[now update] Render the proper tag and improve yarn detection logic (#2595)

* [now update] Render the proper tag and improve `yarn` detection logic

Before this the suggested command would always have you install the
stable version of `now`.

With this change the `@canary` tag will be suggested if the version of
`now` is from the canary release channel.

Also updates the `isYarn` detection logic to not consider the cwd, and
instead check the installed version of now's `package.json` for clues.

* Move `getUpdateCommand` to util

* Add a unit test

* Use integration test instead

src/commands/update.ts

@@ -1,12 +1,11 @@
 import chalk from 'chalk';
-import {  join } from 'path';
-import { pathExists } from 'fs-extra';
 
 import logo from '../util/output/logo';
 import handleError from '../util/handle-error';
 import getArgs from '../util/get-args';
 import { NowContext } from '../types';
 import createOutput from '../util/output';
+import getUpdateCommand from '../util/get-update-command';
 
 const help = () => {
   console.log(`
@@ -32,14 +31,6 @@ const help = () => {
   `);
 };
 
-export async function getUpgradeCommand() {
-  const isYarn = await pathExists(join(process.cwd(), 'yarn.lock'));
-
-  return isYarn
-  ? 'Please run `yarn global upgrade now` to update Now CLI.'
-  : 'Please run `npm install -g now@latest` to update Now CLI.'
-}
-
 export default async function main(ctx: NowContext): Promise<number> {
   let argv;
 
@@ -64,8 +55,6 @@ export default async function main(ctx: NowContext): Promise<number> {
 
   const debugEnabled = argv['--debug'];
   const output = createOutput({ debug: debugEnabled });
-  const { log } = output;
-
-  log(await getUpgradeCommand());
+  output.log(await getUpdateCommand());
   return 0;
 }

src/index.js

@@ -36,7 +36,7 @@ import * as ERRORS from './util/errors-ts';
 import { NowError } from './util/now-error';
 import { SENTRY_DSN } from './util/constants.ts';
 import { metrics, shouldCollectMetrics } from './util/metrics.ts';
-import { getUpgradeCommand } from './commands/update';
+import getUpdateCommand from './util/get-update-command';
 
 const NOW_DIR = getNowDir();
 const NOW_CONFIG_PATH = configFiles.getConfigFilePath();
@@ -145,7 +145,7 @@ const main = async argv_ => {
       )
     );
     console.log(
-      info(await getUpgradeCommand())
+      info(await getUpdateCommand())
     );
     console.log(
       info(

src/util/get-update-command.ts

@@ -0,0 +1,31 @@
+import { Stats } from 'fs';
+import { dirname, join, resolve } from 'path';
+import { readJSON, lstat, readlink } from 'fs-extra';
+
+import cmd from './output/cmd';
+import { version } from '../../package.json';
+
+// `npm` tacks a bunch of extra properties on the `package.json` file,
+// so check for one of them to determine yarn vs. npm.
+async function isYarn(): Promise<boolean> {
+  let s: Stats;
+  let binPath = process.argv[1];
+  while (true) {
+    s = await lstat(binPath);
+    if (s.isSymbolicLink()) {
+      binPath = resolve(dirname(binPath), await readlink(binPath));
+    } else {
+      break;
+    }
+  }
+  const pkgPath = join(dirname(binPath), '..', 'package.json');
+  const pkg = await readJSON(pkgPath);
+  return !('_id' in pkg);
+}
+
+export default async function getUpdateCommand(): Promise<string> {
+  const tag = version.includes('canary') ? 'canary' : 'latest';
+  return (await isYarn())
+    ? `Please run ${cmd(`yarn global add now@${tag}`)} to update Now CLI.`
+    : `Please run ${cmd(`npm install -g now@${tag}`)} to update Now CLI.`;
+}

test/integration.js

@@ -1449,6 +1449,11 @@ test('fail `now dev` dev script without now.json', async t => {
   );
 });
 
+test('detect update command', async t => {
+  const { code, stderr } = await execute(['update']);
+  t.regex(stderr, /yarn global add now@/gm, `Received: "${stderr}"`);
+});
+
 test.after.always(async () => {
   // Make sure the token gets revoked
   await execa(binaryPath, ['logout', ...defaultArgs]);