setup-node/src/installer.ts

import * as assert from 'assert';
import * as core from '@actions/core';
import * as hc from '@actions/http-client';
import * as io from '@actions/io';
import * as tc from '@actions/tool-cache';
import * as os from 'os';
import * as path from 'path';
import * as semver from 'semver';

let osPlat: string = os.platform();
let osArch: string = translateArchToDistUrl(os.arch());

//
// Node versions interface
// see https://nodejs.org/dist/index.json
//
interface INodeVersion {
  version: string;
  files: string[];
}

export async function getNode(versionSpec: string) {
  // check cache
  let toolPath: string;
  toolPath = tc.find('node', versionSpec);

  // If not found in cache, download
  if (!toolPath) {
    let version: string;
    const c = semver.clean(versionSpec) || '';
    // If explicit version
    if (semver.valid(c) != null) {
      // version to download
      version = versionSpec;
    } else {
      // query nodejs.org for a matching version
      version = await queryLatestMatch(versionSpec);
      if (!version) {
        throw new Error(
          `Unable to find Node version '${versionSpec}' for platform ${osPlat} and architecture ${osArch}.`
        );
      }

      // check cache
      toolPath = tc.find('node', version);
    }

    if (!toolPath) {
      // download, extract, cache
      toolPath = await acquireNode(version);
    }
  }

  //
  // a tool installer initimately knows details about the layout of that tool
  // for example, node binary is in the bin folder after the extract on Mac/Linux.
  // layouts could change by version, by platform etc... but that's the tool installers job
  //
  if (osPlat != 'win32') {
    toolPath = path.join(toolPath, 'bin');
  }

  //
  // prepend the tools path. instructs the agent to prepend for future tasks
  core.addPath(toolPath);
}

async function queryLatestMatch(versionSpec: string): Promise<string> {
  // node offers a json list of versions
  let dataFileName: string;
  switch (osPlat) {
    case 'linux':
      dataFileName = `linux-${osArch}`;
      break;
    case 'darwin':
      dataFileName = `osx-${osArch}-tar`;
      break;
    case 'win32':
      dataFileName = `win-${osArch}-exe`;
      break;
    default:
      throw new Error(`Unexpected OS '${osPlat}'`);
  }

  let versions: string[] = [];
  let dataUrl = 'https://nodejs.org/dist/index.json';
  let httpClient = new hc.HttpClient('setup-node', [], {
    allowRetries: true,
    maxRetries: 3
  });
  let response = await httpClient.getJson<INodeVersion[]>(dataUrl);
  let nodeVersions = response.result || [];
  nodeVersions.forEach((nodeVersion: INodeVersion) => {
    // ensure this version supports your os and platform
    if (nodeVersion.files.indexOf(dataFileName) >= 0) {
      versions.push(nodeVersion.version);
    }
  });

  // get the latest version that matches the version spec
  let version: string = evaluateVersions(versions, versionSpec);
  return version;
}

// TODO - should we just export this from @actions/tool-cache? Lifted directly from there
function evaluateVersions(versions: string[], versionSpec: string): string {
  let version = '';
  core.debug(`evaluating ${versions.length} versions`);
  versions = versions.sort((a, b) => {
    if (semver.gt(a, b)) {
      return 1;
    }
    return -1;
  });
  for (let i = versions.length - 1; i >= 0; i--) {
    const potential: string = versions[i];
    const satisfied: boolean = semver.satisfies(potential, versionSpec);
    if (satisfied) {
      version = potential;
      break;
    }
  }

  if (version) {
    core.debug(`matched: ${version}`);
  } else {
    core.debug('match not found');
  }

  return version;
}

async function acquireNode(version: string): Promise<string> {
  //
  // Download - a tool installer intimately knows how to get the tool (and construct urls)
  //
  version = semver.clean(version) || '';
  let fileName: string =
    osPlat == 'win32'
      ? `node-v${version}-win-${osArch}`
      : `node-v${version}-${osPlat}-${osArch}`;
  let urlFileName: string =
    osPlat == 'win32' ? `${fileName}.7z` : `${fileName}.tar.gz`;
  let downloadUrl = `https://nodejs.org/dist/v${version}/${urlFileName}`;

