diff --git a/lib/protocol.d.ts b/lib/protocol.d.ts
index fc9a35893fe..2fc15c3a256 100644
--- a/lib/protocol.d.ts
+++ b/lib/protocol.d.ts
@@ -1790,6 +1790,7 @@ declare namespace ts.server.protocol {
         outDir?: string;
         outFile?: string;
         paths?: MapLike<string[]>;
+        plugins?: PluginImport[];
         preserveConstEnums?: boolean;
         project?: string;
         reactNamespace?: string;
@@ -1886,7 +1887,11 @@ declare namespace ts.server.protocol {
         [index: string]: T;
     }
 
-    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]>;
+    interface PluginImport {
+        name: string;
+    }
+
+    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]> | PluginImport[];
 }
 declare namespace ts {
     // these types are empty stubs for types from services and should not be used directly
diff --git a/lib/tsc.js b/lib/tsc.js
index aeefb1ad857..66bbafecb14 100644
--- a/lib/tsc.js
+++ b/lib/tsc.js
@@ -19730,11 +19730,16 @@ var ts;
         }
     }
     function nodeModuleNameResolver(moduleName, containingFile, compilerOptions, host, cache) {
+        return nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, false);
+    }
+    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    function nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, jsOnly) {
+        if (jsOnly === void 0) { jsOnly = false; }
         var containingDirectory = ts.getDirectoryPath(containingFile);
         var traceEnabled = isTraceEnabled(compilerOptions, host);
         var failedLookupLocations = [];
         var state = { compilerOptions: compilerOptions, host: host, traceEnabled: traceEnabled };
-        var result = tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript);
+        var result = jsOnly ? tryResolve(Extensions.JavaScript) : (tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript));
         if (result && result.value) {
             var _a = result.value, resolved = _a.resolved, isExternalLibraryImport = _a.isExternalLibraryImport;
             return createResolvedModuleWithFailedLookupLocations(resolved, isExternalLibraryImport, failedLookupLocations);
@@ -19760,7 +19765,7 @@ var ts;
             }
         }
     }
-    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    ts.nodeModuleNameResolverWorker = nodeModuleNameResolverWorker;
     function realpath(path, host, traceEnabled) {
         if (!host.realpath) {
             return path;
@@ -52409,6 +52414,15 @@ var ts;
             name: "alwaysStrict",
             type: "boolean",
             description: ts.Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
+        },
+        {
+            name: "plugins",
+            type: "list",
+            isTSConfigOnly: true,
+            element: {
+                name: "plugin",
+                type: "object"
+            }
         }
     ];
     ts.typeAcquisitionDeclarations = [
diff --git a/lib/tsserver.js b/lib/tsserver.js
index 53fd42a0434..43d6afe3dd5 100644
--- a/lib/tsserver.js
+++ b/lib/tsserver.js
@@ -3795,11 +3795,16 @@ var ts;
         }
     }
     function nodeModuleNameResolver(moduleName, containingFile, compilerOptions, host, cache) {
+        return nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, false);
+    }
+    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    function nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, jsOnly) {
+        if (jsOnly === void 0) { jsOnly = false; }
         var containingDirectory = ts.getDirectoryPath(containingFile);
         var traceEnabled = isTraceEnabled(compilerOptions, host);
         var failedLookupLocations = [];
         var state = { compilerOptions: compilerOptions, host: host, traceEnabled: traceEnabled };
-        var result = tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript);
+        var result = jsOnly ? tryResolve(Extensions.JavaScript) : (tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript));
         if (result && result.value) {
             var _a = result.value, resolved = _a.resolved, isExternalLibraryImport = _a.isExternalLibraryImport;
             return createResolvedModuleWithFailedLookupLocations(resolved, isExternalLibraryImport, failedLookupLocations);
@@ -3825,7 +3830,7 @@ var ts;
             }
         }
     }
-    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    ts.nodeModuleNameResolverWorker = nodeModuleNameResolverWorker;
     function realpath(path, host, traceEnabled) {
         if (!host.realpath) {
