Move eslint-plugin-prettier to its own file like all other plugins

Closes #155.

.eslintrc.base.js

@@ -37,7 +37,9 @@ module.exports = {
     strict: "error",
     "prefer-spread": "off",
     "require-jsdoc": "off",
-    "prettier/prettier": ["error", {}],
+    "prettier/prettier": "error",
+    // Force a conflict with eslint-plugin-prettier in test-lint/prettier.js.
+    "prefer-arrow-callback": "error",
     // Force a conflict with Prettier in test-lint/flowtype.js.
     "flowtype/object-type-delimiter": ["error", "semicolon"],
     "react/jsx-filename-extension": "off",

README.md

@@ -12,6 +12,7 @@ Note that this config _only_ turns rules _off,_ so it only makes sense using it
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 
 - [Installation](#installation)
+  - [eslint-plugin-prettier](#eslint-plugin-prettier)
   - [Excluding deprecated rules](#excluding-deprecated-rules)
 - [CLI helper tool](#cli-helper-tool)
   - [Legacy](#legacy)
@@ -62,6 +63,7 @@ A few ESLint plugins are supported as well:
 - [@typescript-eslint/eslint-plugin]
 - [eslint-plugin-babel]
 - [eslint-plugin-flowtype]
+- [eslint-plugin-prettier]
 - [eslint-plugin-react]
 - [eslint-plugin-standard]
 - [eslint-plugin-unicorn]
@@ -78,6 +80,7 @@ Add extra exclusions for the plugins you use like so:
     "prettier/@typescript-eslint",
     "prettier/babel",
     "prettier/flowtype",
+    "prettier/prettier",
     "prettier/react",
     "prettier/standard",
     "prettier/unicorn",
@@ -101,6 +104,54 @@ If you extend a config which uses a plugin, it is recommended to add `"prettier/
 
 If you’re unsure which plugins are used, you can usually find them in your `package.json`.
 
+### eslint-plugin-prettier
+
+In the above section you might have noticed this plugin being mentioned:
+
+[eslint-<strong>plugin</strong>-prettier][eslint-plugin-prettier]
+
+Just to clear any confusion, the repo you’re currently looking at is:
+
+eslint-<strong>config</strong>-prettier
+
+So what’s the difference?
+
+- eslint-<strong>plugin</strong>-prettier adds a new _rule_ that lets you run Prettier from within ESLint as if it was a regular old ESLint rule.
+- eslint-<strong>config</strong>-prettier just turns off a bunch of rules (that are unnecessary or conflict with Prettier).
+
+To make things even more confusing, eslint-<strong>plugin</strong>-prettier _also_ provides a _config_ you can extend. It’s called `"plugin:prettier/recommended"`. All that config does is:
+
+```json
+{
+  "extends": ["prettier", "prettier/prettier"],
+  "plugins": ["prettier"],
+  "rules": {
+    "prettier/prettier": "error"
+  }
+}
+```
+
+Ugh, that’s a lot of `prettier` and `prettier/prettier`! What is all of that doing? Let’s start from the bottom:
+
+- `"rules": { "prettier/prettier": "error" }` turns on the _rule_ that eslint-<strong>plugin</strong>-prettier provides, that lets you run Prettier from within ESLint.
+
+- `"plugins": ["prettier"]` registers eslint-<strong>plugin</strong>-prettier as a plugin, so ESLint knows what `"prettier/prettier": "error"` is.
+
+- `"extends"` is the interesting part. This requires you to also install eslint-<strong>config</strong>-prettier (this repo), because the listed configs comes from _this_ repo, not from the plugin’s repo!
+
+  - `"prettier"` is the base config which disables ESLint core rules.
+  - `"prettier/prettier"` is specific config for eslint-<strong>plugin</strong>-prettier which disables [two ESLint core rules][eslint-plugin-prettier-special] that conflict only with eslint-<strong>plugin</strong>-prettier (not Prettier itself).
+
+Note that even if you use `"plugin:prettier/recommended"`, you might still need to add more stuff to the `"extends"` array, depending on which other plugins you use. For example:
+
+```json
+{
+  "extends": ["plugin:prettier/recommended", "prettier/@typescript-eslint"]
+}
+```
+
+**Note:** [eslint-<strong>plugin</strong>-prettier has some downsides][eslint-plugin-prettier-downsides] that you might want to read about.
+
 ### Excluding deprecated rules
 
 Some of the rules that eslint-config-prettier turns off may be deprecated. **This is perfectly fine,** but if you really need to omit the deprecated rules, you can do so by setting the `ESLINT_CONFIG_PRETTIER_NO_DEPRECATED` environment variable to a non-empty value. For example:
@@ -155,7 +206,7 @@ There a few rules that eslint-config-prettier disables that actually can be enab
 - Some require special attention when writing code. The CLI helper tool warns you if any of those rules are enabled, but can’t tell if anything is problematic.
 - Some can cause problems if using [eslint-plugin-prettier] and `--fix`.
 
