Merge pull request #1916 from nspcc-dev/fix/oraclefilter

oracle: make JSONPath compatible with C# implementation

go.mod

@@ -1,7 +1,6 @@
 module github.com/nspcc-dev/neo-go
 
 require (
-	github.com/PaesslerAG/jsonpath v0.1.1
 	github.com/Workiva/go-datastructures v1.0.50
 	github.com/abiosoft/readline v0.0.0-20180607040430-155bce2042db
 	github.com/alicebob/miniredis v2.5.0+incompatible
@@ -20,6 +19,7 @@ require (
 	github.com/stretchr/testify v1.6.1
 	github.com/syndtr/goleveldb v0.0.0-20180307113352-169b1b37be73
 	github.com/urfave/cli v1.20.0
+	github.com/virtuald/go-ordered-json v0.0.0-20170621173500-b18e6e673d74
 	go.etcd.io/bbolt v1.3.4
 	go.uber.org/atomic v1.4.0
 	go.uber.org/zap v1.10.0

go.sum

@@ -8,11 +8,6 @@ github.com/DataDog/zstd v1.4.1 h1:3oxKN3wbHibqx897utPC2LTQU4J+IHWWJO+glkAkpFM=
 github.com/DataDog/zstd v1.4.1/go.mod h1:1jcaCB/ufaK+sKp1NBhlGmpz41jOoPQ35bpF36t7BBo=
 github.com/OneOfOne/xxhash v1.2.2 h1:KMrpdQIwFcEqXDklaen+P1axHaj9BSKzvpUUfnHldSE=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
-github.com/PaesslerAG/gval v1.0.0 h1:GEKnRwkWDdf9dOmKcNrar9EA1bz1z9DqPIO1+iLzhd8=
-github.com/PaesslerAG/gval v1.0.0/go.mod h1:y/nm5yEyTeX6av0OfKJNp9rBNj2XrGhAf5+v24IBN1I=
-github.com/PaesslerAG/jsonpath v0.1.0/go.mod h1:4BzmtoM/PI8fPO4aQGIusjGxGir2BzcV0grWtFzq1Y8=
-github.com/PaesslerAG/jsonpath v0.1.1 h1:c1/AToHQMVsduPAa4Vh6xp2U0evy4t8SWp8imEsylIk=
-github.com/PaesslerAG/jsonpath v0.1.1/go.mod h1:lVboNxFGal/VwW6d9JzIy56bUsYAP6tH/x80vjnCseY=
 github.com/Workiva/go-datastructures v1.0.50 h1:slDmfW6KCHcC7U+LP3DDBbm4fqTwZGn1beOFPfGaLvo=
 github.com/Workiva/go-datastructures v1.0.50/go.mod h1:Z+F2Rca0qCsVYDS8z7bAGm8f3UkzuWYS/oBZz5a7VVA=
 github.com/abiosoft/ishell v2.0.0+incompatible h1:zpwIuEHc37EzrsIYah3cpevrIc8Oma7oZPxr03tlmmw=
@@ -235,6 +230,8 @@ github.com/syndtr/goleveldb v0.0.0-20180307113352-169b1b37be73/go.mod h1:Z4AUp2K
 github.com/ugorji/go/codec v0.0.0-20181204163529-d75b2dcb6bc8/go.mod h1:VFNgLljTbGfSG7qAOspJ7OScBnGdDN/yBr0sguwnwf0=
 github.com/urfave/cli v1.20.0 h1:fDqGv3UG/4jbVl/QkFwEdddtEDjh/5Ov6X+0B/3bPaw=
 github.com/urfave/cli v1.20.0/go.mod h1:70zkFmudgCuE/ngEzBv17Jvp/497gISqfk5gWijbERA=
+github.com/virtuald/go-ordered-json v0.0.0-20170621173500-b18e6e673d74 h1:JwtAtbp7r/7QSyGz8mKUbYJBg2+6Cd7OjM8o/GNOcVo=
+github.com/virtuald/go-ordered-json v0.0.0-20170621173500-b18e6e673d74/go.mod h1:RmMWU37GKR2s6pgrIEB4ixgpVCt/cf7dnJv3fuH1J1c=
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
 github.com/yuin/gopher-lua v0.0.0-20190514113301-1cd887cd7036/go.mod h1:gqRgreBUhTSL0GeU64rtZ3Uq3wtjOa/TB2YfrtkCbVQ=
 github.com/yuin/gopher-lua v0.0.0-20191128022950-c6266f4fe8d7 h1:Y17pEjKgx2X0A69WQPGa8hx/Myzu+4NdUxlkZpbAYio=

