x/evidence: StoreDecoder simulation (#6035)

* x/evidence: simulations

* update app

* evidence store decoder

* add evidence to sim import export

* fix test

* prevent zero values on randomized genesis

* return empty evidences for genesis state

* address comments from review

CHANGELOG.md

@@ -219,6 +219,7 @@ functionality that requires an online connection.
 * (client) [\#5895](https://github.com/cosmos/cosmos-sdk/issues/5895) show config options in the config command's help screen.
 * (types/rest) [\#5900](https://github.com/cosmos/cosmos-sdk/pull/5900) Add Check*Error function family to spare developers from replicating tons of boilerplate code.
 * (x/evidence) [\#5952](https://github.com/cosmos/cosmos-sdk/pull/5952) Tendermint Consensus parameters can now be changed via parameter change proposals through `x/gov`.
+* (x/evidence) [\#5961](https://github.com/cosmos/cosmos-sdk/issues/5961) Add `StoreDecoder` simulation for evidence module.
 * (x/auth/ante) [\#6040](https://github.com/cosmos/cosmos-sdk/pull/6040) `AccountKeeper` interface used for `NewAnteHandler` and handler's decorators to add support of using custom `AccountKeeper` implementations.
 * (simulation) [\#6002](https://github.com/cosmos/cosmos-sdk/pull/6002) Add randomized consensus params into simulation.
 

simapp/app.go

@@ -271,7 +271,7 @@ func NewSimApp(
 		distr.NewAppModule(appCodec, app.DistrKeeper, app.AccountKeeper, app.BankKeeper, app.StakingKeeper),
 		staking.NewAppModule(appCodec, app.StakingKeeper, app.AccountKeeper, app.BankKeeper),
 		upgrade.NewAppModule(app.UpgradeKeeper),
-		evidence.NewAppModule(app.EvidenceKeeper),
+		evidence.NewAppModule(appCodec, app.EvidenceKeeper),
 		ibc.NewAppModule(app.IBCKeeper),
 		params.NewAppModule(app.ParamsKeeper),
 		transferModule,
@@ -313,6 +313,7 @@ func NewSimApp(
 		distr.NewAppModule(appCodec, app.DistrKeeper, app.AccountKeeper, app.BankKeeper, app.StakingKeeper),
 		slashing.NewAppModule(appCodec, app.SlashingKeeper, app.AccountKeeper, app.BankKeeper, app.StakingKeeper),
 		params.NewAppModule(app.ParamsKeeper),
+		evidence.NewAppModule(appCodec, app.EvidenceKeeper),
 	)
 
 	app.sm.RegisterStoreDecoders()

simapp/sim_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/x/auth"
 	"github.com/cosmos/cosmos-sdk/x/bank"
 	distr "github.com/cosmos/cosmos-sdk/x/distribution"
+	"github.com/cosmos/cosmos-sdk/x/evidence"
 	"github.com/cosmos/cosmos-sdk/x/gov"
 	"github.com/cosmos/cosmos-sdk/x/mint"
 	paramtypes "github.com/cosmos/cosmos-sdk/x/params/types"
@@ -156,6 +157,7 @@ func TestAppImportExport(t *testing.T) {
 		{app.keys[bank.StoreKey], newApp.keys[bank.StoreKey], [][]byte{bank.BalancesPrefix}},
 		{app.keys[paramtypes.StoreKey], newApp.keys[paramtypes.StoreKey], [][]byte{}},
 		{app.keys[gov.StoreKey], newApp.keys[gov.StoreKey], [][]byte{}},
+		{app.keys[evidence.StoreKey], newApp.keys[evidence.StoreKey], [][]byte{}},
 	}
 
 	for _, skp := range storeKeysPrefixes {

x/evidence/module.go

@@ -3,14 +3,17 @@ package evidence
 import (
 	"encoding/json"
 	"fmt"
+	"math/rand"
 
 	"github.com/cosmos/cosmos-sdk/client/context"
 	"github.com/cosmos/cosmos-sdk/codec"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/module"
+	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
 	"github.com/cosmos/cosmos-sdk/x/evidence/client"
 	"github.com/cosmos/cosmos-sdk/x/evidence/client/cli"
 	"github.com/cosmos/cosmos-sdk/x/evidence/client/rest"
+	"github.com/cosmos/cosmos-sdk/x/evidence/simulation"
 
