fix: Wait for child process to be ready (#19792)

Co-authored-by: Zach Bloomquist <[email protected]>
Co-authored-by: Zach Bloomquist <[email protected]>

Author: jhnns

packages/server/lib/plugins/child/run_plugins.js

@@ -212,6 +212,8 @@ const runPlugins = (ipc, pluginsFile, projectRoot) => {
   ipc.on('execute', (event, ids, args) => {
     execute(ipc, event, ids, args)
   })
+
+  ipc.send('ready')
 }
 
 // for testing purposes

packages/server/lib/plugins/index.js

@@ -139,7 +139,9 @@ const init = (config, options) => {
     Object.keys(config).sort().forEach((key) => orderedConfig[key] = config[key])
     config = orderedConfig
 
-    ipc.send('load', config)
+    ipc.on('ready', () => {
+      ipc.send('load', config)
+    })
 
     ipc.on('loaded', (newCfg, registrations) => {
       _.omit(config, 'projectRoot', 'configFile')

packages/server/test/unit/plugins/index_spec.js

@@ -115,15 +115,19 @@ describe('lib/plugins/index', () => {
       })
     })
 
-    it('sends \'load\' event with config via ipc', () => {
-      ipc.on.withArgs('loaded').yields([])
+    it('sends \'load\' event with config via ipc once it receives \'ready\'', () => {
       const config = { pluginsFile: 'cypress-plugin', testingType: 'e2e' }
 
-      return plugins.init(config, getOptions({ testingType: 'e2e' })).then(() => {
-        expect(ipc.send).to.be.calledWith('load', {
-          ...config,
-          ...configExtras,
-        })
+      plugins.init(config, getOptions({ testingType: 'e2e' }))
+
+      expect(ipc.send).to.not.be.called
+
+      // simulate async ready event
+      ipc.on.withArgs('ready').firstCall.callback()
+
+      expect(ipc.send).to.be.calledWith('load', {
+        ...config,
+        ...configExtras,
       })
     })