        self = self.left;
+    // `((arg = undefined) => ...)()` ---> `((arg) => ...)()`
+    let lambda, iife;
+    if (evaluateRight === undefined) {
+        if (
+            (lambda = compressor.parent()) instanceof AST_Lambda
+                ? (
+                    compressor.option("keep_fargs") === false
+                    || (iife = compressor.parent(1)).TYPE === "Call"
+                        && iife.expression === lambda
+                )
+                : true
+        ) {
+            self = self.left;
+        }
     } else if (evaluateRight !== self.right) {
         evaluateRight = make_node_from_constant(evaluateRight, self.right);
         self.right = best_of_expression(evaluateRight, self.right);

diff --git a/test/compress/parameters.js b/test/compress/parameters.js
@@ -194,11 +194,24 @@ keep_default_arg_when_undefined: {
         console.log(x.length)
     }
     expect: {
-        function x(a = undefined) { }
+        function x(a = void 0) { }
         console.log(x.length)
     }
 }
 
+drop_default_arg_when_undefined_and_iife: {
+    options = {
+        keep_fargs: true,
+        evaluate: true,
+    }
+    input: {
+        console.log((function x(a = void 0) { })())
+    }
+    expect: {
+        console.log((function x(a) { })())
+    }
+}
+
 default_values_in_destructurings: {
     beautify = {
         ecma: 2015