 	"github.com/gorilla/mux"
 	"github.com/spf13/cobra"
@@ -18,11 +21,9 @@ import (
 )
 
 var (
-	_ module.AppModule      = AppModule{}
-	_ module.AppModuleBasic = AppModuleBasic{}
-
-	// TODO: Enable simulation once concrete types are defined.
-	// _ module.AppModuleSimulation = AppModuleSimulation{}
+	_ module.AppModule           = AppModule{}
+	_ module.AppModuleBasic      = AppModuleBasic{}
+	_ module.AppModuleSimulation = AppModule{}
 )
 
 // ----------------------------------------------------------------------------
@@ -31,9 +32,11 @@ var (
 
 // AppModuleBasic implements the AppModuleBasic interface for the evidence module.
 type AppModuleBasic struct {
+	cdc              Codec
 	evidenceHandlers []client.EvidenceHandler // client evidence submission handlers
 }
 
+// NewAppModuleBasic crates a AppModuleBasic without the codec.
 func NewAppModuleBasic(evidenceHandlers ...client.EvidenceHandler) AppModuleBasic {
 	return AppModuleBasic{
 		evidenceHandlers: evidenceHandlers,
@@ -103,9 +106,9 @@ type AppModule struct {
 	keeper Keeper
 }
 
-func NewAppModule(keeper Keeper) AppModule {
+func NewAppModule(cdc Codec, keeper Keeper) AppModule {
 	return AppModule{
-		AppModuleBasic: NewAppModuleBasic(),
+		AppModuleBasic: AppModuleBasic{cdc: cdc},
 		keeper:         keeper,
 	}
 }
@@ -166,3 +169,33 @@ func (am AppModule) BeginBlock(ctx sdk.Context, req abci.RequestBeginBlock) {
 func (am AppModule) EndBlock(ctx sdk.Context, _ abci.RequestEndBlock) []abci.ValidatorUpdate {
 	return []abci.ValidatorUpdate{}
 }
+
+//____________________________________________________________________________
+
+// AppModuleSimulation functions
+
+// GenerateGenesisState creates a randomized GenState of the evidence module.
+func (AppModule) GenerateGenesisState(simState *module.SimulationState) {
+	simulation.RandomizedGenState(simState)
+}
+
+// ProposalContents returns all the evidence content functions used to
+// simulate governance proposals.
+func (am AppModule) ProposalContents(simState module.SimulationState) []simtypes.WeightedProposalContent {
+	return nil
+}
+
+// RandomizedParams creates randomized evidence param changes for the simulator.
+func (AppModule) RandomizedParams(r *rand.Rand) []simtypes.ParamChange {
+	return nil
+}
+
+// RegisterStoreDecoder registers a decoder for evidence module's types
+func (am AppModule) RegisterStoreDecoder(sdr sdk.StoreDecoderRegistry) {
+	sdr[StoreKey] = simulation.NewDecodeStore(am.cdc)
+}
+
+// WeightedOperations returns the all the gov module operations with their respective weights.
+func (am AppModule) WeightedOperations(simState module.SimulationState) []simtypes.WeightedOperation {
+	return nil
+}

x/evidence/simulation/decoder.go

@@ -0,0 +1,32 @@
+package simulation
+
+import (
+	"bytes"
+	"fmt"
+
+	tmkv "github.com/tendermint/tendermint/libs/kv"
+
+	"github.com/cosmos/cosmos-sdk/x/evidence/types"
+)
+
+// NewDecodeStore returns a decoder function closure that unmarshals the KVPair's
+// Value to the corresponding evidence type.
+func NewDecodeStore(cdc types.Codec) func(kvA, kvB tmkv.Pair) string {
+	return func(kvA, kvB tmkv.Pair) string {
+		switch {
+		case bytes.Equal(kvA.Key[:1], types.KeyPrefixEvidence):
+			evidenceA, err := cdc.UnmarshalEvidence(kvA.Value)
+			if err != nil {
+				panic(fmt.Sprintf("cannot unmarshal evidence: %s", err.Error()))
+			}
+			evidenceB, err := cdc.UnmarshalEvidence(kvB.Value)
+			if err != nil {
+				panic(fmt.Sprintf("cannot unmarshal evidence: %s", err.Error()))
+			}
+			return fmt.Sprintf("%v\n%v", evidenceA, evidenceB)
+
+		default:
+			panic(fmt.Sprintf("invalid %s key prefix %X", types.ModuleName, kvA.Key[:1]))
+		}
+	}
+}

