Added recommended --prettier flag to include eslint-config-prettier

README.md

@@ -46,6 +46,7 @@ Each of these flags is optional:
 -   **[`editor`](#editor)**: Path to an editor configuration file to convert linter settings within.
 -   **[`eslint`](#eslint)**: Path to an ESLint configuration file to read settings from.
 -   **[`package`](#package)**: Path to a package.json file to read dependencies from.
+-   **[`prettier`](#prettier)**: Add `eslint-config-prettier` to the plugins list.
 -   **[`tslint`](#tslint)**: Path to a TSLint configuration file to read settings from.
 -   **[`typescript`](#typescript)**: Path to a TypeScript configuration file to read TypeScript compiler options from.
 
@@ -97,6 +98,17 @@ _Default: `package.json`_
 Path to a `package.json` file to read dependencies from.
 This will help inform the generated ESLint configuration file's [env](https://eslint.org/docs/user-guide/configuring#specifying-parser-options) settings.
 
+#### `prettier`
+
+```shell
+npx tslint-to-eslint-config --prettier
+```
+
+_Default: `false`_
+
+Add [`eslint-config-prettier`](https://github.com/prettier/eslint-config-prettier) to the list of ESLint plugins.
+We [highly recommend](./docs/FAQs.md#should-i-use-prettier) you use [Prettier](http://prettier.io) for code formatting.
+
 #### `tslint`
 
 ```shell

src/cli/runCli.ts

@@ -20,11 +20,12 @@ export const runCli = async (
     const command = new Command()
         .usage("[options] <file ...> --language [language]")
         .option("--config [config]", "eslint configuration file to output to")
+        .option("--editor [editor]", "editor configuration file to convert")
         .option("--eslint [eslint]", "eslint configuration file to convert using")
         .option("--package [package]", "package configuration file to convert using")
+        .option("--prettier [prettier]", "add eslint-config-prettier to the plugins list")
         .option("--tslint [tslint]", "tslint configuration file to convert using")
         .option("--typescript [typescript]", "typescript configuration file to convert using")
-        .option("--editor [editor]", "editor configuration file to convert")
         .option("-V --version", "output the package version");
 
     const parsedArgv = {

src/conversion/convertConfig.test.ts

@@ -17,7 +17,10 @@ const createStubDependencies = (
     simplifyPackageRules: async (_configurations, data) => ({
         ...data,
         converted: new Map(),
+        extends: [],
         failed: [],
+        missing: [],
+        plugins: new Set(),
     }),
     writeConversionResults: jest.fn().mockReturnValue(Promise.resolve()),
     ...overrides,

src/conversion/convertConfig.ts

@@ -34,14 +34,12 @@ export const convertConfig = async (
     );
 
     // 3. ESLint configurations are simplified based on extended ESLint and TSLint presets
-    const simplifiedConfiguration = {
-        ...ruleConversionResults,
-        ...(await dependencies.simplifyPackageRules(
-            originalConfigurations.data.eslint,
-            originalConfigurations.data.tslint,
-            ruleConversionResults,
-        )),
-    };
+    const simplifiedConfiguration = await dependencies.simplifyPackageRules(
+        originalConfigurations.data.eslint,
+        originalConfigurations.data.tslint,
+        ruleConversionResults,
+        settings.prettier,
+    );
 
     // 4. The simplified configuration is written to the output config file
     const fileWriteError = await dependencies.writeConversionResults(

src/creation/simplification/simplifyPackageRules.test.ts

@@ -25,7 +25,7 @@ const createStubTSLintConfiguration = () => ({
 });
 
 describe("simplifyPackageRules", () => {
-    it("returns the conversion results directly when there is no loaded ESLint configuration and no TSLint extensions", async () => {
+    it("returns equivalent conversion results when there is no loaded ESLint configuration and no TSLint extensions", async () => {
         // Arrange
         const dependencies = createStubDependencies();
         const eslint = undefined;
@@ -41,10 +41,34 @@ describe("simplifyPackageRules", () => {
         );
 
         // Assert
-        expect(simplifiedResults).toBe(ruleConversionResults);
