Add support to report errors in js files

src/compiler/commandLineParser.ts

@@ -481,6 +481,12 @@ namespace ts {
                 name: "plugin",
                 type: "object"
             }
+        },
+        {
+            name: "checkJs",
+            type: "boolean",
+            experimental: true,
+            description: Diagnostics.Report_errors_in_js_files
         }
     ];
 

src/compiler/diagnosticMessages.json

@@ -3362,5 +3362,9 @@
     "Octal literals are not allowed in enums members initializer. Use the syntax '{0}'.": {
         "category": "Error",
         "code": 8018
+    },
+    "Report errors in .js files.": {
+        "category": "Message",
+        "code": 8019
     }
 }

src/compiler/parser.ts

@@ -5817,6 +5817,7 @@ namespace ts {
             const typeReferenceDirectives: FileReference[] = [];
             const amdDependencies: { path: string; name: string }[] = [];
             let amdModuleName: string;
+            let checkJsDirective: CheckJsDirective = undefined;
 
             // Keep scanning all the leading trivia in the file until we get to something that
             // isn't trivia.  Any single line comment will be analyzed to see if it is a
@@ -5878,13 +5879,24 @@ namespace ts {
                             amdDependencies.push(amdDependency);
                         }
                     }
+
+                    const checkJsDirectiveRegEx = /^\/\/\/?\s*@check(\s+(true|false))?/gim;
+                    const checkJsDirectiveMatchResult = checkJsDirectiveRegEx.exec(comment);
+                    if (checkJsDirectiveMatchResult) {
+                        checkJsDirective = {
+                            enabled: compareStrings(checkJsDirectiveMatchResult[2], "false", /*ignoreCase*/ true) !== Comparison.EqualTo,
+                            end: range.end,
+                            pos: range.pos
+                        };
+                    }
                 }
             }
 
             sourceFile.referencedFiles = referencedFiles;
             sourceFile.typeReferenceDirectives = typeReferenceDirectives;
             sourceFile.amdDependencies = amdDependencies;
             sourceFile.moduleName = amdModuleName;
+            sourceFile.checkJsDirective = checkJsDirective;
         }
 
         function setExternalModuleIndicator(sourceFile: SourceFile) {

src/compiler/program.ts

@@ -904,10 +904,10 @@ namespace ts {
 
                 Debug.assert(!!sourceFile.bindDiagnostics);
                 const bindDiagnostics = sourceFile.bindDiagnostics;
-                // For JavaScript files, we don't want to report semantic errors.
-                // Instead, we'll report errors for using TypeScript-only constructs from within a
-                // JavaScript file when we get syntactic diagnostics for the file.
-                const checkDiagnostics = isSourceFileJavaScript(sourceFile) ? [] : typeChecker.getDiagnostics(sourceFile, cancellationToken);
+                // For JavaScript files, we don't want to report semantic errors unless ecplicitlly requested.
+                const includeCheckDiagnostics = !isSourceFileJavaScript(sourceFile) ||
+                    (sourceFile.checkJsDirective ? sourceFile.checkJsDirective.enabled : options.checkJs);
+                const checkDiagnostics = includeCheckDiagnostics ? typeChecker.getDiagnostics(sourceFile, cancellationToken) : [];
                 const fileProcessingDiagnosticsInFile = fileProcessingDiagnostics.getDiagnostics(sourceFile.fileName);
                 const programDiagnosticsInFile = programDiagnostics.getDiagnostics(sourceFile.fileName);
 
@@ -1685,6 +1685,10 @@ namespace ts {
                 programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Option_0_cannot_be_specified_with_option_1, "allowJs", "declaration"));
             }
 
+            if (options.checkJs && !options.allowJs) {
+                programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Option_0_cannot_be_specified_without_specifying_option_1, "checkJs", "allowJs"));
+            }
+
             if (options.emitDecoratorMetadata &&
                 !options.experimentalDecorators) {
                 programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Option_0_cannot_be_specified_without_specifying_option_1, "emitDecoratorMetadata", "experimentalDecorators"));

src/compiler/types.ts

@@ -1940,6 +1940,10 @@
         fileName: string;
     }
 
+    export interface CheckJsDirective extends TextRange {
+        enabled: boolean;
+    }
+
     export type CommentKind = SyntaxKind.SingleLineCommentTrivia | SyntaxKind.MultiLineCommentTrivia;
 
     export interface CommentRange extends TextRange {
@@ -2272,6 +2276,7 @@
         /* @internal */ moduleAugmentations: LiteralExpression[];
         /* @internal */ patternAmbientModules?: PatternAmbientModule[];
         /* @internal */ ambientModuleNames: string[];
+        /* @internal */ checkJsDirective: CheckJsDirective | undefined;
     }
 
     export interface Bundle extends Node {
@@ -3312,6 +3317,7 @@
         alwaysStrict?: boolean;  // Always combine with strict property
         baseUrl?: string;
         charset?: string;
+        checkJs?: boolean;
         /* @internal */ configFilePath?: string;
         declaration?: boolean;
         declarationDir?: string;

