feat: download Deno CLI from Deno repository (#17)

* feat: download Deno CLI from Deno repository

* chore: add comment

* feat: get latest Deno version

* refactor: check that latest version satisfies range

src/bridge.ts

@@ -94,14 +94,17 @@ class DenoBridge {
 
     await fs.mkdir(this.cacheDirectory, { recursive: true })
 
-    const binaryPath = await download(this.cacheDirectory)
-    const version = await DenoBridge.getBinaryVersion(binaryPath)
+    const binaryPath = await download(this.cacheDirectory, this.versionRange)
+    const downloadedVersion = await DenoBridge.getBinaryVersion(binaryPath)
 
-    if (version === undefined) {
+    // We should never get here, because it means that `DENO_VERSION_RANGE` is
+    // a malformed semver range. If this does happen, let's throw an error so
+    // that the tests catch it.
+    if (downloadedVersion === undefined) {
       throw new Error('Could not read downloaded binary')
     }
 
-    await this.writeVersionFile(version)
+    await this.writeVersionFile(downloadedVersion)
 
     if (this.onAfterDownload) {
       this.onAfterDownload()

src/downloader.ts

@@ -3,12 +3,13 @@ import path from 'path'
 
 import fetch from 'node-fetch'
 import StreamZip from 'node-stream-zip'
+import semver from 'semver'
 
 import { getBinaryExtension, getPlatformTarget } from './platform.js'
 
-const download = async (targetDirectory: string) => {
+const download = async (targetDirectory: string, versionRange: string) => {
   const zipPath = path.join(targetDirectory, 'deno-cli-latest.zip')
-  const data = await downloadLatestRelease()
+  const data = await downloadVersion(versionRange)
   const binaryName = `deno${getBinaryExtension()}`
   const binaryPath = path.join(targetDirectory, binaryName)
   const file = fs.createWriteStream(zipPath)
@@ -25,8 +26,9 @@ const download = async (targetDirectory: string) => {
   return binaryPath
 }
 
-const downloadLatestRelease = async () => {
-  const url = getReleaseURL()
+const downloadVersion = async (versionRange: string) => {
+  const version = await getLatestVersionForRange(versionRange)
+  const url = getReleaseURL(version)
   const res = await fetch(url)
 
   if (res.body === null) {
@@ -45,10 +47,48 @@ const extractBinaryFromZip = async (zipPath: string, binaryPath: string, binaryN
   await fs.promises.chmod(binaryPath, '755')
 }
 
-const getReleaseURL = () => {
+const getLatestVersion = async () => {
+  try {
+    const response = await fetch('https://dl.deno.land/release-latest.txt')
+    const data = await response.text()
+
+    // We want to extract <VERSION> from the format `v<VERSION>`.
+    const version = data.match(/^v?(\d+\.\d+\.\d+)/)
+
+    if (version === null) {
+      return
+    }
+
+    return version[1]
+  } catch {
+    // This is a no-op. If we failed to retrieve the latest version, let's
+    // return `undefined` and let the code upstream handle it.
+  }
+}
+
+const getLatestVersionForRange = async (range: string) => {
+  const minimumVersion = semver.minVersion(range)?.version
+
+  // We should never get here, because it means that `DENO_VERSION_RANGE` is
+  // a malformed semver range. If this does happen, let's throw an error so
+  // that the tests catch it.
+  if (minimumVersion === undefined) {
+    throw new Error('Incorrect version range specified by Edge Bundler')
+  }
+
+  const latestVersion = await getLatestVersion()
+
+  if (latestVersion === undefined || !semver.satisfies(latestVersion, range)) {
+    return minimumVersion
+  }
+
+  return latestVersion
+}
+
+const getReleaseURL = (version: string) => {
   const target = getPlatformTarget()
 
-  return `https://github.com/denoland/deno/releases/latest/download/deno-${target}.zip`
+  return `https://dl.deno.land/release/v${version}/deno-${target}.zip`
 }
 
 export { download }

test/main.ts

@@ -9,7 +9,6 @@ import { DenoBridge } from '../src/bridge.js'
 test('Downloads the Deno CLI on demand and caches it for subsequent calls', async (t) => {
   // TODO: Mock HTTP call to Deno source, so that we don't need to download
   // the actual package as part of the test.
-  // eslint-disable-next-line no-magic-numbers
   t.timeout(20_000)
 
   const tmpDir = await tmp.dir()