+        expect(simplifiedResults).toEqual(ruleConversionResults);
     });
 
-    it("returns the conversion results directly when there is an empty ESLint configuration and no TSLint extensions", async () => {
+    it("adds Prettier extensions when the prettier setting is enabled", async () => {
+        // Arrange
+        const dependencies = createStubDependencies();
+        const eslint = undefined;
+        const tslint = createStubTSLintConfiguration();
+        const ruleConversionResults = createEmptyConversionResults();
+
+        // Act
+        const simplifiedResults = await simplifyPackageRules(
+            dependencies,
+            eslint,
+            tslint,
+            ruleConversionResults,
+            true,
+        );
+
+        // Assert
+        expect(simplifiedResults).toEqual({
+            ...ruleConversionResults,
+            converted: undefined,
+            extends: ["eslint-config-prettier", "eslint-config-prettier/@typescript-eslint"],
+        });
+    });
+
+    it("returns equivalent conversion results when there is an empty ESLint configuration and no TSLint extensions", async () => {
         // Arrange
         const dependencies = createStubDependencies();
         const eslint = createStubESLintConfiguration([]);
@@ -60,7 +84,7 @@ describe("simplifyPackageRules", () => {
         );
 
         // Assert
-        expect(simplifiedResults).toBe(ruleConversionResults);
+        expect(simplifiedResults).toEqual(ruleConversionResults);
     });
 
     it("includes deduplicated rules and extension failures when the ESLint configuration extends", async () => {
@@ -98,8 +122,9 @@ describe("simplifyPackageRules", () => {
 
         // Assert
         expect(simplifiedResults).toEqual({
+            ...ruleConversionResults,
             converted: deduplicatedRules,
-            extends: eslintExtends,
+            extends: [...eslintExtends],
             failed: configurationErrors,
         });
     });

src/creation/simplification/simplifyPackageRules.ts

@@ -13,10 +13,7 @@ export type SimplifyPackageRulesDependencies = {
     retrieveExtendsValues: SansDependencies<typeof retrieveExtendsValues>;
 };
 
-export type SimplifiedRuleConversionResults = Pick<
-    RuleConversionResults,
-    "converted" | "failed"
-> & {
+export type SimplifiedResultsConfiguration = RuleConversionResults & {
     extends?: string[];
 };
 
@@ -28,11 +25,17 @@ export const simplifyPackageRules = async (
     dependencies: SimplifyPackageRulesDependencies,
     eslint: Pick<OriginalConfigurations<ESLintConfiguration>, "full"> | undefined,
     tslint: OriginalConfigurations<Pick<TSLintConfiguration, "extends">>,
-    ruleConversionResults: SimplifiedRuleConversionResults,
-): Promise<SimplifiedRuleConversionResults> => {
+    ruleConversionResults: RuleConversionResults,
+    usePrettier?: boolean,
+): Promise<SimplifiedResultsConfiguration> => {
     const extendedESLintRulesets = eslint?.full.extends ?? [];
     const extendedTSLintRulesets = collectTSLintRulesets(tslint);
     const allExtensions = uniqueFromSources(extendedESLintRulesets, extendedTSLintRulesets);
+
+    if (usePrettier) {
+        allExtensions.push("eslint-config-prettier", "eslint-config-prettier/@typescript-eslint");
+    }
+
     if (allExtensions.length === 0) {
         return ruleConversionResults;
     }
@@ -47,6 +50,7 @@ export const simplifyPackageRules = async (
     );
 
     return {
+        ...ruleConversionResults,
         converted,
         extends: allExtensions,
         failed: [...ruleConversionResults.failed, ...configurationErrors],

src/creation/writeConversionResults.test.ts

@@ -1,11 +1,11 @@
 import { createEmptyConversionResults } from "../conversion/conversionResults.stubs";
-import { writeConversionResults } from "./writeConversionResults";
 import { AllOriginalConfigurations } from "../input/findOriginalConfigurations";
 import { formatJsonOutput } from "./formatting/formatters/formatJsonOutput";
-import { SimplifiedRuleConversionResults } from "./simplification/simplifyPackageRules";
+import { SimplifiedResultsConfiguration } from "./simplification/simplifyPackageRules";
+import { writeConversionResults } from "./writeConversionResults";
 
 const createStubOriginalConfigurations = (
