Add separate flag serverMode for server mode (#39735)

* Add separate flag serverMode for server mode to allow back compatibility

* Addressed code review feedback.

Co-authored-by: Daniel Rosenwasser <DanielRosenwasser@users.noreply.github.com>

Author: sheetalkamat

src/server/editorServices.ts

@@ -396,7 +396,9 @@ namespace ts.server {
         pluginProbeLocations?: readonly string[];
         allowLocalPluginLoads?: boolean;
         typesMapLocation?: string;
+        /** @deprecated use serverMode instead */
         syntaxOnly?: boolean;
+        serverMode?: LanguageServiceMode;
     }
 
     interface OriginalFileInfo { fileName: NormalizedPath; path: Path; }
@@ -683,7 +685,9 @@ namespace ts.server {
 
         public readonly typesMapLocation: string | undefined;
 
-        public readonly syntaxOnly?: boolean;
+        /** @deprecated use serverMode instead */
+        public readonly syntaxOnly: boolean;
+        public readonly serverMode: LanguageServiceMode;
 
         /** Tracks projects that we have already sent telemetry for. */
         private readonly seenProjects = new Map<string, true>();
@@ -713,7 +717,18 @@ namespace ts.server {
             this.pluginProbeLocations = opts.pluginProbeLocations || emptyArray;
             this.allowLocalPluginLoads = !!opts.allowLocalPluginLoads;
             this.typesMapLocation = (opts.typesMapLocation === undefined) ? combinePaths(getDirectoryPath(this.getExecutingFilePath()), "typesMap.json") : opts.typesMapLocation;
-            this.syntaxOnly = opts.syntaxOnly;
+            if (opts.serverMode !== undefined) {
+                this.serverMode = opts.serverMode;
+                this.syntaxOnly = this.serverMode === LanguageServiceMode.SyntaxOnly;
+            }
+            else if (opts.syntaxOnly) {
+                this.serverMode = LanguageServiceMode.SyntaxOnly;
+                this.syntaxOnly = true;
+            }
+            else {
+                this.serverMode = LanguageServiceMode.Semantic;
+                this.syntaxOnly = false;
+            }
 
             Debug.assert(!!this.host.createHash, "'ServerHost.createHash' is required for ProjectService");
             if (this.host.realpath) {
@@ -749,7 +764,7 @@ namespace ts.server {
                 this.logger.loggingEnabled() ? WatchLogLevel.TriggerOnly : WatchLogLevel.None;
             const log: (s: string) => void = watchLogLevel !== WatchLogLevel.None ? (s => this.logger.info(s)) : noop;
             this.packageJsonCache = createPackageJsonCache(this);
-            this.watchFactory = this.syntaxOnly ?
+            this.watchFactory = this.serverMode !== LanguageServiceMode.Semantic ?
                 {
                     watchFile: returnNoopFileWatcher,
                     watchFilePath: returnNoopFileWatcher,
@@ -1727,7 +1742,7 @@ namespace ts.server {
          * the newly opened file.
          */
         private forEachConfigFileLocation(info: OpenScriptInfoOrClosedOrConfigFileInfo, action: (configFileName: NormalizedPath, canonicalConfigFilePath: string) => boolean | void) {
-            if (this.syntaxOnly) {
+            if (this.serverMode !== LanguageServiceMode.Semantic) {
                 return undefined;
             }
 
@@ -3014,15 +3029,15 @@ namespace ts.server {
             let retainProjects: ConfiguredProject[] | ConfiguredProject | undefined;
             let projectForConfigFileDiag: ConfiguredProject | undefined;
             let defaultConfigProjectIsCreated = false;
-            if (this.syntaxOnly) {
+            if (this.serverMode === LanguageServiceMode.ApproximateSemanticOnly) {
                 // Invalidate resolutions in the file since this file is now open
                 info.containingProjects.forEach(project => {
                     if (project.resolutionCache.removeRelativeNoResolveResolutionsOfFile(info.path)) {
                         project.markAsDirty();
                     }
                 });
             }
-            else if (!project) { // Checking syntaxOnly is an optimization
+            else if (!project && this.serverMode === LanguageServiceMode.Semantic) { // Checking semantic mode is an optimization
                 configFileName = this.getConfigFileNameForFile(info);
                 if (configFileName) {
                     project = this.findConfiguredProjectByProjectName(configFileName);
@@ -3109,7 +3124,7 @@ namespace ts.server {
                 Debug.assert(this.openFiles.has(info.path));
                 this.assignOrphanScriptInfoToInferredProject(info, this.openFiles.get(info.path));
             }
-            else if (this.syntaxOnly && info.cacheSourceFile?.sourceFile.referencedFiles.length) {
+            else if (this.serverMode === LanguageServiceMode.ApproximateSemanticOnly && info.cacheSourceFile?.sourceFile.referencedFiles.length) {
                 // This file was just opened and references in this file will previously not been resolved so schedule update
                 info.containingProjects.forEach(project => project.markAsDirty());
             }
@@ -3325,7 +3340,7 @@ namespace ts.server {
         }
 