pkg/core/oracle_test.go

@@ -143,7 +143,7 @@ func TestOracle(t *testing.T) {
 	putOracleRequest(t, cs.Hash, bc, "https://get.maxallowed", nil, "handle", []byte{}, 10_000_000)
 	putOracleRequest(t, cs.Hash, bc, "https://get.maxallowed", nil, "handle", []byte{}, 100_000_000)
 
-	flt := "Values[1]"
+	flt := "$.Values[1]"
 	putOracleRequest(t, cs.Hash, bc, "https://get.filter", &flt, "handle", []byte{}, 10_000_000)
 	putOracleRequest(t, cs.Hash, bc, "https://get.filterinv", &flt, "handle", []byte{}, 10_000_000)
 

pkg/services/oracle/filter.go

@@ -1,28 +1,35 @@
 package oracle
 
 import (
-	"encoding/json"
+	"bytes"
 	"errors"
 	"unicode/utf8"
 
-	"github.com/PaesslerAG/jsonpath"
 	"github.com/nspcc-dev/neo-go/pkg/core/state"
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/services/oracle/jsonpath"
+	json "github.com/virtuald/go-ordered-json"
 )
 
 func filter(value []byte, path string) ([]byte, error) {
 	if !utf8.Valid(value) {
 		return nil, errors.New("not an UTF-8")
 	}
+
+	buf := bytes.NewBuffer(value)
+	d := json.NewDecoder(buf)
+	d.UseOrderedObject()
+
 	var v interface{}
-	if err := json.Unmarshal(value, &v); err != nil {
+	if err := d.Decode(&v); err != nil {
 		return nil, err
 	}
-	result, err := jsonpath.Get(path, v)
+
-	if err != nil {
+	result, ok := jsonpath.Get(path, v)
-		return nil, err
+	if !ok {
+		return nil, errors.New("invalid filter")
 	}
-	return json.Marshal([]interface{}{result})
+	return json.Marshal(result)
 }
 
 func filterRequest(result []byte, req *state.OracleRequest) (transaction.OracleResponseCode, []byte) {

pkg/services/oracle/filter_test.go

@@ -29,10 +29,11 @@ func TestFilter(t *testing.T) {
 	testCases := []struct {
 		result, path string
 	}{
-		{`["Acme Co"]`, "Manufacturers[0].Name"},
+		{"[]", "$.Name"},
-		{`[50]`, "Manufacturers[0].Products[0].Price"},
+		{`["Acme Co"]`, "$.Manufacturers[0].Name"},
-		{`["Elbow Grease"]`, "Manufacturers[1].Products[0].Name"},
+		{`[50]`, "$.Manufacturers[0].Products[0].Price"},
-		{`[{"Name":"Elbow Grease","Price":99.95}]`, "Manufacturers[1].Products[0]"},
+		{`["Elbow Grease"]`, "$.Manufacturers[1].Products[0].Name"},
+		{`[{"Name":"Elbow Grease","Price":99.95}]`, "$.Manufacturers[1].Products[0]"},
 	}
 
