feat: detect old version of plugin

Author: Skn0tt

demo/package-lock.json

@@ -0,0 +1,21 @@
+/**
+ * Ensures there's no old version of the same plugin installed.
+ * @param {string} root
+ * @param {function} failBuild
+ * @returns {void}
+ */
+const ensureNoCompetingPlugin = function (root, failBuild) {
+  let packagePath
+  try {
+    // eslint-disable-next-line n/no-missing-require
+    packagePath = require.resolve('@netlify/plugin-angular-universal', { paths: [root] })
+  } catch {}
+
+  if (packagePath) {
+    return failBuild(
+      "Detected @netlify/plugin-angular-universal, the old version of Netlify's Angular runtime. Please uninstall it, the new version was set up automatically for you.",
+    )
+  }
+}
+
+module.exports = ensureNoCompetingPlugin

src/helpers/ensureNoCompetingPlugin.js

@@ -1,3 +1,4 @@
+const ensureNoCompetingPlugin = require('./helpers/ensureNoCompetingPlugin')
 const getAngularJson = require('./helpers/getAngularJson')
 const getAngularRoot = require('./helpers/getAngularRoot')
 const setUpEdgeFunction = require('./helpers/setUpEdgeFunction')
@@ -6,14 +7,16 @@ const validateAngularVersion = require('./helpers/validateAngularVersion')
 let isValidAngularProject = true
 
 module.exports = {
-  async onPreBuild({ netlifyConfig }) {
+  async onPreBuild({ netlifyConfig, utils }) {
     const siteRoot = getAngularRoot({ netlifyConfig })
     isValidAngularProject = await validateAngularVersion(siteRoot)
     if (!isValidAngularProject) {
       console.warn('Skipping build plugin.')
       return
     }
 
+    ensureNoCompetingPlugin(siteRoot, utils.build.failBuild)
+
     netlifyConfig.build.command ??= 'npm run build'
   },
   async onBuild({ utils, netlifyConfig, constants }) {