refactor(yarn-install): convert to async/await and support proxy (#1057)

lib/tasks/yarn-install.js

@@ -7,48 +7,56 @@ const cliPackage = require('../../package.json');
 const packageInfo = require('package-json');
 const {prerelease, satisfies} = require('semver');
 
-const errors = require('../errors');
+const {CliError, SystemError} = require('../errors');
 const yarn = require('../utils/yarn');
 const getProxyAgent = require('../utils/get-proxy-agent');
 
 const subTasks = {
-    dist: ctx => packageInfo('ghost', {
-        version: ctx.version,
-        agent: getProxyAgent()
-    }).then(({dist, engines = {}}) => {
+    async dist(ctx) {
+        const {dist, engines = {}} = await packageInfo('ghost', {
+            version: ctx.version,
+            agent: getProxyAgent()
+        });
+
         const skipNodeVersionCheck = (process.env.GHOST_NODE_VERSION_CHECK === 'false');
         const isPrerelease = Boolean(prerelease(cliPackage.version));
 
         if (!skipNodeVersionCheck && engines.node && !satisfies(process.versions.node, engines.node)) {
-            return Promise.reject(new errors.SystemError(`Ghost v${ctx.version} is not compatible with the current Node version.`));
+            throw new SystemError(`Ghost v${ctx.version} is not compatible with the current Node version.`);
         }
 
         if (engines.cli && !isPrerelease && !satisfies(cliPackage.version, engines.cli)) {
-            return Promise.reject(new errors.SystemError(`Ghost v${ctx.version} is not compatible with this version of the CLI.`));
+            throw new SystemError(`Ghost v${ctx.version} is not compatible with this version of the CLI.`);
         }
 
-        ctx.shasum = dist.shasum;
-        ctx.tarball = dist.tarball;
-    }),
-    download: ctx => download(ctx.tarball).then((data) => {
+        ctx.shasum = dist.shasum; // eslint-disable-line require-atomic-updates
+        ctx.tarball = dist.tarball; // eslint-disable-line require-atomic-updates
+    },
+
+    async download(ctx) {
+        const data = await download(ctx.tarball, {agent: getProxyAgent()});
+
         if (shasum(data) !== ctx.shasum) {
             // shasums don't match - this is not good
-            return Promise.reject(new errors.CliError('Ghost download integrity compromised.' +
-                    'Cancelling install because of potential security issues'));
+            throw new CliError('Ghost download integrity compromised.' +
+                    'Cancelling install because of potential security issues');
         }
 
         fs.ensureDirSync(ctx.installPath);
-        return decompress(data, ctx.installPath, {
-            map: (file) => {
-                file.path = file.path.replace('package/', '');
-                return file;
-            }
-        }).catch((error) => {
+
+        try {
+            await decompress(data, ctx.installPath, {
+                map: (file) => {
+                    file.path = file.path.replace('package/', '');
+                    return file;
+                }
+            });
+        } catch (error) {
             // Clean up the install folder since the decompress failed
             fs.removeSync(ctx.installPath);
-            return Promise.reject(error);
-        });
-    })
+            throw error;
+        }
+    }
 };
 
 module.exports = function yarnInstall(ui, zipFile) {