config: Do not migrate config file if not needed. (#4264)

Also improve the error message returned by `pkg/quick`.

Fixes #4233

pkg/quick/encoding.go

@@ -21,6 +21,7 @@ package quick
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"path/filepath"
 	"runtime"
@@ -55,12 +56,15 @@ func (j jsonEncoding) Unmarshal(b []byte, v interface{}) error {
 	err := json.Unmarshal(b, v)
 	if err != nil {
 		// Try to return a sophisticated json error message if possible
-		switch err := err.(type) {
+		switch jerr := err.(type) {
 		case *json.SyntaxError:
-			return FormatJSONSyntaxError(bytes.NewReader(b), err)
-		default:
-			return err
+			return fmt.Errorf("Unable to parse JSON schema due to a syntax error at '%s'",
+				FormatJSONSyntaxError(bytes.NewReader(b), jerr.Offset))
+		case *json.UnmarshalTypeError:
+			return fmt.Errorf("Unable to parse JSON, type '%v' cannot be converted into the Go '%v' type",
+				jerr.Value, jerr.Type)
 		}
+		return err
 	}
 	return nil
 }

pkg/quick/errorutil.go

@@ -21,28 +21,22 @@ package quick
 import (
 	"bufio"
 	"bytes"
-	"encoding/json"
-	"errors"
 	"fmt"
 	"io"
 
 	"github.com/cheggaaa/pb"
 )
 
-const errorFmt = "%5d: %s <--  "
+const errorFmt = "%5d: %s  <<<<"
 
 // FormatJSONSyntaxError generates a pretty printed json syntax error since
 // golang doesn't provide an easy way to report the location of the error
-func FormatJSONSyntaxError(data io.Reader, sErr *json.SyntaxError) error {
-	if sErr == nil {
-		return nil
-	}
-
+func FormatJSONSyntaxError(data io.Reader, offset int64) (highlight string) {
 	var readLine bytes.Buffer
+	var errLine = 1
+	var readBytes int64
 
 	bio := bufio.NewReader(data)
-	errLine := int64(1)
-	readBytes := int64(0)
 
 	// termWidth is set to a default one to use when we are
 	// not able to calculate terminal width via OS syscalls
@@ -60,13 +54,10 @@ func FormatJSONSyntaxError(data io.Reader, sErr *json.SyntaxError) error {
 	for {
 		b, err := bio.ReadByte()
 		if err != nil {
-			if err != io.EOF {
-				return err
-			}
 			break
 		}
 		readBytes++
-		if readBytes > sErr.Offset {
+		if readBytes > offset {
 			break
 		}
 		switch b {
@@ -88,9 +79,5 @@ func FormatJSONSyntaxError(data io.Reader, sErr *json.SyntaxError) error {
 		idx = 0
 	}
 
-	errorStr := fmt.Sprintf("JSON syntax error at line %d, col %d : %s.\n",
-		errLine, readLine.Len(), sErr)
-	errorStr += fmt.Sprintf(errorFmt, errLine, readLine.String()[idx:])
-
-	return errors.New(errorStr)
+	return fmt.Sprintf(errorFmt, errLine, readLine.String()[idx:])
 }

pkg/quick/quick.go

@@ -127,7 +127,7 @@ func (d config) Diff(c Config) ([]structs.Field, error) {
 	return fields, nil
 }
 
-//DeepDiff  - list fields in A that are missing or not equal to fields in B
+// DeepDiff  - list fields in A that are missing or not equal to fields in B
 func (d config) DeepDiff(c Config) ([]structs.Field, error) {
 	var fields []structs.Field
 
@@ -196,12 +196,22 @@ func New(data interface{}) (Config, error) {
 	return d, nil
 }
 
+// GetVersion - extracts the version information.
+func GetVersion(filename string) (version string, err error) {
+	var qc Config
+	if qc, err = Load(filename, &struct {
+		Version string
+	}{}); err != nil {
+		return "", err
+	}
+	return qc.Version(), err
+}
+
 // Load - loads json config from filename for the a given struct data
 func Load(filename string, data interface{}) (qc Config, err error) {
 	if qc, err = New(data); err == nil {
 		err = qc.Load(filename)
 	}
-
 	return qc, err
 }
 

pkg/quick/quick_test.go

@@ -36,6 +36,42 @@ type MySuite struct{}
 
 var _ = Suite(&MySuite{})
 
+func (s *MySuite) TestReadVersion(c *C) {
+	type myStruct struct {
+		Version string
+	}
+	saveMe := myStruct{"1"}
+	config, err := New(&saveMe)
+	c.Assert(err, IsNil)
+	err = config.Save("test.json")
+	c.Assert(err, IsNil)
+
+	version, err := GetVersion("test.json")
+	c.Assert(err, IsNil)
+	c.Assert(version, Equals, "1")
+}
+
+func (s *MySuite) TestReadVersionErr(c *C) {
+	type myStruct struct {
+		Version int
+	}
+	saveMe := myStruct{1}
+	_, err := New(&saveMe)
+	c.Assert(err, Not(IsNil))
+
+	err = ioutil.WriteFile("test.json", []byte("{ \"version\":2,"), 0644)
+	c.Assert(err, IsNil)
+
+	_, err = GetVersion("test.json")
+	c.Assert(err, Not(IsNil))
+
+	err = ioutil.WriteFile("test.json", []byte("{ \"version\":2 }"), 0644)
+	c.Assert(err, IsNil)
+
+	_, err = GetVersion("test.json")
+	c.Assert(err, Not(IsNil))
+}
+
 func (s *MySuite) TestSaveFailOnDir(c *C) {
 	defer os.RemoveAll("test.json")
 	e := os.MkdirAll("test.json", 0644)