Use TypeScript readonly modifier for external/array types

lib/cli.ts

@@ -16,23 +16,32 @@ import { getCurrentPackageVersion } from './package-json.js';
  * Used for collecting repeated CLI options into an array.
  * Example: --foo bar --foo baz => ['bar', 'baz']
  */
-function collect(value: string, previous: string[]): string[] {
+function collect(
+  value: string,
+  previous: readonly string[]
+): readonly string[] {
   return [...previous, value];
 }
 
 /**
  * Used for collecting CSV CLI options into an array.
  * Example: --foo bar,baz,buz => ['bar', 'baz', 'buz']
  * */
-function collectCSV(value: string, previous: string[]): string[] {
+function collectCSV(
+  value: string,
+  previous: readonly string[]
+): readonly string[] {
   return [...previous, ...value.split(',')];
 }
 
 /**
  * Used for collecting repeated, nested CSV CLI options into an array of arrays.
  * Example: --foo baz,bar --foo biz,buz => [['baz', 'bar'], ['biz', 'buz']]
  * */
-function collectCSVNested(value: string, previous: string[][]): string[][] {
+function collectCSVNested(
+  value: string,
+  previous: readonly string[][]
+): readonly string[][] {
   return [...previous, value.split(',')];
 }
 
@@ -116,13 +125,18 @@ async function loadConfigFileOptions(): Promise<GenerateOptions> {
       );
     }
 
-    if (
-      explorerResults.config.postprocess &&
-      typeof explorerResults.config.postprocess !== 'function'
-    ) {
+    const config = explorerResults.config;
+
+    // Additional validation that couldn't be handled by ajv.
+    if (config.postprocess && typeof config.postprocess !== 'function') {
       throw new Error('postprocess must be a function');
     }
 
+    // Perform any normalization.
+    if (typeof config.pathRuleList === 'string') {
+      config.pathRuleList = [config.pathRuleList];
+    }
+
     return explorerResults.config;
   }
   return {};
@@ -135,7 +149,7 @@ async function loadConfigFileOptions(): Promise<GenerateOptions> {
  * Note: Does not introduce default values. Default values should be handled in the callback function.
  */
 export async function run(
-  argv: string[],
+  argv: readonly string[],
   cb: (path: string, options: GenerateOptions) => Promise<void>
 ) {
   const program = new Command();
@@ -259,11 +273,6 @@ export async function run(
       // Default values should be handled in the callback function.
       const configFileOptions = await loadConfigFileOptions();
 
-      // Perform any normalization needed ahead of merging.
-      if (typeof configFileOptions.pathRuleList === 'string') {
-        configFileOptions.pathRuleList = [configFileOptions.pathRuleList];
-      }
-
       const generateOptions = merge(configFileOptions, options); // Recursive merge.
 
       // Invoke callback.

lib/generator.ts

@@ -57,7 +57,7 @@ function expectContent(
 function expectSectionHeader(
   ruleName: string,
   contents: string,
-  possibleHeaders: string[],
+  possibleHeaders: readonly string[],
   expected: boolean
 ) {
   const found = possibleHeaders.some((header) =>
@@ -84,7 +84,7 @@ function expectSectionHeader(
   }
 }
 
-function stringOrArrayWithFallback<T extends string | string[]>(
+function stringOrArrayWithFallback<T extends string | readonly string[]>(
   stringOrArray: undefined | T,
   fallback: T
 ): T {
@@ -145,7 +145,7 @@ export async function generate(path: string, options?: GenerateOptions) {
     options?.urlRuleDoc ?? OPTION_DEFAULTS[OPTION_TYPE.URL_RULE_DOC];
 
   // Gather details about rules.
-  const details: RuleDetails[] = Object.entries(plugin.rules)
+  const details: readonly RuleDetails[] = Object.entries(plugin.rules)
     .map(([name, rule]): RuleDetails => {
       return typeof rule === 'object'
         ? // Object-style rule.
@@ -177,6 +177,9 @@ export async function generate(path: string, options?: GenerateOptions) {
     .filter(
       // Filter out deprecated rules from being checked, displayed, or updated if the option is set.
       (details) => !ignoreDeprecatedRules || !details.deprecated
+    )
+    .sort(({ name: a }, { name: b }) =>
+      a.toLowerCase().localeCompare(b.toLowerCase())
     );
 
   // Update rule doc for each rule.

lib/option-parsers.ts

@@ -15,7 +15,7 @@ import type { Plugin, ConfigEmojis } from './types.js';
  */
 export function parseConfigEmojiOptions(
   plugin: Plugin,
-  configEmoji?: string[][]
+  configEmoji?: readonly string[][]
 ): ConfigEmojis {
   const configsSeen = new Set<string>();
   const configsWithDefaultEmojiRemoved: string[] = [];
@@ -75,9 +75,9 @@ export function parseConfigEmojiOptions(
  * Parse the option, check for errors, and set defaults.
  */
 export function parseRuleListColumnsOption(
-  ruleListColumns: string[] | undefined
-): COLUMN_TYPE[] {
-  const values = ruleListColumns ?? [];
+  ruleListColumns: readonly string[] | undefined
+): readonly COLUMN_TYPE[] {
+  const values = [...(ruleListColumns ?? [])];
   const VALUES_OF_TYPE = new Set(Object.values(COLUMN_TYPE).map(String));
 
