Add flag to emit modules in loose mode

src/compiler/commandLineParser.ts

@@ -320,6 +320,11 @@ namespace ts {
             name: "allowSyntheticDefaultImports",
             type: "boolean",
             description: Diagnostics.Allow_default_imports_from_modules_with_no_default_export_This_does_not_affect_code_emit_just_typechecking
+        },
+        {
+            name: "emitModulesInLooseMode",
+            type: "boolean",
+            description: Diagnostics.Do_not_emit_use_strict_directives_in_module_output
         }
     ];
 

src/compiler/diagnosticMessages.json

@@ -1,4 +1,4 @@
- {
+{
     "Unterminated string literal.": {
         "category": "Error",
         "code": 1002
@@ -2187,6 +2187,7 @@
         "category": "Error",
         "code": 5062
     },
+
     "Concatenate and emit output to single file.": {
         "category": "Message",
         "code": 6001
@@ -2231,10 +2232,10 @@
         "category": "Message",
         "code": 6011
     },
-  "Specify ECMAScript target version: 'ES3' (default), 'ES5', or 'ES2015' (experimental)": {
-    "category": "Message",
-    "code": 6015
-  },
+    "Specify ECMAScript target version: 'ES3' (default), 'ES5', or 'ES2015' (experimental)": {
+        "category": "Message",
+        "code": 6015
+    },
     "Specify module code generation: 'commonjs', 'amd', 'system', 'umd' or 'es2015'": {
         "category": "Message",
         "code": 6016
@@ -2571,6 +2572,11 @@
         "category": "Message",
         "code": 6111
     },
+    "Do not emit 'use strict' directives in module output.": {
+        "category": "Message",
+        "code": 6112
+    },
+
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005
@@ -2757,23 +2763,23 @@
         "code": 17004
     },
     "A constructor cannot contain a 'super' call when its class extends 'null'": {
-      "category": "Error",
-      "code": 17005
+        "category": "Error",
+        "code": 17005
     },
     "An unary expression with the '{0}' operator is not allowed in the left-hand side of an exponentiation expression. Consider enclosing the expression in parentheses.": {
-      "category": "Error",
-      "code": 17006
+        "category": "Error",
+        "code": 17006
     },
     "A type assertion expression is not allowed in the left-hand side of an exponentiation expression. Consider enclosing the expression in parentheses.": {
-      "category": "Error",
-      "code": 17007
+        "category": "Error",
+        "code": 17007
     },
     "JSX element '{0}' has no corresponding closing tag.": {
-      "category": "Error",
-      "code": 17008
+        "category": "Error",
+        "code": 17008
     },
     "'super' must be called before accessing 'this' in the constructor of a derived class.": {
-      "category": "Error",
-      "code": 17009
+        "category": "Error",
+        "code": 17009
     }
-}
+}

src/compiler/emitter.ts

@@ -7179,7 +7179,7 @@ const _super = (function (geti, seti) {
                 write(`], function(${exportFunctionForFile}, ${contextObjectForFile}) {`);
                 writeLine();
                 increaseIndent();
-                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ true, /*ensureUseStrict*/ true);
+                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ true, /*ensureUseStrict*/ !compilerOptions.emitModulesInLooseMode);
                 writeLine();
                 write(`var __moduleName = ${contextObjectForFile} && ${contextObjectForFile}.id;`);
                 writeLine();
@@ -7285,7 +7285,7 @@ const _super = (function (geti, seti) {
                 writeModuleName(node, emitRelativePathAsModuleName);
                 emitAMDDependencies(node, /*includeNonAmdDependencies*/ true, emitRelativePathAsModuleName);
                 increaseIndent();
-                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ true, /*ensureUseStrict*/ true);
+                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ true, /*ensureUseStrict*/!compilerOptions.emitModulesInLooseMode);
                 emitExportStarHelper();
                 emitCaptureThisForNodeIfNecessary(node);
                 emitLinesStartingAt(node.statements, startIndex);
@@ -7297,7 +7297,7 @@ const _super = (function (geti, seti) {
             }
 
             function emitCommonJSModule(node: SourceFile) {
-                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ false, /*ensureUseStrict*/ true);
+                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ false, /*ensureUseStrict*/ !compilerOptions.emitModulesInLooseMode);
                 emitEmitHelpers(node);
                 collectExternalModuleInfo(node);
                 emitExportStarHelper();
@@ -7326,7 +7326,7 @@ const _super = (function (geti, seti) {
 })(`);
                 emitAMDFactoryHeader(dependencyNames);
                 increaseIndent();
-                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ true, /*ensureUseStrict*/ true);
+                const startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ true, /*ensureUseStrict*/ !compilerOptions.emitModulesInLooseMode);
                 emitExportStarHelper();
                 emitCaptureThisForNodeIfNecessary(node);
                 emitLinesStartingAt(node.statements, startIndex);

src/compiler/types.ts

@@ -2422,6 +2422,7 @@ namespace ts {
         traceModuleResolution?: boolean;
         allowSyntheticDefaultImports?: boolean;
         allowJs?: boolean;
+        emitModulesInLooseMode?: boolean;
         /* @internal */ stripInternal?: boolean;
 
         // Skip checking lib.d.ts to help speed up tests.