Add CommitHeader to TestChain struct (cosmos#5435)

* add CommitHeader to TestChain struct

* imp: add godoc and minor imp

* Update testing/chain.go

---------

Co-authored-by: Lặc <67097720+expertdicer@users.noreply.github.com>
Co-authored-by: Colin Axnér <25233464+colin-axner@users.noreply.github.com>
Co-authored-by: Damian Nolan <damiannolan@gmail.com>

testing/chain.go

@@ -504,6 +504,35 @@ func (chain *TestChain) CurrentTMClientHeader() *ibctm.Header {
 	)
 }
 
+// CommitHeader takes in a proposed header and returns a signed cometbft header.
+// The signers passed in must match the validator set provided. The signers will
+// be used to sign over the proposed header.
+func CommitHeader(proposedHeader cmttypes.Header, valSet *cmttypes.ValidatorSet, signers map[string]cmttypes.PrivValidator) (*cmtproto.SignedHeader, error) {
+	hhash := proposedHeader.Hash()
+	blockID := MakeBlockID(hhash, 3, tmhash.Sum([]byte("part_set")))
+	voteSet := cmttypes.NewVoteSet(proposedHeader.ChainID, proposedHeader.Height, 1, cmtproto.PrecommitType, valSet)
+
+	// MakeExtCommit expects a signer array in the same order as the validator array.
+	// Thus we iterate over the ordered validator set and construct a signer array
+	// from the signer map in the same order.
+	signerArr := make([]cmttypes.PrivValidator, len(valSet.Validators))
+	for i, v := range valSet.Validators { //nolint:staticcheck // need to check for nil validator set
+		signerArr[i] = signers[v.Address.String()]
+	}
+
+	extCommit, err := cmttypes.MakeExtCommit(blockID, proposedHeader.Height, 1, voteSet, signerArr, proposedHeader.Time, false)
+	if err != nil {
+		return nil, err
+	}
+
+	signedHeader := &cmtproto.SignedHeader{
+		Header: proposedHeader.ToProto(),
+		Commit: extCommit.ToCommit().ToProto(),
+	}
+
+	return signedHeader, nil
+}
+
 // CreateTMClientHeader creates a TM header to update the TM client. Args are passed in to allow
 // caller flexibility to use params that differ from the chain.
 func (chain *TestChain) CreateTMClientHeader(chainID string, blockHeight int64, trustedHeight clienttypes.Height, timestamp time.Time, cmtValSet, nextVals, cmtTrustedVals *cmttypes.ValidatorSet, signers map[string]cmttypes.PrivValidator) *ibctm.Header {
@@ -513,7 +542,7 @@ func (chain *TestChain) CreateTMClientHeader(chainID string, blockHeight int64,
 	)
 	require.NotNil(chain.TB, cmtValSet)
 
-	cmtHeader := cmttypes.Header{
+	proposedHeader := cmttypes.Header{
 		Version:            cmtprotoversion.Consensus{Block: cmtversion.BlockProtocol, App: 2},
 		ChainID:            chainID,
 		Height:             blockHeight,
@@ -530,26 +559,9 @@ func (chain *TestChain) CreateTMClientHeader(chainID string, blockHeight int64,
 		ProposerAddress:    cmtValSet.Proposer.Address, //nolint:staticcheck
 	}
 
-	hhash := cmtHeader.Hash()
-	blockID := MakeBlockID(hhash, 3, tmhash.Sum([]byte("part_set")))
-	voteSet := cmttypes.NewVoteSet(chainID, blockHeight, 1, cmtproto.PrecommitType, cmtValSet)
-
-	// MakeCommit expects a signer array in the same order as the validator array.
-	// Thus we iterate over the ordered validator set and construct a signer array
-	// from the signer map in the same order.
-	var signerArr []cmttypes.PrivValidator   //nolint:prealloc // using prealloc here would be needlessly complex
-	for _, v := range cmtValSet.Validators { //nolint:staticcheck // need to check for nil validator set
-		signerArr = append(signerArr, signers[v.Address.String()])
-	}
-
-	extCommit, err := cmttypes.MakeExtCommit(blockID, blockHeight, 1, voteSet, signerArr, timestamp, false)
+	signedHeader, err := CommitHeader(proposedHeader, cmtValSet, signers)
 	require.NoError(chain.TB, err)
 
-	signedHeader := &cmtproto.SignedHeader{
-		Header: cmtHeader.ToProto(),
-		Commit: extCommit.ToCommit().ToProto(),
-	}
-
 	if cmtValSet != nil { //nolint:staticcheck
 		valSet, err = cmtValSet.ToProto()
 		require.NoError(chain.TB, err)