New: function-paren-newline rule (fixes #6074)

eslint · Aug 19, 2017 · 855af35 · 855af35
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diff --git a/docs/rules/function-paren-newline.md b/docs/rules/function-paren-newline.md
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+# enforce consistent line breaks inside function parentheses (function-paren-newline)
+
+(fixable) The `--fix` option on the [command line](../user-guide/command-line-interface#fix) automatically fixes problems reported by this rule.
+
+Many styleguides require or disallow newlines inside of function parentheses.
+
+## Rule Details
+
+This rule enforces consistent line breaks inside parentheses of function parameters or arguments.
+
+### Options
+
+This rule has a single option, which can either be a string or an object.
+
+* `"always"` requires line breaks inside all function parentheses.
+* `"never"` disallows line breaks inside all function parentheses.
+* `"multiline"` (default) requires linebreaks inside function parentheses if any of the parameters/arguments have a line break between them. Otherwise, it disallows linebreaks.
+* `{ "minItems": value }` requires linebreaks inside function parentheses if the number of parameters/arguments is at least `value`. Otherwise, it disallows linebreaks.
+
+Example configurations:
+
+```json
+{
+  "rules": {
+    "function-paren-newline": ["error", "never"]
+  }
+}
+```
+
+```json
+{
+  "rules": {
+    "function-paren-newline": ["error", { "minItems": 3 }]
+  }
+}
+```
+
+Examples of **incorrect** code for this rule with the `"always"` option:
+
+```js
+/* eslint function-paren-newline: ["error", "always"] */
+
+function foo(bar, baz) {}
+
+var foo = function(bar, baz) {};
+
+var foo = (bar, baz) => {};
+
+foo(bar, baz);
+```
+
+Examples of **correct** code for this rule with the `"always"` option:
+
+```js
+/* eslint function-paren-newline: ["error", "always"] */
+
+function foo(
+  bar,
+  baz
+) {}
+
+var foo = function(
+  bar, baz
+) {};
+
+var foo = (
+  bar,
+  baz
+) => {};
+
+foo(
+  bar,
+  baz
+);
+```
+
+Examples of **incorrect** code for this rule with the `"never"` option:
+
+```js
+/* eslint function-paren-newline: ["error", "never"] */
+
+function foo(
+  bar,
+  baz
+) {}
+
+var foo = function(
+  bar, baz
+) {};
+
+var foo = (
+  bar,
+  baz
+) => {};
+
+foo(
+  bar,
+  baz
+);
+```
+
+Examples of **correct** code for this rule with the `"never"` option:
+
+```js
+/* eslint function-paren-newline: ["error", "never"] */
+
+function foo(bar, baz) {}
+
+function foo(bar,
+             baz) {}
+
+var foo = function(bar, baz) {};
+
+var foo = (bar, baz) => {};
+
+foo(bar, baz);
+
+foo(bar,
+  baz);
+```
+
+Examples of **incorrect** code for this rule with the default `"multiline"` option:
+
+```js
+/* eslint function-paren-newline: ["error", "multiline"] */
+
+function foo(bar,
+  baz
+) {}
+
+var foo = function(
+  bar, baz
+) {};
+
+var foo = (
+  bar,
+  baz) => {};
+
+foo(bar,
+  baz);
+
+foo(
+  function() {
+    return baz;
+  }
+);
+```
+
+Examples of **correct** code for this rule with the default `"multiline"` option:
+
+```js
+/* eslint function-paren-newline: ["error", "multiline"] */
+
+function foo(bar, baz) {}
+
+var foo = function(
+  bar,
+  baz
+) {};
+
+var foo = (bar, baz) => {};
+
+foo(bar, baz, qux);
+
+foo(
+  bar,
+  baz,
+  qux
+);
+
+foo(function() {
+  return baz;
+});
+```
+
+Examples of **incorrect** code for this rule with the `{ "minItems": 3 }` option:
+
+```js
+/* eslint function-paren-newline: ["error", { "minItems": 3 }] */
+
+function foo(
+  bar,
+  baz
+) {}
+
+function foo(bar, baz, qux) {}
+
+var foo = function(
+  bar, baz
+) {};
+
+var foo = (bar,
+  baz) => {};
+
+foo(bar,
+  baz);
+```
+
+Examples of **correct** code for this rule with the `{ "minItems": 3 }` option:
+
+```js
+/* eslint function-paren-newline: ["error", { "minItems": 3 }] */
+
+function foo(bar, baz) {}
+
+var foo = function(
+  bar,
+  baz,
+  qux
+) {};
+
+var foo = (
+  bar, baz, qux
+) => {};
+
+foo(bar, baz);
+
+foo(
+  bar, baz, qux
+);
+```
+
+## When Not To Use It
+
+If don't want to enforce consistent linebreaks inside function parentheses, do not turn on this rule.