 	for _, tc := range testCases {

pkg/services/oracle/jsonpath/jsonpath.go

@@ -0,0 +1,445 @@
+package jsonpath
+
+import (
+	"strconv"
+	"strings"
+
+	json "github.com/virtuald/go-ordered-json"
+)
+
+type (
+	// pathTokenType represents single JSONPath token.
+	pathTokenType byte
+
+	// pathParser combines JSONPath and a position to start parsing from.
+	pathParser struct {
+		s     string
+		i     int
+		depth int
+	}
+)
+
+const (
+	pathInvalid pathTokenType = iota
+	pathRoot
+	pathDot
+	pathLeftBracket
+	pathRightBracket
+	pathAsterisk
+	pathComma
+	pathColon
+	pathIdentifier
+	pathString
+	pathNumber
+)
+
+const maxNestingDepth = 6
+
+// Get returns substructures of value selected by path.
+// The result is always non-nil unless path is invalid.
+func Get(path string, value interface{}) ([]interface{}, bool) {
+	if path == "" {
+		return []interface{}{value}, true
+	}
+
+	p := pathParser{
+		depth: maxNestingDepth,
+		s:     path,
+	}
+
+	typ, _ := p.nextToken()
+	if typ != pathRoot {
+		return nil, false
+	}
+
+	objs := []interface{}{value}
+	for p.i < len(p.s) {
+		var ok bool
+
+		switch typ, _ := p.nextToken(); typ {
+		case pathDot:
+			objs, ok = p.processDot(objs)
+		case pathLeftBracket:
+			objs, ok = p.processLeftBracket(objs)
+		}
+
+		if !ok {
+			return nil, false
+		}
+	}
+
+	if objs == nil {
+		objs = []interface{}{}
+	}
+	return objs, true
+}
+
+func (p *pathParser) nextToken() (pathTokenType, string) {
+	var (
+		typ     pathTokenType
+		value   string
+		ok      = true
+		numRead = 1
+	)
+
+	if p.i >= len(p.s) {
+		return pathInvalid, ""
+	}
+
+	switch c := p.s[p.i]; c {
+	case '$':
+		typ = pathRoot
+	case '.':
+		typ = pathDot
+	case '[':
+		typ = pathLeftBracket
+	case ']':
+		typ = pathRightBracket
+	case '*':
+		typ = pathAsterisk
+	case ',':
+		typ = pathComma
+	case ':':
+		typ = pathColon
+	case '\'':
+		typ = pathString
+		value, numRead, ok = p.parseString()
+	default:
+		switch {
+		case c == '_' || ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'):
+			typ = pathIdentifier
+			value, numRead, ok = p.parseIdent()
+		case c == '-' || ('0' <= c && c <= '9'):
+			typ = pathNumber
+			value, numRead, ok = p.parseNumber()
+		default:
+			return pathInvalid, ""
+		}
+	}
+
+	if !ok {
+		return pathInvalid, ""
+	}
+
+	p.i += numRead
+	return typ, value
+}
+
+// parseString parses JSON string surrounded by single quotes.
+// It returns number of characters were consumed and true on success.
+func (p *pathParser) parseString() (string, int, bool) {
+	var end int
+	for end = p.i + 1; end < len(p.s); end++ {
+		if p.s[end] == '\'' {
+			return p.s[p.i : end+1], end + 1 - p.i, true
+		}
+	}
+
+	return "", 0, false
+}
+
+// parseIdent parses alphanumeric identifier.
+// It returns number of characters were consumed and true on success.
+func (p *pathParser) parseIdent() (string, int, bool) {
+	var end int
+	for end = p.i + 1; end < len(p.s); end++ {
+		c := p.s[end]
+		if c != '_' && !('a' <= c && c <= 'z') &&
+			!('A' <= c && c <= 'Z') && !('0' <= c && c <= '9') {
+			break
+		}
+	}
+
+	return p.s[p.i:end], end - p.i, true
+}
+
+// parseNumber parses integer number.
+// Only string representation is returned, size-checking is done on the first use.
+// It also returns number of characters were consumed and true on success.
