Added recommended --prettier flag to include eslint-config-prettier (#412)

* Made extending eslint-config-prettier built-in, with --ugly flag to opt out

* Switched to --prettier

* Switched to --prettier and normalized output

* Moved to a rcommendation printed in reporting

* Removed typings from .gitignore

* Described --prettier behavior in README.md

* Wording nit: 'when'

* A few more cleanups, why not...

* Ok last one

* Agh, found a README.md typo: 'have'

Author: Josh Goldberg

.gitignore

@@ -1,5 +1,6 @@
 *.tsbuildinfo
 *.d.ts
+!src/typings/**/*.d.ts
 *.log
 *.map
 coverage/

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 +98,22 @@ _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.
+
+When `--prettier` isn't enabled:
+
+-   If the output configuration already doesn't enable any formatting rules, it'll extend from `eslint-config-prettier`.
+-   Otherwise, a CLI message will suggest running with `--prettier`.
+
 #### `tslint`
 
 ```shell

docs/Architecture.md

@@ -14,6 +14,7 @@ Within `src/conversion/convertConfig.ts`, the following steps occur:
 1. Existing configurations are read from disk
 2. TSLint rules are converted into their ESLint configurations
 3. ESLint configurations are simplified based on extended ESLint and TSLint presets
+    - 3a. If no output rules conflict with `eslint-config-prettier`, it's added in
 4. The simplified configuration is written to the output config file
 5. A summary of the results is printed to the user's console
 

package-lock.json

@@ -12,6 +12,7 @@
     "dependencies": {
         "chalk": "4.0.0",
         "commander": "5.1.0",
+        "eslint-config-prettier": "^6.11.0",
         "strip-json-comments": "3.1.0",
         "tslint": "6.1.1",
         "typescript": "3.8.3"
@@ -28,7 +29,6 @@
         "@typescript-eslint/parser": "2.29.0",
         "babel-jest": "25.4.0",
         "eslint": "6.8.0",
-        "eslint-config-prettier": "6.11.0",
         "husky": "4.2.5",
         "jest": "25.4.0",
         "lint-staged": "10.1.7",

package.json

@@ -10,6 +10,7 @@ import {
     convertEditorConfig,
     ConvertEditorConfigDependencies,
 } from "../conversion/convertEditorConfig";
+import { addPrettierExtensions } from "../creation/simplification/prettier/addPrettierExtensions";
 import { removeExtendsDuplicatedRules } from "../creation/simplification/removeExtendsDuplicatedRules";
 import {
     retrieveExtendsValues,
@@ -103,6 +104,7 @@ const retrieveExtendsValuesDependencies: RetrieveExtendsValuesDependencies = {
 };
 
 const simplifyPackageRulesDependencies: SimplifyPackageRulesDependencies = {
+    addPrettierExtensions,
     removeExtendsDuplicatedRules,
     retrieveExtendsValues: bind(retrieveExtendsValues, retrieveExtendsValuesDependencies),
 };

src/cli/main.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/cli/runCli.ts

@@ -1,9 +1,9 @@
 import { EditorSettingConversionResults } from "../editorSettings/convertEditorSettings";
-import { RuleConversionResults } from "../rules/convertRules";
+import { SimplifiedResultsConfiguration } from "../creation/simplification/simplifyPackageRules";
 
 export const createEmptyConversionResults = (
-    overrides: Partial<RuleConversionResults> = {},
-): RuleConversionResults => ({
+    overrides: Partial<SimplifiedResultsConfiguration> = {},
+): SimplifiedResultsConfiguration => ({
     converted: new Map(),
     failed: [],
     missing: [],

src/conversion/conversionResults.stubs.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.test.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(