New: jsx-curly-newline rule

CHANGELOG.md

@@ -2576,3 +2576,4 @@ If you're still not using React 15 you can keep the old behavior by setting the
 [`state-in-constructor`]: docs/rules/state-in-constructor.md
 [`jsx-props-no-spreading`]: docs/rules/jsx-props-no-spreading.md
 [`static-property-placement`]: docs/rules/static-property-placement.md
+[`jsx-curly-newline`]: docs/rules/jsx-curly-newline.md

docs/rules/jsx-curly-newline.md

@@ -0,0 +1,149 @@
+# Enforce linebreaks in curly braces in JSX attributes and expressions. (react/jsx-curly-newline)
+
+Many style guides require or disallow newlines inside of jsx curly expressions.
+
+**Fixable:** This rule is automatically fixable using the `--fix` flag on the command line.
+
+## Rule Details
+
+This rule enforces consistent linebreaks inside of curlies of jsx curly expressions.
+
+## Rule Options
+
+This rule accepts either an object option:
+
+```ts
+{
+  multiline: "consistent" | "forbid" | "require", // default to 'consistent'
+  singleline: "consistent" | "forbid" | "require", // default to 'consistent'
+}
+```
+Option `multiline` takes effect when the jsx expression inside the curlies occupies multiple lines.
+
+Option `singleline` takes effect when the jsx expression inside the curlies occupies a single line.
+
+* `consistent` enforces either both curly braces have a line break directly inside them, or no line breaks are present.
+* `forbid` disallows linebreaks directly inside curly braces.
+* `require` enforces the presence of linebreaks directly inside curlies.
+
+or a string option:
+
+* `consistent` (default) is an alias for `{ multiline: "consistent", singleline: "consistent" }`.
+* `never` is an alias for `{ multiline: "forbid", singleline: "forbid" }`
+
+or an
+
+### consistent (default)
+
+When `consistent` or `{ multiline: "consistent", singleline: "consistent" }` is set, the following patterns are considered warnings:
+
+```jsx
+<div>
+  { foo
+  }
+</div>
+
+<div>
+  {
+    foo }
+</div>
+
+<div>
+  { foo &&
+    foo.bar
+  }
+</div>
+```
+
+The following patterns are **not** warnings:
+
+```jsx
+<div>
+  { foo }
+</div>
+
+<div>
+  {
+    foo
+  }
+</div>
+```
+
+### never
+
+When `never` or `{ multiline: "forbid", singleline: "forbid" }` is set, the following patterns are considered warnings:
+
+```jsx
+<div>
+  {
+    foo &&
+    foo.bar
+  }
+</div>
+
+<div>
+  {
+    foo
+  }
+</div>
+
+<div>
+  { foo
+  }
+</div>
+```
+
+The following patterns are **not** warnings:
+
+```jsx
+<div>
+  { foo &&
+    foo.bar }
+</div>
+
+<div>
+  { foo }
+</div>
+```
+
+## require
+
+When `{ multiline: "require", singleline: "require" }` is set, the following patterns are considered warnings:
+
+```jsx
+<div>
+  { foo &&
+    foo.bar }
+</div>
+
+<div>
+  { foo }
+</div>
+
+<div>
+  { foo
+  }
+</div>
+```
+
+The following patterns are **not** warnings:
+
+```jsx
+<div>
+  {
+    foo &&
+    foo.bar
+  }
+</div>
+
+<div>
+  {
+    foo
+  }
+</div>
+```
+
+
+## When Not To Use It
+
+You can turn this rule off if you are not concerned with the consistency of padding linebreaks inside of JSX attributes or expressions.

index.js

@@ -19,6 +19,7 @@ const allRules = {
   'jsx-closing-bracket-location': require('./lib/rules/jsx-closing-bracket-location'),
   'jsx-closing-tag-location': require('./lib/rules/jsx-closing-tag-location'),
   'jsx-curly-spacing': require('./lib/rules/jsx-curly-spacing'),
+  'jsx-curly-newline': require('./lib/rules/jsx-curly-newline'),
   'jsx-equals-spacing': require('./lib/rules/jsx-equals-spacing'),
   'jsx-filename-extension': require('./lib/rules/jsx-filename-extension'),
   'jsx-first-prop-new-line': require('./lib/rules/jsx-first-prop-new-line'),

