From 56f78882c6d20bdd0a0ee3ee14d26d71dadd330c Mon Sep 17 00:00:00 2001
From: James Garbutt <43081j@users.noreply.github.com>
Date: Thu, 17 Sep 2026 14:14:07 +0100
Subject: [PATCH] fix(prefer-array-from-map): don't flag mappers with >2 params

If a mapper has more than 2 parameters, it can't be represented in
`Array.from` since those mappers only receive two arguments.
---
 src/rules/prefer-array-from-map.test.ts |  9 ++++++++-
 src/rules/prefer-array-from-map.ts      | 19 ++++++++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/rules/prefer-array-from-map.test.ts b/src/rules/prefer-array-from-map.test.ts
index 825cab5..8164e6e 100644
--- a/src/rules/prefer-array-from-map.test.ts
+++ b/src/rules/prefer-array-from-map.test.ts
@@ -33,7 +33,14 @@ ruleTester.run('prefer-array-from-map', preferArrayFromMap, {
     'const result = [arr].map(x => x * 2)',
 
     // Empty array
-    'const result = [].map(x => x * 2)'
+    'const result = [].map(x => x * 2)',
+
+    // Mapper can access the third `array` argument, which Array.from's
+    // mapper is never given
+    'const result = [...arr].map((x, i, all) => all[i - 1])',
+    'const result = [...arr].map(function(x, i, all) { return all[i - 1] })',
+    'const result = [...arr].map((...args) => args[2])',
+    'const result = [...arr].map((x, ...rest) => rest[1])'
   ],
 
   invalid: [
diff --git a/src/rules/prefer-array-from-map.ts b/src/rules/prefer-array-from-map.ts
index c556d21..375a30c 100644
--- a/src/rules/prefer-array-from-map.ts
+++ b/src/rules/prefer-array-from-map.ts
@@ -54,12 +54,29 @@ export const preferArrayFromMap: Rule.RuleModule = {
           return;
         }
 
+        const mapper = node.arguments[0]!;
+
+        // Array.from's mapper is called with (element, index) only, so a
+        // callback which can access the third `array` argument can't be
+        // converted
+        if (
+          mapper.type === 'FunctionExpression' ||
+          mapper.type === 'ArrowFunctionExpression'
+        ) {
+          if (
+            mapper.params.length > 2 ||
+            mapper.params.some((param) => param.type === 'RestElement')
+          ) {
+            return;
+          }
+        }
+
         const spreadElement = arrayExpr.elements[0];
         const iterableText = formatArguments(
           [spreadElement.argument],
           sourceCode
         );
-        const mapperText = formatArguments([node.arguments[0]!], sourceCode);
+        const mapperText = formatArguments([mapper], sourceCode);
 
         context.report({
           node,