Fix: Add Storybook ESLint plugin to defineConfig from eslint/config

[Copilot]

Storybook init adds the eslint-plugin-storybook import but fails to register it in Next.js projects using defineConfig([...]) from eslint/config.

Changes

code/core/src/cli/eslintPlugin.ts

• Extended configureFlatConfig Case 3 to handle CallExpressions wrapping array arguments
• Added tracking for defineConfig imports specifically from "eslint/config"
• Validates the callee matches the imported defineConfig identifier before modifying
• Added type guards (t.isExpression) and null checks before unwrapping and modifying arrays

code/core/src/cli/eslintPlugin.test.ts

• Added test case validating Next.js defineConfig pattern from "eslint/config"
• Added test case ensuring defineConfig from other packages is not modified

Behavior

Before:

import storybook from "eslint-plugin-storybook";

const eslintConfig = defineConfig([
  ...nextVitals,
  ...nextTs,
]); // Plugin import added but not registered

After:

// Only modifies defineConfig from "eslint/config"
import { defineConfig } from "eslint/config";
import storybook from "eslint-plugin-storybook";

const eslintConfig = defineConfig([
  ...nextVitals,
  ...nextTs,
  ...storybook.configs["flat/recommended"]
]);

// defineConfig from other packages is left unchanged (import only added)
import { defineConfig } from "some-other-lib";
const config = defineConfig([...]); // Not modified

All existing ESLint config formats (direct arrays, tseslint.config(), legacy .eslintrc) remain unaffected.

• Fixes [Bug]: Storybook plugin not added to eslint.config during init in Next.js projects #32858

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Bug]: Storybook plugin not added to eslint.config during init in Next.js projects</issue_title>
<issue_description>### Describe the bug

When initializing Storybook in a Next.js project, the setup modifies the eslint.config file to include an import for the Storybook ESLint plugin, but does not actually register the plugin in the ESLint configuration array.

Current generated eslint.config:

// 👇 only the import is added, but the plugin isn't added to the config
import storybook from "eslint-plugin-storybook";

import { defineConfig, globalIgnores } from "eslint/config";
import nextVitals from "eslint-config-next/core-web-vitals";
import nextTs from "eslint-config-next/typescript";

const eslintConfig = defineConfig([
  ...nextVitals,
  ...nextTs,
  // Override default ignores of eslint-config-next.
  globalIgnores([
    ".next/**",
    "out/**",
    "build/**",
    "next-env.d.ts",
  ]),
]);

export default eslintConfig;

Expected behaviour
Storybook’s init process should both:

• Add the eslint-plugin-storybook import and
• Extend the ESLint configuration with the Storybook plugin, e.g.:

Reproduction steps

1. Create a new Next.js project (npx gitpick storybookjs/sandboxes/tree/next/nextjs-vite/default-ts/before-storybook)
2. Run npx storybook@latest init
3. Inspect the generated eslint.config.mjs (or eslint.config.mjs)

System

-

Additional context

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Bug]: Storybook plugin not added to eslint.config during init in Next.js projects #32858

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch copilot/fix-storybook-plugin-eslint-config

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[yannbf]

@copilot only if it's defineConfig from import { defineConfig } from "eslint/config"

[Copilot]

Fixed in 72ec435. Now specifically checks that defineConfig is imported from "eslint/config" before modifying the array. Added test to verify we don't modify defineConfig from other sources.