From 1e8667082a937843b5109e747e431d6cf20b6736 Mon Sep 17 00:00:00 2001
From: Kirk Waiblinger <kirk.waiblinger@gmail.com>
Date: Tue, 6 Feb 2024 08:55:27 -0700
Subject: [PATCH 1/2] fix #8386: Stop throwing type errors when converting
 symbols to numbers

---
 .../eslint-plugin/src/rules/prefer-find.ts    | 29 ++++++++++++-------
 .../tests/rules/prefer-find.test.ts           | 18 ++++++++++++
 2 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/prefer-find.ts b/packages/eslint-plugin/src/rules/prefer-find.ts
index babee93bab8..f1440dcd826 100644
--- a/packages/eslint-plugin/src/rules/prefer-find.ts
+++ b/packages/eslint-plugin/src/rules/prefer-find.ts
@@ -125,7 +125,7 @@ export default createRule({
       return isAtLeastOneArrayishComponent;
     }
 
-    function getObjectIfArrayAtExpression(
+    function getObjectIfArrayAtZeroExpression(
       node: TSESTree.CallExpression,
     ): TSESTree.Expression | undefined {
       // .at() should take exactly one argument.
@@ -133,14 +133,14 @@ export default createRule({
         return undefined;
       }
 
-      const atArgument = getStaticValue(node.arguments[0], globalScope);
-      if (atArgument != null && isTreatedAsZeroByArrayAt(atArgument.value)) {
-        const callee = node.callee;
-        if (
-          callee.type === AST_NODE_TYPES.MemberExpression &&
-          !callee.optional &&
-          isStaticMemberAccessOfValue(callee, 'at', globalScope)
-        ) {
+      const callee = node.callee;
+      if (
+        callee.type === AST_NODE_TYPES.MemberExpression &&
+        !callee.optional &&
+        isStaticMemberAccessOfValue(callee, 'at', globalScope)
+      ) {
+        const atArgument = getStaticValue(node.arguments[0], globalScope);
+        if (atArgument != null && isTreatedAsZeroByArrayAt(atArgument.value)) {
           return callee.object;
         }
       }
@@ -153,7 +153,14 @@ export default createRule({
      * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at#parameters
      */
     function isTreatedAsZeroByArrayAt(value: unknown): boolean {
-      const asNumber = Number(value);
+      let asNumber: number;
+
+      try {
+        asNumber = Number(value);
+      } catch (e) {
+        // This will happen if trying to convert a symbol.
+        return false;
+      }
 
       if (isNaN(asNumber)) {
         return true;
@@ -215,7 +222,7 @@ export default createRule({
     return {
       // This query will be used to find things like `filteredResults.at(0)`.
       CallExpression(node): void {
-        const object = getObjectIfArrayAtExpression(node);
+        const object = getObjectIfArrayAtZeroExpression(node);
         if (object) {
           const filterExpression = parseIfArrayFilterExpression(object);
           if (filterExpression) {
diff --git a/packages/eslint-plugin/tests/rules/prefer-find.test.ts b/packages/eslint-plugin/tests/rules/prefer-find.test.ts
index 6b303ea9aed..59f6d9a07be 100644
--- a/packages/eslint-plugin/tests/rules/prefer-find.test.ts
+++ b/packages/eslint-plugin/tests/rules/prefer-find.test.ts
@@ -56,6 +56,24 @@ ruleTester.run('prefer-find', rule, {
     "['Just', 'a', 'find'].find(x => x.length > 4);",
     'undefined.filter(x => x)[0];',
     'null?.filter(x => x)[0];',
+    // Should not throw. See https://github.com/typescript-eslint/typescript-eslint/issues/8386
+    `
+      declare function foo(param: any): any;
+      foo(Symbol.for('foo'));
+    `,
+    // Specifically need to test Symbol.for(), not just Symbol(), since only
+    // Symbol.for() creates a static value that the rule inspects.
+    `
+      declare const arr: string[];
+      const s = Symbol.for("Don't throw!");
+      arr.filter(item => item === 'aha').at(s);
+    `,
+    `
+      [1, 2, 3].filter(x => x)[Symbol('0')];
+    `,
+    `
+      [1, 2, 3].filter(x => x)[Symbol.for('0')];
+    `,
   ],
 
   invalid: [

From a8d2c210242cddac1a7f674d6e763a518640c921 Mon Sep 17 00:00:00 2001
From: Kirk Waiblinger <kirk.waiblinger@gmail.com>
Date: Tue, 6 Feb 2024 10:22:51 -0700
Subject: [PATCH 2/2] Address PR feedback

---
 packages/eslint-plugin/src/rules/prefer-find.ts       | 11 +++++------
 .../eslint-plugin/tests/rules/prefer-find.test.ts     |  8 ++------
 2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/prefer-find.ts b/packages/eslint-plugin/src/rules/prefer-find.ts
index f1440dcd826..154d27d1a86 100644
--- a/packages/eslint-plugin/src/rules/prefer-find.ts
+++ b/packages/eslint-plugin/src/rules/prefer-find.ts
@@ -153,15 +153,14 @@ export default createRule({
      * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at#parameters
      */
     function isTreatedAsZeroByArrayAt(value: unknown): boolean {
-      let asNumber: number;
-
-      try {
-        asNumber = Number(value);
-      } catch (e) {
-        // This will happen if trying to convert a symbol.
+      // This would cause the number constructor coercion to throw. Other static
+      // values are safe.
+      if (typeof value === 'symbol') {
         return false;
       }
 
+      const asNumber = Number(value);
+
       if (isNaN(asNumber)) {
         return true;
       }
diff --git a/packages/eslint-plugin/tests/rules/prefer-find.test.ts b/packages/eslint-plugin/tests/rules/prefer-find.test.ts
index 59f6d9a07be..dddb56f14d3 100644
--- a/packages/eslint-plugin/tests/rules/prefer-find.test.ts
+++ b/packages/eslint-plugin/tests/rules/prefer-find.test.ts
@@ -68,12 +68,8 @@ ruleTester.run('prefer-find', rule, {
       const s = Symbol.for("Don't throw!");
       arr.filter(item => item === 'aha').at(s);
     `,
-    `
-      [1, 2, 3].filter(x => x)[Symbol('0')];
-    `,
-    `
-      [1, 2, 3].filter(x => x)[Symbol.for('0')];
-    `,
+    "[1, 2, 3].filter(x => x)[Symbol('0')];",
+    "[1, 2, 3].filter(x => x)[Symbol.for('0')];",
   ],
 
   invalid: [