+func (p *pathParser) parseNumber() (string, int, bool) {
+	var end int
+	for end = p.i + 1; end < len(p.s); end++ {
+		c := p.s[end]
+		if c < '0' || '9' < c {
+			break
+		}
+	}
+
+	return p.s[p.i:end], end - p.i, true
+}
+
+// processDot handles `.` operator.
+// It either descends 1 level down or performs recursive descent.
+func (p *pathParser) processDot(objs []interface{}) ([]interface{}, bool) {
+	typ, value := p.nextToken()
+	switch typ {
+	case pathAsterisk:
+		return p.descend(objs)
+	case pathDot:
+		return p.descendRecursive(objs)
+	case pathIdentifier:
+		return p.descendByIdent(objs, value)
+	default:
+		return nil, false
+	}
+}
+
+// descend descends 1 level down.
+// It flattens arrays and returns map values for maps.
+func (p *pathParser) descend(objs []interface{}) ([]interface{}, bool) {
+	if p.depth <= 0 {
+		return nil, false
+	}
+	p.depth--
+
+	var values []interface{}
+	for i := range objs {
+		switch obj := objs[i].(type) {
+		case []interface{}:
+			values = append(values, obj...)
+		case json.OrderedObject:
+			for i := range obj {
+				values = append(values, obj[i].Value)
+			}
+		}
+	}
+
+	return values, true
+}
+
+// descendRecursive performs recursive descent.
+func (p *pathParser) descendRecursive(objs []interface{}) ([]interface{}, bool) {
+	typ, val := p.nextToken()
+	if typ != pathIdentifier {
+		return nil, false
+	}
+
+	var values []interface{}
+
+	for len(objs) > 0 {
+		newObjs, _ := p.descendByIdentAux(objs, false, val)
+		values = append(values, newObjs...)
+		objs, _ = p.descend(objs)
+	}
+
+	return values, true
+}
+
+// descendByIdent performs map's field access by name.
+func (p *pathParser) descendByIdent(objs []interface{}, names ...string) ([]interface{}, bool) {
+	return p.descendByIdentAux(objs, true, names...)
+}
+
+func (p *pathParser) descendByIdentAux(objs []interface{}, checkDepth bool, names ...string) ([]interface{}, bool) {
+	if checkDepth {
+		if p.depth <= 0 {
+			return nil, false
+		}
+		p.depth--
+	}
+
+	var values []interface{}
+	for i := range objs {
+		obj, ok := objs[i].(json.OrderedObject)
+		if !ok {
+			continue
+		}
+
+		for j := range names {
+			for k := range obj {
+				if obj[k].Key == names[j] {
+					values = append(values, obj[k].Value)
+					break
+				}
+			}
+		}
+	}
+	return values, true
+}
+
+// descendByIndex performs array access by index.
+func (p *pathParser) descendByIndex(objs []interface{}, indices ...int) ([]interface{}, bool) {
+	if p.depth <= 0 {
+		return nil, false
+	}
+	p.depth--
+
+	var values []interface{}
+	for i := range objs {
+		obj, ok := objs[i].([]interface{})
+		if !ok {
+			continue
+		}
+
+		for _, j := range indices {
+			if j < 0 {
+				j += len(obj)
+			}
+			if 0 <= j && j < len(obj) {
+				values = append(values, obj[j])
+			}
+		}
+	}
+
+	return values, true
+}
+
+// processLeftBracket processes index expressions which can be either
+// array/map access, array sub-slice or union of indices.
+func (p *pathParser) processLeftBracket(objs []interface{}) ([]interface{}, bool) {
+	typ, value := p.nextToken()
+	switch typ {
+	case pathAsterisk:
+		typ, _ := p.nextToken()
+		if typ != pathRightBracket {
+			return nil, false
+		}
+
+		return p.descend(objs)
+	case pathColon:
+		return p.processSlice(objs, 0)