  let downloadPath: string;

  try {
    downloadPath = await tc.downloadTool(downloadUrl);
  } catch (err) {
    if (err instanceof tc.HTTPError && err.httpStatusCode == 404) {
      return await acquireNodeFromFallbackLocation(version);
    }

    throw err;
  }

  //
  // Extract
  //
  let extPath: string;
  if (osPlat == 'win32') {
    let _7zPath = path.join(__dirname, '..', 'externals', '7zr.exe');
    extPath = await tc.extract7z(downloadPath, undefined, _7zPath);
  } else {
    extPath = await tc.extractTar(downloadPath);
  }

  //
  // Install into the local tool cache - node extracts with a root folder that matches the fileName downloaded
  //
  let toolRoot = path.join(extPath, fileName);
  return await tc.cacheDir(toolRoot, 'node', version);
}

// For non LTS versions of Node, the files we need (for Windows) are sometimes located
// in a different folder than they normally are for other versions.
// Normally the format is similar to: https://nodejs.org/dist/v5.10.1/node-v5.10.1-win-x64.7z
// In this case, there will be two files located at:
//      /dist/v5.10.1/win-x64/node.exe
//      /dist/v5.10.1/win-x64/node.lib
// If this is not the structure, there may also be two files located at:
//      /dist/v0.12.18/node.exe
//      /dist/v0.12.18/node.lib
// This method attempts to download and cache the resources from these alternative locations.
// Note also that the files are normally zipped but in this case they are just an exe
// and lib file in a folder, not zipped.
async function acquireNodeFromFallbackLocation(
  version: string
): Promise<string> {
  // Create temporary folder to download in to
  const tempDownloadFolder: string =
    'temp_' + Math.floor(Math.random() * 2000000000);
  const tempDirectory = process.env['RUNNER_TEMP'] || '';
  assert.ok(tempDirectory, 'Expected RUNNER_TEMP to be defined');
  const tempDir: string = path.join(tempDirectory, tempDownloadFolder);
  await io.mkdirP(tempDir);
  let exeUrl: string;
  let libUrl: string;
  try {
    exeUrl = `https://nodejs.org/dist/v${version}/win-${osArch}/node.exe`;
    libUrl = `https://nodejs.org/dist/v${version}/win-${osArch}/node.lib`;

    const exePath = await tc.downloadTool(exeUrl);
    await io.cp(exePath, path.join(tempDir, 'node.exe'));
    const libPath = await tc.downloadTool(libUrl);
    await io.cp(libPath, path.join(tempDir, 'node.lib'));
  } catch (err) {
    if (err instanceof tc.HTTPError && err.httpStatusCode == 404) {
      exeUrl = `https://nodejs.org/dist/v${version}/node.exe`;
      libUrl = `https://nodejs.org/dist/v${version}/node.lib`;

      const exePath = await tc.downloadTool(exeUrl);
      await io.cp(exePath, path.join(tempDir, 'node.exe'));
      const libPath = await tc.downloadTool(libUrl);
      await io.cp(libPath, path.join(tempDir, 'node.lib'));
    } else {
      throw err;
    }
  }
  return await tc.cacheDir(tempDir, 'node', version);
}

// os.arch does not always match the relative download url, e.g.
// os.arch == 'arm' != node-v12.13.1-linux-armv7l.tar.gz
// All other currently supported architectures match, e.g.:
//   os.arch = arm64 => https://nodejs.org/dist/v{VERSION}/node-v{VERSION}-{OS}-arm64.tar.gz
//   os.arch = x64 => https://nodejs.org/dist/v{VERSION}/node-v{VERSION}-{OS}-x64.tar.gz
function translateArchToDistUrl(arch: string): string {
  switch (arch) {
    case 'arm':
      return 'armv7l';
    default:
      return arch;
  }
}