-For maximum ease of use, the special rules are disabled by default. If you want them, you need to explicitly specify them in your ESLint config.
+For maximum ease of use, the special rules are disabled by default (provided that you include all needed things in `"extends"`). If you want them, you need to explicitly specify them in your ESLint config.
 
 ### [arrow-body-style] and [prefer-arrow-callback]
 
@@ -180,6 +231,10 @@ See these issues for more information:
 
 When the autofix bug in ESLint has been fixed, the special case for these rules can be removed.
 
+Note: You need to put `"prettier/prettier"` in your `"extends"` array if you want these rules to be turned off. (Yes, there’s both a _rule_ called `"prettier/prettier"` and a _config_ called `"prettier/prettier"`.)
+
+Note: The CLI tool only reports these as problematic if the `"prettier/prettier"` _rule_ is enabled for the same file.
+
 ### [curly]
 
 **This rule requires certain options.**
@@ -692,6 +747,7 @@ eslint-config-prettier has been tested with:
 - @typescript-eslint/eslint-plugin 4.8.2
 - eslint-plugin-babel 5.3.1
 - eslint-plugin-flowtype 5.2.0
+- eslint-plugin-prettier 3.1.4
 - eslint-plugin-react 7.21.5
 - eslint-plugin-standard 4.0.2
 - eslint-plugin-unicorn 23.0.0
@@ -733,7 +789,7 @@ Finally, you need to mention the plugin in several places:
 - Add `"foobar.js"` to the "files" field in `package.json`.
 - Add eslint-plugin-foobar to the "devDependencies" field in `package.json`.
 - Make sure that at least one rule from eslint-plugin-foobar gets used in `.eslintrc.base.js`.
-- Add it to the list of supported plugins, to the example config and to Contributing section in `README.md`.
+- Add it to the list of supported plugins and to the Contributing section in `README.md`.
 
 When you’re done, run `npm test` to verify that you got it all right. It runs several other npm scripts:
 
@@ -752,18 +808,19 @@ When you’re done, run `npm test` to verify that you got it all right. It runs
 
 [@typescript-eslint/eslint-plugin]: https://github.com/typescript-eslint/typescript-eslint
 [@typescript-eslint/quotes]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/quotes.md
-[eslint 5.7.0]: https://eslint.org/blog/2018/10/eslint-v5.7.0-released
-[prettier]: https://github.com/prettier/prettier
 [arrow-body-style]: https://eslint.org/docs/rules/arrow-body-style
 [babel/quotes]: https://github.com/babel/eslint-plugin-babel#rules
 [curly]: https://eslint.org/docs/rules/curly
+[eslint 5.7.0]: https://eslint.org/blog/2018/10/eslint-v5.7.0-released
 [eslint-config-airbnb]: https://www.npmjs.com/package/eslint-config-airbnb
 [eslint-config-prettier#31]: https://github.com/prettier/eslint-config-prettier/issues/31
 [eslint-config-prettier#71]: https://github.com/prettier/eslint-config-prettier/issues/71
 [eslint-plugin-babel]: https://github.com/babel/eslint-plugin-babel
 [eslint-plugin-flowtype]: https://github.com/gajus/eslint-plugin-flowtype
-[eslint-plugin-prettier#65]: https://github.com/prettier/eslint-plugin-prettier/issues/65
+[eslint-plugin-prettier-downsides]: https://prettier.io/docs/en/integrating-with-linters.html#notes
+[eslint-plugin-prettier-special]: #arrow-body-style-and-prefer-arrow-callback
 [eslint-plugin-prettier]: https://github.com/prettier/eslint-plugin-prettier
+[eslint-plugin-prettier#65]: https://github.com/prettier/eslint-plugin-prettier/issues/65
 [eslint-plugin-react]: https://github.com/yannickcr/eslint-plugin-react
 [eslint-plugin-standard]: https://github.com/xjamundx/eslint-plugin-standard
 [eslint-plugin-unicorn]: https://github.com/sindresorhus/eslint-plugin-unicorn
@@ -780,6 +837,7 @@ When you’re done, run `npm test` to verify that you got it all right. It runs
 [no-unexpected-multiline]: https://eslint.org/docs/rules/no-unexpected-multiline
 [overrides]: https://eslint.org/docs/user-guide/configuring#configuration-based-on-glob-patterns
 [prefer-arrow-callback]: https://eslint.org/docs/rules/prefer-arrow-callback
+[prettier]: https://github.com/prettier/prettier
 [quotes]: https://eslint.org/docs/rules/quotes
 [singlequote]: https://prettier.io/docs/en/options.html#quotes
 [string formatting rules]: https://prettier.io/docs/en/rationale.html#strings