+	case pathNumber:
+		subTyp, _ := p.nextToken()
+		switch subTyp {
+		case pathColon:
+			index, err := strconv.ParseInt(value, 10, 32)
+			if err != nil {
+				return nil, false
+			}
+
+			return p.processSlice(objs, int(index))
+		case pathComma:
+			return p.processUnion(objs, pathNumber, value)
+		case pathRightBracket:
+			index, err := strconv.ParseInt(value, 10, 32)
+			if err != nil {
+				return nil, false
+			}
+
+			return p.descendByIndex(objs, int(index))
+		default:
+			return nil, false
+		}
+	case pathString:
+		subTyp, _ := p.nextToken()
+		switch subTyp {
+		case pathComma:
+			return p.processUnion(objs, pathString, value)
+		case pathRightBracket:
+			s := strings.Trim(value, "'")
+			err := json.Unmarshal([]byte(`"`+s+`"`), &s)
+			if err != nil {
+				return nil, false
+			}
+			return p.descendByIdent(objs, s)
+		default:
+			return nil, false
+		}
+	default:
+		return nil, false
+	}
+}
+
+// processUnion processes union of multiple indices.
+// firstTyp is assumed to be either pathNumber or pathString.
+func (p *pathParser) processUnion(objs []interface{}, firstTyp pathTokenType, firstVal string) ([]interface{}, bool) {
+	items := []string{firstVal}
+	for {
+		typ, val := p.nextToken()
+		if typ != firstTyp {
+			return nil, false
+		}
+
+		items = append(items, val)
+		typ, val = p.nextToken()
+		if typ == pathRightBracket {
+			break
+		} else if typ != pathComma {
+			return nil, false
+		}
+	}
+
+	switch firstTyp {
+	case pathNumber:
+		values := make([]int, len(items))
+		for i := range items {
+			index, err := strconv.ParseInt(items[i], 10, 32)
+			if err != nil {
+				return nil, false
+			}
+			values[i] = int(index)
+		}
+		return p.descendByIndex(objs, values...)
+	case pathString:
+		for i := range items {
+			s := strings.Trim(items[i], "'")
+			err := json.Unmarshal([]byte(`"`+s+`"`), &items[i])
+			if err != nil {
+				return nil, false
+			}
+		}
+		return p.descendByIdent(objs, items...)
+	default:
+		panic("token in union must be either number or string")
+	}
+}
+
+// processSlice processes slice with the specified start index.
+func (p *pathParser) processSlice(objs []interface{}, start int) ([]interface{}, bool) {
+	typ, val := p.nextToken()
+	switch typ {
+	case pathNumber:
+		typ, _ := p.nextToken()
+		if typ != pathRightBracket {
+			return nil, false
+		}
+
+		index, err := strconv.ParseInt(val, 10, 32)
+		if err != nil {
+			return nil, false
+		}
+
+		return p.descendByRange(objs, start, int(index))
+	case pathRightBracket:
+		return p.descendByRange(objs, start, 0)
+	default:
+		return nil, false
+	}
+}
+
+// descendByRange is similar to descend but skips maps and returns sub-slices for arrays.
+func (p *pathParser) descendByRange(objs []interface{}, start, end int) ([]interface{}, bool) {
+	if p.depth <= 0 {
+		return nil, false
+	}
+	p.depth--
+
+	var values []interface{}
+	for i := range objs {
+		arr, ok := objs[i].([]interface{})
+		if !ok {
+			continue
+		}
+
+		subStart := start
+		if subStart < 0 {
+			subStart += len(arr)
+		}
+
+		subEnd := end
+		if subEnd <= 0 {
+			subEnd += len(arr)
+		}
+
+		if subEnd > len(arr) {
+			subEnd = len(arr)
+		}
+
+		if subEnd <= subStart {
+			continue
+		}
+		values = append(values, arr[subStart:subEnd]...)
+	}
+
+	return values, true
+}

