Overwrite CoreDiagnostics framework with framework passed in. (#2560)

Author: ryanwilson

ZipBuilder/Sources/ZipBuilder/ZipBuilder.swift

@@ -209,12 +209,33 @@ struct ZipBuilder {
     // Create an array that has the Pod name as the key and the array of frameworks needed - this
     // will be used as the source of truth for all frameworks to be copied in each product's
     // directory.
-    let frameworks = filesToInstall.mapValues { $0.frameworks }
+    var frameworks = filesToInstall.mapValues { $0.frameworks }
     for (framework, paths) in frameworks {
       print("Frameworks for pod: \(framework) were compiled at \(paths)")
     }
 
-    // TODO: Overwrite the `CoreDiagnostics.framework` in the generated framework.
+    // Overwrite the `FirebaseCoreDiagnostics.framework` in the `FirebaseAnalytics` folder. This is
+    // needed because it was compiled specifically with the `ZIP` bit enabled, helping us understand
+    // the distribution of CocoaPods vs Zip file integrations.
+    if subspecsToInstall.contains(.analytics) {
+      let overriddenAnalytics: [URL] = {
+        guard let currentFrameworks = frameworks["FirebaseAnalytics"] else {
+          fatalError("Attempted to replace CoreDiagnostics framework but the FirebaseAnalytics " +
+            "directory does not exist. Existing directories: \(frameworks.keys)")
+        }
+
+        // Filter out any CoreDiagnostics directories from the frameworks to install. There should
+        // only be one.
+        let withoutDiagnostics: [URL] = currentFrameworks.filter { url in
+          url.lastPathComponent != "FirebaseCoreDiagnostics.framework"
+        }
+
+        return withoutDiagnostics + [paths.coreDiagnosticsDir]
+      }()
+
+      // Set the newly required framework paths for Analytics.
+      frameworks["FirebaseAnalytics"] = overriddenAnalytics
+    }
 
     // TODO: The folder heirarchy should change in Firebase 6.
     // Time to assemble the folder structure of the Zip file. In order to get the frameworks