             return path;
@@ -52419,6 +52424,15 @@ var ts;
             name: "alwaysStrict",
             type: "boolean",
             description: ts.Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
+        },
+        {
+            name: "plugins",
+            type: "list",
+            isTSConfigOnly: true,
+            element: {
+                name: "plugin",
+                type: "object"
+            }
         }
     ];
     ts.typeAcquisitionDeclarations = [
@@ -68381,6 +68395,16 @@ var ts;
             Project.prototype.getCachedUnresolvedImportsPerFile_TestOnly = function () {
                 return this.cachedUnresolvedImportsPerFile;
             };
+            Project.resolveModule = function (moduleName, initialDir, host, log) {
+                var resolvedPath = ts.normalizeSlashes(host.resolvePath(ts.combinePaths(initialDir, "node_modules")));
+                log("Loading " + moduleName + " from " + initialDir + " (resolved to " + resolvedPath + ")");
+                var result = host.require(resolvedPath, moduleName);
+                if (result.error) {
+                    log("Failed to load module: " + JSON.stringify(result.error));
+                    return undefined;
+                }
+                return result.module;
+            };
             Project.prototype.setInternalCompilerOptionsForEmittingJsFiles = function () {
                 if (this.projectKind === ProjectKind.Inferred || this.projectKind === ProjectKind.External) {
                     this.compilerOptions.noEmitForJsFiles = true;
@@ -68424,6 +68448,9 @@ var ts;
             Project.prototype.getProjectName = function () {
                 return this.projectName;
             };
+            Project.prototype.getExternalFiles = function () {
+                return [];
+            };
             Project.prototype.getSourceFile = function (path) {
                 if (!this.program) {
                     return undefined;
@@ -68891,15 +68918,63 @@ var ts;
             __extends(ConfiguredProject, _super);
             function ConfiguredProject(configFileName, projectService, documentRegistry, hasExplicitListOfFiles, compilerOptions, wildcardDirectories, languageServiceEnabled, compileOnSaveEnabled) {
                 var _this = _super.call(this, configFileName, ProjectKind.Configured, projectService, documentRegistry, hasExplicitListOfFiles, languageServiceEnabled, compilerOptions, compileOnSaveEnabled) || this;
+                _this.configFileName = configFileName;
                 _this.wildcardDirectories = wildcardDirectories;
                 _this.compileOnSaveEnabled = compileOnSaveEnabled;
+                _this.plugins = [];
                 _this.openRefCount = 0;
                 _this.canonicalConfigFilePath = server.asNormalizedPath(projectService.toCanonicalFileName(configFileName));
+                _this.enablePlugins();
                 return _this;
             }
             ConfiguredProject.prototype.getConfigFilePath = function () {
                 return this.getProjectName();
             };
+            ConfiguredProject.prototype.enablePlugins = function () {
+                var _this = this;
+                var host = this.projectService.host;
+                var options = this.getCompilerOptions();
+                var log = function (message) {
+                    _this.projectService.logger.info(message);
+                };
+                if (!(options.plugins && options.plugins.length)) {
+                    this.projectService.logger.info("No plugins exist");
+                    return;
+                }
+                if (!host.require) {
+                    this.projectService.logger.info("Plugins were requested but not running in environment that supports 'require'. Nothing will be loaded");
+                    return;
+                }
+                for (var _i = 0, _a = options.plugins; _i < _a.length; _i++) {
+                    var pluginConfigEntry = _a[_i];
+                    var searchPath = ts.getDirectoryPath(this.configFileName);
+                    var resolvedModule = Project.resolveModule(pluginConfigEntry.name, searchPath, host, log);
+                    if (resolvedModule) {
+                        this.enableProxy(resolvedModule, pluginConfigEntry);
+                    }
+                }
+            };
+            ConfiguredProject.prototype.enableProxy = function (pluginModuleFactory, configEntry) {
