Make many 'static' variables readonly (#17306)

src/harness/fourslash.ts

@@ -130,7 +130,7 @@ namespace FourSlash {
         // 0 - cancelled
         // >0 - not cancelled
         // <0 - not cancelled and value denotes number of isCancellationRequested after which token become cancelled
-        private static NotCanceled: number = -1;
+        private static readonly NotCanceled: number = -1;
         private numberOfCallsBeforeCancellation: number = TestCancellationToken.NotCanceled;
 
         public isCancellationRequested(): boolean {

src/harness/harnessLanguageService.ts

@@ -108,7 +108,7 @@ namespace Harness.LanguageService {
     }
 
     class DefaultHostCancellationToken implements ts.HostCancellationToken {
-        public static Instance = new DefaultHostCancellationToken();
+        public static readonly Instance = new DefaultHostCancellationToken();
 
         public isCancellationRequested() {
             return false;

src/harness/rwcRunner.ts

@@ -238,10 +238,8 @@ namespace RWC {
 }
 
 class RWCRunner extends RunnerBase {
-    private static sourcePath = "internal/cases/rwc/";
-
     public enumerateTestFiles() {
-        return Harness.IO.listFiles(RWCRunner.sourcePath, /.+\.json$/);
+        return Harness.IO.listFiles("internal/cases/rwc/", /.+\.json$/);
     }
 
     public kind(): TestRunnerKind {

src/harness/test262Runner.ts

@@ -4,19 +4,19 @@
 /* tslint:disable:no-null-keyword */
 
 class Test262BaselineRunner extends RunnerBase {
-    private static basePath = "internal/cases/test262";
-    private static helpersFilePath = "tests/cases/test262-harness/helpers.d.ts";
-    private static helperFile: Harness.Compiler.TestFile = {
+    private static readonly basePath = "internal/cases/test262";
+    private static readonly helpersFilePath = "tests/cases/test262-harness/helpers.d.ts";
+    private static readonly helperFile: Harness.Compiler.TestFile = {
         unitName: Test262BaselineRunner.helpersFilePath,
         content: Harness.IO.readFile(Test262BaselineRunner.helpersFilePath),
     };
-    private static testFileExtensionRegex = /\.js$/;
-    private static options: ts.CompilerOptions = {
+    private static readonly testFileExtensionRegex = /\.js$/;
+    private static readonly options: ts.CompilerOptions = {
         allowNonTsExtensions: true,
         target: ts.ScriptTarget.Latest,
         module: ts.ModuleKind.CommonJS
     };
-    private static baselineOptions: Harness.Baseline.BaselineOptions = {
+    private static readonly baselineOptions: Harness.Baseline.BaselineOptions = {
         Subfolder: "test262",
         Baselinefolder: "internal/baselines"
     };

src/server/editorServices.ts

@@ -1614,7 +1614,7 @@ namespace ts.server {
         }
 
         /** Makes a filename safe to insert in a RegExp */
-        private static filenameEscapeRegexp = /[-\/\\^$*+?.()|[\]{}]/g;
+        private static readonly filenameEscapeRegexp = /[-\/\\^$*+?.()|[\]{}]/g;
         private static escapeFilenameForRegex(filename: string) {
             return filename.replace(this.filenameEscapeRegexp, "\\$&");
         }

src/server/project.ts

@@ -837,7 +837,7 @@ namespace ts.server {
      */
     export class InferredProject extends Project {
 
-        private static newName = (() => {
+        private static readonly newName = (() => {
             let nextId = 1;
             return () => {
                 const id = nextId;

src/services/formatting/ruleOperationContext.ts

@@ -4,13 +4,13 @@
 namespace ts.formatting {
 
     export class RuleOperationContext {
-        private customContextChecks: { (context: FormattingContext): boolean; }[];
+        private readonly customContextChecks: { (context: FormattingContext): boolean; }[];
 
         constructor(...funcs: { (context: FormattingContext): boolean; }[]) {
             this.customContextChecks = funcs;
         }
 
-        static Any: RuleOperationContext = new RuleOperationContext();
+        static readonly Any: RuleOperationContext = new RuleOperationContext();
 
         public IsAny(): boolean {
             return this === RuleOperationContext.Any;