Add GetTrustedHeader (#390)

* funcion added

* GetTrustedHeader added

relayer/client-tx.go

@@ -197,7 +197,7 @@ func (c *Chain) UpdateClients(dst *Chain) (err error) {
 	return nil
 }
 
-// UpgradesClients upgrades the client on src after dst chain has undergone an upgrade.
+// UpgradeClients upgrades the client on src after dst chain has undergone an upgrade.
 func (c *Chain) UpgradeClients(dst *Chain, height int64) error {
 	sh, err := NewSyncHeaders(c, dst)
 	if err != nil {
@@ -211,10 +211,10 @@ func (c *Chain) UpgradeClients(dst *Chain, height int64) error {
 		height = int64(sh.GetHeight(dst.ChainID))
 	}
 
-	// TODO: construct method of only attempting to get dst header
-	// Note: we explicitly do not check the error since the source
-	// trusted header will fail
-	_, dstUpdateHeader, _ := sh.GetTrustedHeaders(c, dst)
+	dstUpdateHeader, err := sh.GetTrustedHeader(dst, c)
+	if err != nil {
+		return err
+	}
 
 	// query proofs on counterparty
 	clientState, proofUpgradeClient, _, err := dst.QueryUpgradedClient(height)

relayer/headers.go

@@ -100,6 +100,17 @@ func (uh *SyncHeaders) GetTrustedHeaders(src, dst *Chain) (srcTh, dstTh *tmclien
 	return
 }
 
+// GetTrustedHeader returns given chain ID's trusted header
+func (uh *SyncHeaders) GetTrustedHeader(src, dst *Chain) (header *tmclient.Header, err error) {
+	eg := new(errgroup.Group)
+	eg.Go(func() error {
+		header, err = InjectTrustedFields(src, dst, uh.GetHeader(src.ChainID))
+		return err
+	})
+	err = eg.Wait()
+	return
+}
+
 // InjectTrustedFields injects the necessary trusted fields for a srcHeader coming from a srcChain
 // destined for an IBC client stored on the dstChain
 // TrustedHeight is the latest height of the IBC client on dstChain