-    overrides: Partial<AllOriginalConfigurations & SimplifiedRuleConversionResults> = {},
+    overrides: Partial<AllOriginalConfigurations & SimplifiedResultsConfiguration> = {},
 ) => ({
     tslint: {
         full: {

src/creation/writeConversionResults.ts

@@ -1,10 +1,9 @@
 import { FileSystem } from "../adapters/fileSystem";
-import { RuleConversionResults } from "../rules/convertRules";
 import { AllOriginalConfigurations } from "../input/findOriginalConfigurations";
 import { createEnv } from "./eslint/createEnv";
 import { formatConvertedRules } from "./formatConvertedRules";
 import { formatOutput } from "./formatting/formatOutput";
-import { SimplifiedRuleConversionResults } from "./simplification/simplifyPackageRules";
+import { SimplifiedResultsConfiguration } from "./simplification/simplifyPackageRules";
 
 export type WriteConversionResultsDependencies = {
     fileSystem: Pick<FileSystem, "writeFile">;
@@ -13,7 +12,7 @@ export type WriteConversionResultsDependencies = {
 export const writeConversionResults = async (
     dependencies: WriteConversionResultsDependencies,
     outputPath: string,
-    ruleConversionResults: RuleConversionResults & SimplifiedRuleConversionResults,
+    ruleConversionResults: SimplifiedResultsConfiguration,
     originalConfigurations: AllOriginalConfigurations,
 ) => {
     const plugins = ["@typescript-eslint"];

src/input/findESLintConfiguration.ts

@@ -39,9 +39,9 @@ export type FindESLintConfigurationDependencies = {
 
 export const findESLintConfiguration = async (
     dependencies: FindESLintConfigurationDependencies,
-    rawSettings: Pick<TSLintToESLintSettings, "config" | "eslint">,
+    config: Pick<TSLintToESLintSettings, "config" | "eslint">,
 ): Promise<OriginalConfigurations<ESLintConfiguration> | Error> => {
-    const filePath = rawSettings.eslint ?? rawSettings.config;
+    const filePath = config.eslint ?? config.config;
     const [rawConfiguration, reportedConfiguration] = await Promise.all([
         findRawConfiguration<ESLintConfiguration>(dependencies.importer, filePath, {
             extends: [],
@@ -67,7 +67,7 @@ export const findESLintConfiguration = async (
         full: {
             ...defaultESLintConfiguration,
             ...reportedConfiguration,
-            extends: Array.from(new Set(extensions)),
+            extends: extensions,
         },
         raw: rawConfiguration,
     };

src/reporting/reportConversionResults.test.ts

@@ -43,7 +43,7 @@ describe("reportConversionResults", () => {
             logger.stdout.write,
             `✨ 1 rule replaced with its ESLint equivalent. ✨`,
             ``,
-            `⚡ 3 packages are required for running with ESLint. ⚡`,
+            `⚡ 3 packages are required for this ESLint configuration. ⚡`,
             `  yarn add @typescript-eslint/eslint-plugin @typescript-eslint/parser eslint --dev`,
         );
     });
@@ -80,7 +80,7 @@ describe("reportConversionResults", () => {
             `❗ 1 ESLint rule behaves differently from its TSLint counterpart ❗`,
             `  Check ${logger.debugFileName} for details.`,
             ``,
-            `⚡ 3 packages are required for running with ESLint. ⚡`,
+            `⚡ 3 packages are required for this ESLint configuration. ⚡`,
             `  yarn add @typescript-eslint/eslint-plugin @typescript-eslint/parser eslint --dev`,
         );
         expectEqualWrites(
@@ -134,7 +134,7 @@ describe("reportConversionResults", () => {
             `❗ 2 ESLint rules behave differently from their TSLint counterparts ❗`,
             `  Check ${logger.debugFileName} for details.`,
             ``,
-            `⚡ 3 packages are required for running with ESLint. ⚡`,
+            `⚡ 3 packages are required for this ESLint configuration. ⚡`,
             `  yarn add @typescript-eslint/eslint-plugin @typescript-eslint/parser eslint --dev`,
         );
         expectEqualWrites(
@@ -223,7 +223,7 @@ describe("reportConversionResults", () => {
             `  The "@typescript-eslint/tslint/config" section of .eslintrc.js configures eslint-plugin-tslint to run it in TSLint within ESLint.`,
             `  Check ${logger.debugFileName} for details.`,
             ``,
