Do not warn if .flat() has more than one parameter or if the one parameter is not 1 (#317)

Author: MrHen

rules/prefer-flat-map.js

@@ -98,6 +98,14 @@ const create = context => ({
 			return;
 		}
 
+		if (node.arguments.length > 1) {
+			return;
+		}
+
+		if (node.arguments.length === 1 && node.arguments[0].type === 'Literal' && node.arguments[0].value !== 1) {
+			return;
+		}
+
 		const parent = node.callee.object;
 
 		if (!isMethodNamed(parent, 'map')) {

test/prefer-flat-map.js

@@ -26,7 +26,9 @@ ruleTester.run('prefer-flat-map', rule, {
 		outdent`
 			let bar = [1,2,3].map(i => [i]);
 			bar = bar.flat();
-		`
+		`,
+		'const bar = [[1],[2],[3]].map(i => [i]).flat(2)',
+		'const bar = [[1],[2],[3]].map(i => [i]).flat(1, null)'
 	],
 	invalid: [
 		{
@@ -157,6 +159,11 @@ ruleTester.run('prefer-flat-map', rule, {
 			output: 'let bar = [1,2,3] . flatMap( x => y )  // 🤪',
 			errors: [error]
 		},
+		{
+			code: 'const bar = [1,2,3].map(i => [i]).flat(1);',
+			output: 'const bar = [1,2,3].flatMap(i => [i]);',
+			errors: [error]
+		},
 		{
 			code: outdent`
 				const foo = bars