Firestore Listing Error: Undefined 'createdBy' Field in Security Rules

The error indicates that when you run a list query, Firestore is evaluating the potential result set and it encountered a document that doesn’t have the createdBy field. Even if your single test document is correctly populated, the query will fail if any document in the collection (or even a non-matching “shadow” document in the emulator) is missing that field.

Here are a few steps to resolve the issue:

1. Ensure All Documents Have createdBy:
   Verify that every document in your /patients collection has the createdBy field. In a list query, Firestore checks every document against the rule constraint.

2. Modify the Security Rule to Check Field Existence:
   You can modify your rule to check that the createdBy field exists before comparing. For example:

   HCLCopied
   service cloud.firestore {
     match /databases/{database}/documents {
       match /patients/{patientId} {
         allow create: if request.auth != null;
         allow read, update, delete: if request.auth != null &&
           resource.data.createdBy != null &&
           resource.data.createdBy == request.auth.uid;
       }
     }
   }

   This change prevents the rule from failing on documents that are missing the createdBy field.

3. Review Your Query:
   If you expect only your own documents to be listed, consider adding a query filter on the client side:

   JSCopied
   const user = firebase.auth().currentUser;
   db.collection('patients')
     .where('createdBy', '==', user.uid)
     .get()
     .then(snapshot => {
       // process your data here
     })
     .catch(error => console.error(error));

This way the query is guaranteed to only include documents that have the createdBy field set to the user's ID, matching the security rule.

By ensuring field existence or adjusting your query accordingly, you can resolve the “Property createdBy is undefined” error.