CLI: support .json in eslint-plugin migration

code/lib/cli/package.json

@@ -55,6 +55,7 @@
     "commander": "^6.2.1",
     "cross-spawn": "^7.0.3",
     "degit": "^2.8.4",
+    "detect-indent": "^6.1.0",
     "envinfo": "^7.7.3",
     "execa": "^5.0.0",
     "express": "^4.17.1",

code/lib/cli/src/automigrate/fixes/eslint-plugin.ts

@@ -2,6 +2,8 @@ import chalk from 'chalk';
 import { dedent } from 'ts-dedent';
 import { ConfigFile, readConfig, writeConfig } from '@storybook/csf-tools';
 import { getStorybookInfo } from '@storybook/core-common';
+import { readFile, readJson, writeJson } from 'fs-extra';
+import detectIndent from 'detect-indent';
 
 import { findEslintFile, SUPPORTED_ESLINT_EXTENSIONS } from '../helpers/getEslintInfo';
 
@@ -79,26 +81,39 @@ export const eslintPlugin: Fix<EslintPluginRunOptions> = {
     if (!dryRun) packageManager.addDependencies({ installAsDevDependencies: true }, deps);
 
     if (!dryRun && unsupportedExtension) {
-      throw new Error(dedent`
-          ⚠️ The plugin was successfuly installed but failed to configure.
+      logger.info(dedent`
+          ⚠️ The plugin was successfully installed but failed to configure.
 
-          Found an .eslintrc config file with an unsupported automigration format: ${unsupportedExtension}.
-          Supported formats for automigration are: ${SUPPORTED_ESLINT_EXTENSIONS.join(', ')}.
+          Found an eslint config file with an unsupported automigration format: .eslintrc.${unsupportedExtension}.
+          The supported formats for this automigration are: ${SUPPORTED_ESLINT_EXTENSIONS.join(
+            ', '
+          )}.
 
           Please refer to https://github.com/storybookjs/eslint-plugin-storybook#usage to finish setting up the plugin manually.
       `);
+      return;
     }
 
-    const eslint = await readConfig(eslintFile);
-    logger.info(`✅ Configuring eslint rules in ${eslint.fileName}`);
-
+    logger.info(`✅ Adding Storybook plugin to ${eslintFile}`);
     if (!dryRun) {
-      logger.info(`✅ Adding Storybook to extends list`);
-      const extendsConfig = eslint.getFieldValue(['extends']) || [];
-      const existingConfigValue = Array.isArray(extendsConfig) ? extendsConfig : [extendsConfig];
-      eslint.setFieldValue(['extends'], [...existingConfigValue, 'plugin:storybook/recommended']);
-
-      await writeConfig(eslint);
+      if (eslintFile.endsWith('json')) {
+        const eslintConfig = (await readJson(eslintFile)) as { extends?: string[] };
+        const existingConfigValue = Array.isArray(eslintConfig.extends)
+          ? eslintConfig.extends
+          : [eslintConfig.extends];
+        eslintConfig.extends = [...(existingConfigValue || []), 'plugin:storybook/recommended'];
+
+        const eslintFileContents = await readFile(eslintFile, 'utf8');
+        const spaces = detectIndent(eslintFileContents).amount || 2;
+        await writeJson(eslintFile, eslintConfig, { spaces });
+      } else {
+        const eslint = await readConfig(eslintFile);
+        const extendsConfig = eslint.getFieldValue(['extends']) || [];
+        const existingConfigValue = Array.isArray(extendsConfig) ? extendsConfig : [extendsConfig];
+        eslint.setFieldValue(['extends'], [...existingConfigValue, 'plugin:storybook/recommended']);
+
+        await writeConfig(eslint);
+      }
     }
   },
 };

code/lib/cli/src/automigrate/helpers/getEslintInfo.ts

@@ -1,7 +1,7 @@
 import fse from 'fs-extra';
 
-export const SUPPORTED_ESLINT_EXTENSIONS = ['js', 'cjs'];
-const UNSUPPORTED_ESLINT_EXTENSIONS = ['yaml', 'yml', 'json'];
+export const SUPPORTED_ESLINT_EXTENSIONS = ['js', 'cjs', 'json'];
+const UNSUPPORTED_ESLINT_EXTENSIONS = ['yaml', 'yml'];
 
 export const findEslintFile = () => {
   const filePrefix = '.eslintrc';

code/yarn.lock

@@ -7318,6 +7318,7 @@ __metadata:
     commander: ^6.2.1
     cross-spawn: ^7.0.3
     degit: ^2.8.4
+    detect-indent: ^6.1.0
     envinfo: ^7.7.3
     execa: ^5.0.0
     express: ^4.17.1
@@ -16755,7 +16756,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"detect-indent@npm:^6.0.0":
+"detect-indent@npm:^6.0.0, detect-indent@npm:^6.1.0":
   version: 6.1.0
   resolution: "detect-indent@npm:6.1.0"
   checksum: dd83cdeda9af219cf77f5e9a0dc31d828c045337386cfb55ce04fad94ba872ee7957336834154f7647b89b899c3c7acc977c57a79b7c776b506240993f97acc7