Add ErrKeyNotFound (cosmos#148)

* add new ErrKeyNotFound and handle it

da/mock/mock.go

@@ -2,6 +2,7 @@ package mock
 
 import (
 	"encoding/binary"
+	"errors"
 
 	"github.com/celestiaorg/optimint/da"
 	"github.com/celestiaorg/optimint/log"
@@ -71,9 +72,12 @@ func (m *MockDataAvailabilityLayerClient) SubmitBlock(block *types.Block) da.Res
 func (m *MockDataAvailabilityLayerClient) CheckBlockAvailability(header *types.Header) da.ResultCheckBlock {
 	hash := header.Hash()
 	_, err := m.dalcKV.Get(hash[:])
-	if err != nil {
+	if errors.Is(err, store.ErrKeyNotFound) {
 		return da.ResultCheckBlock{DAResult: da.DAResult{Code: da.StatusSuccess}, DataAvailable: false}
 	}
+	if err != nil {
+		return da.ResultCheckBlock{DAResult: da.DAResult{Code: da.StatusError, Message: err.Error()}, DataAvailable: false}
+	}
 	return da.ResultCheckBlock{DAResult: da.DAResult{Code: da.StatusSuccess}, DataAvailable: true}
 }
 

store/badger.go

@@ -1,9 +1,18 @@
 package store
 
-import "github.com/dgraph-io/badger/v3"
+import (
+	"errors"
+
+	"github.com/dgraph-io/badger/v3"
+)
 
 var _ KVStore = &BadgerKV{}
 
+var (
+	// ErrKeyNotFound is returned if key is not found in KVStore.
+	ErrKeyNotFound = errors.New("key not found")
+)
+
 // BadgerKV is a implementation of KVStore using Badger v3.
 type BadgerKV struct {
 	db *badger.DB
@@ -14,6 +23,9 @@ func (b *BadgerKV) Get(key []byte) ([]byte, error) {
 	txn := b.db.NewTransaction(false)
 	defer txn.Discard()
 	item, err := txn.Get(key)
+	if errors.Is(err, badger.ErrKeyNotFound) {
+		return nil, ErrKeyNotFound
+	}
 	if err != nil {
 		return nil, err
 	}

store/badger_test.go

@@ -0,0 +1,75 @@
+package store
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/dgraph-io/badger/v3"
+)
+
+func TestGetErrors(t *testing.T) {
+	dalcKV := NewInMemoryKVStore()
+
+	tc := []struct {
+		name string
+		key  []byte
+		err  error
+	}{
+		{"empty key", []byte{}, badger.ErrEmptyKey},
+		{"not found key", []byte("missing key"), ErrKeyNotFound},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := dalcKV.Get(tt.key)
+			if !errors.Is(err, tt.err) {
+				t.Errorf("Invalid err, got: %v expected %v", err, tt.err)
+			}
+		})
+	}
+}
+
+func TestSetErrors(t *testing.T) {
+	dalcKV := NewInMemoryKVStore()
+
+	tc := []struct {
+		name  string
+		key   []byte
+		value []byte
+		err   error
+	}{
+		{"empty key", []byte{}, []byte{}, badger.ErrEmptyKey},
+		{"invalid key", []byte("!badger!key"), []byte("invalid header"), badger.ErrInvalidKey},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			err := dalcKV.Set(tt.key, tt.value)
+			if !errors.Is(tt.err, err) {
+				t.Errorf("Invalid err, got: %v expected %v", err, tt.err)
+			}
+		})
+	}
+}
+
+func TestDeleteErrors(t *testing.T) {
+	dalcKV := NewInMemoryKVStore()
+
+	tc := []struct {
+		name string
+		key  []byte
+		err  error
+	}{
+		{"empty key", []byte{}, badger.ErrEmptyKey},
+		{"invalid key", []byte("!badger!key"), badger.ErrInvalidKey},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			err := dalcKV.Delete(tt.key)
+			if !errors.Is(err, tt.err) {
+				t.Errorf("Invalid err, got: %v expected %v", err, tt.err)
+			}
+		})
+	}
+}