docker-setup-qemu-action/src/main.ts

import * as context from './context';
import * as core from '@actions/core';
import * as actionsToolkit from '@docker/actions-toolkit';
import {Docker} from '@docker/actions-toolkit/lib/docker';
import {Exec} from '@docker/actions-toolkit/lib/exec';

interface Platforms {
  supported: string[];
  available: string[];
}

actionsToolkit.run(
  // main
  async () => {
    const input: context.Inputs = context.getInputs();

    await core.group(`Docker info`, async () => {
      await Docker.printVersion();
      await Docker.printInfo();
    });

    await core.group(`Pulling binfmt Docker image`, async () => {
      await Exec.exec('docker', ['pull', input.image]);
    });

    await core.group(`Image info`, async () => {
      await Exec.exec('docker', ['image', 'inspect', input.image]);
    });

    await core.group(`Installing QEMU static binaries`, async () => {
      await Exec.exec('docker', ['run', '--rm', '--privileged', input.image, '--install', input.platforms]);
    });

    await core.group(`Extracting available platforms`, async () => {
      await Exec.getExecOutput('docker', ['run', '--rm', '--privileged', input.image], {
        ignoreReturnCode: true,
        silent: true
      }).then(res => {
        if (res.stderr.length > 0 && res.exitCode != 0) {
          throw new Error(res.stderr.trim());
        }
        const platforms: Platforms = JSON.parse(res.stdout.trim());
        core.info(`${platforms.supported.join(',')}`);
        core.setOutput('platforms', platforms.supported.join(','));
      });
    });
  }
);