lib/rules/jsx-curly-newline.js

@@ -0,0 +1,187 @@
+/**
+ * @fileoverview enforce consistent line breaks inside jsx curly
+ */
+
+'use strict';
+
+const docsUrl = require('../util/docsUrl');
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+function getNormalizedOption(context) {
+  const rawOption = context.options[0] || 'consistent';
+
+  if (rawOption === 'consistent') {
+    return {
+      multiline: 'consistent',
+      singleline: 'consistent'
+    };
+  }
+
+  if (rawOption === 'never') {
+    return {
+      multiline: 'forbid',
+      singleline: 'forbid'
+    };
+  }
+
+  return {
+    multiline: rawOption.multiline || 'consistent',
+    singleline: rawOption.singleline || 'consistent'
+  };
+}
+
+module.exports = {
+  meta: {
+    type: 'layout',
+
+    docs: {
+      description: 'enforce consistent line breaks inside jsx curly',
+      category: 'Stylistic Issues',
+      recommended: false,
+      url: docsUrl('jsx-curly-newline')
+    },
+
+    fixable: 'whitespace',
+
+    schema: [
+      {
+        oneOf: [
+          {
+            enum: ['consistent', 'never']
+          },
+          {
+            type: 'object',
+            properties: {
+              singleline: {enum: ['consistent', 'require', 'forbid']},
+              multiline: {enum: ['consistent', 'require', 'forbid']}
+            },
+            additionalProperties: false
+          }
+        ]
+      }
+    ],
+
+
+    messages: {
+      expectedBefore: 'Expected newline before \'}\'.',
+      expectedAfter: 'Expected newline after \'{\'.',
+      unexpectedBefore: 'Unexpected newline before \'{\'.',
+      unexpectedAfter: 'Unexpected newline after \'}\'.'
+    }
+  },
+
+  create(context) {
+    const sourceCode = context.getSourceCode();
+    const option = getNormalizedOption(context);
+
+    // ----------------------------------------------------------------------
+    // Helpers
+    // ----------------------------------------------------------------------
+
+    /**
+     * Determines whether two adjacent tokens are on the same line.
+     * @param {Object} left - The left token object.
+     * @param {Object} right - The right token object.
+     * @returns {boolean} Whether or not the tokens are on the same line.
+     */
+    function isTokenOnSameLine(left, right) {
+      return left.loc.end.line === right.loc.start.line;
+    }
+
+    /**
+     * Determines whether there should be newlines inside curlys
+     * @param {ASTNode} expression The expression contained in the curlys
+     * @param {boolean} hasLeftNewline `true` if the left curly has a newline in the current code.
+     * @returns {boolean} `true` if there should be newlines inside the function curlys
+     */
+    function shouldHaveNewlines(expression, hasLeftNewline) {
+      const isMultiline = expression.loc.start.line !== expression.loc.end.line;
+
+      switch (isMultiline ? option.multiline : option.singleline) {
+        case 'forbid': return false;
+        case 'require': return true;
+        case 'consistent':
+        default: return hasLeftNewline;
+      }
+    }
+
+    /**
+     * Validates curlys
+     * @param {Object} curlys An object with keys `leftParen` for the left paren token, and `rightParen` for the right paren token
+     * @param {ASTNode} expression The expression inside the curly
+     * @returns {void}
+     */
+    function validateCurlys(curlys, expression) {
+      const leftCurly = curlys.leftCurly;
+      const rightCurly = curlys.rightCurly;
+      const tokenAfterLeftCurly = sourceCode.getTokenAfter(leftCurly);
+      const tokenBeforeRightCurly = sourceCode.getTokenBefore(rightCurly);
+      const hasLeftNewline = !isTokenOnSameLine(leftCurly, tokenAfterLeftCurly);
+      const hasRightNewline = !isTokenOnSameLine(tokenBeforeRightCurly, rightCurly);
+      const needsNewlines = shouldHaveNewlines(expression, hasLeftNewline);
+
+      if (hasLeftNewline && !needsNewlines) {
+        context.report({
+          node: leftCurly,
+          messageId: 'unexpectedAfter',
+          fix(fixer) {
+            return sourceCode
+              .getText()
+              .slice(leftCurly.range[1], tokenAfterLeftCurly.range[0])
+              .trim() ?
+              null : // If there is a comment between the { and the first element, don't do a fix.
+              fixer.removeRange([leftCurly.range[1], tokenAfterLeftCurly.range[0]]);
+          }
+        });
+      } else if (!hasLeftNewline && needsNewlines) {
+        context.report({
+          node: leftCurly,
+          messageId: 'expectedAfter',
+          fix: fixer => fixer.insertTextAfter(leftCurly, '\n')
+        });
+      }
+
+      if (hasRightNewline && !needsNewlines) {
+        context.report({
+          node: rightCurly,
+          messageId: 'unexpectedBefore',
+          fix(fixer) {
+            return sourceCode
+              .getText()
+              .slice(tokenBeforeRightCurly.range[1], rightCurly.range[0])
+              .trim() ?
+              null : // If there is a comment between the last element and the }, don't do a fix.
+              fixer.removeRange([
+                tokenBeforeRightCurly.range[1],
+                rightCurly.range[0]
+              ]);
+          }
+        });
+      } else if (!hasRightNewline && needsNewlines) {
+        context.report({
+          node: rightCurly,
+          messageId: 'expectedBefore',
+          fix: fixer => fixer.insertTextBefore(rightCurly, '\n')
+        });
+      }
+    }
+
+
+    // ----------------------------------------------------------------------
+    // Public
+    // ----------------------------------------------------------------------
+
+    return {
+      JSXExpressionContainer(node) {
+        const curlyTokens = {
+          leftCurly: sourceCode.getFirstToken(node),
+          rightCurly: sourceCode.getLastToken(node)
+        };
+        validateCurlys(curlyTokens, node.expression);
+      }
+    };
+  }
+};