ESLint custom rule to enforce consistent indentation in i18n blocks in .vue files

vue-i18n-indentation.ts

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import type { Rule } from 'eslint'

const rule: Rule.RuleModule = {
  meta: {
    docs: {
      category: 'Best Practices',
      description: 'Enforce consistent indentation in i18n blocks',
      recommended: true,
    },
    fixable: 'whitespace',
    messages: {
      indentError: 'Invalid indentation for i18n content. Expected {{expected}} spaces.',
      invalidJson: 'Invalid JSON in i18n block: {{error}}',
    },
    schema: [],
    type: 'problem',
  },

  create(context) {
    if (!context.filename.endsWith('.vue')) {
      return {}
    }

    return {
      Program() {
        const source = context.sourceCode.getText()
        const i18nMatch = source.match(/(<i18n\s+lang=["']json["']>)([\s\S]*?)(<\/i18n>)/i)

        if (i18nMatch) {
          const startOffset = i18nMatch.index! + i18nMatch[1].length
          const i18nContent = i18nMatch[2]

          try {
            const parsed = JSON.parse(i18nContent.trim())
            const totalSpaces = 2

            // Format the content with proper indentation
            const formattedContent = `\n${JSON.stringify(parsed, null, totalSpaces)}\n`

            // Compare the trimmed versions to check for actual content differences
            if (formattedContent.trim() !== i18nContent.trim()) {
              context.report({
                data: { expected: String(totalSpaces) },
                fix(fixer) {
                  return fixer.replaceTextRange(
                    [startOffset, startOffset + i18nContent.length],
                    formattedContent,
                  )
                },
                loc: {
                  end: context.sourceCode.getLocFromIndex(startOffset + i18nContent.length),
                  start: context.sourceCode.getLocFromIndex(startOffset),
                },
                messageId: 'indentError',
              })
            }
          }
          catch (error: any) {
            context.report({
              data: { error: error.message },
              loc: {
                end: context.sourceCode.getLocFromIndex(startOffset + i18nContent.length),
                start: context.sourceCode.getLocFromIndex(startOffset),
              },
              messageId: 'invalidJson',
            })
          }
        }
      },
    }
  },
}

export default rule