+                try {
+                    if (typeof pluginModuleFactory !== "function") {
+                        this.projectService.logger.info("Skipped loading plugin " + configEntry.name + " because it did expose a proper factory function");
+                        return;
+                    }
+                    var info = {
+                        config: configEntry,
+                        project: this,
+                        languageService: this.languageService,
+                        languageServiceHost: this.lsHost,
+                        serverHost: this.projectService.host
+                    };
+                    var pluginModule = pluginModuleFactory({ typescript: ts });
+                    this.languageService = pluginModule.create(info);
+                    this.plugins.push(pluginModule);
+                }
+                catch (e) {
+                    this.projectService.logger.info("Plugin activation failed: " + e);
+                }
+            };
             ConfiguredProject.prototype.getProjectRootPath = function () {
                 return ts.getDirectoryPath(this.getConfigFilePath());
             };
@@ -68912,6 +68987,21 @@ var ts;
             ConfiguredProject.prototype.getTypeAcquisition = function () {
                 return this.typeAcquisition;
             };
+            ConfiguredProject.prototype.getExternalFiles = function () {
+                var items = [];
+                for (var _i = 0, _a = this.plugins; _i < _a.length; _i++) {
+                    var plugin = _a[_i];
+                    if (typeof plugin.getExternalFiles === "function") {
+                        try {
+                            items.push.apply(items, plugin.getExternalFiles(this));
+                        }
+                        catch (e) {
+                            this.projectService.logger.info("A plugin threw an exception in getExternalFiles: " + e);
+                        }
+                    }
+                }
+                return items;
+            };
             ConfiguredProject.prototype.watchConfigFile = function (callback) {
                 var _this = this;
                 this.projectFileWatcher = this.projectService.host.watchFile(this.getConfigFilePath(), function (_) { return callback(_this); });
@@ -73011,6 +73101,15 @@ var ts;
         if (typeof global !== "undefined" && global.gc) {
             sys.gc = function () { return global.gc(); };
         }
+        sys.require = function (initialDir, moduleName) {
+            var result = ts.nodeModuleNameResolverWorker(moduleName, initialDir + "/program.ts", { moduleResolution: ts.ModuleResolutionKind.NodeJs, allowJs: true }, sys, undefined, true);
+            try {
+                return { module: require(result.resolvedModule.resolvedFileName), error: undefined };
+            }
+            catch (e) {
+                return { module: undefined, error: e };
+            }
+        };
         var cancellationToken;
         try {
             var factory = require("./cancellationToken");
diff --git a/lib/tsserverlibrary.d.ts b/lib/tsserverlibrary.d.ts
index ab8d2e141e3..95d11503c6e 100644
--- a/lib/tsserverlibrary.d.ts
+++ b/lib/tsserverlibrary.d.ts
@@ -1908,7 +1908,10 @@ declare namespace ts {
         Classic = 1,
         NodeJs = 2,
     }
-    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]>;
+    interface PluginImport {
+        name: string;
+    }
+    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]> | PluginImport[];
     interface CompilerOptions {
         allowJs?: boolean;
         allowSyntheticDefaultImports?: boolean;
@@ -2017,6 +2020,7 @@ declare namespace ts {
         JSX = 2,
         TS = 3,
         TSX = 4,
+        External = 5,
     }
     const enum ScriptTarget {
         ES3 = 0,
@@ -3206,6 +3210,13 @@ declare namespace ts.server {
         compressionKind: string;
         data: any;
     }
+    type RequireResult = {
+        module: {};
+        error: undefined;
+    } | {
+        module: undefined;
+        error: {};
+    };
     interface ServerHost extends System {
         setTimeout(callback: (...args: any[]) => void, ms: number, ...args: any[]): any;
         clearTimeout(timeoutId: any): void;
@@ -3213,6 +3224,7 @@ declare namespace ts.server {
         clearImmediate(timeoutId: any): void;
         gc?(): void;
         trace?(s: string): void;
+        require?(initialPath: string, moduleName: string): RequireResult;
