docs: update ADR-064 (#15771)

docs/architecture/adr-064-abci-2.0.md

@@ -4,10 +4,11 @@
 
 * 2023-01-17: Initial Draft (@alexanderbez)
 * 2023-04-06: Add upgrading section (@alexanderbez)
+* 2023-04-10: Simplify vote extension state persistence (@alexanderbez)
 
 ## Status
 
-PROPOSED
+ACCEPTED
 
 ## Abstract
 
@@ -277,22 +278,14 @@ decision based on the vote extensions.
 
 #### Vote Extension Persistence
 
-In order to make any data derived from vote extensions persistent, we propose to
-allow application developers to "merge" the `processProposalState` into the
-`finalizeState`, such that when processing transactions during `FinalizeBlock`,
-the base state includes any state changes from processing votes extensions
-(see [`FinalizeBlock`](#finalizeblock-1) below).
-
-However, we DO NOT want to pollute `finalizeState` with any state changes from
-verifying transactions during `ProcessProposal`, so we will introduce a new API,
-`ResetProcessProposalState`, that will allow applications to essentially reset
-the `ProcessProposal` state, effectively allowing any state transitions after to
-be committed.
-
-What this means is that any explicit state changes in a `ProcessProposal` handler
-using the injected `processProposalState.Context` will be written to state! An
-application must be careful to execute `ResetProcessProposalState` where and when
-appropriate.
+In certain contexts, it may be useful or necessary for applications to persist
+data derived from vote extensions. In order to facilitate this use case, we
+propose to allow application developers to manually retrieve the `finalizeState`
+context (see [`FinalizeBlock`](#finalizeblock-1) below). Using this context,
+state can be directly written to `finalizeState`, which will be used during
+`FinalizeBlock` and eventually committed to the application state. Note, since
+`ProcessProposal` can timeout and thus require another round of consensus, we
+will reset `finalizeState` in the beginning of `ProcessProposal`.
 
 A `ProcessProposal` handler could look like the following:
 
@@ -306,17 +299,10 @@ func (h MyHandler) ProcessProposalHandler() sdk.ProcessProposalHandler {
 			}
 		}
 
-		// Reset the ProposalProposal state, which, up to this point, has accumulated
-		// possible state transitions from transaction verification and processing.
-		// Any subsequent state transitions after this will be merged into the
-		// FinalizeState before processing Begin/EndBlock and transactions.
-		// 
-		// NOTE: Applications must call this to ensure no state transactions up to now
-		// are committed!
-		h.app.ResetProcessProposalState()
-
-		// Any state changes that occur on the provided ctx WILL be written to state!
-		h.myKeeper.SetVoteExtResult(ctx, ...)
+		fCtx := h.app.GetFinalizeState()
+
+		// Any state changes that occur on the provided fCtx WILL be written to state!
+		h.myKeeper.SetVoteExtResult(fCtx, ...)
 
 		return abci.ResponseProcessProposal{Status: abci.ResponseProcessProposal_ACCEPT}
 	}