♻️ Core server improvements (#781)

* ✨ Utilize inheritance to create more robust custom server

* ✅ Add and improve core tests

* ✅ Adjust test helpers for better compat

* 🐛 Fix support for Node < 15.7.0

package.json

@@ -53,6 +53,7 @@
     "memfs": "^3.4.0",
     "nock": "^13.1.1",
     "nyc": "^15.1.0",
+    "quibble": "^0.6.8",
     "rollup": "^2.53.2",
     "tsd": "^0.19.0"
   }

packages/core/package.json

@@ -34,8 +34,11 @@
     "@percy/config": "1.0.0-beta.75",
     "@percy/dom": "1.0.0-beta.75",
     "@percy/logger": "1.0.0-beta.75",
+    "content-disposition": "^0.5.4",
     "cross-spawn": "^7.0.3",
     "extract-zip": "^2.0.1",
+    "mime-types": "^2.1.34",
+    "path-to-regexp": "^6.2.0",
     "rimraf": "^3.0.2",
     "ws": "^8.0.0"
   }

packages/core/src/api.js

@@ -0,0 +1,68 @@
+import fs from 'fs';
+import logger from '@percy/logger';
+import Server from './server';
+import pkg from '../package.json';
+
+export function createPercyServer(percy, port) {
+  return new Server({ port })
+  // facilitate logger websocket connections
+    .websocket(ws => logger.connect(ws))
+  // general middleware
+    .route((req, res, next) => {
+      // treat all request bodies as json
+      if (req.body) try { req.body = JSON.parse(req.body); } catch {}
+
+      // add version header
+      res.setHeader('Access-Control-Expose-Headers', '*, X-Percy-Core-Version');
+      res.setHeader('X-Percy-Core-Version', pkg.version);
+
+      // return json errors
+      return next().catch(e => res.json(e.status ?? 500, {
+        error: e.message,
+        success: false
+      }));
+    })
+  // healthcheck returns basic information
+    .route('get', '/percy/healthcheck', (req, res) => res.json(200, {
+      loglevel: percy.loglevel(),
+      config: percy.config,
+      build: percy.build,
+      success: true
+    }))
+  // get or set config options
+    .route(['get', 'post'], '/percy/config', async (req, res) => res.json(200, {
+      config: req.body ? await percy.setConfig(req.body) : percy.config,
+      success: true
+    }))
+  // responds once idle (may take a long time)
+    .route('get', '/percy/idle', async (req, res) => res.json(200, {
+      success: await percy.idle().then(() => true)
+    }))
+  // convenient @percy/dom bundle
+    .route('get', '/percy/dom.js', (req, res) => {
+      return res.file(200, require.resolve('@percy/dom'));
+    })
+  // legacy agent wrapper for @percy/dom
+    .route('get', '/percy-agent.js', async (req, res) => {
+      logger('core:server').deprecated([
+        'It looks like you’re using @percy/cli with an older SDK.',
+        'Please upgrade to the latest version to fix this warning.',
+        'See these docs for more info: https:docs.percy.io/docs/migrating-to-percy-cli'
+      ].join(' '));
+
+      let content = await fs.promises.readFile(require.resolve('@percy/dom'), 'utf-8');
+      let wrapper = '(window.PercyAgent = class { snapshot(n, o) { return PercyDOM.serialize(o); } });';
+      return res.send(200, 'applicaton/javascript', content.concat(wrapper));
+    })
+  // post one or more snapshots
+    .route('post', '/percy/snapshot', async (req, res) => {
+      let snapshot = percy.snapshot(req.body);
+      if (!req.url.searchParams.has('async')) await snapshot;
+      return res.json(200, { success: true });
+    })
+  // stops percy at the end of the current event loop
+    .route('/percy/stop', (req, res) => {
+      setImmediate(() => percy.stop());
+      return res.json(200, { success: true });
+    });
+}

packages/core/src/percy.js

@@ -4,7 +4,7 @@ import { merge } from '@percy/config/dist/utils';
 import logger from '@percy/logger';
 import Queue from './queue';
 import Browser from './browser';
-import createPercyServer from './server';
+import { createPercyServer } from './api';
 
 import {
   getSnapshotConfig,
@@ -85,8 +85,7 @@ export class Percy {
     });
 
     if (server) {
-      this.server = createPercyServer(this);
-      this.port = port;
+      this.server = createPercyServer(this, port);
     }
   }
 
@@ -97,7 +96,7 @@ export class Percy {
 
   // Snapshot server API address
   address() {
-    return `http://localhost:${this.port}`;
+    return this.server?.address();
   }
 
   // Set client & environment info, and override loaded config options
@@ -185,7 +184,7 @@ export class Percy {
       }
 
       // start the server after everything else is ready
-      yield this.server?.listen(this.port);
+      yield this.server?.listen();
 
       // mark instance as started
       this.log.info('Percy has started!');