     }
     interface SortedReadonlyArray<T> extends ReadonlyArray<T> {
         " __sortedReadonlyArrayBrand": any;
@@ -4115,6 +4127,7 @@ declare namespace ts.server.protocol {
         outDir?: string;
         outFile?: string;
         paths?: MapLike<string[]>;
+        plugins?: PluginImport[];
         preserveConstEnums?: boolean;
         project?: string;
         reactNamespace?: string;
@@ -4598,6 +4611,22 @@ declare namespace ts.server {
         get(path: Path): ReadonlyArray<string>;
         set(path: Path, value: ReadonlyArray<string>): void;
     }
+    interface PluginCreateInfo {
+        project: Project;
+        languageService: LanguageService;
+        languageServiceHost: LanguageServiceHost;
+        serverHost: ServerHost;
+        config: any;
+    }
+    interface PluginModule {
+        create(createInfo: PluginCreateInfo): LanguageService;
+        getExternalFiles?(proj: Project): string[];
+    }
+    interface PluginModuleFactory {
+        (mod: {
+            typescript: typeof ts;
+        }): PluginModule;
+    }
     abstract class Project {
         private readonly projectName;
         readonly projectKind: ProjectKind;
@@ -4607,12 +4636,12 @@ declare namespace ts.server {
         compileOnSaveEnabled: boolean;
         private rootFiles;
         private rootFilesMap;
-        private lsHost;
         private program;
         private cachedUnresolvedImportsPerFile;
         private lastCachedUnresolvedImportsList;
-        private readonly languageService;
+        protected languageService: LanguageService;
         languageServiceEnabled: boolean;
+        protected readonly lsHost: LSHost;
         builder: Builder;
         private updatedFileNames;
         private lastReportedFileNames;
@@ -4625,6 +4654,7 @@ declare namespace ts.server {
         isNonTsProject(): boolean;
         isJsOnlyProject(): boolean;
         getCachedUnresolvedImportsPerFile_TestOnly(): UnresolvedImportsMap;
+        static resolveModule(moduleName: string, initialDir: string, host: ServerHost, log: (message: string) => void): {};
         constructor(projectName: string, projectKind: ProjectKind, projectService: ProjectService, documentRegistry: ts.DocumentRegistry, hasExplicitListOfFiles: boolean, languageServiceEnabled: boolean, compilerOptions: CompilerOptions, compileOnSaveEnabled: boolean);
         private setInternalCompilerOptionsForEmittingJsFiles();
         getProjectErrors(): Diagnostic[];
@@ -4636,6 +4666,7 @@ declare namespace ts.server {
         getProjectName(): string;
         abstract getProjectRootPath(): string | undefined;
         abstract getTypeAcquisition(): TypeAcquisition;
+        getExternalFiles(): string[];
         getSourceFile(path: Path): SourceFile;
         updateTypes(): void;
         close(): void;
@@ -4682,6 +4713,7 @@ declare namespace ts.server {
         getTypeAcquisition(): TypeAcquisition;
     }
     class ConfiguredProject extends Project {
+        private configFileName;
         private wildcardDirectories;
         compileOnSaveEnabled: boolean;
         private typeAcquisition;
@@ -4690,13 +4722,17 @@ declare namespace ts.server {
         private directoriesWatchedForWildcards;
         private typeRootsWatchers;
         readonly canonicalConfigFilePath: NormalizedPath;
+        private plugins;
         openRefCount: number;
         constructor(configFileName: NormalizedPath, projectService: ProjectService, documentRegistry: ts.DocumentRegistry, hasExplicitListOfFiles: boolean, compilerOptions: CompilerOptions, wildcardDirectories: Map<WatchDirectoryFlags>, languageServiceEnabled: boolean, compileOnSaveEnabled: boolean);
         getConfigFilePath(): string;
+        enablePlugins(): void;
+        private enableProxy(pluginModuleFactory, configEntry);
         getProjectRootPath(): string;
         setProjectErrors(projectErrors: Diagnostic[]): void;
         setTypeAcquisition(newTypeAcquisition: TypeAcquisition): void;
         getTypeAcquisition(): TypeAcquisition;
+        getExternalFiles(): string[];
         watchConfigFile(callback: (project: ConfiguredProject) => void): void;
         watchTypeRoots(callback: (project: ConfiguredProject, path: string) => void): void;
         watchConfigDirectory(callback: (project: ConfiguredProject, path: string) => void): void;
@@ -4752,7 +4788,7 @@ declare namespace ts.server {
     function convertFormatOptions(protocolOptions: protocol.FormatCodeSettings): FormatCodeSettings;
