From ea808f52fe3dd70dedc6294ebda26a4100767ad1 Mon Sep 17 00:00:00 2001
From: Slawomir Sadziak <slsadzia@microsoft.com>
Date: Mon, 10 Oct 2016 12:15:34 +0200
Subject: [PATCH] Fix #10758 Add compiler option to parse in strict mode

 * add unit test to ensure "use strict" is not added twice
 * fix code
---
 src/compiler/factory.ts                       | 30 +++++++++++++++++++
 src/compiler/transformers/ts.ts               |  9 +-----
 .../reference/alwaysStrictAlreadyUseStrict.js | 11 +++++++
 .../alwaysStrictAlreadyUseStrict.symbols      |  8 +++++
 .../alwaysStrictAlreadyUseStrict.types        | 11 +++++++
 .../compiler/alwaysStrictAlreadyUseStrict.ts  |  5 ++++
 6 files changed, 66 insertions(+), 8 deletions(-)
 create mode 100644 tests/baselines/reference/alwaysStrictAlreadyUseStrict.js
 create mode 100644 tests/baselines/reference/alwaysStrictAlreadyUseStrict.symbols
 create mode 100644 tests/baselines/reference/alwaysStrictAlreadyUseStrict.types
 create mode 100644 tests/cases/compiler/alwaysStrictAlreadyUseStrict.ts

diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index 97a36f46b1..6bf6259c36 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -2235,6 +2235,36 @@ namespace ts {
         return statementOffset;
     }
 
+    /**
+     * Ensures "use strict" directive is added
+     * 
+     * @param node source file
+     */
+    export function ensureUseStrict(node: SourceFile): SourceFile {
+        let foundUseStrict = false;
+        let statementOffset = 0;
+        const numStatements = node.statements.length;
+        while (statementOffset < numStatements) {
+            const statement = node.statements[statementOffset];
+            if (isPrologueDirective(statement)) {
+                if (isUseStrictPrologue(statement as ExpressionStatement)) {
+                    foundUseStrict = true;
+                }
+            }
+            else {
+                break;
+            }
+            statementOffset++;
+        }
+        if (!foundUseStrict) {
+            const statements: Statement[] = [];
+            statements.push(startOnNewLine(createStatement(createLiteral("use strict"))));
+            // add "use strict" as the first statement
+            return updateSourceFileNode(node, statements.concat(node.statements));
+        }
+        return node;
+    }
+
     /**
      * Wraps the operand to a BinaryExpression in parentheses if they are needed to preserve the intended
      * order of operations.
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index 7b6c28a8f4..112f838a37 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -438,7 +438,7 @@ namespace ts {
 
             // ensure "use strict"" is emitted in all scenarios in alwaysStrict mode
             if (compilerOptions.alwaysStrict) {
-                node = emitUseStrict(node);
+                node = ensureUseStrict(node);
             }
 
             // If the source file requires any helpers and is an external module, and
@@ -477,13 +477,6 @@ namespace ts {
             return node;
         }
 
-        function emitUseStrict(node: SourceFile): SourceFile {
-            const statements: Statement[] = [];
-            statements.push(startOnNewLine(createStatement(createLiteral("use strict"))));
-            // add "use strict" as the first statement
-            return updateSourceFileNode(node, statements.concat(node.statements));
-        }
-
         /**
          * Tests whether we should emit a __decorate call for a class declaration.
          */
diff --git a/tests/baselines/reference/alwaysStrictAlreadyUseStrict.js b/tests/baselines/reference/alwaysStrictAlreadyUseStrict.js
new file mode 100644
index 0000000000..cc3be45ded
--- /dev/null
+++ b/tests/baselines/reference/alwaysStrictAlreadyUseStrict.js
@@ -0,0 +1,11 @@
+//// [alwaysStrictAlreadyUseStrict.ts]
+"use strict"
+function f() {
+    var a = [];
+}
+
+//// [alwaysStrictAlreadyUseStrict.js]
+"use strict";
+function f() {
+    var a = [];
+}
diff --git a/tests/baselines/reference/alwaysStrictAlreadyUseStrict.symbols b/tests/baselines/reference/alwaysStrictAlreadyUseStrict.symbols
new file mode 100644
index 0000000000..143f579b94
--- /dev/null
+++ b/tests/baselines/reference/alwaysStrictAlreadyUseStrict.symbols
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/alwaysStrictAlreadyUseStrict.ts ===
+"use strict"
+function f() {
+>f : Symbol(f, Decl(alwaysStrictAlreadyUseStrict.ts, 0, 12))
+
+    var a = [];
+>a : Symbol(a, Decl(alwaysStrictAlreadyUseStrict.ts, 2, 7))
+}
diff --git a/tests/baselines/reference/alwaysStrictAlreadyUseStrict.types b/tests/baselines/reference/alwaysStrictAlreadyUseStrict.types
new file mode 100644
index 0000000000..0181b40de2
--- /dev/null
+++ b/tests/baselines/reference/alwaysStrictAlreadyUseStrict.types
@@ -0,0 +1,11 @@
+=== tests/cases/compiler/alwaysStrictAlreadyUseStrict.ts ===
+"use strict"
+>"use strict" : "use strict"
+
+function f() {
+>f : () => void
+
+    var a = [];
+>a : any[]
+>[] : undefined[]
+}
diff --git a/tests/cases/compiler/alwaysStrictAlreadyUseStrict.ts b/tests/cases/compiler/alwaysStrictAlreadyUseStrict.ts
new file mode 100644
index 0000000000..1d804a6cf9
--- /dev/null
+++ b/tests/cases/compiler/alwaysStrictAlreadyUseStrict.ts
@@ -0,0 +1,5 @@
+// @alwaysStrict: true
+"use strict"
+function f() {
+    var a = [];
+}
\ No newline at end of file