ContainerRuntime: Remove the contents property of batchBegin/batchEnd…

…'s "op" event arg (microsoft#22791)

## Description

Fixes
[AB#19784](https://dev.azure.com/fluidframework/235294da-091d-4c29-84fc-cdfc3d90890b/_workitems/edit/19784)

ContainerRuntime's 'batchBegin'/'batchEnd' events: Removing the
`contents` property on event arg `op`

The 'batchBegin'/'batchEnd' events on ContainerRuntime indicate when a
batch is beginning/finishing being processed.
The `contents` property on there is not useful or relevant when
reasoning over incoming changes at the batch level.
So it has been removed from the `op` event arg.

## Breaking Changes

Yes this is a breaking change.  See changeset.

---------

Co-authored-by: Kian Thompson <[email protected]>

.changeset/fruity-sites-boil.md

@@ -0,0 +1,12 @@
+---
+"@fluidframework/runtime-definitions": minor
+---
+---
+"section": other
+---
+
+ContainerRuntime's 'batchBegin'/'batchEnd' events: Removing the `contents` property on event arg `op`
+
+The 'batchBegin'/'batchEnd' events on ContainerRuntime indicate when a batch is beginning/finishing being processed.
+The `contents` property on there is not useful or relevant when reasoning over incoming changes at the batch level.
+So it has been removed from the `op` event arg.

packages/runtime/container-runtime/src/containerRuntime.ts

@@ -2819,17 +2819,6 @@ export class ContainerRuntime
 					: false /* groupedBatch */,
 			);
 		} else {
-			if (!runtimeBatch) {
-				// The DeltaManager used to do this, but doesn't anymore as of Loader v2.4
-				// Anyone listening to our "op" event would expect the contents to be parsed per this same logic
-				if (
-					typeof messageCopy.contents === "string" &&
-					messageCopy.contents !== "" &&
-					messageCopy.type !== MessageType.ClientLeave
-				) {
-					messageCopy.contents = JSON.parse(messageCopy.contents);
-				}
-			}
 			this.processInboundMessages(
 				[{ message: messageCopy, localOpMetadata: undefined }],
 				{ batchStart: true, batchEnd: true }, // Single message
@@ -2996,6 +2985,16 @@ export class ContainerRuntime
 			this.updateDocumentDirtyState(false);
 		}
 
+		// The DeltaManager used to do this, but doesn't anymore as of Loader v2.4
+		// Anyone listening to our "op" event would expect the contents to be parsed per this same logic
+		if (
+			typeof message.contents === "string" &&
+			message.contents !== "" &&
+			message.type !== MessageType.ClientLeave
+		) {
+			message.contents = JSON.parse(message.contents);
+		}
+
 		this.emit("op", message, false /* runtimeMessage */);
 	}
 

packages/runtime/runtime-definitions/api-report/runtime-definitions.legacy.alpha.api.md

@@ -94,15 +94,8 @@ export interface IContainerRuntimeBase extends IEventProvider<IContainerRuntimeB
 
 // @alpha @sealed (undocumented)
 export interface IContainerRuntimeBaseEvents extends IEvent {
-    // (undocumented)
-    (event: "batchBegin", listener: (op: Omit<ISequencedDocumentMessage, "contents"> & {
-        contents: unknown;
-    }) => void): any;
-    // (undocumented)
-    (event: "batchEnd", listener: (error: any, op: Omit<ISequencedDocumentMessage, "contents"> & {
-        contents: unknown;
-    }) => void): any;
-    // (undocumented)
+    (event: "batchBegin", listener: (op: Omit<ISequencedDocumentMessage, "contents">) => void): any;
+    (event: "batchEnd", listener: (error: any, op: Omit<ISequencedDocumentMessage, "contents">) => void): any;
     (event: "op", listener: (op: ISequencedDocumentMessage, runtimeMessage?: boolean) => void): any;
     // (undocumented)
     (event: "signal", listener: (message: IInboundSignalMessage, local: boolean) => void): any;

packages/runtime/runtime-definitions/src/dataStoreContext.ts

@@ -122,28 +122,24 @@ export type VisibilityState = (typeof VisibilityState)[keyof typeof VisibilitySt
  * @sealed
  */
 export interface IContainerRuntimeBaseEvents extends IEvent {
-	(
-		event: "batchBegin",
-		listener: (
-			op: Omit<ISequencedDocumentMessage, "contents"> & {
-				/** @deprecated Use the "op" event to get details about the message contents */
-				contents: unknown;
-			},
-		) => void,
-	);
+	/**
+	 * Indicates the beginning of an incoming batch of ops
+	 * @param op - The first op in the batch. Can be inspected to learn about the sequence numbers relevant for this batch.
+	 */
+	(event: "batchBegin", listener: (op: Omit<ISequencedDocumentMessage, "contents">) => void);
+	/**
+	 * Indicates the end of an incoming batch of ops
+	 * @param error - If an error occurred while processing the batch, it is provided here.
+	 * @param op - The last op in the batch. Can be inspected to learn about the sequence numbers relevant for this batch.
+	 */
 	(
 		event: "batchEnd",
-		listener: (
-			error: any,
-			op: Omit<ISequencedDocumentMessage, "contents"> & {
-				/** @deprecated Use the "op" event to get details about the message contents */
-				contents: unknown;
-			},
-		) => void,
+		listener: (error: any, op: Omit<ISequencedDocumentMessage, "contents">) => void,
 	);
 	/**
+	 * Indicates that an incoming op has been processed.
 	 * @param runtimeMessage - tells if op is runtime op. If it is, it was unpacked, i.e. its type and content
-	 * represent internal container runtime type / content.
+	 * represent internal container runtime type / content. i.e. A grouped batch of N ops will result in N "op" events
 	 */
 	(event: "op", listener: (op: ISequencedDocumentMessage, runtimeMessage?: boolean) => void);
 	(event: "signal", listener: (message: IInboundSignalMessage, local: boolean) => void);