eslint.config.js

import cspell from '@cspell/eslint-plugin';
import eslint from '@eslint/js';
import cypress from 'eslint-plugin-cypress';
import jsdoc from 'eslint-plugin-jsdoc';
import json from 'eslint-plugin-json';
import lodash from 'eslint-plugin-lodash';
import markdown from 'eslint-plugin-markdown';
import noOnlyTests from 'eslint-plugin-no-only-tests';
import tsdoc from 'eslint-plugin-tsdoc';
import unicorn from 'eslint-plugin-unicorn';
import globals from 'globals';
import tseslint from 'typescript-eslint';

export default tseslint.config(
  eslint.configs.recommended,
  ...tseslint.configs.recommendedTypeChecked,
  ...tseslint.configs.stylisticTypeChecked,
  {
    ignores: [
      '**/*.d.ts',
      '**/dist/',
      '**/node_modules/',
      '.git/',
      '.claude/',
      '**/generated/',
      '**/coverage/',
      'packages/mermaid/src/config.type.ts',
      'packages/mermaid/src/docs/.vitepress/components.d.ts',
    ],
  },
  {
    languageOptions: {
      parserOptions: {
        project: [
          './tsconfig.eslint.json',
          './packages/*/tsconfig.json',
          './packages/*/tsconfig.eslint.json',
          './packages/mermaid/src/docs/tsconfig.json',
        ],
        tsconfigRootDir: import.meta.dirname,
      },
      globals: {
        ...globals.browser,
        ...globals.node,
        ...globals.es2020,
        ...globals.jest,
        cy: 'readonly',
        Cypress: 'readonly',
      },
    },
  },
  {
    plugins: {
      json,
      '@cspell': cspell,
      'no-only-tests': noOnlyTests,
      lodash,
      unicorn,
      cypress,
      markdown,
      tsdoc,
      jsdoc,
    },
    rules: {
      curly: 'error',
      'no-console': 'error',
      'no-prototype-builtins': 'off',
      'no-unused-vars': 'off',
      'cypress/no-async-tests': 'off',
      '@typescript-eslint/consistent-type-imports': 'error',
      '@typescript-eslint/no-explicit-any': 'warn',
      '@typescript-eslint/no-floating-promises': 'error',
      '@typescript-eslint/no-misused-promises': 'error',
      '@typescript-eslint/no-unused-vars': [
        'error',
        {
          args: 'after-used',
          argsIgnorePattern: '^_',
          caughtErrors: 'all',
          caughtErrorsIgnorePattern: '^_',
          destructuredArrayIgnorePattern: '^_',
          varsIgnorePattern: '^_',
          ignoreRestSiblings: true,
        },
      ],
      '@typescript-eslint/consistent-type-definitions': 'error',
      '@typescript-eslint/ban-ts-comment': [
        'error',
        {
          'ts-expect-error': 'allow-with-description',
          'ts-ignore': 'allow-with-description',
          'ts-nocheck': 'allow-with-description',
          'ts-check': 'allow-with-description',
          minimumDescriptionLength: 10,
        },
      ],
      '@typescript-eslint/naming-convention': [
        'error',
        {
          selector: 'typeLike',
          format: ['PascalCase'],
          custom: {
            regex: '^I[A-Z]',
            match: false,
          },
        },
      ],
      // START: These rules should be turned on once the codebase is cleaned up
      '@typescript-eslint/no-unsafe-argument': 'off',
      '@typescript-eslint/no-unsafe-assignment': 'off',
      '@typescript-eslint/no-unsafe-call': 'off',
      '@typescript-eslint/no-unsafe-member-access': 'off',
      '@typescript-eslint/no-unsafe-return': 'off',
      '@typescript-eslint/only-throw-error': 'warn',
      '@typescript-eslint/prefer-nullish-coalescing': 'warn',
      '@typescript-eslint/prefer-promise-reject-errors': 'warn',
      // END
      'json/*': ['error', 'allowComments'],
      '@cspell/spellchecker': [
        'error',
        {
          checkIdentifiers: true,
          checkStrings: true,
          checkStringTemplates: true,
        },
      ],
      'no-empty': [
        'error',
        {
          allowEmptyCatch: true,
        },
      ],
      'no-only-tests/no-only-tests': 'error',
      'lodash/import-scope': ['error', 'method'],
      'unicorn/better-regex': 'error',
      'unicorn/no-abusive-eslint-disable': 'error',
      'unicorn/no-array-push-push': 'error',
      'unicorn/no-for-loop': 'error',
      'unicorn/no-instanceof-array': 'error',
      'unicorn/no-typeof-undefined': 'error',
      'unicorn/no-unnecessary-await': 'error',
      'unicorn/no-useless-promise-resolve-reject': 'error',
      'unicorn/prefer-array-find': 'error',
      'unicorn/prefer-array-flat-map': 'error',
      'unicorn/prefer-array-index-of': 'error',
      'unicorn/prefer-array-some': 'error',
      'unicorn/prefer-default-parameters': 'error',
      'unicorn/prefer-includes': 'error',
      'unicorn/prefer-negative-index': 'error',
      'unicorn/prefer-object-from-entries': 'error',
      'unicorn/prefer-string-starts-ends-with': 'error',
      'unicorn/prefer-string-trim-start-end': 'error',
      'unicorn/string-content': 'error',
      'unicorn/prefer-spread': 'error',
      'unicorn/no-lonely-if': 'error',
    },
  },
  {
    files: ['cypress/**', 'demos/**', '.esbuild/**'],
    rules: {
      'no-console': 'off',
      // Dev tooling files often use lower-friction style (single-line ifs,
      // type aliases over interfaces). Loosen the strict project rules here.
