[IDEA] Enforce clean dependency refresh for Gradle Dependencies (elastic#136490)

We enforce a full rewrite of module dependencies. We have seen problems with idea
classpaths when major dependency updates have been made (e.g. lucene updates). This
should avoid keeping stale dependencies on the idea classpath causing trouble for
our engineers.

Author: breskeby

build-tools-internal/src/main/groovy/elasticsearch.ide.gradle

@@ -21,6 +21,17 @@ import java.nio.file.StandardCopyOption
 allprojects {
   apply plugin: 'idea'
 
+  // We got reports of invalid idea classpaths when major classpath changes (e.g. lucene update)
+  // has been merged and developers switching back and forth. This should enforce idea
+  // to not try to be smart.
+  // This enforces A "complete rewrite" causing all existing content to be discarded,
+  // thereby losing any changes made directly in the IDE but that should be fine for us.
+  idea.module.iml {
+    beforeMerged { module ->
+      module.dependencies.clear()
+    }
+  }
+
   tasks.named('idea').configure {
     doFirst { throw new GradleException("Use of the 'idea' task has been deprecated. For details on importing into IntelliJ see CONTRIBUTING.md.") }
   }