Merge pull request #12134 from Microsoft/release-2.1_fix11806_omitUseStrict

[Release 2.1] fix11806 omit use strict

Author: yuit

src/compiler/transformers/ts.ts

@@ -457,7 +457,11 @@ namespace ts {
             currentSourceFile = node;
 
             // ensure "use strict" is emitted in all scenarios in alwaysStrict mode
-            if (compilerOptions.alwaysStrict) {
+            // There is no need to emit "use strict" in the following cases:
+            //      1. The file is an external module and target is es2015 or higher
+            //      or 2. The file is an external module and module-kind is es6 or es2015 as such value is not allowed when targeting es5 or lower
+            if (compilerOptions.alwaysStrict &&
+                !(isExternalModule(node) && (compilerOptions.target >= ScriptTarget.ES2015 || compilerOptions.module === ModuleKind.ES2015))) {
                 node = ensureUseStrict(node);
             }
 

tests/baselines/reference/alwaysStrictModule3.js

@@ -0,0 +1,8 @@
+//// [alwaysStrictModule3.ts]
+
+// module ES2015
+export const a = 1;
+
+//// [alwaysStrictModule3.js]
+// module ES2015
+export var a = 1;

tests/baselines/reference/alwaysStrictModule3.symbols

@@ -0,0 +1,6 @@
+=== tests/cases/compiler/alwaysStrictModule3.ts ===
+
+// module ES2015
+export const a = 1;
+>a : Symbol(a, Decl(alwaysStrictModule3.ts, 2, 12))
+

tests/baselines/reference/alwaysStrictModule3.types

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/alwaysStrictModule3.ts ===
+
+// module ES2015
+export const a = 1;
+>a : 1
+>1 : 1
+

tests/baselines/reference/alwaysStrictModule4.js

@@ -0,0 +1,9 @@
+//// [alwaysStrictModule4.ts]
+
+// Module commonjs
+export const a = 1
+
+//// [alwaysStrictModule4.js]
+"use strict";
+// Module commonjs
+exports.a = 1;

tests/baselines/reference/alwaysStrictModule4.symbols

@@ -0,0 +1,6 @@
+=== tests/cases/compiler/alwaysStrictModule4.ts ===
+
+// Module commonjs
+export const a = 1
+>a : Symbol(a, Decl(alwaysStrictModule4.ts, 2, 12))
+

tests/baselines/reference/alwaysStrictModule4.types

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/alwaysStrictModule4.ts ===
+
+// Module commonjs
+export const a = 1
+>a : 1
+>1 : 1
+

tests/baselines/reference/alwaysStrictModule5.js

@@ -0,0 +1,8 @@
+//// [alwaysStrictModule5.ts]
+
+// Targeting ES6
+export const a = 1; 
+
+//// [alwaysStrictModule5.js]
+// Targeting ES6
+export const a = 1;

tests/baselines/reference/alwaysStrictModule5.symbols

@@ -0,0 +1,6 @@
+=== tests/cases/compiler/alwaysStrictModule5.ts ===
+
+// Targeting ES6
+export const a = 1; 
+>a : Symbol(a, Decl(alwaysStrictModule5.ts, 2, 12))
+

tests/baselines/reference/alwaysStrictModule5.types

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/alwaysStrictModule5.ts ===
+
+// Targeting ES6
+export const a = 1; 
+>a : 1
+>1 : 1
+