Generic ast (#1829)

Remove dependency on yaml.Node for internal AST representation. Yaml decoder is now just another decoder.

pkg/yqlib/decoder_test.go

@@ -27,11 +27,14 @@ func processFormatScenario(s formatScenario, decoder Decoder, encoder Encoder) (
 		decoder = NewYamlDecoder(ConfiguredYamlPreferences)
 	}
 
+	log.Debugf("reading docs")
 	inputs, err := readDocuments(strings.NewReader(s.input), "sample.yml", 0, decoder)
 	if err != nil {
 		return "", err
 	}
 
+	log.Debugf("done reading the documents")
+
 	expression := s.expression
 	if expression == "" {
 		expression = "."
@@ -45,6 +48,8 @@ func processFormatScenario(s formatScenario, decoder Decoder, encoder Encoder) (
 
 	context, err := NewDataTreeNavigator().GetMatchingNodes(Context{MatchingNodes: inputs}, exp)
 
+	log.Debugf("Going to print: %v", NodesToString(context.MatchingNodes))
+
 	if err != nil {
 		return "", err
 	}