fix #2203: export default of /* @__PURE__ */

evanw · Apr 22, 2022 · e876856 · e876856
1 parent e9728a6
commit e876856
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,25 @@
 # Changelog
 
+## Unreleased
+
+* Fix code generation for `export default` and `/* @__PURE__ */` call ([#2203](https://github.com/evanw/esbuild/issues/2203))
+
+    The `/* @__PURE__ */` comment annotation can be added to function calls to indicate that they are side-effect free. These annotations are passed through into the output by esbuild since many JavaScript tools understand them. However, there was an edge case where printing this comment before a function call caused esbuild to fail to parenthesize a function literal because it thought it was no longer at the start of the expression. This problem has been fixed:
+
+    ```js
+    // Original code
+    export default /* @__PURE__ */ (function() {
+    })()
+
+    // Old output
+    export default /* @__PURE__ */ function() {
+    }();
+
+    // New output
+    export default /* @__PURE__ */ (function() {
+    })();
+    ```
+
 ## 0.14.38
 
 * Further fixes to TypeScript 4.7 instantiation expression parsing ([#2201](https://github.com/evanw/esbuild/issues/2201))

diff --git a/internal/js_printer/js_printer.go b/internal/js_printer/js_printer.go
@@ -1817,10 +1817,14 @@ func (p *printer) printExpr(expr js_ast.Expr, level js_ast.L, flags printExprFla
 
 		if hasPureComment {
 			wasStmtStart := p.stmtStart == len(p.js)
+			wasExportDefaultStart := p.exportDefaultStart == len(p.js)
 			p.print("/* @__PURE__ */ ")
 			if wasStmtStart {
 				p.stmtStart = len(p.js)
 			}
+			if wasExportDefaultStart {
+				p.exportDefaultStart = len(p.js)
+			}
 		}
 
 		// We don't ever want to accidentally generate a direct eval expression here

diff --git a/internal/js_printer/js_printer_test.go b/internal/js_printer/js_printer_test.go
@@ -547,6 +547,16 @@ func TestPureComment(t *testing.T) {
 	expectPrinted(t,
 		"/*@__PURE__*/new (function() {})()",
 		"/* @__PURE__ */ new function() {\n}();\n")
+
+	expectPrinted(t,
+		"export default (function() {})",
+		"export default (function() {\n});\n")
+	expectPrinted(t,
+		"export default (function() {})()",
+		"export default (function() {\n})();\n")
+	expectPrinted(t,
+		"export default /*@__PURE__*/(function() {})()",
+		"export default /* @__PURE__ */ (function() {\n})();\n")
 }
 
 func TestGenerator(t *testing.T) {