docs: split rules documentation

docs/src/contribute/contribute-core-rule.md

@@ -0,0 +1,141 @@
+---
+title: Contribute to Core Rules
+eleventyNavigation:
+    key: contribute core rule
+    parent: contribute to eslint
+    title: Contribute to Core Rules
+    order: 10
+---
+
+The ESLint core rules are the rules included in the ESLint package.
+
+## Rule Writing Documentation
+
+For full reference information on writing rules, refer to [Custom Rules](../extend/custom-rules). Both custom rules and core rules have the same structure and API. The primary difference between core and custom rules are:
+
+1. Core rules are included in the `eslint` package.
+1. Core rules must adhere to the structure documented on this page.
+
+## Core Rule Structure
+
+Each core rule in ESLint has three files named with its identifier (for example, `no-extra-semi`).
+
+* in the `lib/rules` directory: a source file (for example, `no-extra-semi.js`)
+* in the `tests/lib/rules` directory: a test file (for example, `no-extra-semi.js`)
+* in the `docs/src/rules` directory: a Markdown documentation file (for example, `no-extra-semi.md`)
+
+**Important:** If you submit a **core** rule to the ESLint repository, you **must** follow some conventions explained below.
+
+Here is the basic format of the source file for a rule:
+
+```js
+/**
+ * @fileoverview Rule to disallow unnecessary semicolons
+ * @author Nicholas C. Zakas
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "disallow unnecessary semicolons",
+            recommended: true,
+            url: "https://eslint.org/docs/rules/no-extra-semi"
+        },
+        fixable: "code",
+        schema: [] // no options
+    },
+    create: function(context) {
+        return {
+            // callback functions
+        };
+    }
+};
+```
+
+## Rule Unit Tests
+
+Each bundled rule for ESLint core must have a set of unit tests submitted with it to be accepted. The test file is named the same as the source file but lives in `tests/lib/`. For example, if the rule source file is `lib/rules/foo.js` then the test file should be `tests/lib/rules/foo.js`.
+
+ESLint provides the [`RuleTester`](../integrate/nodejs-api#ruletester) utility to make it easy to write tests for rules.
+
+## Performance Testing
+
+To keep the linting process efficient and unobtrusive, it is useful to verify the performance impact of new rules or modifications to existing rules.
+
+### Overall Performance
+
+When developing in the ESLint core repository, the `npm run perf` command gives a high-level overview of ESLint running time with all core rules enabled.
+
+```bash
+$ git checkout main
+Switched to branch 'main'
+
+$ npm run perf
+CPU Speed is 2200 with multiplier 7500000
+Performance Run #1:  1394.689313ms
+Performance Run #2:  1423.295351ms
+Performance Run #3:  1385.09515ms
+Performance Run #4:  1382.406982ms
+Performance Run #5:  1409.68566ms
+Performance budget ok:  1394.689313ms (limit: 3409.090909090909ms)
+
+$ git checkout my-rule-branch
+Switched to branch 'my-rule-branch'
+
+$ npm run perf
+CPU Speed is 2200 with multiplier 7500000
+Performance Run #1:  1443.736547ms
+Performance Run #2:  1419.193291ms
+Performance Run #3:  1436.018228ms
+Performance Run #4:  1473.605485ms
+Performance Run #5:  1457.455283ms
+Performance budget ok:  1443.736547ms (limit: 3409.090909090909ms)
+```
+
+### Per-rule Performance
+
+ESLint has a built-in method to track performance of individual rules. Setting the `TIMING` environment variable will trigger the display, upon linting completion, of the ten longest-running rules, along with their individual running time (rule creation + rule execution) and relative performance impact as a percentage of total rule processing time (rule creation + rule execution).
+
+```bash
+$ TIMING=1 eslint lib
+Rule                    | Time (ms) | Relative
+:-----------------------|----------:|--------:
+no-multi-spaces         |    52.472 |     6.1%
+camelcase               |    48.684 |     5.7%
+no-irregular-whitespace |    43.847 |     5.1%
+valid-jsdoc             |    40.346 |     4.7%
+handle-callback-err     |    39.153 |     4.6%
+space-infix-ops         |    35.444 |     4.1%
+no-undefined            |    25.693 |     3.0%
+no-shadow               |    22.759 |     2.7%
+no-empty-class          |    21.976 |     2.6%
+semi                    |    19.359 |     2.3%
+```
+
+To test one rule explicitly, combine the `--no-eslintrc`, and `--rule` options:
+
+```bash
+$ TIMING=1 eslint --no-eslintrc --rule "quotes: [2, 'double']" lib
+Rule   | Time (ms) | Relative
+:------|----------:|--------:
+quotes |    18.066 |   100.0%
+```
+
+To see a longer list of results (more than 10), set the environment variable to another value such as `TIMING=50` or `TIMING=all`.
+
+## Rule Naming Conventions
+
+The rule naming conventions for ESLint are fairly simple:
+
+* If your rule is disallowing something, prefix it with `no-` such as `no-eval` for disallowing `eval()` and `no-debugger` for disallowing `debugger`.
+* If your rule is enforcing the inclusion of something, use a short name without a special prefix.
+* Use dashes between words.

