feat: add rule logical-assignment-operators

docs/src/rules/logical-assignment-operators.md

@@ -0,0 +1,131 @@
+---
+title: logical-assignment-operators
+layout: doc
+rule_type: suggestion
+---
+
+ES2021 introduces the assignment operator shorthand for the logical operators `||`, `&&` and `??`.
+Before, this was only allowed for mathematical operations such as `+` or `*` (see the rule [operator-assignment](./operator-assignment)).
+The shorthand can be used if the assignment target and the left expression of a logical expression are the same.
+For example `a = a || b` can be shortened to `a ||= b`.
+
+## Rule Details
+
+This rule requires or disallows logical assignment operator shorthand.  
+
+### Options
+
+This rule has a string and an object option.
+String option:
+
+* `"always"` (default)
+* `"never"`
+
+Object option (only available if string option is set to `"always"`):
+
+* `"enforceForIfStatements": false`(default) Do *not* check for equivalent `if` statements
+* `"enforceForIfStatements": true` Check for equivalent `if` statements
+
+#### always
+
+Examples of **incorrect** code for this rule with the default `"always"` option:
+
+::: incorrect
+
+```js
+/*eslint logical-assignment-operators: ["error", "always"]*/
+
+a = a || b
+a = a && b
+a = a ?? b
+a || (a = b)
+a && (a = b)
+a ?? (a = b)
+```
+
+:::
+
+Examples of **correct** code for this rule with the default `"always"` option:
+
+::: correct
+
+```js
+/*eslint logical-assignment-operators: ["error", "always"]*/
+
+a = b
+a += b
+a ||= b
+a = b || c
+a || (b = c)
+
+if (a) a = b
+```
+
+:::
+
+#### never
+
+Examples of **incorrect** code for this rule with the `"never"` option:
+
+::: incorrect
+
+```js
+/*eslint logical-assignment-operators: ["error", "never"]*/
+
+a ||= b
+a &&= b
+a ??= b
+```
+
+:::
+
+Examples of **correct** code for this rule with the `"never"` option:
+
+::: correct
+
+```js
+/*eslint logical-assignment-operators: ["error", "never"]*/
+
+a = a || b
+a = a && b
+a = a ?? b
+```
+
+:::
+
+#### enforceForIfStatements
+
+This option checks for additional patterns with if statements which could be expressed with the logical assignment operator.
+
+::: incorrect
+
+Examples of **incorrect** code for this rule with the `["always", { enforceIfStatements: true }]` option:
+
+```js
+/*eslint logical-assignment-operators: ["error", "always", { enforceForIfStatements: true }]*/
+
+if (a) a = b // <=> a &&= b
+if (!a) a = b // <=> a ||= b
+
+if (a == null) a = b // <=> a ??= b
+if (a === null || a === undefined) a = b // <=> a ??= b
+```
+
+:::
+
+Examples of **correct** code for this rule with the `["always", { enforceIfStatements: true }]` option:
+
+::: correct
+
+```js
+/*eslint logical-assignment-operators: ["error", "always", { enforceForIfStatements: true }]*/
+
+if (a) b = c
+if (a === 0) a = b
+```
+
+:::
+
+## When Not To Use It
+
+Use of logical operator assignment shorthand is a stylistic choice. Leaving this rule turned off would allow developers to choose which style is more readable on a case-by-case basis.

lib/rules/index.js

@@ -72,6 +72,7 @@ module.exports = new LazyLoadingRuleMap(Object.entries({
     "lines-around-comment": () => require("./lines-around-comment"),
     "lines-around-directive": () => require("./lines-around-directive"),
     "lines-between-class-members": () => require("./lines-between-class-members"),
+    "logical-assignment-operators": () => require("./logical-assignment-operators"),
     "max-classes-per-file": () => require("./max-classes-per-file"),
     "max-depth": () => require("./max-depth"),
     "max-len": () => require("./max-len"),