     function convertCompilerOptions(protocolOptions: protocol.ExternalProjectCompilerOptions): CompilerOptions & protocol.CompileOnSaveMixin;
     function tryConvertScriptKindName(scriptKindName: protocol.ScriptKindName | ScriptKind): ScriptKind;
-    function convertScriptKindName(scriptKindName: protocol.ScriptKindName): ScriptKind;
+    function convertScriptKindName(scriptKindName: protocol.ScriptKindName): ScriptKind.Unknown | ScriptKind.JS | ScriptKind.JSX | ScriptKind.TS | ScriptKind.TSX;
     function combineProjectOutput<T>(projects: Project[], action: (project: Project) => T[], comparer?: (a: T, b: T) => number, areEqual?: (a: T, b: T) => boolean): T[];
     interface HostConfiguration {
         formatCodeOptions: FormatCodeSettings;
diff --git a/lib/tsserverlibrary.js b/lib/tsserverlibrary.js
index 26499261e02..037936d6cb0 100644
--- a/lib/tsserverlibrary.js
+++ b/lib/tsserverlibrary.js
@@ -5351,6 +5351,15 @@ var ts;
             name: "alwaysStrict",
             type: "boolean",
             description: ts.Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
+        },
+        {
+            name: "plugins",
+            type: "list",
+            isTSConfigOnly: true,
+            element: {
+                name: "plugin",
+                type: "object"
+            }
         }
     ];
     ts.typeAcquisitionDeclarations = [
@@ -6474,11 +6483,16 @@ var ts;
         }
     }
     function nodeModuleNameResolver(moduleName, containingFile, compilerOptions, host, cache) {
+        return nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, false);
+    }
+    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    function nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, jsOnly) {
+        if (jsOnly === void 0) { jsOnly = false; }
         var containingDirectory = ts.getDirectoryPath(containingFile);
         var traceEnabled = isTraceEnabled(compilerOptions, host);
         var failedLookupLocations = [];
         var state = { compilerOptions: compilerOptions, host: host, traceEnabled: traceEnabled };
-        var result = tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript);
+        var result = jsOnly ? tryResolve(Extensions.JavaScript) : (tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript));
         if (result && result.value) {
             var _a = result.value, resolved = _a.resolved, isExternalLibraryImport = _a.isExternalLibraryImport;
             return createResolvedModuleWithFailedLookupLocations(resolved, isExternalLibraryImport, failedLookupLocations);
@@ -6504,7 +6518,7 @@ var ts;
             }
         }
     }
-    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    ts.nodeModuleNameResolverWorker = nodeModuleNameResolverWorker;
     function realpath(path, host, traceEnabled) {
         if (!host.realpath) {
             return path;
@@ -70121,6 +70135,16 @@ var ts;
             Project.prototype.getCachedUnresolvedImportsPerFile_TestOnly = function () {
                 return this.cachedUnresolvedImportsPerFile;
             };
+            Project.resolveModule = function (moduleName, initialDir, host, log) {
+                var resolvedPath = ts.normalizeSlashes(host.resolvePath(ts.combinePaths(initialDir, "node_modules")));
+                log("Loading " + moduleName + " from " + initialDir + " (resolved to " + resolvedPath + ")");
+                var result = host.require(resolvedPath, moduleName);
+                if (result.error) {
+                    log("Failed to load module: " + JSON.stringify(result.error));
+                    return undefined;
+                }
+                return result.module;
+            };
             Project.prototype.setInternalCompilerOptionsForEmittingJsFiles = function () {
                 if (this.projectKind === ProjectKind.Inferred || this.projectKind === ProjectKind.External) {
                     this.compilerOptions.noEmitForJsFiles = true;
@@ -70164,6 +70188,9 @@ var ts;
             Project.prototype.getProjectName = function () {
                 return this.projectName;
             };
+            Project.prototype.getExternalFiles = function () {
+                return [];
+            };
             Project.prototype.getSourceFile = function (path) {
                 if (!this.program) {
                     return undefined;
@@ -70631,15 +70658,63 @@ var ts;
             __extends(ConfiguredProject, _super);
