Extend set/omit expr function

It updates 1st parameter of set expr function from merger type to interface, so It will accept constant values, also extend set/omit usage for ComposeRecordValues.

pkg/expr/expr_types.go

@@ -64,7 +64,20 @@ func ResolveTypes(rt resolvableType, resolver func(typ string) Type) error {
 	return rt.ResolveTypes(resolver)
 }
 
-func set(m merger, key string, val interface{}) (out TypedValue, err error) {
+func set(i interface{}, key string, val interface{}) (out TypedValue, err error) {
+	m, ok := i.(merger)
+	if !ok {
+		i, err = Typify(i)
+		if err != nil {
+			return
+		}
+
+		m, ok = i.(merger)
+		if !ok {
+			return out, fmt.Errorf("cannot set on unexpected type: %T", i)
+		}
+	}
+
 	out, err = m.Merge()
 	if err != nil {
 		return

pkg/expr/vars.go

@@ -75,7 +75,7 @@ func (t *Vars) ResolveTypes(res func(typ string) Type) (err error) {
 }
 
 // Merge combines the given Vars(es) into Vars
-// NOTE: It will return CLONE of the original Vars, if its called without any parameters
+// NOTE: It will return CLONE of the original Vars, if it's called without any parameters
 func (t *Vars) Merge(nn ...Iterator) (out TypedValue, err error) {
 	return t.MustMerge(nn...), nil
 }
@@ -336,7 +336,7 @@ func (t *Vars) Each(fn func(k string, v TypedValue) error) (err error) {
 	return
 }
 
-// Set set/update the specific key value in KV
+// Set or update the specific key value in Vars
 func (t *Vars) Set(k string, v interface{}) (err error) {
 	t.mux.RLock()
 	defer t.mux.RUnlock()
@@ -485,7 +485,7 @@ func CastToVars(val interface{}) (out map[string]TypedValue, err error) {
 	return nil, fmt.Errorf("unable to cast type %T to %T", val, out)
 }
 
-// Filter take keys returns KV with only those key value pair
+// Filter take keys returns Vars with only those key value pair
 func (t *Vars) Filter(keys ...string) (out TypedValue, err error) {
 	t.mux.RLock()
 	defer t.mux.RUnlock()
@@ -505,7 +505,7 @@ func (t *Vars) Filter(keys ...string) (out TypedValue, err error) {
 	return vars, nil
 }
 
-// Delete take keys returns KV without those key value pair
+// Delete take keys returns Vars without those key value pair
 func (t *Vars) Delete(keys ...string) (out TypedValue, err error) {
 	t.mux.RLock()
 	defer t.mux.RUnlock()