typescript-eslint · JoshuaKGoldberg · Aug 19, 2024 · Mar 14, 2024 · Mar 27, 2024 · Apr 10, 2024
diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-template-expression.ts b/packages/eslint-plugin/src/rules/no-unnecessary-template-expression.ts
@@ -5,6 +5,7 @@ import * as ts from 'typescript';
 import {
   createRule,
   getConstrainedTypeAtLocation,
+  getMovedNodeCode,
   getParserServices,
   isTypeFlagSet,
   isUndefinedIdentifier,
@@ -106,21 +107,14 @@ export default createRule<[], MessageId>({
           context.report({
             node: node.expressions[0],
             messageId: 'noUnnecessaryTemplateExpression',
-            fix(fixer): TSESLint.RuleFix[] {
-              const [prevQuasi, nextQuasi] = node.quasis;
-
-              // Remove the quasis and backticks.
-              return [
-                fixer.removeRange([
-                  prevQuasi.range[1] - 3,
-                  node.expressions[0].range[0],
-                ]),
-
-                fixer.removeRange([
-                  node.expressions[0].range[1],
-                  nextQuasi.range[0] + 2,
-                ]),
-              ];
+            fix(fixer): TSESLint.RuleFix | null {
+              const wrappingCode = getMovedNodeCode({
+                sourceCode: context.sourceCode,
+                nodeToMove: node.expressions[0],
+                destinationNode: node,
+              });
+
+              return fixer.replaceText(node, wrappingCode);
             },
           });
 

diff --git a/packages/eslint-plugin/src/util/getWrappingFixer.ts b/packages/eslint-plugin/src/util/getWrappingFixer.ts
@@ -74,6 +74,33 @@
     return fixer.replaceText(node, code);
   };
 }
+/**
+ * If the node to be moved and the destination node require parentheses, include parentheses in the node to be moved.
+ * @param sourceCode Source code of current file
+ * @param nodeToMove Nodes that need to be moved
+ * @param destinationNode Final destination node with nodeToMove
+ * @returns If parentheses are required, code for the nodeToMove node is returned with parentheses at both ends of the code.
+ */
+export function getMovedNodeCode(params: {
+  sourceCode: Readonly<TSESLint.SourceCode>;
+  nodeToMove: TSESTree.Node;
+  destinationNode: TSESTree.Node;
+}): string {
+  const { sourceCode, nodeToMove: existingNode, destinationNode } = params;
+  const code = sourceCode.getText(existingNode);
+  if (isStrongPrecedenceNode(existingNode)) {
+    // Moved node never needs parens
+    return code;
+  }
+
+  if (!isWeakPrecedenceParent(destinationNode)) {
+    // Destination would never needs parens, regardless what node moves there
+    return code;
+  }
+
+  // Parens may be necessary
+  return `(${code})`;
+}
 
 /*
DA09
*
  * Check if a node will always have the same precedence if it's parent changes.
@@ -98,8 +125,10 @@
  * Check if a node's parent could have different precedence if the node changes.
  */
 function isWeakPrecedenceParent(node: TSESTree.Node): boolean {
-  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-  const parent = node.parent!;
+  const parent = node.parent;
+  if (!parent) {
+    return false;
+  }
 
   if (
     parent.type === AST_NODE_TYPES.UpdateExpression ||

diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-template-expression.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-template-expression.test.ts
@@ -1127,5 +1127,14 @@ declare const nested: string, interpolation: string;
         },
       ],
     },
+    {
+      code: "true ? `${'test' || ''}`.trim() : undefined;",
+      output: "true ? ('test' || '').trim() : undefined;",
+      errors: [
+        {
+          messageId: 'noUnnecessaryTemplateExpression',
+        },
+      ],
+    },
   ],
 });