         private telemetryOnOpenFile(scriptInfo: ScriptInfo): void {
-            if (this.syntaxOnly || !this.eventHandler || !scriptInfo.isJavaScript() || !addToSeen(this.allJsFilesForOpenFileTelemetry, scriptInfo.path)) {
+            if (this.serverMode !== LanguageServiceMode.Semantic || !this.eventHandler || !scriptInfo.isJavaScript() || !addToSeen(this.allJsFilesForOpenFileTelemetry, scriptInfo.path)) {
                 return;
             }
 
@@ -3637,7 +3652,7 @@ namespace ts.server {
             for (const file of proj.rootFiles) {
                 const normalized = toNormalizedPath(file.fileName);
                 if (getBaseConfigFileName(normalized)) {
-                    if (!this.syntaxOnly && this.host.fileExists(normalized)) {
+                    if (this.serverMode === LanguageServiceMode.Semantic && this.host.fileExists(normalized)) {
                         (tsConfigFiles || (tsConfigFiles = [])).push(normalized);
                     }
                 }

src/server/project.ts

@@ -279,9 +279,21 @@ namespace ts.server {
                 this.compilerOptions.allowNonTsExtensions = true;
             }
 
-            this.languageServiceEnabled = true;
-            if (projectService.syntaxOnly) {
-                this.compilerOptions.types = [];
+            switch (projectService.serverMode) {
+                case LanguageServiceMode.Semantic:
+                    this.languageServiceEnabled = true;
+                    break;
+                case LanguageServiceMode.ApproximateSemanticOnly:
+                    this.languageServiceEnabled = true;
+                    this.compilerOptions.types = [];
+                    break;
+                case LanguageServiceMode.SyntaxOnly:
+                    this.languageServiceEnabled = false;
+                    this.compilerOptions.noResolve = true;
+                    this.compilerOptions.types = [];
+                    break;
+                default:
+                    Debug.assertNever(projectService.serverMode);
             }
 
             this.setInternalCompilerOptionsForEmittingJsFiles();
@@ -298,10 +310,10 @@ namespace ts.server {
             this.resolutionCache = createResolutionCache(
                 this,
                 currentDirectory && this.currentDirectory,
-                projectService.syntaxOnly ? ResolutionKind.RelativeReferencesInOpenFileOnly : ResolutionKind.All,
+                projectService.serverMode === LanguageServiceMode.Semantic ? ResolutionKind.All : ResolutionKind.RelativeReferencesInOpenFileOnly,
                 /*logChangesWhenResolvingModule*/ true
             );
-            this.languageService = createLanguageService(this, this.documentRegistry, this.projectService.syntaxOnly);
+            this.languageService = createLanguageService(this, this.documentRegistry, this.projectService.serverMode);
             if (lastFileExceededProgramSize) {
                 this.disableLanguageService(lastFileExceededProgramSize);
             }
@@ -456,7 +468,16 @@ namespace ts.server {
 
         /*@internal*/
         includeTripleslashReferencesFrom(containingFile: string) {
-            return !this.projectService.syntaxOnly || this.fileIsOpen(this.toPath(containingFile));
+            switch (this.projectService.serverMode) {
+                case LanguageServiceMode.Semantic:
+                    return true;
+                case LanguageServiceMode.ApproximateSemanticOnly:
+                    return this.fileIsOpen(this.toPath(containingFile));
+                case LanguageServiceMode.SyntaxOnly:
+                    return false;
+                default:
+                    Debug.assertNever(this.projectService.serverMode);
+            }
         }
 
         directoryExists(path: string): boolean {
@@ -656,7 +677,7 @@ namespace ts.server {
         }
 
         enableLanguageService() {
-            if (this.languageServiceEnabled) {
+            if (this.languageServiceEnabled || this.projectService.serverMode === LanguageServiceMode.SyntaxOnly) {
                 return;
             }
             this.languageServiceEnabled = true;
@@ -668,6 +689,7 @@ namespace ts.server {
             if (!this.languageServiceEnabled) {
                 return;
             }
+            Debug.assert(this.projectService.serverMode !== LanguageServiceMode.SyntaxOnly);
             this.languageService.cleanupSemanticCache();
             this.languageServiceEnabled = false;
             this.lastFileExceededProgramSize = lastFileExceededProgramSize;
@@ -997,7 +1019,7 @@ namespace ts.server {
 