src/harness/harness.ts

@@ -202,7 +202,7 @@ namespace Utils {
             for (const childName in node) {
                 if (childName === "parent" || childName === "nextContainer" || childName === "modifiers" || childName === "externalModuleIndicator" ||
                     // for now ignore jsdoc comments
-                    childName === "jsDocComment") {
+                    childName === "jsDocComment" || childName === "checkJsDirective") {
                     continue;
                 }
                 const child = (<any>node)[childName];

src/services/services.ts

@@ -473,6 +473,7 @@ namespace ts {
         public moduleAugmentations: LiteralExpression[];
         private namedDeclarations: Map<Declaration[]>;
         public ambientModuleNames: string[];
+        public checkJsDirective: CheckJsDirective | undefined;
 
         constructor(kind: SyntaxKind, pos: number, end: number) {
             super(kind, pos, end);

tests/baselines/reference/checkJsFiles.errors.txt

@@ -0,0 +1,9 @@
+tests/cases/compiler/a.js(3,1): error TS2322: Type '0' is not assignable to type 'string'.
+
+
+==== tests/cases/compiler/a.js (1 errors) ====
+
+    var x = "string";
+    x = 0;
+    ~
+!!! error TS2322: Type '0' is not assignable to type 'string'.

tests/baselines/reference/checkJsFiles2.errors.txt

@@ -0,0 +1,10 @@
+tests/cases/compiler/a.js(4,1): error TS2322: Type '0' is not assignable to type 'string'.
+
+
+==== tests/cases/compiler/a.js (1 errors) ====
+
+    // @check
+    var x = "string";
+    x = 0;
+    ~
+!!! error TS2322: Type '0' is not assignable to type 'string'.

tests/baselines/reference/checkJsFiles3.errors.txt

@@ -0,0 +1,10 @@
+tests/cases/compiler/a.js(4,1): error TS2322: Type '0' is not assignable to type 'string'.
+
+
+==== tests/cases/compiler/a.js (1 errors) ====
+
+    // @check
+    var x = "string";
+    x = 0;
+    ~
+!!! error TS2322: Type '0' is not assignable to type 'string'.

tests/baselines/reference/checkJsFiles4.errors.txt

@@ -0,0 +1,10 @@
+tests/cases/compiler/a.js(4,1): error TS2322: Type '0' is not assignable to type 'string'.
+
+
+==== tests/cases/compiler/a.js (1 errors) ====
+
+    // @check true
+    var x = "string";
+    x = 0;
+    ~
+!!! error TS2322: Type '0' is not assignable to type 'string'.

tests/baselines/reference/checkJsFiles5.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/a.js ===
+
+// @check false
+var x = "string";
+>x : Symbol(x, Decl(a.js, 2, 3))
+
+x = 0;
+>x : Symbol(x, Decl(a.js, 2, 3))
+

tests/baselines/reference/checkJsFiles5.types

@@ -0,0 +1,12 @@
+=== tests/cases/compiler/a.js ===
+
+// @check false
+var x = "string";
+>x : string
+>"string" : "string"
+
+x = 0;
+>x = 0 : 0
+>x : string
+>0 : 0
+

tests/baselines/reference/checkJsFiles6.errors.txt

@@ -0,0 +1,9 @@
+error TS5052: Option 'checkJs' cannot be specified without specifying option 'allowJs'.
+error TS6054: File 'tests/cases/compiler/a.js' has unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts'.
+
+
+!!! error TS5052: Option 'checkJs' cannot be specified without specifying option 'allowJs'.
+!!! error TS6054: File 'tests/cases/compiler/a.js' has unsupported extension. The only supported extensions are '.ts', '.tsx', '.d.ts'.
+==== tests/cases/compiler/a.js (0 errors) ====
+
+    var x;

tests/cases/compiler/checkJsFiles.ts

@@ -0,0 +1,7 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+
+// @fileName: a.js
+var x = "string";
+x = 0;

tests/cases/compiler/checkJsFiles2.ts

@@ -0,0 +1,8 @@
+// @allowJs: true
+// @checkJs: false
+// @noEmit: true
+
+// @fileName: a.js
+// @check
+var x = "string";
+x = 0;

tests/cases/compiler/checkJsFiles3.ts

@@ -0,0 +1,7 @@
+// @allowJs: true
+// @noEmit: true
+
+// @fileName: a.js
+// @check
+var x = "string";
+x = 0;

tests/cases/compiler/checkJsFiles4.ts

@@ -0,0 +1,8 @@
+// @allowJs: true
+// @checkJs: false
+// @noEmit: true
+
+// @fileName: a.js
+// @check true
+var x = "string";
+x = 0;

tests/cases/compiler/checkJsFiles5.ts

@@ -0,0 +1,8 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+
+// @fileName: a.js
+// @check false
+var x = "string";
+x = 0;

tests/cases/compiler/checkJsFiles6.ts

@@ -0,0 +1,6 @@
+// @allowJs: false
+// @checkJs: true
+// @noEmit: true
+
+// @fileName: a.js
+var x;