docs/src/contribute/governance.md

@@ -4,7 +4,7 @@ eleventyNavigation:
     key: governance
     parent: contribute to eslint
     title: Governance
-    order: 10
+    order: 11
 
 ---
 

docs/src/contribute/index.md

@@ -54,6 +54,10 @@ Have some extra time and want to contribute? This section talks about the proces
 
 We're always looking for contributions from the community. This section explains the requirements for pull requests and the process of contributing code.
 
+## [Contribute to Core Rules](contribute-core-rule)
+
+This section explains how to add to the core rules of ESLint.
+
 ## [Governance](governance)
 
 Describes the governance policy for ESLint, including the rights and privileges of individuals inside the project.

docs/src/extend/custom-rules.md

@@ -8,50 +8,9 @@ eleventyNavigation:
 
 ---
 
-**Note:** This page covers the most recent rule format for ESLint >= 3.0.0. There is also a [deprecated rule format](./custom-rules-deprecated).
-
-Each rule in ESLint has three files named with its identifier (for example, `no-extra-semi`).
-
-* in the `lib/rules` directory: a source file (for example, `no-extra-semi.js`)
-* in the `tests/lib/rules` directory: a test file (for example, `no-extra-semi.js`)
-* in the `docs/src/rules` directory: a Markdown documentation file (for example, `no-extra-semi.md`)
-
-**Important:** If you submit a **core** rule to the ESLint repository, you **must** follow some conventions explained below.
-
-Here is the basic format of the source file for a rule:
+You can create custom rules to use with ESLint. You might want to create a custom rule if the [core rules](../rules/) do not cover your use case.
 
-```js
-/**
- * @fileoverview Rule to disallow unnecessary semicolons
- * @author Nicholas C. Zakas
- */
-
-"use strict";
-
-//------------------------------------------------------------------------------
-// Rule Definition
-//------------------------------------------------------------------------------
-
-/** @type {import('eslint').Rule.RuleModule} */
-module.exports = {
-    meta: {
-        type: "suggestion",
-
-        docs: {
-            description: "disallow unnecessary semicolons",
-            recommended: true,
-            url: "https://eslint.org/docs/rules/no-extra-semi"
-        },
-        fixable: "code",
-        schema: [] // no options
-    },
-    create: function(context) {
-        return {
-            // callback functions
-        };
-    }
-};
-```
+**Note:** This page covers the most recent rule format for ESLint >= 3.0.0. There is also a [deprecated rule format](./custom-rules-deprecated).
 
 ## Rule Basics
 
@@ -712,82 +671,11 @@ You can access that code path objects with five events related to code paths.
 
