pass additional Electron launch args from env variable (#5891)

* pass additional Electron launch args from env variable

* iterate over keys

* add environment test

* hmm, print error

* do not rethrow error

* do not swallow error in development, stub disable hw acc method

* use app.command.appendArgument

packages/server/lib/environment.coffee

@@ -17,6 +17,26 @@ Error.stackTraceLimit = Infinity
 ## would not be available
 pkg = require("@packages/root")
 
+## instead of setting NODE_ENV we will
+## use our own separate CYPRESS_ENV so
+## as not to conflict with CI providers
+
+## use env from package first
+## or development as default
+env = process.env["CYPRESS_ENV"] or= pkg.env ? "development"
+
+config = {
+  ## uses cancellation for automation timeouts
+  cancellation: true
+}
+
+if env is "development"
+  ## enable long stack traces in dev
+  config.longStackTraces = true
+
+Promise.config(config)
+
+# note: we print error in development mode only
 try
   ## i wish we didn't have to do this but we have to append
   ## these command line switches immediately
@@ -39,23 +59,12 @@ try
   if os.platform() is "linux"
     app.disableHardwareAcceleration()
 
-## instead of setting NODE_ENV we will
-## use our own separate CYPRESS_ENV so
-## as not to conflict with CI providers
+  if process.env.ELECTRON_EXTRA_LAUNCH_ARGS
+    electronLaunchArguments = process.env.ELECTRON_EXTRA_LAUNCH_ARGS.split(' ')
+    electronLaunchArguments.forEach app.commandLine.appendArgument
 
-## use env from package first
-## or development as default
-env = process.env["CYPRESS_ENV"] or= pkg.env ? "development"
-
-config = {
-  ## uses cancellation for automation timeouts
-  cancellation: true
-}
-
-if env is "dev"
-  ## enable long stack traces in dev
-  config.longStackTraces = true
-
-Promise.config(config)
+catch e
+  if env is "development"
+    console.error(e.message)
 
 module.exports = env

packages/server/test/support/helpers/electron_stub.coffee

@@ -15,7 +15,9 @@ module.exports = {
     exit: ->
     commandLine: {
       appendSwitch: ->
-    }
+      appendArgument: ->
+    },
+    disableHardwareAcceleration: ->
   }
   systemPreferences: {
     isDarkMode: ->

packages/server/test/unit/environment_spec.coffee

@@ -3,6 +3,8 @@ require("../spec_helper")
 Promise = require("bluebird")
 pkg = require("@packages/root")
 fs = require("#{root}lib/util/fs")
+mockedEnv = require('mocked-env')
+app = require("electron").app
 
 setEnv = (env) =>
   process.env["CYPRESS_ENV"] = env
@@ -31,6 +33,24 @@ describe "lib/environment", ->
   after ->
     process.env["CYPRESS_ENV"] = env
 
+  context "parses ELECTRON_EXTRA_LAUNCH_ARGS", ->
+    restore = null
+
+    beforeEach ->
+      restore = mockedEnv({
+        ELECTRON_EXTRA_LAUNCH_ARGS: "--foo --bar=baz --quux=true"
+      })
+
+    it "sets launch args", ->
+      sinon.stub(app.commandLine, "appendArgument")
+      require("#{root}lib/environment")
+      expect(app.commandLine.appendArgument).to.have.been.calledWith("--foo")
+      expect(app.commandLine.appendArgument).to.have.been.calledWith("--bar=baz")
+      expect(app.commandLine.appendArgument).to.have.been.calledWith("--quux=true")
+
+    afterEach ->
+      restore()
+
   context "#existing process.env.CYPRESS_ENV", ->
     it "is production", ->
       setEnv("production")