all, state: unexpose GenesisDoc, ChainID fields make them accessor methods

Fixes #671

Unexpose GenesisDoc and ChainID fields to avoid them being
serialized to the DB on every block write/state.Save()

A GenesisDoc can now be alternatively written to the state's
database, by serializing its JSON as a value of key "genesis-doc".

There are now accessors and a setter for these attributes:
- state.GenesisDoc() (*types.GenesisDoc, error)
- state.ChainID() (string, error)
- state.SetGenesisDoc(*types.GenesisDoc)

This is a breaking change since it changes how the state's
serialization and requires that if loading the GenesisDoc entirely
from the database, you'll need to set its value in the database
as the GenesisDoc's JSON marshaled bytes.

state/state_test.go

@@ -2,16 +2,21 @@ package state
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	cfg "github.com/tendermint/tendermint/config"
 	"github.com/tendermint/tendermint/types"
 
 	abci "github.com/tendermint/abci/types"
 	crypto "github.com/tendermint/go-crypto"
+
+	"github.com/tendermint/go-wire/data"
 	cmn "github.com/tendermint/tmlibs/common"
 	dbm "github.com/tendermint/tmlibs/db"
 	"github.com/tendermint/tmlibs/log"
@@ -127,7 +132,9 @@ func TestValidatorChangesSaveLoad(t *testing.T) {
 	// each valset is just one validator.
 	// create list of them
 	pubkeys := make([]crypto.PubKey, N+1)
-	pubkeys[0] = state.GenesisDoc.Validators[0].PubKey
+	genDoc, err := state.GenesisDoc()
+	assert.Nil(err, "want successful genDoc retrieval")
+	pubkeys[0] = genDoc.Validators[0].PubKey
 	for i := 1; i < N+1; i++ {
 		pubkeys[i] = crypto.GenPrivKeyEd25519().PubKey()
 	}
@@ -199,3 +206,104 @@ type valChangeTestCase struct {
 	height int
 	vals   crypto.PubKey
 }
+
+var (
+	aPrivKey       = crypto.GenPrivKeyEd25519()
+	_1stGenesisDoc = &types.GenesisDoc{
+		GenesisTime: time.Now().Add(-60 * time.Minute).Round(time.Second),
+		ChainID:     "tendermint_state_test",
+		AppHash:     data.Bytes{},
+		ConsensusParams: &types.ConsensusParams{
+			BlockSizeParams: types.BlockSizeParams{
+				MaxBytes: 100,
+				MaxGas:   2000,
+				MaxTxs:   56,
+			},
+
+			BlockGossipParams: types.BlockGossipParams{
+				BlockPartSizeBytes: 65336,
+			},
+		},
+		Validators: []types.GenesisValidator{
+			{PubKey: aPrivKey.PubKey(), Power: 10000, Name: "TendermintFoo"},
+		},
+	}
+	_2ndGenesisDoc = func() *types.GenesisDoc {
+		copy := new(types.GenesisDoc)
+		*copy = *_1stGenesisDoc
+		copy.GenesisTime = time.Now().Round(time.Second)
+		return copy
+	}()
+)
+
+// See Issue https://github.com/tendermint/tendermint/issues/671.
+func TestGenesisDocAndChainIDAccessorsAndSetter(t *testing.T) {
+	tearDown, dbm, state := setupTestCase(t)
+	defer tearDown(t)
+	require := require.New(t)
+
+	// Fire up the initial genesisDoc
+	_, err := state.GenesisDoc()
+	require.Nil(err, "expecting no error on first load of genesisDoc")
+
+	// By contract, state doesn't expose the dbm, however we need to change
+	// it to test out that the respective chainID and genesisDoc will be changed
+	state.cachedGenesisDoc = nil
+	_1stBlob, err := json.Marshal(_1stGenesisDoc)
+	require.Nil(err, "expecting no error serializing _1stGenesisDoc")
+	dbm.Set(genesisDBKey, _1stBlob)
+
+	retrGenDoc, err := state.GenesisDoc()
+	require.Nil(err, "unexpected error")
+	require.Equal(retrGenDoc, _1stGenesisDoc, "expecting the newly set-in-Db genesis doc")
+	chainID, err := state.ChainID()
+	require.Nil(err, "unexpected error")
+	require.Equal(chainID, _1stGenesisDoc.ChainID, "expecting the chainIDs to be equal")
+
+	require.NotNil(state.cachedGenesisDoc, "after retrieval expecting a non-nil cachedGenesisDoc")
+	// Save should not discard the previous cachedGenesisDoc
+	// which was the point of filing https://github.com/tendermint/tendermint/issues/671.
+	state.Save()
+	require.NotNil(state.cachedGenesisDoc, "even after flush with .Save(), expecting a non-nil cachedGenesisDoc")
+
+	// Now change up the data but ensure
+	// that a Save discards the old validator
+	_2ndBlob, err := json.Marshal(_2ndGenesisDoc)
+	require.Nil(err, "unexpected error")
+	dbm.Set(genesisDBKey, _2ndBlob)
+
+	refreshGenDoc, err := state.GenesisDoc()
+	require.Nil(err, "unexpected error")
+	require.Equal(refreshGenDoc, _1stGenesisDoc, "despite setting the new genesisDoc in DB, it shouldn't affect the one in state")
+	state.SetGenesisDoc(_2ndGenesisDoc)
+
+	refreshGenDoc, err = state.GenesisDoc()
+	require.Nil(err, "unexpected error")
+	require.Equal(refreshGenDoc, _2ndGenesisDoc, "expecting the newly set-in-Db genesis doc to have been reloaded after a .Save()")
+
+	// Test that .Save() should never overwrite the currently set content in the DB
+	dbm.Set(genesisDBKey, _1stBlob)
+	state.Save()
+	require.Equal(dbm.Get(genesisDBKey), _1stBlob, ".Save() should NEVER serialize back the current genesisDoc")
+
+	// ChainID on a nil cachedGenesisDoc should do a DB fetch
+	state.SetGenesisDoc(nil)
+	dbm.Set(genesisDBKey, _2ndBlob)
+	chainID, err = state.ChainID()
+	require.Nil(err, "unexpected error")
+	require.Equal(chainID, _2ndGenesisDoc.ChainID, "expecting the 2ndGenesisDoc.ChainID")
+
+	// Now test what happens if we cannot find the genesis doc in the DB
+	// Checkpoint and discard
+	state.Save()
+	dbm.Set(genesisDBKey, nil)
+	state.SetGenesisDoc(nil)
+	gotGenDoc, err := state.GenesisDoc()
+	require.NotNil(err, "could not parse out a genesisDoc from the DB")
+	require.Nil(gotGenDoc, "since we couldn't parse the genesis doc, expecting a nil genesis doc")
+
+	dbm.Set(genesisDBKey, []byte(`{}`))
+	gotGenDoc, err = state.GenesisDoc()
+	require.NotNil(err, "despite {}, that's not a valid serialization for a genesisDoc")
+	require.Nil(gotGenDoc, "since we couldn't parse the genesis doc, expecting a nil genesis doc")
+}