             // update builder only if language service is enabled
             // otherwise tell it to drop its internal state
-            if (this.languageServiceEnabled && !this.projectService.syntaxOnly) {
+            if (this.languageServiceEnabled && this.projectService.serverMode === LanguageServiceMode.Semantic) {
                 // 1. no changes in structure, no changes in unresolved imports - do nothing
                 // 2. no changes in structure, unresolved imports were changed - collect unresolved imports for all files
                 // (can reuse cached imports for files that were not changed)
@@ -1128,7 +1150,7 @@ namespace ts.server {
                 }
 
                 // Watch the type locations that would be added to program as part of automatic type resolutions
-                if (this.languageServiceEnabled && !this.projectService.syntaxOnly) {
+                if (this.languageServiceEnabled && this.projectService.serverMode === LanguageServiceMode.Semantic) {
                     this.resolutionCache.updateTypeRootsWatch();
                 }
             }

src/server/session.ts

@@ -585,7 +585,7 @@ namespace ts.server {
             undefined;
     }
 
-    const invalidSyntaxOnlyCommands: readonly CommandNames[] = [
+    const invalidApproximateSemanticOnlyCommands: readonly CommandNames[] = [
         CommandNames.OpenExternalProject,
         CommandNames.OpenExternalProjects,
         CommandNames.CloseExternalProject,
@@ -621,6 +621,36 @@ namespace ts.server {
         CommandNames.ProvideCallHierarchyOutgoingCalls,
     ];
 
+    const invalidSyntaxOnlyCommands: readonly CommandNames[] = [
+        ...invalidApproximateSemanticOnlyCommands,
+        CommandNames.Definition,
+        CommandNames.DefinitionFull,
+        CommandNames.DefinitionAndBoundSpan,
+        CommandNames.DefinitionAndBoundSpanFull,
+        CommandNames.TypeDefinition,
+        CommandNames.Implementation,
+        CommandNames.ImplementationFull,
+        CommandNames.References,
+        CommandNames.ReferencesFull,
+        CommandNames.Rename,
+        CommandNames.RenameLocationsFull,
+        CommandNames.RenameInfoFull,
+        CommandNames.Quickinfo,
+        CommandNames.QuickinfoFull,
+        CommandNames.CompletionInfo,
+        CommandNames.Completions,
+        CommandNames.CompletionsFull,
+        CommandNames.CompletionDetails,
+        CommandNames.CompletionDetailsFull,
+        CommandNames.SignatureHelp,
+        CommandNames.SignatureHelpFull,
+        CommandNames.Navto,
+        CommandNames.NavtoFull,
+        CommandNames.Occurrences,
+        CommandNames.DocumentHighlights,
+        CommandNames.DocumentHighlightsFull,
+    ];
+
     export interface SessionOptions {
         host: ServerHost;
         cancellationToken: ServerCancellationToken;
@@ -637,7 +667,9 @@ namespace ts.server {
         eventHandler?: ProjectServiceEventHandler;
         /** Has no effect if eventHandler is also specified. */
         suppressDiagnosticEvents?: boolean;
+        /** @deprecated use serverMode instead */
         syntaxOnly?: boolean;
+        serverMode?: LanguageServiceMode;
         throttleWaitMilliseconds?: number;
         noGetErrOnBackgroundUpdate?: boolean;
 
@@ -709,18 +741,32 @@ namespace ts.server {
                 allowLocalPluginLoads: opts.allowLocalPluginLoads,
                 typesMapLocation: opts.typesMapLocation,
                 syntaxOnly: opts.syntaxOnly,
+                serverMode: opts.serverMode,
             };
             this.projectService = new ProjectService(settings);
             this.projectService.setPerformanceEventHandler(this.performanceEventHandler.bind(this));
             this.gcTimer = new GcTimer(this.host, /*delay*/ 7000, this.logger);
 
-            // Make sure to setup handlers to throw error for not allowed commands on syntax server;
-            if (this.projectService.syntaxOnly) {
-                invalidSyntaxOnlyCommands.forEach(commandName =>
-                    this.handlers.set(commandName, request => {
-                        throw new Error(`Request: ${request.command} not allowed on syntaxServer`);
-                    })
-                );
+            // Make sure to setup handlers to throw error for not allowed commands on syntax server
+            switch (this.projectService.serverMode) {
+                case LanguageServiceMode.Semantic:
+                    break;
+                case LanguageServiceMode.ApproximateSemanticOnly:
+                    invalidApproximateSemanticOnlyCommands.forEach(commandName =>
+                        this.handlers.set(commandName, request => {
+                            throw new Error(`Request: ${request.command} not allowed on approximate semantic only server`);
+                        })
+                    );
+                    break;
+                case LanguageServiceMode.SyntaxOnly:
+                    invalidSyntaxOnlyCommands.forEach(commandName =>
+                        this.handlers.set(commandName, request => {
+                            throw new Error(`Request: ${request.command} not allowed on syntax only server`);
+                        })
+                    );
+                    break;
+                default:
+                    Debug.assertNever(this.projectService.serverMode);
             }
         }
 

