[Cypress runner] Set `HAS_ENTERPRISE_TOKEN` using Configuration API (#17006) (#17016)

* Set `HAS_ENTERPRISE_TOKEN` using Cypress Configuration and Plugins API

* Re-organize webpack preprocessor options

frontend/test/__runner__/run_cypress_tests.js

@@ -90,11 +90,6 @@ const init = async () => {
   // See: https://docs.cypress.io/guides/references/configuration#Command-Line
   const commandLineConfig = JSON.stringify(config);
 
-  // These env vars provide the token to the backend.
-  // If they're not present, we skip some tests that depend on a valid token.
-  const hasEnterpriseToken =
-    process.env["ENTERPRISE_TOKEN"] && process.env["MB_EDITION"] === "ee";
-
   const cypressProcess = spawn(
     "yarn",
     [
@@ -112,7 +107,6 @@ const init = async () => {
             "mochaFile=cypress/results/results-[hash].xml",
           ]
         : []),
-      ...(hasEnterpriseToken ? ["--env", "HAS_ENTERPRISE_TOKEN=true"] : []),
     ],
     { stdio: "inherit" },
   );

frontend/test/__support__/e2e/cypress-plugins.js

 // ***********************************************************
-// This example plugins/index.js can be used to load plugins
+// This file can be used to load plugins and to register events.
 //
 // You can change the location of this file or turn off loading
 // the plugins file with the 'pluginsFile' configuration option.
@@ -8,9 +8,24 @@
 // https://on.cypress.io/plugins-guide
 // ***********************************************************
 
+/**
+ * This env var provides the token to the backend.
+ * If it is not present, we skip some tests that depend on a valid token.
+ *
+ * @type {boolean}
+ */
+const hasEnterpriseToken =
+  process.env["ENTERPRISE_TOKEN"] && process.env["MB_EDITION"] === "ee";
+
 // This function is called when a project is opened or re-opened (e.g. due to
 // the project's config changing)
 const webpack = require("@cypress/webpack-preprocessor");
+const { resolve } = require("../../../../webpack.config.js");
+
+const webpackPluginOptions = {
+  webpackOptions: { resolve },
+  watchOptions: {},
+};
 
 module.exports = (on, config) => {
   // `on` is used to hook into various events Cypress emits
@@ -19,13 +34,8 @@ module.exports = (on, config) => {
   /********************************************************************
    **                          WEBPACK                               **
    ********************************************************************/
-  const { resolve } = require("../../../../webpack.config.js");
-  const options = {
-    webpackOptions: { resolve },
-    watchOptions: {},
-  };
 
-  on("file:preprocessor", webpack(options));
+  on("file:preprocessor", webpack(webpackPluginOptions));
 
   /********************************************************************
    **                         BROWSERS                               **
@@ -39,4 +49,12 @@ module.exports = (on, config) => {
       return launchOptions;
     }
   });
+
+  /********************************************************************
+   **                          CONFIG                                **
+   ********************************************************************/
+
+  config.env.HAS_ENTERPRISE_TOKEN = hasEnterpriseToken;
+
+  return config;
 };