feat: add migrations for balances with zero coins (backport cosmos#9664…

…) (cosmos#9687)

* feat: add migrations for balances with zero coins (cosmos#9664)

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## Description

Closes: cosmos#9653

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are the most critical to review. -->

---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

(cherry picked from commit d56c8cd)

# Conflicts:
#	x/bank/legacy/v043/json.go
#	x/bank/legacy/v043/json_test.go
#	x/bank/legacy/v043/keys.go
#	x/bank/legacy/v043/store_test.go

* fix conflicts

* fix tests

Co-authored-by: atheeshp <[email protected]>
Co-authored-by: atheesh <[email protected]>

x/bank/legacy/v043/json.go

@@ -0,0 +1,32 @@
+package v043
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/bank/types"
+)
+
+// pruneZeroBalancesJSON removes the zero balance addresses from exported genesis.
+func pruneZeroBalancesJSON(oldBalances []types.Balance) []types.Balance {
+	var balances []types.Balance
+
+	for _, b := range oldBalances {
+		if !b.Coins.IsZero() {
+			b.Coins = sdk.NewCoins(b.Coins...) // prunes zero denom.
+			balances = append(balances, b)
+		}
+	}
+
+	return balances
+}
+
+// MigrateJSON accepts exported v0.40 x/bank genesis state and migrates it to
+// v0.43 x/bank genesis state. The migration includes:
+// - Prune balances & supply with zero coins (ref: https://github.com/cosmos/cosmos-sdk/pull/9229)
+func MigrateJSON(oldState *types.GenesisState) *types.GenesisState {
+	return &types.GenesisState{
+		Params:        oldState.Params,
+		Balances:      pruneZeroBalancesJSON(oldState.Balances),
+		Supply:        sdk.NewCoins(oldState.Supply...), // NewCoins used here to remove zero coin denoms from supply.
+		DenomMetadata: oldState.DenomMetadata,
+	}
+}

x/bank/legacy/v043/json_test.go

@@ -0,0 +1,93 @@
+package v043_test
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cosmos/cosmos-sdk/client"
+	"github.com/cosmos/cosmos-sdk/simapp"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	v043bank "github.com/cosmos/cosmos-sdk/x/bank/legacy/v043"
+	"github.com/cosmos/cosmos-sdk/x/bank/types"
+)
+
+func TestMigrateJSON(t *testing.T) {
+	encodingConfig := simapp.MakeTestEncodingConfig()
+	clientCtx := client.Context{}.
+		WithInterfaceRegistry(encodingConfig.InterfaceRegistry).
+		WithTxConfig(encodingConfig.TxConfig).
+		WithCodec(encodingConfig.Marshaler)
+
+	voter, err := sdk.AccAddressFromBech32("cosmos1fl48vsnmsdzcv85q5d2q4z5ajdha8yu34mf0eh")
+	require.NoError(t, err)
+	bankGenState := &types.GenesisState{
+		Balances: []types.Balance{
+			{
+				Address: voter.String(),
+				Coins: sdk.Coins{
+					sdk.NewCoin("foo", sdk.NewInt(10)),
+					sdk.NewCoin("bar", sdk.NewInt(20)),
+					sdk.NewCoin("foobar", sdk.NewInt(0)),
+				},
+			},
+		},
+		Supply: sdk.Coins{
+			sdk.NewCoin("foo", sdk.NewInt(10)),
+			sdk.NewCoin("bar", sdk.NewInt(20)),
+			sdk.NewCoin("foobar", sdk.NewInt(0)),
+			sdk.NewCoin("barfoo", sdk.NewInt(0)),
+		},
+	}
+
+	migrated := v043bank.MigrateJSON(bankGenState)
+
+	bz, err := clientCtx.Codec.MarshalJSON(migrated)
+	require.NoError(t, err)
+
+	// Indent the JSON bz correctly.
+	var jsonObj map[string]interface{}
+	err = json.Unmarshal(bz, &jsonObj)
+	require.NoError(t, err)
+	indentedBz, err := json.MarshalIndent(jsonObj, "", "\t")
+	require.NoError(t, err)
+
+	// Make sure about:
+	// - zero coin balances pruned.
+	// - zero supply denoms pruned.
+	expected := `{
+	"balances": [
+		{
+			"address": "cosmos1fl48vsnmsdzcv85q5d2q4z5ajdha8yu34mf0eh",
+			"coins": [
+				{
+					"amount": "20",
+					"denom": "bar"
+				},
+				{
+					"amount": "10",
+					"denom": "foo"
+				}
+			]
+		}
+	],
+	"denom_metadata": [],
+	"params": {
+		"default_send_enabled": false,
+		"send_enabled": []
+	},
+	"supply": [
+		{
+			"amount": "20",
+			"denom": "bar"
+		},
+		{
+			"amount": "10",
+			"denom": "foo"
+		}
+	]
+}`
+
+	require.Equal(t, expected, string(indentedBz))
+}

x/bank/legacy/v043/keys.go

@@ -0,0 +1,12 @@
+package v043
+
+const (
+	// ModuleName is the name of the module
+	ModuleName = "bank"
+)
+
+// KVStore keys
+var (
+	BalancesPrefix = []byte{0x02}
+	SupplyKey      = []byte{0x00}
+)