Fix json path

decode.go

@@ -88,6 +88,9 @@ var (
 )
 
 func extractFromPath(path *Path, data []byte, optFuncs ...DecodeOptionFunc) ([][]byte, error) {
+	if path.path.RootSelectorOnly {
+		return [][]byte{data}, nil
+	}
 	src := make([]byte, len(data)+1) // append nul byte to the end
 	copy(src, data)
 

internal/decoder/map.go

@@ -265,8 +265,9 @@ func (d *mapDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]b
 			if err != nil {
 				return nil, 0, err
 			}
-			cursor = skipWhiteSpace(buf, c)
+			cursor = c
 		}
+		cursor = skipWhiteSpace(buf, cursor)
 		if buf[cursor] == '}' {
 			cursor++
 			return ret, cursor, nil

internal/decoder/path.go

@@ -30,6 +30,7 @@ func (b *PathBuilder) Build(buf []rune) (*Path, error) {
 	}
 	return &Path{
 		node:                    node,
+		RootSelectorOnly:        node == nil,
 		SingleQuotePathSelector: b.singleQuotePathSelector,
 		DoubleQuotePathSelector: b.doubleQuotePathSelector,
 	}, nil
@@ -57,8 +58,8 @@ func (b *PathBuilder) build(buf []rune) (PathNode, error) {
 }
 
 func (b *PathBuilder) buildNextCharIfExists(buf []rune, cursor int) (int, error) {
-	if len(buf) > cursor+1 {
-		offset, err := b.buildNext(buf[cursor+1:])
+	if len(buf) > cursor {
+		offset, err := b.buildNext(buf[cursor:])
 		if err != nil {
 			return 0, err
 		}
@@ -166,14 +167,16 @@ func (b *PathBuilder) buildQuoteSelector(buf []rune, sel QuotePathSelector) (int
 			}
 			selector := buf[:cursor]
 			b.addSelectorNode(string(selector))
-			return b.buildNextCharIfExists(buf, cursor+1)
+			b.singleQuotePathSelector = true
+			return b.buildNextCharIfExists(buf, cursor+2)
 		case '"':
 			if sel != DoubleQuotePathSelector {
 				return 0, errors.ErrInvalidPath("found single quote character in field selector with double quote context")
 			}
 			selector := buf[:cursor]
 			b.addSelectorNode(string(selector))
-			return b.buildNextCharIfExists(buf, cursor)
+			b.doubleQuotePathSelector = true
+			return b.buildNextCharIfExists(buf, cursor+1)
 		}
 	}
 	return 0, errors.ErrInvalidPath("couldn't find quote character in selector quote path context")
@@ -256,7 +259,7 @@ func (b *PathBuilder) buildIndex(buf []rune) (int, error) {
 				return 0, errors.ErrInvalidPath("%q is unexpected index path", buf[:cursor])
 			}
 			b.addIndexNode(int(index))
-			return b.buildNextCharIfExists(buf, cursor)
+			return b.buildNextCharIfExists(buf, cursor+1)
 		}
 	}
 	return 0, errors.ErrInvalidPath("couldn't find right bracket character in index path context")
@@ -311,18 +314,32 @@ const (
 
 type Path struct {
 	node                    PathNode
+	RootSelectorOnly        bool
 	SingleQuotePathSelector bool
 	DoubleQuotePathSelector bool
 }
 
 func (p *Path) Field(sel string) (PathNode, bool, error) {
+	if p.node == nil {
+		return nil, false, nil
+	}
 	return p.node.Field(sel)
 }
 
 func (p *Path) Get(src, dst reflect.Value) error {
+	if p.node == nil {
+		return nil
+	}
 	return p.node.Get(src, dst)
 }
 
+func (p *Path) String() string {
+	if p.node == nil {
+		return "$"
+	}
+	return p.node.String()
+}
+
 type PathNode interface {
 	fmt.Stringer
 	Index(idx int) (PathNode, bool, error)

internal/decoder/slice.go

@@ -350,14 +350,16 @@ func (d *sliceDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][
 							return nil, 0, err
 						}
 						ret = append(ret, buf[start:end])
+						cursor = end
 					}
 				} else {
 					c, err := skipValue(buf, cursor, depth)
 					if err != nil {
 						return nil, 0, err
 					}
-					cursor = skipWhiteSpace(buf, c)
+					cursor = c
 				}
+				cursor = skipWhiteSpace(buf, cursor)
 				switch buf[cursor] {
 				case ']':
 					cursor++

path.go

@@ -33,6 +33,11 @@ type Path struct {
 	path *decoder.Path
 }
 
+// RootSelectorOnly whether only the root selector ($) is used.
+func (p *Path) RootSelectorOnly() bool {
+	return p.path.RootSelectorOnly
+}
+
 // UsedSingleQuotePathSelector whether single quote-based escaping was done when building the JSON Path.
 func (p *Path) UsedSingleQuotePathSelector() bool {
 	return p.path.SingleQuotePathSelector
@@ -48,6 +53,11 @@ func (p *Path) Extract(data []byte, optFuncs ...DecodeOptionFunc) ([][]byte, err
 	return extractFromPath(p, data, optFuncs...)
 }
 
+// PathString returns original JSON Path string.
+func (p *Path) PathString() string {
+	return p.path.String()
+}
+
 // Unmarshal extract and decode the value of the part corresponding to JSON Path from the input data.
 func (p *Path) Unmarshal(data []byte, v interface{}, optFuncs ...DecodeOptionFunc) error {
 	contents, err := extractFromPath(p, data, optFuncs...)