             function ConfiguredProject(configFileName, projectService, documentRegistry, hasExplicitListOfFiles, compilerOptions, wildcardDirectories, languageServiceEnabled, compileOnSaveEnabled) {
                 var _this = _super.call(this, configFileName, ProjectKind.Configured, projectService, documentRegistry, hasExplicitListOfFiles, languageServiceEnabled, compilerOptions, compileOnSaveEnabled) || this;
+                _this.configFileName = configFileName;
                 _this.wildcardDirectories = wildcardDirectories;
                 _this.compileOnSaveEnabled = compileOnSaveEnabled;
+                _this.plugins = [];
                 _this.openRefCount = 0;
                 _this.canonicalConfigFilePath = server.asNormalizedPath(projectService.toCanonicalFileName(configFileName));
+                _this.enablePlugins();
                 return _this;
             }
             ConfiguredProject.prototype.getConfigFilePath = function () {
                 return this.getProjectName();
             };
+            ConfiguredProject.prototype.enablePlugins = function () {
+                var _this = this;
+                var host = this.projectService.host;
+                var options = this.getCompilerOptions();
+                var log = function (message) {
+                    _this.projectService.logger.info(message);
+                };
+                if (!(options.plugins && options.plugins.length)) {
+                    this.projectService.logger.info("No plugins exist");
+                    return;
+                }
+                if (!host.require) {
+                    this.projectService.logger.info("Plugins were requested but not running in environment that supports 'require'. Nothing will be loaded");
+                    return;
+                }
+                for (var _i = 0, _a = options.plugins; _i < _a.length; _i++) {
+                    var pluginConfigEntry = _a[_i];
+                    var searchPath = ts.getDirectoryPath(this.configFileName);
+                    var resolvedModule = Project.resolveModule(pluginConfigEntry.name, searchPath, host, log);
+                    if (resolvedModule) {
+                        this.enableProxy(resolvedModule, pluginConfigEntry);
+                    }
+                }
+            };
+            ConfiguredProject.prototype.enableProxy = function (pluginModuleFactory, configEntry) {
+                try {
+                    if (typeof pluginModuleFactory !== "function") {
+                        this.projectService.logger.info("Skipped loading plugin " + configEntry.name + " because it did expose a proper factory function");
+                        return;
+                    }
+                    var info = {
+                        config: configEntry,
+                        project: this,
+                        languageService: this.languageService,
+                        languageServiceHost: this.lsHost,
+                        serverHost: this.projectService.host
+                    };
+                    var pluginModule = pluginModuleFactory({ typescript: ts });
+                    this.languageService = pluginModule.create(info);
+                    this.plugins.push(pluginModule);
+                }
+                catch (e) {
+                    this.projectService.logger.info("Plugin activation failed: " + e);
+                }
+            };
             ConfiguredProject.prototype.getProjectRootPath = function () {
                 return ts.getDirectoryPath(this.getConfigFilePath());
             };
@@ -70652,6 +70727,21 @@ var ts;
             ConfiguredProject.prototype.getTypeAcquisition = function () {
                 return this.typeAcquisition;
             };
+            ConfiguredProject.prototype.getExternalFiles = function () {
+                var items = [];
+                for (var _i = 0, _a = this.plugins; _i < _a.length; _i++) {
+                    var plugin = _a[_i];
+                    if (typeof plugin.getExternalFiles === "function") {
+                        try {
+                            items.push.apply(items, plugin.getExternalFiles(this));
+                        }
+                        catch (e) {
+                            this.projectService.logger.info("A plugin threw an exception in getExternalFiles: " + e);
+                        }
+                    }
+                }
+                return items;
+            };