x/evidence/simulation/decoder_test.go

@@ -0,0 +1,64 @@
+package simulation_test
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"github.com/tendermint/tendermint/crypto/ed25519"
+	tmkv "github.com/tendermint/tendermint/libs/kv"
+
+	codecstd "github.com/cosmos/cosmos-sdk/codec/std"
+	"github.com/cosmos/cosmos-sdk/simapp"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/evidence/simulation"
+	"github.com/cosmos/cosmos-sdk/x/evidence/types"
+)
+
+func TestDecodeStore(t *testing.T) {
+	cdc := codecstd.NewAppCodec(codecstd.MakeCodec(simapp.ModuleBasics))
+	dec := simulation.NewDecodeStore(cdc)
+
+	delPk1 := ed25519.GenPrivKey().PubKey()
+
+	ev := types.Equivocation{
+		Height:           10,
+		Time:             time.Now().UTC(),
+		Power:            1000,
+		ConsensusAddress: sdk.ConsAddress(delPk1.Address()),
+	}
+
+	evBz, err := cdc.MarshalEvidence(&ev)
+	require.NoError(t, err)
+
+	kvPairs := tmkv.Pairs{
+		tmkv.Pair{
+			Key:   types.KeyPrefixEvidence,
+			Value: evBz,
+		},
+		tmkv.Pair{
+			Key:   []byte{0x99},
+			Value: []byte{0x99},
+		},
+	}
+	tests := []struct {
+		name        string
+		expectedLog string
+	}{
+		{"Evidence", fmt.Sprintf("%v\n%v", ev, ev)},
+		{"other", ""},
+	}
+
+	for i, tt := range tests {
+		i, tt := i, tt
+		t.Run(tt.name, func(t *testing.T) {
+			switch i {
+			case len(tests) - 1:
+				require.Panics(t, func() { dec(kvPairs[i], kvPairs[i]) }, tt.name)
+			default:
+				require.Equal(t, tt.expectedLog, dec(kvPairs[i], kvPairs[i]), tt.name)
+			}
+		})
+	}
+}

x/evidence/simulation/genesis.go

@@ -0,0 +1,37 @@
+package simulation
+
+// DONTCOVER
+
+import (
+	"fmt"
+	"math/rand"
+
+	"github.com/cosmos/cosmos-sdk/codec"
+
+	"github.com/cosmos/cosmos-sdk/types/module"
+	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
+	"github.com/cosmos/cosmos-sdk/x/evidence/exported"
+	"github.com/cosmos/cosmos-sdk/x/evidence/types"
+)
+
+// Simulation parameter constants
+const evidence = "evidence"
+
+// GenEvidences returns an empty slice of evidences.
+func GenEvidences(_ *rand.Rand, _ []simtypes.Account) []exported.Evidence {
+	return []exported.Evidence{}
+}
+
+// RandomizedGenState generates a random GenesisState for evidence
+func RandomizedGenState(simState *module.SimulationState) {
+	var ev []exported.Evidence
+	simState.AppParams.GetOrGenerate(
+		simState.Cdc, evidence, &ev, simState.Rand,
+		func(r *rand.Rand) { ev = GenEvidences(r, simState.Accounts) },
+	)
+
+	evidenceGenesis := types.GenesisState{Evidence: ev}
+
+	fmt.Printf("Selected randomly generated %s parameters:\n%s\n", types.ModuleName, codec.MustMarshalJSONIndent(simState.Cdc, evidenceGenesis))
+	simState.GenState[types.ModuleName] = simState.Cdc.MustMarshalJSON(evidenceGenesis)
+}

x/evidence/types/genesis.go

@@ -1,6 +1,8 @@
 package types
 
 import (
+	"fmt"
+
 	"github.com/cosmos/cosmos-sdk/x/evidence/exported"
 )
 
@@ -27,7 +29,10 @@ func DefaultGenesisState() GenesisState {
 // Validate performs basic gensis state validation returning an error upon any
 // failure.
 func (gs GenesisState) Validate() error {
-	for _, e := range gs.Evidence {
+	for i, e := range gs.Evidence {
+		if e == nil {
+			return fmt.Errorf("evidence %d cannot be nil", i)
+		}
 		if err := e.ValidateBasic(); err != nil {
 			return err
 		}