Merge branch 'yaml'

* yaml:
  Add 'yaml' build tag for conditionally using gopkg.in/yaml.v2
  Add YAML() for generating YAML blocks

Author: wking

util/tap.go

@@ -151,3 +151,15 @@ func (t *T) Diagnostic(message string) {
 func (t *T) Diagnosticf(format string, a ...interface{}) {
 	t.printf("# "+escapeNewlines(format)+"\n", a...)
 }
+
+// YAML generates a YAML block from the message.
+func (t *T) YAML(message interface{}) error {
+	bytes, err := yaml(message, "  ")
+	if err != nil {
+		return err
+	}
+	t.printf("  ---\n  ")
+	t.printf(string(bytes))
+	t.printf("  ...\n")
+	return nil
+}

util/yaml_json.go

@@ -0,0 +1,22 @@
+// +build !yaml
+
+package tap
+
+import (
+	"encoding/json"
+)
+
+// yaml serializes a message to YAML.  This implementation uses JSON,
+// which is a subset of YAML [1] and is implemented by Go's standard
+// library.
+//
+// [1]: http://www.yaml.org/spec/1.2/spec.html#id2759572
+func yaml(message interface{}, prefix string) (marshaled []byte, err error) {
+	marshaled, err = json.MarshalIndent(message, prefix, "  ")
+	if err != nil {
+		return marshaled, err
+	}
+
+	marshaled = append(marshaled, []byte("\n")...)
+	return marshaled, err
+}

util/yaml_yaml.go

@@ -0,0 +1,23 @@
+// +build yaml
+
+package tap
+
+import (
+	"bytes"
+
+	goyaml "gopkg.in/yaml.v2"
+)
+
+// yaml serializes a message to YAML.  This implementation uses
+// non-JSON YAML, which has better prove support [1].
+//
+// [1]: https://rt.cpan.org/Public/Bug/Display.html?id=121606
+func yaml(message interface{}, prefix string) (marshaled []byte, err error) {
+	marshaled, err = goyaml.Marshal(message)
+	if err != nil {
+		return marshaled, err
+	}
+
+	marshaled = bytes.Replace(marshaled, []byte("\n"), []byte("\n"+prefix), -1)
+	return marshaled[:len(marshaled)-len(prefix)], err
+}