             ConfiguredProject.prototype.watchConfigFile = function (callback) {
                 var _this = this;
                 this.projectFileWatcher = this.projectService.host.watchFile(this.getConfigFilePath(), function (_) { return callback(_this); });
diff --git a/lib/typescript.d.ts b/lib/typescript.d.ts
index e4b99514255..2f361cffc99 100644
--- a/lib/typescript.d.ts
+++ b/lib/typescript.d.ts
@@ -1992,7 +1992,10 @@ declare namespace ts {
         Classic = 1,
         NodeJs = 2,
     }
-    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]>;
+    interface PluginImport {
+        name: string;
+    }
+    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]> | PluginImport[];
     interface CompilerOptions {
         allowJs?: boolean;
         allowSyntheticDefaultImports?: boolean;
@@ -2102,6 +2105,7 @@ declare namespace ts {
         JSX = 2,
         TS = 3,
         TSX = 4,
+        External = 5,
     }
     enum ScriptTarget {
         ES3 = 0,
diff --git a/lib/typescript.js b/lib/typescript.js
index 2637569891b..c0c6a62a410 100644
--- a/lib/typescript.js
+++ b/lib/typescript.js
@@ -823,6 +823,7 @@ var ts;
         ScriptKind[ScriptKind["JSX"] = 2] = "JSX";
         ScriptKind[ScriptKind["TS"] = 3] = "TS";
         ScriptKind[ScriptKind["TSX"] = 4] = "TSX";
+        ScriptKind[ScriptKind["External"] = 5] = "External";
     })(ScriptKind = ts.ScriptKind || (ts.ScriptKind = {}));
     var ScriptTarget;
     (function (ScriptTarget) {
@@ -24301,11 +24302,17 @@ var ts;
         }
     }
     function nodeModuleNameResolver(moduleName, containingFile, compilerOptions, host, cache) {
+        return nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, /* jsOnly*/ false);
+    }
+    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    /* @internal */
+    function nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, jsOnly) {
+        if (jsOnly === void 0) { jsOnly = false; }
         var containingDirectory = ts.getDirectoryPath(containingFile);
         var traceEnabled = isTraceEnabled(compilerOptions, host);
         var failedLookupLocations = [];
         var state = { compilerOptions: compilerOptions, host: host, traceEnabled: traceEnabled };
-        var result = tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript);
+        var result = jsOnly ? tryResolve(Extensions.JavaScript) : (tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript));
         if (result && result.value) {
             var _a = result.value, resolved = _a.resolved, isExternalLibraryImport = _a.isExternalLibraryImport;
             return createResolvedModuleWithFailedLookupLocations(resolved, isExternalLibraryImport, failedLookupLocations);
@@ -24332,7 +24339,7 @@ var ts;
             }
         }
     }
-    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    ts.nodeModuleNameResolverWorker = nodeModuleNameResolverWorker;
     function realpath(path, host, traceEnabled) {
         if (!host.realpath) {
             return path;
@@ -65572,6 +65579,16 @@ var ts;
             name: "alwaysStrict",
             type: "boolean",
             description: ts.Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
+        },
+        {
+            // A list of plugins to load in the language service
+            name: "plugins",
+            type: "list",
+            isTSConfigOnly: true,
+            element: {
+                name: "plugin",
+                type: "object"
+            }
         }
     ];
     /* @internal */
diff --git a/lib/typescriptServices.d.ts b/lib/typescriptServices.d.ts
index 6a8ffedc46a..0482926ea26 100644
--- a/lib/typescriptServices.d.ts
+++ b/lib/typescriptServices.d.ts
@@ -1992,7 +1992,10 @@ declare namespace ts {
         Classic = 1,
         NodeJs = 2,
     }
-    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]>;
+    interface PluginImport {
+        name: string;
+    }
+    type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]> | PluginImport[];
     interface CompilerOptions {
         allowJs?: boolean;
         allowSyntheticDefaultImports?: boolean;
@@ -2102,6 +2105,7 @@ declare namespace ts {
         JSX = 2,
         TS = 3,
         TSX = 4,
+        External = 5,
     }
     enum ScriptTarget {
         ES3 = 0,
diff --git a/lib/typescriptServices.js b/lib/typescriptServices.js
index 2637569891b..c0c6a62a410 100644
--- a/lib/typescriptServices.js
+++ b/lib/typescriptServices.js
@@ -823,6 +823,7 @@ var ts;
