fix mangle props with TS parameter properties

Author: evanw

CHANGELOG.md

@@ -1,5 +1,22 @@
 # Changelog
 
+## Unreleased
+
+* Fix property name mangling for TypeScript parameter properties
+
+    This release adds TypeScript parameter properties to the set of syntax constructs affected by the new `--mangle-props=` setting. Parameter properties are a TypeScript-only shorthand way of initializing a class field directly from the constructor argument list like this:
+
+    ```ts
+    // Original code
+    class Foo { constructor(public foo_) {} }
+
+    // Old output (with --minify --mangle-props=_)
+    class Foo{constructor(c){this.foo_=c}}
+
+    // New output (with --minify --mangle-props=_)
+    class Foo{constructor(o){this.c=o}}
+    ```
+
 ## 0.14.15
 
 * Add property name mangling with `--mangle-props=` ([#218](https://github.com/evanw/esbuild/issues/218))

internal/bundler/bundler_default_test.go

@@ -5660,3 +5660,27 @@ func TestManglePropsAvoidCollisions(t *testing.T) {
 		},
 	})
 }
+
+func TestManglePropsTSParameterProperties(t *testing.T) {
+	loader_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/entry.ts": `
+				class Foo {
+					constructor(
+						public bar: number,
+						public baz_: number,
+					) {
+					}
+				}
+				let foo = new Foo
+				console.log(foo.bar, foo.baz_)
+			`,
+		},
+		entryPaths: []string{"/entry.js"},
+		options: config.Options{
+			Mode:          config.ModePassThrough,
+			AbsOutputFile: "/out.js",
+			MangleProps:   regexp.MustCompile("_$"),
+		},
+	})
+}

internal/bundler/snapshots/snapshots_loader.txt

@@ -670,6 +670,18 @@ export default function(x) {
   x?.a["bar_"];
 }
 
+================================================================================
+TestManglePropsTSParameterProperties
+---------- /out.js ----------
+class Foo {
+  constructor(bar, baz_) {
+    this.bar = bar;
+    this.a = baz_;
+  }
+}
+let foo = new Foo();
+console.log(foo.bar, foo.a);
+
 ================================================================================
 TestMinifyIdentifiersImportPathFrequencyAnalysis
 ---------- /out/import.js ----------

internal/js_parser/js_parser_lower.go

@@ -2443,12 +2443,21 @@ func (p *parser) lowerClass(stmt js_ast.Stmt, expr js_ast.Expr, shadowRef js_ast
 						for _, arg := range ctor.Fn.Args {
 							if arg.IsTypeScriptCtorField {
 								if id, ok := arg.Binding.Data.(*js_ast.BIdentifier); ok {
-									parameterFields = append(parameterFields, js_ast.AssignStmt(
-										js_ast.Expr{Loc: arg.Binding.Loc, Data: &js_ast.EDot{
+									var target js_ast.Expr
+									if name := p.symbols[id.Ref.InnerIndex].OriginalName; p.isMangledProperty(name) {
+										target = js_ast.Expr{Loc: arg.Binding.Loc, Data: &js_ast.EIndex{
+											Target: js_ast.Expr{Loc: arg.Binding.Loc, Data: js_ast.EThisShared},
+											Index:  js_ast.Expr{Loc: arg.Binding.Loc, Data: &js_ast.EMangledProp{Ref: p.symbolForMangledProperty(name)}},
+										}}
+									} else {
+										target = js_ast.Expr{Loc: arg.Binding.Loc, Data: &js_ast.EDot{
 											Target:  js_ast.Expr{Loc: arg.Binding.Loc, Data: js_ast.EThisShared},
-											Name:    p.symbols[id.Ref.InnerIndex].OriginalName,
+											Name:    name,
 											NameLoc: arg.Binding.Loc,
-										}},
+										}}
+									}
+									parameterFields = append(parameterFields, js_ast.AssignStmt(
+										target,
 										js_ast.Expr{Loc: arg.Binding.Loc, Data: &js_ast.EIdentifier{Ref: id.Ref}},
 									))
 								}