   // Check for invalid.
@@ -98,16 +98,16 @@ export function parseRuleListColumnsOption(
     );
   }
 
-  return values as COLUMN_TYPE[];
+  return values as readonly COLUMN_TYPE[];
 }
 
 /**
  * Parse the option, check for errors, and set defaults.
  */
 export function parseRuleDocNoticesOption(
-  ruleDocNotices: string[] | undefined
-): NOTICE_TYPE[] {
-  const values = ruleDocNotices ?? [];
+  ruleDocNotices: readonly string[] | undefined
+): readonly NOTICE_TYPE[] {
+  const values = [...(ruleDocNotices ?? [])];
   const VALUES_OF_TYPE = new Set(Object.values(NOTICE_TYPE).map(String));
 
   // Check for invalid.
@@ -128,5 +128,5 @@ export function parseRuleDocNoticesOption(
     );
   }
 
-  return values as NOTICE_TYPE[];
+  return values as readonly NOTICE_TYPE[];
 }

lib/package-json.ts

@@ -43,13 +43,8 @@ export async function loadPlugin(path: string): Promise<Plugin> {
     ) {
       // Check various properties on the `exports` object.
       // https://nodejs.org/api/packages.html#conditional-exports
-      const propertiesToCheck: (keyof PackageJson.ExportConditions)[] = [
-        '.',
-        'node',
-        'import',
-        'require',
-        'default',
-      ];
+      const propertiesToCheck: readonly (keyof PackageJson.ExportConditions)[] =
+        ['.', 'node', 'import', 'require', 'default'];
       for (const prop of propertiesToCheck) {
         // @ts-expect-error -- The union type for the object is causing trouble.
         const value = exports[prop];

lib/plugin-config-resolution.ts

@@ -33,7 +33,7 @@ async function resolveConfigRules(config: Config): Promise<Rules> {
 }
 
 async function resolveConfigExtends(
-  extendItems: string[] | string
+  extendItems: readonly string[] | string
 ): Promise<Rules> {
   const rules: Rules = {};
   for (const extend of Array.isArray(extendItems)

lib/plugin-configs.ts

@@ -10,7 +10,7 @@ export function getConfigsThatSetARule(
   plugin: Plugin,
   configsToRules: ConfigsToRules,
   pluginPrefix: string,
-  ignoreConfig: string[],
+  ignoreConfig: readonly string[],
   severityType?: SEVERITY_TYPE
 ) {
   /* istanbul ignore next -- this shouldn't happen */

lib/rule-doc-notices.ts

@@ -37,7 +37,7 @@ function severityToTerminology(severity: SEVERITY_TYPE) {
 }
 
 function configsToNoticeSentence(
-  configs: string[],
+  configs: readonly string[],
   severity: SEVERITY_TYPE,
   configsLinkOrWord: string,
   configLinkOrWord: string,
@@ -75,9 +75,9 @@ const RULE_NOTICES: {
     | undefined
     | ((data: {
         ruleName: string;
-        configsError: string[];
-        configsWarn: string[];
-        configsOff: string[];
+        configsError: readonly string[];
+        configsWarn: readonly string[];
+        configsOff: readonly string[];
         configEmojis: ConfigEmojis;
         fixable: boolean;
         hasSuggestions: boolean;
@@ -228,10 +228,10 @@ const RULE_NOTICES: {
  */
 function getNoticesForRule(
   rule: RuleModule,
-  configsError: string[],
-  configsWarn: string[],
-  configsOff: string[],
-  ruleDocNotices: NOTICE_TYPE[]
+  configsError: readonly string[],
+  configsWarn: readonly string[],
+  configsOff: readonly string[],
+  ruleDocNotices: readonly NOTICE_TYPE[]
 ) {
   const notices: {
     [key in NOTICE_TYPE]: boolean;
@@ -272,8 +272,8 @@ function getRuleNoticeLines(
   pathPlugin: string,
   pathRuleDoc: string,
   configEmojis: ConfigEmojis,
-  ignoreConfig: string[],
-  ruleDocNotices: NOTICE_TYPE[],
+  ignoreConfig: readonly string[],
+  ruleDocNotices: readonly NOTICE_TYPE[],
   urlConfigs?: string,
   urlRuleDoc?: string
 ) {
@@ -429,8 +429,8 @@ export function generateRuleHeaderLines(
   pathPlugin: string,
   pathRuleDoc: string,
   configEmojis: ConfigEmojis,
-  ignoreConfig: string[],
-  ruleDocNotices: NOTICE_TYPE[],
+  ignoreConfig: readonly string[],
+  ruleDocNotices: readonly NOTICE_TYPE[],
   ruleDocTitleFormat: RuleDocTitleFormat,
   urlConfigs?: string,
   urlRuleDoc?: string

