fix(linter): ensure all spreads are removed from rules before parsing (#23292)

(cherry picked from commit 613fdb0)

Author: JamesHenry

packages/eslint/src/generators/utils/flat-config/ast-utils.ts

@@ -8,6 +8,12 @@ import { Linter } from 'eslint';
 import * as ts from 'typescript';
 import { mapFilePath } from './path-utils';
 
+/**
+ * Supports direct identifiers, and those nested within an object (of arbitrary depth)
+ * E.g. `...foo` and `...foo.bar.baz.qux` etc
+ */
+const SPREAD_ELEMENTS_REGEXP = /\s*\.\.\.[a-zA-Z0-9_]+(\.[a-zA-Z0-9_]+)*,?\n?/g;
+
 /**
  * Remove all overrides from the config file
  */
@@ -87,11 +93,13 @@ export function hasOverride(
       let objSource;
       if (ts.isObjectLiteralExpression(node)) {
         objSource = node.getFullText();
+        // strip any spread elements
+        objSource = objSource.replace(SPREAD_ELEMENTS_REGEXP, '');
       } else {
         const fullNodeText =
           node['expression'].arguments[0].body.expression.getFullText();
         // strip any spread elements
-        objSource = fullNodeText.replace(/\s*\.\.\.[a-zA-Z0-9_]+,?\n?/, '');
+        objSource = fullNodeText.replace(SPREAD_ELEMENTS_REGEXP, '');
       }
       const data = parseJson(
         objSource
@@ -107,8 +115,6 @@ export function hasOverride(
   return false;
 }
 
-const STRIP_SPREAD_ELEMENTS = /\s*\.\.\.[a-zA-Z0-9_]+,?\n?/g;
-
 function parseTextToJson(text: string): any {
   return parseJson(
     text
@@ -153,7 +159,7 @@ export function replaceOverride(
         const fullNodeText =
           node['expression'].arguments[0].body.expression.getFullText();
         // strip any spread elements
-        objSource = fullNodeText.replace(STRIP_SPREAD_ELEMENTS, '');
+        objSource = fullNodeText.replace(SPREAD_ELEMENTS_REGEXP, '');
         start =
           node['expression'].arguments[0].body.expression.properties.pos +
           (fullNodeText.length - objSource.length);
@@ -415,7 +421,7 @@ export function removePlugin(
             const plugins = parseTextToJson(
               pluginsElem.initializer
                 .getText()
-                .replace(STRIP_SPREAD_ELEMENTS, '')
+                .replace(SPREAD_ELEMENTS_REGEXP, '')
             );
 
             if (plugins.length > 1) {