         ScriptKind[ScriptKind["JSX"] = 2] = "JSX";
         ScriptKind[ScriptKind["TS"] = 3] = "TS";
         ScriptKind[ScriptKind["TSX"] = 4] = "TSX";
+        ScriptKind[ScriptKind["External"] = 5] = "External";
     })(ScriptKind = ts.ScriptKind || (ts.ScriptKind = {}));
     var ScriptTarget;
     (function (ScriptTarget) {
@@ -24301,11 +24302,17 @@ var ts;
         }
     }
     function nodeModuleNameResolver(moduleName, containingFile, compilerOptions, host, cache) {
+        return nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, /* jsOnly*/ false);
+    }
+    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    /* @internal */
+    function nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, jsOnly) {
+        if (jsOnly === void 0) { jsOnly = false; }
         var containingDirectory = ts.getDirectoryPath(containingFile);
         var traceEnabled = isTraceEnabled(compilerOptions, host);
         var failedLookupLocations = [];
         var state = { compilerOptions: compilerOptions, host: host, traceEnabled: traceEnabled };
-        var result = tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript);
+        var result = jsOnly ? tryResolve(Extensions.JavaScript) : (tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript));
         if (result && result.value) {
             var _a = result.value, resolved = _a.resolved, isExternalLibraryImport = _a.isExternalLibraryImport;
             return createResolvedModuleWithFailedLookupLocations(resolved, isExternalLibraryImport, failedLookupLocations);
@@ -24332,7 +24339,7 @@ var ts;
             }
         }
     }
-    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    ts.nodeModuleNameResolverWorker = nodeModuleNameResolverWorker;
     function realpath(path, host, traceEnabled) {
         if (!host.realpath) {
             return path;
@@ -65572,6 +65579,16 @@ var ts;
             name: "alwaysStrict",
             type: "boolean",
             description: ts.Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
+        },
+        {
+            // A list of plugins to load in the language service
+            name: "plugins",
+            type: "list",
+            isTSConfigOnly: true,
+            element: {
+                name: "plugin",
+                type: "object"
+            }
         }
     ];
     /* @internal */
diff --git a/lib/typingsInstaller.js b/lib/typingsInstaller.js
index cb9d2334266..449a55c3ee9 100644
--- a/lib/typingsInstaller.js
+++ b/lib/typingsInstaller.js
@@ -5351,6 +5351,15 @@ var ts;
             name: "alwaysStrict",
             type: "boolean",
             description: ts.Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
+        },
+        {
+            name: "plugins",
+            type: "list",
+            isTSConfigOnly: true,
+            element: {
+                name: "plugin",
+                type: "object"
+            }
         }
     ];
     ts.typeAcquisitionDeclarations = [
@@ -6662,11 +6671,16 @@ var ts;
         }
     }
     function nodeModuleNameResolver(moduleName, containingFile, compilerOptions, host, cache) {
+        return nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, false);
+    }
+    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    function nodeModuleNameResolverWorker(moduleName, containingFile, compilerOptions, host, cache, jsOnly) {
+        if (jsOnly === void 0) { jsOnly = false; }
         var containingDirectory = ts.getDirectoryPath(containingFile);
         var traceEnabled = isTraceEnabled(compilerOptions, host);
         var failedLookupLocations = [];
         var state = { compilerOptions: compilerOptions, host: host, traceEnabled: traceEnabled };
-        var result = tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript);
+        var result = jsOnly ? tryResolve(Extensions.JavaScript) : (tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript));
         if (result && result.value) {
             var _a = result.value, resolved = _a.resolved, isExternalLibraryImport = _a.isExternalLibraryImport;
             return createResolvedModuleWithFailedLookupLocations(resolved, isExternalLibraryImport, failedLookupLocations);
@@ -6692,7 +6706,7 @@ var ts;
             }
         }
     }
-    ts.nodeModuleNameResolver = nodeModuleNameResolver;
+    ts.nodeModuleNameResolverWorker = nodeModuleNameResolverWorker;
     function realpath(path, host, traceEnabled) {
         if (!host.realpath) {
             return path;