Display line number on JSON errors

pkg/util/yaml/decoder.go

@@ -20,7 +20,10 @@ import (
 	"bufio"
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"io"
+	"io/ioutil"
+	"strings"
 	"unicode"
 
 	"github.com/ghodss/yaml"
@@ -203,7 +206,20 @@ func (d *YAMLOrJSONDecoder) Decode(into interface{}) error {
 			d.decoder = NewYAMLToJSONDecoder(buffer)
 		}
 	}
-	return d.decoder.Decode(into)
+	err := d.decoder.Decode(into)
+	if jsonDecoder, ok := d.decoder.(*json.Decoder); ok {
+		if syntax, ok := err.(*json.SyntaxError); ok {
+			data, readErr := ioutil.ReadAll(jsonDecoder.Buffered())
+			if readErr != nil {
+				glog.V(4).Infof("reading stream failed: %v", readErr)
+			}
+			js := string(data)
+			start := strings.LastIndex(js[:syntax.Offset], "\n") + 1
+			line := strings.Count(js[:start], "\n")
+			return fmt.Errorf("json: line %d: %s", line, syntax.Error())
+		}
+	}
+	return err
 }
 
 // GuessJSONStream scans the provided reader up to size, looking

pkg/util/yaml/decoder_test.go

@@ -22,6 +22,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"strings"
 	"testing"
 )
 
@@ -125,6 +126,41 @@ stuff: 1
 	}
 }
 
+func TestDecodeBrokenYAML(t *testing.T) {
+	s := NewYAMLOrJSONDecoder(bytes.NewReader([]byte(`---
+stuff: 1
+		test-foo: 1
+
+---       
+  `)), 100)
+	obj := generic{}
+	err := s.Decode(&obj)
+	if err == nil {
+		t.Fatal("expected error with yaml: prefix, got no error")
+	}
+	if !strings.HasPrefix(err.Error(), "yaml: line 2:") {
+		t.Fatalf("expected %q to have 'yaml: line 2:' prefix", err.Error())
+	}
+}
+
+func TestDecodeBrokenJSON(t *testing.T) {
+	s := NewYAMLOrJSONDecoder(bytes.NewReader([]byte(`{
+	"foo": {
+		"stuff": 1
+		"otherStuff": 2
+	}
+}
+  `)), 100)
+	obj := generic{}
+	err := s.Decode(&obj)
+	if err == nil {
+		t.Fatal("expected error with json: prefix, got no error")
+	}
+	if !strings.HasPrefix(err.Error(), "json: line 3:") {
+		t.Fatalf("expected %q to have 'json: line 3:' prefix", err.Error())
+	}
+}
+
 type generic map[string]interface{}
 
 func TestYAMLOrJSONDecoder(t *testing.T) {