[Fix] jsx-newline: prevent a crash when allowMultilines

Fixes #3633

Author: ljharb

CHANGELOG.md

@@ -11,7 +11,9 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 ### Fixed
 * [`jsx-no-leaked-render`]: preserve RHS parens for multiline jsx elements while fixing ([#3623][] @akulsr0)
 * [`jsx-key`]: detect conditional returns ([#3630][] @yialo)
+* [`jsx-newline`]: prevent a crash when `allowMultilines ([#3633][] @ljharb)
 
+[#3633]: https://github.com/jsx-eslint/eslint-plugin-react/issues/3633
 [#3630]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3630
 [#3623]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3623
 [#3615]: https://github.com/jsx-eslint/eslint-plugin-react/pull/3615

lib/rules/jsx-newline.js

@@ -20,7 +20,7 @@ const messages = {
 };
 
 function isMultilined(node) {
-  return node.loc.start.line !== node.loc.end.line;
+  return node && node.loc.start.line !== node.loc.end.line;
 }
 
 module.exports = {
@@ -103,7 +103,6 @@ module.exports = {
               const isWithoutNewLine = !/\n\s*\n/.test(firstAdjacentSibling.value);
 
               if (isBlockCommentInCurlyBraces(element)) return;
-
               if (
                 allowMultilines
                 && (

tests/lib/rules/jsx-newline.js

@@ -649,5 +649,76 @@ new RuleTester({ parserOptions }).run('jsx-newline', rule, {
       ],
       options: [{ prevent: true, allowMultilines: true }],
     },
+    {
+      code: `
+        const frag: DocumentFragment = (
+          <Fragment>
+            <sni-sequence-editor-tool
+              name="forward"
+              direction="forward"
+              type="control"
+              onClick={ () => this.onClickNavigate('forward') }
+            />
+            <sni-sequence-editor-tool
+              name="rotate"
+              direction="left"
+              type="control"
+              onClick={ () => this.onClickNavigate('left') }
+            />
+    
+            <sni-sequence-editor-tool
+              name="rotate"
+              direction="right"
+              type="control"
+              onClick={ (): void => this.onClickNavigate('right') }
+            />
+    
+            <div className="sni-sequence-editor-control-panel__delete" data-name="delete" onClick={ this.onDeleteCommand } />
+    
+            {
+              ...Array.from(this.children)
+            }
+          </Fragment>
+        )
+      `,
+      output: `
+        const frag: DocumentFragment = (
+          <Fragment>
+            <sni-sequence-editor-tool
+              name="forward"
+              direction="forward"
+              type="control"
+              onClick={ () => this.onClickNavigate('forward') }
+            />
+
+            <sni-sequence-editor-tool
+              name="rotate"
+              direction="left"
+              type="control"
+              onClick={ () => this.onClickNavigate('left') }
+            />
+${'    '}
+            <sni-sequence-editor-tool
+              name="rotate"
+              direction="right"
+              type="control"
+              onClick={ (): void => this.onClickNavigate('right') }
+            />
+    
+            <div className="sni-sequence-editor-control-panel__delete" data-name="delete" onClick={ this.onDeleteCommand } />
+    
+            {
+              ...Array.from(this.children)
+            }
+          </Fragment>
+        )
+      `,
+      features: ['types'],
+      options: [{ prevent: true, allowMultilines: true }],
+      errors: [
+        { messageId: 'allowMultilines', line: 10 },
+        { messageId: 'prevent', line: 26 },
+      ],
+    },
   ]),
 });