getESLint.ts

import type { ESLint as ProjectESLint, Linter as ProjectLinter } from 'eslint';
import { existsSync } from 'node:fs';
import { resolve } from 'node:path';
import { cwd } from 'node:process';
import { pathToFileURL } from 'node:url';
import { notice } from '@actions/core';

export async function getESLint(eslintLibPath: string, configPath: string) {
  const absoluteDirectory = cwd();
  const eslintJsPath = resolve(absoluteDirectory, eslintLibPath);
  if (!existsSync(eslintJsPath)) {
    throw new Error(`ESLint JavaScript cannot be found at ${eslintJsPath}`);
  }
  notice(`Using ESLint from: ${eslintJsPath}`);
  // Use `new Function` to bypass ncc/webpack static analysis, which would
  // otherwise replace a dynamic `import()` with a stub that always throws.
  // eslint-disable-next-line @typescript-eslint/no-implied-eval
  const dynamicImport = new Function('url', 'return import(url)') as (
    url: string,
  ) => Promise<unknown>;
  const { ESLint, loadESLint } = (await dynamicImport(
    pathToFileURL(eslintJsPath).href,
  )) as {
    ESLint: typeof ProjectESLint;
    loadESLint: (() => Promise<typeof ProjectESLint>) | undefined;
  };
  notice(`ESLint version: ${ESLint.version}`);

  if (configPath) {
    const absoluteConfigPath = resolve(absoluteDirectory, configPath);
    notice(`Using ESLint config from: ${absoluteConfigPath}`);
    const eslint = new ESLint({ overrideConfigFile: absoluteConfigPath });
    return eslint;
  }

  if (loadESLint) {
    // ESLint 8.57.0 and later
    notice('Using ESLint with default configuration');
    const eslint = new (await loadESLint())();
    return eslint;
  }

  const eslintConfig = (await new ESLint().calculateConfigForFile(
    'package.json',
  )) as ProjectLinter.Config | undefined;
  if (!eslintConfig) {
    throw new Error(
      'Failed to find ESLint configuration. Please set the config-path input.',
    );
  }
  const eslint = new ESLint({ baseConfig: eslintConfig });
  return eslint;
}