feat: support truncated output and validation error should write in buffer

errors.go

@@ -1,6 +1,7 @@
 package jsonschema
 
 import (
+	"bytes"
 	"fmt"
 	"strings"
 )
@@ -98,16 +99,22 @@ func (ve *ValidationError) Error() string {
 	return fmt.Sprintf("jsonschema: %s does not validate with %s: %s", quote(leaf.InstanceLocation), u+"#"+leaf.KeywordLocation, leaf.Message)
 }
 
-func (ve *ValidationError) GoString() string {
+func (ve *ValidationError) writeIntoBuffer(msgBuf *bytes.Buffer, indent int) {
 	sloc := ve.AbsoluteKeywordLocation
 	sloc = sloc[strings.IndexByte(sloc, '#')+1:]
-	msg := fmt.Sprintf("[I#%s] [S#%s] %s", ve.InstanceLocation, sloc, ve.Message)
+	indentStr := strings.Repeat(" ", indent)
+	msgBuf.WriteString(indentStr)
+	msgBuf.WriteString(fmt.Sprintf("[I#%s] [S#%s] %s", ve.InstanceLocation, sloc, ve.Message))
 	for _, c := range ve.Causes {
-		for _, line := range strings.Split(c.GoString(), "\n") {
-			msg += "\n  " + line
-		}
+		msgBuf.WriteRune('\n')
+		c.writeIntoBuffer(msgBuf, indent+2)
 	}
-	return msg
+}
+
+func (ve *ValidationError) GoString() string {
+	var msgBuf bytes.Buffer
+	ve.writeIntoBuffer(&msgBuf, 0)
+	return msgBuf.String()
 }
 
 func joinPtr(ptr1, ptr2 string) string {

output.go

@@ -75,3 +75,38 @@ func (ve *ValidationError) DetailedOutput() Detailed {
 		Errors:                  errors,
 	}
 }
+
+// Truncated return output in format
+type Truncated struct {
+	Valid                   bool         `json:"valid"`
+	KeywordLocation         string       `json:"keywordLocation"`
+	AbsoluteKeywordLocation string       `json:"absoluteKeywordLocation"`
+	InstanceLocation        string       `json:"instanceLocation"`
+	Error                   string       `json:"error,omitempty"`
+	Errors                  []BasicError `json:"errors,omitempty"`
+}
+
+func (ve *ValidationError) TruncatedOutput() Truncated {
+	var errors []BasicError
+	var flatten func(*ValidationError)
+	flatten = func(ve *ValidationError) {
+		errors = append(errors, BasicError{
+			KeywordLocation:         ve.KeywordLocation,
+			AbsoluteKeywordLocation: ve.AbsoluteKeywordLocation,
+			InstanceLocation:        ve.InstanceLocation,
+			Error:                   ve.Message,
+		})
+		for _, cause := range ve.Causes {
+			flatten(cause)
+			break
+		}
+	}
+	flatten(ve)
+	return Truncated{
+		KeywordLocation:         ve.KeywordLocation,
+		AbsoluteKeywordLocation: ve.AbsoluteKeywordLocation,
+		InstanceLocation:        ve.InstanceLocation,
+		Error:                   ve.Message,
+		Errors:                  errors,
+	}
+}