fix(eslint-plugin): [prefer-string-starts-ends-with] Check negative i…

…ndices in the second position for slice (#2696)
typescript-eslint · Oct 25, 2020 · 66e9c6e · 66e9c6e
1 parent 343d20d
commit 66e9c6e
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diff --git a/packages/eslint-plugin/src/rules/prefer-string-starts-ends-with.ts b/packages/eslint-plugin/src/rules/prefer-string-starts-ends-with.ts
@@ -575,7 +575,8 @@ export default createRule({
         const isStartsWith =
           !isEndsWith &&
           callNode.arguments.length === 2 &&
-          isNumber(callNode.arguments[0], 0);
+          isNumber(callNode.arguments[0], 0) &&
+          !isNegativeIndexExpression(callNode.arguments[1], node.object);
         if (!isStartsWith && !isEndsWith) {
           return;
         }

diff --git a/packages/eslint-plugin/tests/rules/prefer-string-starts-ends-with.test.ts b/packages/eslint-plugin/tests/rules/prefer-string-starts-ends-with.test.ts
@@ -230,6 +230,16 @@ ruleTester.run('prefer-string-starts-ends-with', rule, {
         x.test(s)
       }
     `,
+    `
+      function f(s: string) {
+        s.slice(0, -4) === "car"
+      }
+    `,
+    `
+      function f(x: string, s: string) {
+        x.endsWith('foo') && x.slice(0, -4) === 'bar'
+      }
+    `,
   ]),
   invalid: addOptional([
     // String indexing.