bin/cli.js

@@ -23,7 +23,9 @@ if (module === require.main) {
   Promise.all(args.map((file) => eslint.calculateConfigForFile(file)))
     .then((configs) => {
       const rules = [].concat(
-        ...configs.map((config) => Object.entries(config.rules))
+        ...configs.map((config, index) =>
+          Object.entries(config.rules).map((entry) => [...entry, args[index]])
+        )
       );
       const result = processRules(rules);
       if (result.stderr) {
@@ -83,11 +85,13 @@ function processRules(configRules) {
   );
 
   const flaggedRules = configRules
-    .map(([ruleName, value]) => {
+    .map(([ruleName, value, source]) => {
       const arrayValue = Array.isArray(value) ? value : [value];
       const [level, ...options] = arrayValue;
       const isOff = level === "off" || level === 0;
-      return !isOff && ruleName in allRules ? { ruleName, options } : null;
+      return !isOff && ruleName in allRules
+        ? { ruleName, options, source }
+        : null;
     })
     .filter(Boolean);
 
@@ -97,8 +101,9 @@ function processRules(configRules) {
   );
   const optionsFlaggedRuleNames = filterRuleNames(
     flaggedRules,
-    (ruleName, options) =>
-      ruleName in optionsRules && !validators[ruleName](options)
+    (ruleName, options, source) =>
+      ruleName in optionsRules &&
+      !validators[ruleName](options, source, configRules)
   );
   const specialFlaggedRuleNames = filterRuleNames(
     flaggedRules,
@@ -177,7 +182,7 @@ function filterRuleNames(rules, fn) {
   return [
     ...new Set(
       rules
-        .filter((rule) => fn(rule.ruleName, rule.options))
+        .filter((rule) => fn(rule.ruleName, rule.options, rule.source))
         .map((rule) => rule.ruleName)
     ),
   ];

bin/validators.js

@@ -4,6 +4,8 @@
 // `false` if the options DO conflict with Prettier, and `true` if they don’t.
 
 module.exports = {
+  "arrow-body-style": checkEslintConfigPrettier,
+
   curly(options) {
     if (options.length === 0) {
       return true;
@@ -48,6 +50,8 @@ module.exports = {
     return Boolean(firstOption && firstOption.allowIndentationTabs);
   },
 
+  "prefer-arrow-callback": checkEslintConfigPrettier,
+
   "vue/html-self-closing"(options) {
     if (options.length === 0) {
       return false;
@@ -61,3 +65,10 @@ module.exports = {
     );
   },
 };
+
+function checkEslintConfigPrettier(_options, source, rules) {
+  return !rules.some(
+    ([name, _options2, source2]) =>
+      name === "prettier/prettier" && source === source2
+  );
+}

index.js

@@ -7,15 +7,13 @@ module.exports = {
     // The following rules can be used in some cases. See the README for more
     // information. (These are marked with `0` instead of `"off"` so that a
     // script can distinguish them.)
-    "arrow-body-style": 0,
     curly: 0,
     "lines-around-comment": 0,
     "max-len": 0,
     "no-confusing-arrow": 0,
     "no-mixed-operators": 0,
     "no-tabs": 0,
     "no-unexpected-multiline": 0,
-    "prefer-arrow-callback": 0,
     quotes: 0,
     // The rest are rules that you never need to enable when using Prettier.
     "array-bracket-newline": "off",

package.json

@@ -11,6 +11,7 @@
     "babel.js",
     "flowtype.js",
     "index.js",
+    "prettier.js",
     "react.js",
     "standard.js",
     "unicorn.js",

prettier.js

@@ -0,0 +1,10 @@
+"use strict";
+
+module.exports = {
+  rules: {
+    // These are safe to use as long as the `"prettier/prettier"` rule from
+    // eslint-plugin-prettier isn’t enabled.
+    "arrow-body-style": 0,
+    "prefer-arrow-callback": 0,
+  },
+};

test-lint/prettier.js

@@ -0,0 +1,14 @@
+/* eslint-disable quotes */
+/* eslint-disable space-before-function-paren */
+"use strict";
+
+function foo() {
+  return (
+    isTrue &&
+    [0, 1, 2].map(function (num) {
+      return num * 2;
+    })
+  );
+}
+
+foo();