Move step definition validators to the end

This allows the init to correct invalid/missing bits.

pkg/dal/def_aggregate.go

@@ -75,11 +75,6 @@ func (def *Aggregate) Optimize(reqFilter internalFilter) (rspFilter internalFilt
 }
 
 func (def *Aggregate) init(ctx context.Context) (err error) {
-	err = def.validate()
-	if err != nil {
-		return
-	}
-
 	if def.Filter != nil {
 		def.filter, err = toInternalFilter(def.Filter)
 		if err != nil {
@@ -91,6 +86,11 @@ func (def *Aggregate) init(ctx context.Context) (err error) {
 		def.SourceAttributes = collectAttributes(def.rel)
 	}
 
+	err = def.validate()
+	if err != nil {
+		return
+	}
+
 	return nil
 }
 

pkg/dal/def_datasource.go

@@ -60,11 +60,6 @@ func (def *Datasource) Optimize(req internalFilter) (res internalFilter, err err
 }
 
 func (def *Datasource) init(ctx context.Context, s iterProvider) (err error) {
-	err = def.validate()
-	if err != nil {
-		return
-	}
-
 	if def.Filter != nil {
 		def.filter, err = toInternalFilter(def.Filter)
 		if err != nil {
@@ -83,6 +78,11 @@ func (def *Datasource) init(ctx context.Context, s iterProvider) (err error) {
 
 	def.auxIter = iter
 
+	err = def.validate()
+	if err != nil {
+		return
+	}
+
 	return nil
 }
 

pkg/dal/def_join.go

@@ -84,11 +84,6 @@ func (def *Join) Optimize(req internalFilter) (res internalFilter, err error) {
 }
 
 func (def *Join) init(ctx context.Context) (err error) {
-	err = def.validate()
-	if err != nil {
-		return
-	}
-
 	if len(def.LeftAttributes) == 0 {
 		def.LeftAttributes = collectAttributes(def.relLeft)
 	}
@@ -107,6 +102,11 @@ func (def *Join) init(ctx context.Context) (err error) {
 		}
 	}
 
+	err = def.validate()
+	if err != nil {
+		return
+	}
+
 	return nil
 }