      curly: 'off',
      'prefer-const': 'warn',
      '@typescript-eslint/consistent-type-definitions': 'off',
      '@typescript-eslint/no-unnecessary-type-assertion': 'off',
      'unicorn/no-lonely-if': 'off',
    },
  },
  {
    // TODO(swimlanes): the swimlanes / ddlt / layout-utils layout-algorithm code
    // was authored against a sibling repo's lint baseline and still trips some
    // project-strict style rules (mostly in its own spec files). These are
    // loosened here as tracked tech debt — the intent is to bring this code to
    // the project lint baseline and remove this override entirely.
    // The shared production helpers (createGraph.ts, cloneLayoutDataForMeasure.ts,
    // lineJump.ts) were brought to baseline and removed from this override; the
    // lineJump *specs* stay here since, like the other layout specs, they use
    // console for debug output.
    files: [
      'packages/mermaid/src/rendering-util/layout-algorithms/swimlanes/**',
      'packages/mermaid/src/rendering-util/layout-algorithms/ddlt/**',
      'packages/mermaid/src/rendering-util/layout-algorithms/layout-utils/**',
      'packages/mermaid/src/rendering-util/rendering-elements/lineJump*.spec.ts',
    ],
    rules: {
      'no-console': 'off',
      curly: 'off',
      'unicorn/no-lonely-if': 'off',
      '@typescript-eslint/require-await': 'off',
    },
  },
  {
    files: ['**/*.{js,jsx,mjs,cjs}'],
    rules: {
      'jsdoc/check-indentation': 'off',
      'jsdoc/check-alignment': 'off',
      'jsdoc/check-line-alignment': 'off',
      'jsdoc/multiline-blocks': 'off',
      'jsdoc/newline-after-description': 'off',
      'jsdoc/tag-lines': 'off',
      'jsdoc/require-param-description': 'off',
      'jsdoc/require-param-type': 'off',
      'jsdoc/require-returns': 'off',
      'jsdoc/require-returns-description': 'off',
    },
  },
  {
    files: ['**/*.{ts,tsx}'],
    rules: {
      'no-restricted-syntax': [
        'error',
        {
          selector: 'TSEnumDeclaration',
          message:
            'Prefer using TypeScript union types over TypeScript enum, since TypeScript enums have a bunch of issues, see https://dev.to/dvddpl/whats-the-problem-with-typescript-enums-2okj',
        },
      ],
      'tsdoc/syntax': 'error',
    },
  },
  {
    files: ['**/*.spec.{ts,js}', 'cypress/**', 'demos/**', '**/docs/**'],
    rules: {
      'jsdoc/require-jsdoc': 'off',
      '@typescript-eslint/no-unused-vars': 'off',
    },
  },
  {
    files: ['**/*.spec.{ts,js}', 'tests/**', 'cypress/**/*.js'],
    rules: {
      '@cspell/spellchecker': [
        'error',
        {
          checkIdentifiers: false,
          checkStrings: false,
          checkStringTemplates: false,
        },
      ],
    },
  },
  {
    files: ['*.html', '*.md', '**/*.md/*'],
    rules: {
      'no-var': 'error',
      'no-undef': 'off',
      '@typescript-eslint/no-unused-vars': 'off',
      '@typescript-eslint/no-floating-promises': 'off',
      '@typescript-eslint/no-misused-promises': 'off',
    },
    processor: 'markdown/markdown',
  }
);