PR fixes

Author: joehan

skills/firestore-basics/references/android_sdk_usage.md

@@ -7,6 +7,7 @@ This guide uses **Kotlin** and **KTX extensions**, which correspond to the moder
 ```kotlin
 // In your Activity or Application class
 import com.google.firebase.firestore.ktx.firestore
+import com.google.firebase.firestore.SetOptions
 import com.google.firebase.ktx.Firebase
 
 val db = Firebase.firestore
@@ -73,7 +74,7 @@ db.runTransaction { transaction ->
     val snapshot = transaction.get(sfDocRef)
 
     // Note: You can also use FieldValue.increment() for simple counters
-    val newPopulation = snapshot.getDouble("population")!! + 1
+    val newPopulation = (snapshot.getDouble("population") ?: 0.0) + 1
     transaction.update(sfDocRef, "population", newPopulation)
 
     // Success
@@ -151,6 +152,6 @@ db.collection("cities")
 
 ```kotlin
 db.collection("cities")
-    .orderBy("name", Query.Direction.KEY_ASCENDING)
+    .orderBy("name", Query.Direction.ASCENDING)
     .limit(3)
 ```

skills/firestore-basics/references/ios_sdk_usage.md

@@ -48,7 +48,7 @@ db.collection("cities").document("LA").setData(city) { err in
 db.collection("cities").document("LA").setData([ "population": 3900000 ], merge: true)
 ```
 
-### Add a Document with Auto-ID (`addDocument`)
+###// Add a Document with Auto-ID (`addDocument`)
 
 ```swift
 var ref: DocumentReference? = nil
@@ -59,7 +59,7 @@ ref = db.collection("cities").addDocument(data: [
     if let err = err {
         print("Error adding document: \(err)")
     } else {
-        print("Document added with ID: \(ref!.documentID)")
+        print("Document added with ID: \(ref?.documentID ?? "unknown")")
     }
 }
 ```
@@ -141,7 +141,7 @@ db.collection("cities").getDocuments() { (querySnapshot, err) in
     if let err = err {
         print("Error getting documents: \(err)")
     } else {
-        for document in querySnapshot!.documents {
+        for document in querySnapshot?.documents ?? [] {
             print("\(document.documentID) => \(document.data())")
         }
     }

skills/firestore-basics/references/provisioning.md

@@ -79,16 +79,14 @@ Create a file named `firestore.indexes.json` with an empty configuration to star
 
 
 ## Deploy rules and indexes
-To deploy all rules and indexes
-```
+```bash
+# To deploy all rules and indexes
 firebase deploy --only firestore
-```
-To deploy just rules
-```
+
+# To deploy just rules
 firebase deploy --only firestore:rules
-```
-To deploy just indexes
-```
+
+# To deploy just indexes
 firebase deploy --only firestore:indexes
 ```
 

skills/firestore-basics/references/security_rules.md

@@ -65,14 +65,12 @@ match /users/{userId} {
 ### Allow only verified emails
 Requires users to verify ownership of the email address before using it to read or write data
 ```
-  match /databases/{database}/documents {
-    // Allow access based on email domain
-    match /some_collection/{document} {
-     allow read: if request.auth != null
-                 && request.auth.email_verified
-                 && request.auth.email.endsWith('@example.com')
-    }
-  }
+// Allow access based on email domain
+match /some_collection/{document} {
+  allow read: if request.auth != null
+              && request.auth.email_verified
+              && request.auth.email.endsWith('@example.com');
+}
 ```
 
 ### Validate data in write operations

skills/firestore-basics/references/web_sdk_usage.md

@@ -4,8 +4,10 @@ This guide focuses on the **Modular Web SDK** (v9+), which is tree-shakeable and
 
 ## Initialization
 
+```javascript
 import { initializeApp } from "firebase/app";
 import { getFirestore } from "firebase/firestore";
+```
 
 const firebaseConfig = {
   // Your config options. Get the values by running 'firebase apps:sdkconfig <platform> <app-id>'