Merge branch '10758-always-strict' of https://github.com/slawomir/TypeScript into slawomir-10758-always-strict

src/compiler/binder.ts

@@ -121,7 +121,8 @@ namespace ts {
 
         // If this file is an external module, then it is automatically in strict-mode according to
         // ES6.  If it is not an external module, then we'll determine if it is in strict mode or
-        // not depending on if we see "use strict" in certain places (or if we hit a class/namespace).
+        // not depending on if we see "use strict" in certain places or if we hit a class/namespace
+        // or if compiler options contain alwaysStrict.
         let inStrictMode: boolean;
 
         let symbolCount = 0;
@@ -139,7 +140,7 @@ namespace ts {
             file = f;
             options = opts;
             languageVersion = getEmitScriptTarget(options);
-            inStrictMode = !!file.externalModuleIndicator;
+            inStrictMode = bindInStrictMode(file, opts);
             classifiableNames = createMap<string>();
             symbolCount = 0;
             skipTransformFlagAggregation = isDeclarationFile(file);
@@ -174,6 +175,16 @@ namespace ts {
 
         return bindSourceFile;
 
+        function bindInStrictMode(file: SourceFile, opts: CompilerOptions): boolean {
+            if (opts.alwaysStrict && !isDeclarationFile(file)) {
+                // bind in strict mode source files with alwaysStrict option
+                return true;
+            }
+            else {
+                return !!file.externalModuleIndicator;
+            }
+        }
+
         function createSymbol(flags: SymbolFlags, name: string): Symbol {
             symbolCount++;
             return new Symbol(flags, name);

src/compiler/commandLineParser.ts

@@ -444,6 +444,11 @@ namespace ts {
             name: "importHelpers",
             type: "boolean",
             description: Diagnostics.Import_emit_helpers_from_tslib
+        },
+        {
+            name: "alwaysStrict",
+            type: "boolean",
+            description: Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
         }
     ];
 

src/compiler/diagnosticMessages.json

@@ -2861,6 +2861,10 @@
         "category": "Error",
         "code": 6140
     },
+    "Parse in strict mode and emit \"use strict\" for each source file": {
+        "category": "Message",
+        "code": 6141
+    },
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005

src/compiler/factory.ts

@@ -2235,6 +2235,33 @@ namespace ts {
         return statementOffset;
     }
 
+    /**
+     * Ensures "use strict" directive is added
+     * 
+     * @param node source file
+     */
+    export function ensureUseStrict(node: SourceFile): SourceFile {
+        let foundUseStrict = false;
+        for (const statement of node.statements) {
+            if (isPrologueDirective(statement)) {
+                if (isUseStrictPrologue(statement as ExpressionStatement)) {
+                    foundUseStrict = true;
+                    break;
+                }
+            }
+            else {
+                break;
+            }
+        }
+        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.

src/compiler/transformers/ts.ts

@@ -436,6 +436,11 @@ namespace ts {
         function visitSourceFile(node: SourceFile) {
             currentSourceFile = node;
 
+            // ensure "use strict" is emitted in all scenarios in alwaysStrict mode
+            if (compilerOptions.alwaysStrict) {
+                node = ensureUseStrict(node);
+            }
+
             // If the source file requires any helpers and is an external module, and
             // the importHelpers compiler option is enabled, emit a synthesized import
             // statement for the helpers library.

src/compiler/types.ts

@@ -2925,6 +2925,7 @@ namespace ts {
         allowSyntheticDefaultImports?: boolean;
         allowUnreachableCode?: boolean;
         allowUnusedLabels?: boolean;
+        alwaysStrict?: boolean;
         baseUrl?: string;
         charset?: string;
         /* @internal */ configFilePath?: string;

src/harness/unittests/transpile.ts

@@ -253,6 +253,10 @@ var x = 0;`, {
             options: { compilerOptions: { allowUnusedLabels: true }, fileName: "input.js", reportDiagnostics: true }
         });
 
+        transpilesCorrectly("Supports setting 'alwaysStrict'", "x;", {
+            options: { compilerOptions: { alwaysStrict: true }, fileName: "input.js", reportDiagnostics: true }
+        });
+
         transpilesCorrectly("Supports setting 'baseUrl'", "x;", {
             options: { compilerOptions: { baseUrl: "./folder/baseUrl" }, fileName: "input.js", reportDiagnostics: true }
         });