Update language service to use getDeclarationDiagnostics instead of emitFile to get declaration errors

Author: Yui T

src/compiler/checker.ts

@@ -71,6 +71,7 @@ module ts {
         var checker: TypeChecker = {
             getProgram: () => program,
             getDiagnostics: getDiagnostics,
+            getDeclarationDiagnostics: getDeclarationDiagnosticsFromSourceFile,
             getGlobalDiagnostics: getGlobalDiagnostics,
             getNodeCount: () => sum(program.getSourceFiles(), "nodeCount"),
             getIdentifierCount: () => sum(program.getSourceFiles(), "identifierCount"),
@@ -7038,6 +7039,29 @@ module ts {
             return getSortedDiagnostics();
         }
 
+        function getDeclarationDiagnosticsFromSourceFile(targetSourceFile: SourceFile): Diagnostic[] {
+            var resolver: EmitResolver = {
+                getProgram: () => program,
+                getLocalNameOfContainer: getLocalNameOfContainer,
+                getExpressionNamePrefix: getExpressionNamePrefix,
+                getExportAssignmentName: getExportAssignmentName,
+                isReferencedImportDeclaration: isReferencedImportDeclaration,
+                getNodeCheckFlags: getNodeCheckFlags,
+                getEnumMemberValue: getEnumMemberValue,
+                isTopLevelValueImportedViaEntityName: isTopLevelValueImportedViaEntityName,
+                hasSemanticErrors: hasSemanticErrors,
+                isDeclarationVisible: isDeclarationVisible,
+                isImplementationOfOverload: isImplementationOfOverload,
+                writeTypeAtLocation: writeTypeAtLocation,
+                writeReturnTypeOfSignatureDeclaration: writeReturnTypeOfSignatureDeclaration,
+                isSymbolAccessible: isSymbolAccessible,
+                isImportDeclarationEntityNameReferenceDeclarationVisible: isImportDeclarationEntityNameReferenceDeclarationVisible,
+                getConstantValue: getConstantValue,
+            };
+            checkProgram();
+            return getDeclarationDiagnostics(program, resolver, targetSourceFile);
+        }
+
         function getGlobalDiagnostics(): Diagnostic[] {
             return filter(getSortedDiagnostics(), d => !d.file);
         }

src/compiler/emitter.ts

@@ -1233,6 +1233,13 @@ module ts {
         }
     }
 
+    export function getDeclarationDiagnostics(program: Program, resolver: EmitResolver, targetSourceFile: SourceFile): Diagnostic[] {
+        var diagnostics: Diagnostic[] = [];
+        var jsFilePath = getOwnEmitOutputFilePath(targetSourceFile, program, ".js");
+        emitDeclarations(program, resolver, diagnostics, jsFilePath, targetSourceFile);
+        return diagnostics;
+    }
+
     // targetSourceFile is when users only want one file in entire project to be emitted. This is used in compilerOnSave feature
     export function emitFiles(resolver: EmitResolver, targetSourceFile?: SourceFile): EmitResult {
         var program = resolver.getProgram();

src/compiler/types.ts

@@ -624,6 +624,7 @@ module ts {
     export interface TypeChecker {
         getProgram(): Program;
         getDiagnostics(sourceFile?: SourceFile): Diagnostic[];
+        getDeclarationDiagnostics(sourceFile: SourceFile): Diagnostic[];
         getGlobalDiagnostics(): Diagnostic[];
         getNodeCount(): number;
         getIdentifierCount(): number;

src/services/services.ts

@@ -2206,7 +2206,7 @@ module ts {
                 // Get emitter-diagnostics requires calling TypeChecker.emitFiles so we have to define CompilerHost.writer which does nothing because emitFiles function has side effects defined by CompilerHost.writer
                 var savedWriter = writer;
                 writer = (filename: string, data: string, writeByteOrderMark: boolean) => { };
-                allDiagnostics = allDiagnostics.concat(checker.emitFiles(targetSourceFile).errors);
+                allDiagnostics = allDiagnostics.concat(checker.getDeclarationDiagnostics(targetSourceFile));
                 writer = savedWriter;
             }
             return allDiagnostics