VDB-919 Generalise converter (#152)

* Generalise transformer stack to use InsertionModel

* Add tests for event repository

* Restrict accepted values in InsertionModel

* Add call to repository.SetDB

* Improve error propagation/clarity on GetABI()

* Remove maker references in example

* Please golint

* refactor rollback error handling in repository

* Cleaner errors in repository, refactor tests

pkg/contract_watcher/shared/getter/getter_test.go

@@ -47,7 +47,8 @@ var _ = Describe("Interface Getter", func() {
 			transactionConverter := rpc2.NewRpcTransactionConverter(ethClient)
 			blockChain := geth.NewBlockChain(blockChainClient, rpcClient, node, transactionConverter)
 			interfaceGetter := getter.NewInterfaceGetter(blockChain)
-			abi := interfaceGetter.GetABI(constants.PublicResolverAddress, blockNumber)
+			abi, err := interfaceGetter.GetABI(constants.PublicResolverAddress, blockNumber)
+			Expect(err).NotTo(HaveOccurred())
 			Expect(abi).To(Equal(expectedABI))
 			_, err = geth.ParseAbi(abi)
 			Expect(err).ToNot(HaveOccurred())

pkg/contract_watcher/shared/getter/interface_getter.go

@@ -17,6 +17,7 @@
 package getter
 
 import (
+	"fmt"
 	"github.com/vulcanize/vulcanizedb/pkg/contract_watcher/shared/constants"
 	"github.com/vulcanize/vulcanizedb/pkg/contract_watcher/shared/fetcher"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
@@ -40,14 +41,18 @@ func NewInterfaceGetter(blockChain core.BlockChain) *interfaceGetter {
 }
 
 // Used to construct a custom ABI based on the results from calling supportsInterface
-func (g *interfaceGetter) GetABI(resolverAddr string, blockNumber int64) string {
+func (g *interfaceGetter) GetABI(resolverAddr string, blockNumber int64) (string, error) {
 	a := constants.SupportsInterfaceABI
 	args := make([]interface{}, 1)
 	args[0] = constants.MetaSig.Bytes()
 	supports, err := g.getSupportsInterface(a, resolverAddr, blockNumber, args)
-	if err != nil || !supports {
-		return ""
+	if err != nil {
+		return "", fmt.Errorf("call to getSupportsInterface failed: %v", err)
 	}
+	if !supports {
+		return "", fmt.Errorf("contract does not support interface")
+	}
+
 	abiStr := `[`
 	args[0] = constants.AddrChangeSig.Bytes()
 	supports, err = g.getSupportsInterface(a, resolverAddr, blockNumber, args)
@@ -91,7 +96,7 @@ func (g *interfaceGetter) GetABI(resolverAddr string, blockNumber int64) string
 	}
 	abiStr = abiStr[:len(abiStr)-1] + `]`
 
-	return abiStr
+	return abiStr, nil
 }
 
 // Use this method to check whether or not a contract supports a given method/event interface