Extend DiffKVStores to return an array of KVPairs

[fedekunze]

Summary

Extend DiffKVStores to return a []KVPair to improve import/export simulation logs

Problem Definition

As part of #4607, I noticed that for the import/export simulation, at the moment of comparing the two stores, the function DiffKVStores returns the first KVPair that is not equal.

cosmos-sdk/simapp/sim_test.go

Line 931 in 1cf40bf

kvA, kvB, count, equal := sdk.DiffKVStores(storeA, storeB, prefixes)

cosmos-sdk/store/types/utils.go

Lines 19 to 22 in a579156

	// Compare two KVstores, return either the first key/value pair
	// at which they differ and whether or not they are equal, skipping
	// value comparison for a set of provided prefixes
	func DiffKVStores(a KVStore, b KVStore, prefixesToSkip [][]byte) (kvA cmn.KVPair, kvB cmn.KVPair, count int64, equal bool) {

Ideally, we should extend that function to return an array of KVPairs so that the person who's looking at the simulation logs can identify all the types that differ between the compared stores.

Proposal

• extend DiffKVStores to return []KVPair
• update Import/Export simulation to decode each of the KVPairs, returning a single log with all the decoded values.

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