toml.Unmarshaler supports leaf nodes (#444)

Fixes #437

marshal_test.go

@@ -3,6 +3,7 @@ package toml
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -3976,3 +3977,59 @@ func TestGithubIssue431(t *testing.T) {
 		t.Errorf("UnmarshalTOML should not have been called")
 	}
 }
+
+type durationString struct {
+	time.Duration
+}
+
+func (d *durationString) UnmarshalTOML(v interface{}) error {
+	d.Duration = 10 * time.Second
+	return nil
+}
+
+type config437Error struct {
+}
+
+func (e *config437Error) UnmarshalTOML(v interface{}) error {
+	return errors.New("expected")
+}
+
+type config437 struct {
+	HTTP struct {
+		PingTimeout durationString `toml:"PingTimeout"`
+		ErrorField  config437Error
+	} `toml:"HTTP"`
+}
+
+func TestGithubIssue437(t *testing.T) {
+	src := `
+[HTTP]
+PingTimeout = "32m"
+`
+	cfg := &config437{}
+	cfg.HTTP.PingTimeout = durationString{time.Second}
+
+	r := strings.NewReader(src)
+	err := NewDecoder(r).Decode(cfg)
+	if err != nil {
+		t.Fatalf("unexpected errors %s", err)
+	}
+	expected := durationString{10 * time.Second}
+	if cfg.HTTP.PingTimeout != expected {
+		t.Fatalf("expected '%s', got '%s'", expected, cfg.HTTP.PingTimeout)
+	}
+}
+
+func TestLeafUnmarshalerError(t *testing.T) {
+	src := `
+[HTTP]
+ErrorField = "foo"
+`
+	cfg := &config437{}
+
+	r := strings.NewReader(src)
+	err := NewDecoder(r).Decode(cfg)
+	if err == nil {
+		t.Fatalf("error was expected")
+	}
+}