reenable support for substreams with only 'params' as inputs, fix sto…

…p-block-num validation when set to 0

docs/release-notes/change-log.md

@@ -9,9 +9,10 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## v1.6.1 (Unreleased)
+## v1.6.1
 
-* Fix error handling when resolved start-block == stop-block
+* Revert sanity check to support the special case of a substreams with only 'params' as input. This allows a chain-agnostic event to be sent, along with the clock. 
+* Fix error handling when resolved start-block == stop-block and stop-block is defined as non-zero
 
 ## v1.6.0
 

pipeline/exec/graph.go

@@ -233,6 +233,9 @@ func computeStages(mods []*pbsubstreams.Module, initBlocks map[string]uint64) (s
 				var depModName string
 				switch input := dep.Input.(type) {
 				case *pbsubstreams.Module_Input_Params_:
+					if len(mod.Inputs) == 1 {
+						validInputsAtInitialBlock = true // special case where a module has only params as input, to extract the clock
+					}
 					continue
 				case *pbsubstreams.Module_Input_Source_:
 					validInputsAtInitialBlock = true

service/tier1.go

@@ -365,7 +365,7 @@ func (s *Tier1Service) blocks(ctx context.Context, request *pbsubstreamsrpc.Requ
 		return fmt.Errorf("build request details: %w", err)
 	}
 
-	if requestDetails.ResolvedStartBlockNum == request.StopBlockNum {
+	if requestDetails.ResolvedStartBlockNum == request.StopBlockNum && request.StopBlockNum != 0 {
 		return bsstream.NewErrInvalidArg("start block and stop block are the same")
 	}