DRIVERS-3278 Revert field presence changes from server 8.2.0 (#1913)

Author: abr-egn

source/change-streams/change-streams.md

@@ -138,8 +138,15 @@ class ChangeStreamDocument {
   to: Optional<Document>;
 
   /**
-   * Only present for ops of type 'rename', 'create', 'modify', 'createIndexes', 'dropIndexes', 'shardCollection', 'reshardCollection', 'refineCollectionShardKey'.
-   * Prior to server version 8.2.0, only present when the `showExpandedEvents` change stream option is enabled.
+   * * Only present when the `showExpandedEvents` change stream option is enabled and for the following events:
+   *  - 'rename'
+   *  - 'create'
+   *  - 'modify'
+   *  - 'createIndexes'
+   *  - 'dropIndexes'
+   *  - 'shardCollection'
+   *  - 'reshardCollection'
+   *  - 'refineCollectionShardKey'
    *
    * A description of the operation.
    * 
@@ -202,7 +209,7 @@ class ChangeStreamDocument {
   /**
    * The `ui` field from the oplog entry corresponding to the change event.
    * 
-   * Only present for the following events:
+   * Only present when the `showExpandedEvents` change stream option is enabled and for the following events:
    *  - 'insert'
    *  - 'update'
    *  - 'delete'
@@ -214,7 +221,6 @@ class ChangeStreamDocument {
    *  - 'shardCollection'
    *  - 'reshardCollection'
    *  - 'refineCollectionShardKey'
-   * Prior to server versions 8.2, only present when the `showExpandedEvents` change stream option is enabled.
    *  
    * This field is a value of binary subtype 4 (UUID).
    *  
@@ -299,6 +305,8 @@ class UpdateDescription {
    * 
    * In each array, all elements will be returned as strings with the exception of array indices, which will be returned as 32 bit integers.
    * 
+   * Only present when the `showExpandedEvents` change stream option is enabled.
+   * 
    * @since 6.1.0
    */
   disambiguatedPaths: Optional<Document>
@@ -1026,6 +1034,8 @@ There should be no backwards compatibility concerns.
 
 ## Changelog
 
+- 2026-03-18: Revert expanded field visibility change.
+
 - 2025-09-08: Clarify resume behavior.
 
 - 2025-03-31: Update for expanded field visibility in server 8.2+

source/change-streams/tests/unified/change-streams-disambiguatedPaths.json

@@ -24,6 +24,41 @@ initialData:
     documents: []
 
 tests:
+  - description: "disambiguatedPaths is not present when showExpandedEvents is false/unset"
+    # skip server version 8.2.0, which emits disambiguatedPaths unconditionally
+    runOnRequirements:
+      - minServerVersion: "6.1.0"
+        maxServerVersion: "8.1.99"
+        topologies: [ replicaset, load-balanced, sharded ]
+        serverless: forbid
+      - minServerVersion: "8.2.1"
+        topologies: [ replicaset, load-balanced, sharded ]
+        serverless: forbid
+    operations:
+      - name: insertOne
+        object: *collection0
+        arguments:
+          document: { _id: 1, 'a': { '1': 1 } }
+      - name: createChangeStream
+        object: *collection0
+        arguments: { pipeline: [] }
+        saveResultAsEntity: &changeStream0 changeStream0
+      - name: updateOne
+        object: *collection0
+        arguments:
+          filter: { _id: 1 }
+          update: { $set: { 'a.1': 2 } }
+      - name: iterateUntilDocumentOrError
+        object: *changeStream0
+        expectResult:
+          operationType: "update"
+          ns: { db: *database0, coll: *collection0 }
+          updateDescription:
+            updatedFields: { $$exists: true }
+            removedFields: { $$exists: true }
+            truncatedArrays: { $$exists: true }
+            disambiguatedPaths: { $$exists: false }
+
   - description: "disambiguatedPaths is present on updateDescription when an ambiguous path is present"
     operations:
       - name: insertOne