 ## Rule Unit Tests
 
-Each bundled rule for ESLint core must have a set of unit tests submitted with it to be accepted. The test file is named the same as the source file but lives in `tests/lib/`. For example, if the rule source file is `lib/rules/foo.js` then the test file should be `tests/lib/rules/foo.js`.
-
 ESLint provides the [`RuleTester`](../integrate/nodejs-api#ruletester) utility to make it easy to write tests for rules.
 
-## Performance Testing
-
-To keep the linting process efficient and unobtrusive, it is useful to verify the performance impact of new rules or modifications to existing rules.
-
-### Overall Performance
-
-When developing in the ESLint core repository, the `npm run perf` command gives a high-level overview of ESLint running time with all core rules enabled.
-
-```bash
-$ git checkout main
-Switched to branch 'main'
-
-$ npm run perf
-CPU Speed is 2200 with multiplier 7500000
-Performance Run #1:  1394.689313ms
-Performance Run #2:  1423.295351ms
-Performance Run #3:  1385.09515ms
-Performance Run #4:  1382.406982ms
-Performance Run #5:  1409.68566ms
-Performance budget ok:  1394.689313ms (limit: 3409.090909090909ms)
-
-$ git checkout my-rule-branch
-Switched to branch 'my-rule-branch'
-
-$ npm run perf
-CPU Speed is 2200 with multiplier 7500000
-Performance Run #1:  1443.736547ms
-Performance Run #2:  1419.193291ms
-Performance Run #3:  1436.018228ms
-Performance Run #4:  1473.605485ms
-Performance Run #5:  1457.455283ms
-Performance budget ok:  1443.736547ms (limit: 3409.090909090909ms)
-```
-
-### Per-rule Performance
-
-ESLint has a built-in method to track performance of individual rules. Setting the `TIMING` environment variable will trigger the display, upon linting completion, of the ten longest-running rules, along with their individual running time (rule creation + rule execution) and relative performance impact as a percentage of total rule processing time (rule creation + rule execution).
-
-```bash
-$ TIMING=1 eslint lib
-Rule                    | Time (ms) | Relative
-:-----------------------|----------:|--------:
-no-multi-spaces         |    52.472 |     6.1%
-camelcase               |    48.684 |     5.7%
-no-irregular-whitespace |    43.847 |     5.1%
-valid-jsdoc             |    40.346 |     4.7%
-handle-callback-err     |    39.153 |     4.6%
-space-infix-ops         |    35.444 |     4.1%
-no-undefined            |    25.693 |     3.0%
-no-shadow               |    22.759 |     2.7%
-no-empty-class          |    21.976 |     2.6%
-semi                    |    19.359 |     2.3%
-```
-
-To test one rule explicitly, combine the `--no-eslintrc`, and `--rule` options:
-
-```bash
-$ TIMING=1 eslint --no-eslintrc --rule "quotes: [2, 'double']" lib
-Rule   | Time (ms) | Relative
-:------|----------:|--------:
-quotes |    18.066 |   100.0%
-```
-
-To see a longer list of results (more than 10), set the environment variable to another value such as `TIMING=50` or `TIMING=all`.
-
 ## Rule Naming Conventions
 
-The rule naming conventions for ESLint are fairly simple:
-
-* If your rule is disallowing something, prefix it with `no-` such as `no-eval` for disallowing `eval()` and `no-debugger` for disallowing `debugger`.
-* If your rule is enforcing the inclusion of something, use a short name without a special prefix.
-* Use dashes between words.
+While you can give a custom rule any name you'd like, the core rules have naming conventions that it could be clearer to apply to your custom rule. To learn more, refer to the [Core Rule Naming Conventions](../contribute/contribute-core-rule#rule-naming-conventions) documentation.
 
 ## Runtime Rules
 

docs/src/extend/index.md

@@ -23,7 +23,7 @@ You've developed custom rules for ESLint and you want to share them with the com
 
 ## [Custom Rules](custom-rules)
 
-This section explains how to create and modify rules to use with ESLint.
+This section explains how to create custom rules to use with ESLint.
 
 ## [Custom Formatters](custom-formatters)