lib/rule-list-columns.ts

@@ -17,7 +17,9 @@ import type { RuleDetails, ConfigsToRules, Plugin } from './types.js';
  * An object containing the column header for each column (as a string or function to generate the string).
  */
 export const COLUMN_HEADER: {
-  [key in COLUMN_TYPE]: string | ((data: { details: RuleDetails[] }) => string);
+  [key in COLUMN_TYPE]:
+    | string
+    | ((data: { details: readonly RuleDetails[] }) => string);
 } = {
   [COLUMN_TYPE.NAME]: ({ details }) => {
     const ruleNames = details.map((detail) => detail.name);
@@ -65,11 +67,11 @@ export const COLUMN_HEADER: {
  */
 export function getColumns(
   plugin: Plugin,
-  details: RuleDetails[],
+  details: readonly RuleDetails[],
   configsToRules: ConfigsToRules,
-  ruleListColumns: COLUMN_TYPE[],
+  ruleListColumns: readonly COLUMN_TYPE[],
   pluginPrefix: string,
-  ignoreConfig: string[]
+  ignoreConfig: readonly string[]
 ): Record<COLUMN_TYPE, boolean> {
   const columns: {
     [key in COLUMN_TYPE]: boolean;

lib/rule-list-legend.ts

@@ -34,16 +34,16 @@ const LEGEND_HAS_SUGGESTIONS = `${EMOJI_HAS_SUGGESTIONS} Manually fixable by [ed
  */
 const LEGENDS: {
   [key in COLUMN_TYPE]:
-    | string[]
+    | readonly string[]
     | undefined // For no legend.
     | ((data: {
         plugin: Plugin;
         configsToRules: ConfigsToRules;
         configEmojis: ConfigEmojis;
         pluginPrefix: string;
-        ignoreConfig: string[];
+        ignoreConfig: readonly string[];
         urlConfigs?: string;
-      }) => string[]);
+      }) => readonly string[]);
 } = {
   [COLUMN_TYPE.CONFIGS_ERROR]: ({
     plugin,
@@ -155,7 +155,7 @@ function getLegendForConfigColumnOfSeverity({
   configsToRules: ConfigsToRules;
   configEmojis: ConfigEmojis;
   pluginPrefix: string;
-  ignoreConfig: string[];
+  ignoreConfig: readonly string[];
   severityType: SEVERITY_TYPE;
   urlConfigs?: string;
 }): string {
@@ -186,9 +186,9 @@ function getLegendsForIndividualConfigs({
   configsToRules: ConfigsToRules;
   configEmojis: ConfigEmojis;
   pluginPrefix: string;
-  ignoreConfig: string[];
+  ignoreConfig: readonly string[];
   urlConfigs?: string;
-}): string[] {
+}): readonly string[] {
   /* istanbul ignore next -- this shouldn't happen */
   if (!plugin.configs || !plugin.rules) {
     throw new Error(
@@ -225,32 +225,32 @@ export function generateLegend(
   configsToRules: ConfigsToRules,
   configEmojis: ConfigEmojis,
   pluginPrefix: string,
-  ignoreConfig: string[],
+  ignoreConfig: readonly string[],
   urlConfigs?: string
 ) {
-  const legends = (Object.entries(columns) as [COLUMN_TYPE, boolean][]).flatMap(
-    ([columnType, enabled]) => {
-      if (!enabled) {
-        // This column is turned off.
-        return [];
-      }
-      const legendArrayOrFn = LEGENDS[columnType];
-      if (!legendArrayOrFn) {
-        // No legend specified for this column.
-        return [];
-      }
-      return typeof legendArrayOrFn === 'function'
-        ? legendArrayOrFn({
-            plugin,
-            configsToRules,
-            configEmojis,
-            pluginPrefix,
-            urlConfigs,
-            ignoreConfig,
-          })
-        : legendArrayOrFn;
+  const legends = (
+    Object.entries(columns) as readonly [COLUMN_TYPE, boolean][]
+  ).flatMap(([columnType, enabled]) => {
+    if (!enabled) {
+      // This column is turned off.
+      return [];
     }
-  );
+    const legendArrayOrFn = LEGENDS[columnType];
+    if (!legendArrayOrFn) {
+      // No legend specified for this column.
+      return [];
+    }
+    return typeof legendArrayOrFn === 'function'
+      ? legendArrayOrFn({
+          plugin,
+          configsToRules,
+          configEmojis,
+          pluginPrefix,
+          urlConfigs,
+          ignoreConfig,
+        })
+      : legendArrayOrFn;
+  });
 
   if (legends.some((legend) => legend.includes('Configurations'))) {
     // Add legends for individual configs after the config column legend(s).