Merge pull request #7924 from Microsoft/correctStrictPrologueCheck

Emit "use strict" if a prologue only contains "use strict" somewhere inside of it

Author: DanielRosenwasser

src/compiler/emitter.ts

@@ -7652,7 +7652,7 @@ const _super = (function (geti, seti) {
             }
 
             function isUseStrictPrologue(node: ExpressionStatement): boolean {
-                return !!(node.expression as StringLiteral).text.match(/use strict/);
+                return (node.expression as StringLiteral).text === "use strict";
             }
 
             function ensureUseStrictPrologue(startWithNewLine: boolean, writeUseStrict: boolean) {

tests/baselines/reference/useStrictLikePrologueString01.js

@@ -0,0 +1,14 @@
+//// [useStrictLikePrologueString01.ts]
+
+"hey!"
+" use strict "
+export function f() {   
+}
+
+//// [useStrictLikePrologueString01.js]
+"hey!";
+" use strict ";
+"use strict";
+function f() {
+}
+exports.f = f;

tests/baselines/reference/useStrictLikePrologueString01.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/useStrictLikePrologueString01.ts ===
+
+"hey!"
+" use strict "
+export function f() {   
+>f : Symbol(f, Decl(useStrictLikePrologueString01.ts, 2, 14))
+}

tests/baselines/reference/useStrictLikePrologueString01.types

@@ -0,0 +1,11 @@
+=== tests/cases/compiler/useStrictLikePrologueString01.ts ===
+
+"hey!"
+>"hey!" : string
+
+" use strict "
+>" use strict " : string
+
+export function f() {   
+>f : () => void
+}

tests/cases/compiler/useStrictLikePrologueString01.ts

@@ -0,0 +1,7 @@
+//@target: commonjs
+//@target: es5
+
+"hey!"
+" use strict "
+export function f() {   
+}