fix(eslint-plugin): [no-unnecessary-condition] handle union array and…

… tuple type (#8592)
typescript-eslint · Mar 6, 2024 · 25e6518 · 25e6518
1 parent ef0e5cc
commit 25e6518
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Showing 2 changed files with 21 additions and 2 deletions.
diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts b/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
@@ -175,11 +175,16 @@ export default createRule<Options, MessageId>({
 
  function nodeIsArrayType(node: TSESTree.Expression): boolean {
  const nodeType = getConstrainedTypeAtLocation(services, node);
- return checker.isArrayType(nodeType);
+ return tsutils
+ .unionTypeParts(nodeType)
+ .some(part => checker.isArrayType(part));
  }
+
  function nodeIsTupleType(node: TSESTree.Expression): boolean {
  const nodeType = getConstrainedTypeAtLocation(services, node);
- return checker.isTupleType(nodeType);
+ return tsutils
+ .unionTypeParts(nodeType)
+ .some(part => checker.isTupleType(part));
  }
 
  function isArrayIndexExpression(node: TSESTree.Expression): boolean {

diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -365,6 +365,20 @@ if (arr?.[42]) {
 }
  `,
  `
+type ItemA = { bar: string; baz: string };
+type ItemB = { bar: string; qux: string };
+declare const foo: ItemA[] | ItemB[];
+foo[0]?.bar;
+ `,
+ `
+type TupleA = [string, number];
+type TupleB = [string, number];
+
+declare const foo: TupleA | TupleB;
+declare const index: number;
+foo[index]?.toString();
+ `,
+ `
 declare const returnsArr: undefined | (() => string[]);
 if (returnsArr?.()[42]) {
 }