LedgerChangeReader: Support State Expiration & Eviction (#4941)

* Simplify ScError.Equals

* Add missing case for ScVal.Equals

* Add LedgerEntry.SetContractData and LedgerEntry.SetContractCode methods

* update generated xdr to 0f5e556

* Add LedgerCloseMetaV2 support

* Update ledgerTransaction.GetOperationEvents

* Make LedgerChangeReader emit evictions

* Fixing up after merge

* Add test for LedgerChangeReader extensions and evictions

* Fix typo

* Add xdr.LedgerEntryData.ExpirationLedgerSeq helper

* review feedback

ingest/change.go

@@ -2,6 +2,7 @@ package ingest
 
 import (
 	"bytes"
+	"fmt"
 
 	"github.com/stellar/go/support/errors"
 	"github.com/stellar/go/xdr"
@@ -68,6 +69,45 @@ func GetChangesFromLedgerEntryChanges(ledgerEntryChanges xdr.LedgerEntryChanges)
 	return changes
 }
 
+// GetChangesFromLedgerEntryEvictions transforms evicted LedgerKeys to []Change.
+// The generated changes always remove the entries.
+func GetChangesFromLedgerEntryEvictions(keys []xdr.LedgerKey) ([]Change, error) {
+	changes := []Change{}
+
+	for _, key := range keys {
+		state := xdr.LedgerEntry{}
+		switch key.Type {
+		case xdr.LedgerEntryTypeContractData:
+			err := state.Data.SetContractData(&xdr.ContractDataEntry{
+				Contract:   key.ContractData.Contract,
+				Key:        key.ContractData.Key,
+				Durability: key.ContractData.Durability,
+			})
+			if err != nil {
+				return nil, errors.Wrap(err, "error setting ContractDataEntry")
+			}
+		case xdr.LedgerEntryTypeContractCode:
+			err := state.Data.SetContractCode(&xdr.ContractCodeEntry{
+				Hash: key.ContractCode.Hash,
+			})
+			if err != nil {
+				return nil, errors.Wrap(err, "error setting ContractCodeEntry")
+			}
+		default:
+			// Currently only contractData and contractCode are evicted by core, so
+			// we only need to handle those two.
+			return nil, fmt.Errorf("invalid LedgerEntry eviction type: %s", key.Type)
+		}
+		changes = append(changes, Change{
+			Type: key.Type,
+			Pre:  &state,
+			Post: nil,
+		})
+	}
+
+	return changes, nil
+}
+
 // LedgerEntryChangeType returns type in terms of LedgerEntryChangeType.
 func (c *Change) LedgerEntryChangeType() xdr.LedgerEntryChangeType {
 	switch {

ingest/ledger_change_reader.go

@@ -25,9 +25,11 @@ type ledgerChangeReaderState int
 const (
 	// feeChangesState is active when LedgerChangeReader is reading fee changes.
 	feeChangesState ledgerChangeReaderState = iota
-	// feeChangesState is active when LedgerChangeReader is reading transaction meta changes.
+	// metaChangesState is active when LedgerChangeReader is reading transaction meta changes.
 	metaChangesState
-	// feeChangesState is active when LedgerChangeReader is reading upgrade changes.
+	// evictionChangesState is active when LedgerChangeReader is reading ledger entry evictions.
+	evictionChangesState
+	// upgradeChanges is active when LedgerChangeReader is reading upgrade changes.
 	upgradeChangesState
 )
 
@@ -122,6 +124,15 @@ func (r *LedgerChangeReader) Read() (Change, error) {
 			r.pending = append(r.pending, metaChanges...)
 		}
 		return r.Read()
+	case evictionChangesState:
+		// Get contract ledgerEntry evictions
+		changes, err := GetChangesFromLedgerEntryEvictions(r.ledgerCloseMeta.EvictedLedgerKeys())
+		if err != nil {
+			return Change{}, err
+		}
+		r.pending = append(r.pending, changes...)
+		r.state++
+		return r.Read()
 	case upgradeChangesState:
 		// Get upgrade changes
 		if r.upgradeIndex < len(r.LedgerTransactionReader.ledgerCloseMeta.UpgradesProcessing()) {