-            `⚡ 4 packages are required for running with ESLint. ⚡`,
+            `⚡ 4 packages are required for this ESLint configuration. ⚡`,
             `  yarn add @typescript-eslint/eslint-plugin @typescript-eslint/parser @typescript-eslint/tslint-eslint-plugin eslint --dev`,
         );
         expectEqualWrites(
@@ -266,7 +266,7 @@ describe("reportConversionResults", () => {
             `  The "@typescript-eslint/tslint/config" section of .eslintrc.js configures eslint-plugin-tslint to run them in TSLint within ESLint.`,
             `  Check ${logger.debugFileName} for details.`,
             ``,
-            `⚡ 4 packages are required for running with ESLint. ⚡`,
+            `⚡ 4 packages are required for this ESLint configuration. ⚡`,
             `  yarn add @typescript-eslint/eslint-plugin @typescript-eslint/parser @typescript-eslint/tslint-eslint-plugin eslint --dev`,
         );
         expectEqualWrites(
@@ -295,7 +295,7 @@ describe("reportConversionResults", () => {
         // Assert
         expectEqualWrites(
             logger.stdout.write,
-            `⚡ 5 packages are required for running with ESLint. ⚡`,
+            `⚡ 5 packages are required for this ESLint configuration. ⚡`,
             `  yarn add @typescript-eslint/eslint-plugin @typescript-eslint/parser eslint plugin-one plugin-two --dev`,
         );
     });

src/reporting/reportConversionResults.ts

@@ -3,7 +3,7 @@ import { EOL } from "os";
 
 import { Logger } from "../adapters/logger";
 import { SansDependencies } from "../binding";
-import { RuleConversionResults } from "../rules/convertRules";
+import { SimplifiedResultsConfiguration } from "../creation/simplification/simplifyPackageRules";
 import { ESLintRuleOptions, TSLintRuleOptions } from "../rules/types";
 import { choosePackageManager } from "./packages/choosePackageManager";
 import {
@@ -21,7 +21,7 @@ export type ReportConversionResultsDependencies = {
 export const reportConversionResults = async (
     dependencies: ReportConversionResultsDependencies,
     outputPath: string,
-    ruleConversionResults: RuleConversionResults,
+    ruleConversionResults: SimplifiedResultsConfiguration,
 ) => {
     const packageManager = await dependencies.choosePackageManager();
 
@@ -49,6 +49,7 @@ export const reportConversionResults = async (
     }
 
     logMissingPackages(ruleConversionResults, packageManager, dependencies.logger);
+    logPrettierExtension(ruleConversionResults, dependencies.logger);
 };
 
 type RuleWithNotices = {
@@ -70,9 +71,9 @@ const logNotices = (converted: Map<string, ESLintRuleOptions>, logger: Logger) =
             ? " behaves differently from its TSLint counterpart"
             : "s behave differently from their TSLint counterparts";
 
-    logger.stdout.write(
-        chalk.blueBright(`${EOL}❗ ${rulesWithNotices.length} ESLint rule${behavior} ❗${EOL}`),
-    );
+    logger.stdout.write(chalk.blueBright(`${EOL}❗ ${rulesWithNotices.length}`));
+    logger.stdout.write(chalk.blue(` ESLint rule${behavior} `));
+    logger.stdout.write(chalk.blueBright(`❗${EOL}`));
     logger.stdout.write(chalk.blue(`  Check ${logger.debugFileName} for details.${EOL}`));
     logger.info.write(`${rulesWithNotices.length} ESLint rule${behavior}:${EOL}`);
 
@@ -86,3 +87,22 @@ const logNotices = (converted: Map<string, ESLintRuleOptions>, logger: Logger) =
 
     logger.info.write(EOL);
 };
+
+const logPrettierExtension = (
+    ruleConversionResults: SimplifiedResultsConfiguration,
+    logger: Logger,
+) => {
+    if (!ruleConversionResults.extends?.includes("eslint-config-prettier")) {
+        logger.stdout.write(chalk.redBright(`${EOL}🔥 Prettier`));
+        logger.stdout.write(chalk.red(` plugins are missing from your configuration. `));
+        logger.stdout.write(chalk.redBright(`🔥${EOL}`));
+        logger.stdout.write(chalk.red(`  We highly recommend running `));
+        logger.stdout.write(chalk.redBright(`tslint-to-eslint-config --prettier`));
+        logger.stdout.write(chalk.red(` to disable formatting ESLint rules.${EOL}`));
+        logger.stdout.write(
+            chalk.red(
+                `  See https://github/typescript-eslint/tslint-to-eslint-config/docs/FAQs.md#should-i-use-prettier.${EOL}`,
+            ),
+        );
+    }
+};