src/services/services.ts

@@ -1171,7 +1171,7 @@ namespace ts {
         }
     }
 
-    const invalidOperationsOnSyntaxOnly: readonly (keyof LanguageService)[] = [
+    const invalidOperationsOnApproximateSemanticOnly: readonly (keyof LanguageService)[] = [
         "getSyntacticDiagnostics",
         "getSemanticDiagnostics",
         "getSuggestionDiagnostics",
@@ -1191,10 +1191,42 @@ namespace ts {
         "provideCallHierarchyOutgoingCalls",
     ];
 
+    const invalidOperationsOnSyntaxOnly: readonly (keyof LanguageService)[] = [
+        ...invalidOperationsOnApproximateSemanticOnly,
+        "getCompletionsAtPosition",
+        "getCompletionEntryDetails",
+        "getCompletionEntrySymbol",
+        "getSignatureHelpItems",
+        "getQuickInfoAtPosition",
+        "getDefinitionAtPosition",
+        "getDefinitionAndBoundSpan",
+        "getImplementationAtPosition",
+        "getTypeDefinitionAtPosition",
+        "getReferencesAtPosition",
+        "findReferences",
+        "getOccurrencesAtPosition",
+        "getDocumentHighlights",
+        "getNavigateToItems",
+        "getRenameInfo",
+        "findRenameLocations",
+        "getApplicableRefactors",
+    ];
     export function createLanguageService(
         host: LanguageServiceHost,
         documentRegistry: DocumentRegistry = createDocumentRegistry(host.useCaseSensitiveFileNames && host.useCaseSensitiveFileNames(), host.getCurrentDirectory()),
-        syntaxOnly = false): LanguageService {
+        syntaxOnlyOrLanguageServiceMode?: boolean | LanguageServiceMode,
+    ): LanguageService {
+        let languageServiceMode: LanguageServiceMode;
+        if (syntaxOnlyOrLanguageServiceMode === undefined) {
+            languageServiceMode = LanguageServiceMode.Semantic;
+        }
+        else if (typeof syntaxOnlyOrLanguageServiceMode === "boolean") {
+            // languageServiceMode = SyntaxOnly
+            languageServiceMode = syntaxOnlyOrLanguageServiceMode ? LanguageServiceMode.SyntaxOnly : LanguageServiceMode.Semantic;
+        }
+        else {
+            languageServiceMode = syntaxOnlyOrLanguageServiceMode;
+        }
 
         const syntaxTreeCache: SyntaxTreeCache = new SyntaxTreeCache(host);
         let program: Program;
@@ -1244,6 +1276,7 @@ namespace ts {
         }
 
         function synchronizeHostData(): void {
+            Debug.assert(languageServiceMode !== LanguageServiceMode.SyntaxOnly);
             // perform fast check if host supports it
             if (host.getProjectVersion) {
                 const hostProjectVersion = host.getProjectVersion();
@@ -1429,6 +1462,11 @@ namespace ts {
 
         // TODO: GH#18217 frequently asserted as defined
         function getProgram(): Program | undefined {
+            if (languageServiceMode === LanguageServiceMode.SyntaxOnly) {
+                Debug.assert(program === undefined);
+                return undefined;
+            }
+
             synchronizeHostData();
 
             return program;
@@ -2504,14 +2542,26 @@ namespace ts {
             uncommentSelection,
         };
 
-        if (syntaxOnly) {
-            invalidOperationsOnSyntaxOnly.forEach(key =>
-                ls[key] = () => {
-                    throw new Error(`LanguageService Operation: ${key} not allowed on syntaxServer`);
-                }
-            );
+        switch (languageServiceMode) {
+            case LanguageServiceMode.Semantic:
+                break;
+            case LanguageServiceMode.ApproximateSemanticOnly:
+                invalidOperationsOnApproximateSemanticOnly.forEach(key =>
+                    ls[key] = () => {
+                        throw new Error(`LanguageService Operation: ${key} not allowed on approximate semantic only server`);
+                    }
+                );
+                break;
+            case LanguageServiceMode.SyntaxOnly:
+                invalidOperationsOnSyntaxOnly.forEach(key =>
+                    ls[key] = () => {
+                        throw new Error(`LanguageService Operation: ${key} not allowed on syntax only server`);
+                    }
+                );
+                break;
+            default:
+                Debug.assertNever(languageServiceMode);
         }
-
         return ls;
     }