Add no-misleading-capturing-group rule and improve optimal-quantifier-concatenation (#483)

* Simplify quantifiers

* Fixed false positive for lazy quantifiers

* Improved absorb condition

* Added more tests

* No non-atomic groups v1

* Typo

* Typos

* Added trading-based detection method

* Added another test case

* Added docs

* Added `reportBacktrackingEnds` option

Author: RunDevelopment

README.md

@@ -119,6 +119,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
 | [regexp/no-escape-backspace](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-escape-backspace.html) | disallow escape backspace (`[\b]`) | :star: |
 | [regexp/no-invalid-regexp](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-invalid-regexp.html) | disallow invalid regular expression strings in `RegExp` constructors | :star: |
 | [regexp/no-lazy-ends](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-lazy-ends.html) | disallow lazy quantifiers at the end of an expression | :star: |
+| [regexp/no-misleading-capturing-group](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-misleading-capturing-group.html) | disallow capturing groups that do not behave as one would expect |  |
 | [regexp/no-misleading-unicode-character](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-misleading-unicode-character.html) | disallow multi-code-point characters in character classes and quantifiers | :wrench: |
 | [regexp/no-missing-g-flag](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-missing-g-flag.html) | disallow missing `g` flag in patterns used in `String#matchAll` and `String#replaceAll` | :wrench: |
 | [regexp/no-optional-assertion](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-optional-assertion.html) | disallow optional assertions | :star: |

docs/rules/index.md

@@ -25,6 +25,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
 | [regexp/no-escape-backspace](./no-escape-backspace.md) | disallow escape backspace (`[\b]`) | :star: |
 | [regexp/no-invalid-regexp](./no-invalid-regexp.md) | disallow invalid regular expression strings in `RegExp` constructors | :star: |
 | [regexp/no-lazy-ends](./no-lazy-ends.md) | disallow lazy quantifiers at the end of an expression | :star: |
+| [regexp/no-misleading-capturing-group](./no-misleading-capturing-group.md) | disallow capturing groups that do not behave as one would expect |  |
 | [regexp/no-misleading-unicode-character](./no-misleading-unicode-character.md) | disallow multi-code-point characters in character classes and quantifiers | :wrench: |
 | [regexp/no-missing-g-flag](./no-missing-g-flag.md) | disallow missing `g` flag in patterns used in `String#matchAll` and `String#replaceAll` | :wrench: |
 | [regexp/no-optional-assertion](./no-optional-assertion.md) | disallow optional assertions | :star: |

docs/rules/no-misleading-capturing-group.md

@@ -0,0 +1,65 @@
+---
+pageClass: "rule-details"
+sidebarDepth: 0
+title: "regexp/no-misleading-capturing-group"
+description: "disallow capturing groups that do not behave as one would expect"
+---
+# regexp/no-misleading-capturing-group
+
+> disallow capturing groups that do not behave as one would expect
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+
+## :book: Rule Details
+
+This rule reports capturing groups that capture less text than their pattern might suggest.
+
+E.g. in `/a+(a*)/`, `(a*)` will **always** capture 0 characters because all `a`s are already consumed by `a+`. This is quite surprising behavior because `a*` suggests that the capturing group captures as many `a`s as possible.
+
+Misleading capturing groups in regex indicate either unnecessary code that can be removed or an error in the regex. Which one it is, depends on the intended behavior of the regex and cannot be determined by this rule.
+
+E.g. if the above example is really supposed to capture 0 characters, then the regex should be changed to `/a+()/` to make the intention explicit. Otherwise, then the parts of the regex surrounding `(a*)` have to be rewritten.
+
+This rule generally assumes that the regex behaves correctly, despite its misleading form, when suggesting fixes. Suggested fixes therefor remove the misleading elements **without changing the behavior** of the regex.
+
+<eslint-code-block>
+
+```js
+/* eslint regexp/no-misleading-capturing-group: "error" */
+
+/* ✓ GOOD */
+var foo = /a+(b*)/
+
+/* ✗ BAD */
+var foo = /a+(a*)/
+var foo = /\w+(\d*)/
+var foo = /^(a*).+/
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+```json
+{
+  "regexp/no-misleading-capturing-group": [
+    "error",
+    {
+      "reportBacktrackingEnds": true,
+    }
+  ]
+}
+```
+
+- `reportBacktrackingEnds`
+
+  This rule will report quantifiers at the end of capturing groups that might backtrack for certain strings.
+
+  E.g. when `/^(a*).+$/m` is used to match the string `"aa"`, then `a*` will capture both `a`s at first, but is then force to give up the last `a` to `.+` to make the whole regex accept. So `(a*)` only capture the first `a`. This is misleading because one would expect that `(a*)` should capture all `a`s at the start of the string, but this is not the case.
+
+  Because this behavior might be intentional, some users might want to turn off this type of reporting.
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/lib/rules/no-misleading-capturing-group.ts)
+- [Test source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/tests/lib/rules/no-misleading-capturing-group.ts)