pkg/services/oracle/jsonpath/jsonpath_test.go

@@ -0,0 +1,282 @@
+package jsonpath
+
+import (
+	"bytes"
+	"math"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	json "github.com/virtuald/go-ordered-json"
+)
+
+type pathTestCase struct {
+	path   string
+	result string
+}
+
+func unmarshalGet(t *testing.T, js string, path string) ([]interface{}, bool) {
+	var v interface{}
+	buf := bytes.NewBuffer([]byte(js))
+	d := json.NewDecoder(buf)
+	d.UseOrderedObject()
+	require.NoError(t, d.Decode(&v))
+	return Get(path, v)
+}
+
+func (p *pathTestCase) testUnmarshalGet(t *testing.T, js string) {
+	res, ok := unmarshalGet(t, js, p.path)
+	require.True(t, ok)
+
+	data, err := json.Marshal(res)
+	require.NoError(t, err)
+	require.JSONEq(t, p.result, string(data))
+}
+
+func TestInvalidPaths(t *testing.T) {
+	bigNum := strconv.FormatInt(int64(math.MaxInt32)+1, 10)
+
+	// errCases contains invalid json path expressions.
+	// These are either invalid(&) or unexpected token in some positions
+	// or big number/invalid string.
+	errCases := []string{
+		".",
+		"$1",
+		"&",
+		"$&",
+		"$.&",
+		"$.[0]",
+		"$..",
+		"$..*",
+		"$..&",
+		"$..1",
+		"$[&]",
+		"$[**]",
+		"$[1&]",
+		"$[" + bigNum + "]",
+		"$[" + bigNum + ":]",
+		"$[:" + bigNum + "]",
+		"$[1," + bigNum + "]",
+		"$[" + bigNum + "[]]",
+		"$['a'&]",
+		"$['a'1]",
+		"$['a",
+		"$['\\u123']",
+		"$['s','\\u123']",
+		"$[[]]",
+		"$[1,'a']",
+		"$[1,1&",
+		"$[1,1[]]",
+		"$[1:&]",
+		"$[1:1[]]",
+		"$[1:[]]",
+		"$[1:[]]",
+		"$[",
+	}
+
+	for _, tc := range errCases {
+		t.Run(tc, func(t *testing.T) {
+			_, ok := unmarshalGet(t, "{}", tc)
+			require.False(t, ok)
+		})
+	}
+}
+
+func TestDescendByIdent(t *testing.T) {
+	js := `{
+		"store": {
+			"name": "big",
+			"sub": [
+				{ "name": "sub1" },
+				{ "name": "sub2" }
+			],
+			"partner": { "name": "ppp" }
+		},
+		"another": { "name": "small" }
+	}`
+
+	testCases := []pathTestCase{
+		{"$.store.name", `["big"]`},
+		{"$['store']['name']", `["big"]`},
+		{"$[*].name", `["big","small"]`},
+		{"$.*.name", `["big","small"]`},
+		{"$..store.name", `["big"]`},
+		{"$.store..name", `["big","ppp","sub1","sub2"]`},
+		{"$..sub.name", `[]`},
+		{"$..sub..name", `["sub1","sub2"]`},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.path, func(t *testing.T) {
+			tc.testUnmarshalGet(t, js)
+		})
+	}
+
+	t.Run("big depth", func(t *testing.T) {
+		js := `{"a":{"b":{"c":{"d":{"e":{"f":{"g":1}}}}}}}`
+		t.Run("single field", func(t *testing.T) {
+			t.Run("max", func(t *testing.T) {
+				p := pathTestCase{"$.a.b.c.d.e.f", `[{"g":1}]`}
+				p.testUnmarshalGet(t, js)
+			})
+
+			_, ok := unmarshalGet(t, js, "$.a.b.c.d.e.f.g")
+			require.False(t, ok)
+		})
+		t.Run("wildcard", func(t *testing.T) {
+			t.Run("max", func(t *testing.T) {
+				p := pathTestCase{"$.*.*.*.*.*.*", `[{"g":1}]`}
+				p.testUnmarshalGet(t, js)
+			})
+
+			_, ok := unmarshalGet(t, js, "$.*.*.*.*.*.*.*")
+			require.False(t, ok)
+		})
+	})
+}
+
+func TestDescendByIndex(t *testing.T) {
+	js := `["a","b","c","d"]`
+
+	testCases := []pathTestCase{
+		{"$[0]", `["a"]`},
+		{"$[3]", `["d"]`},
+		{"$[1:2]", `["b"]`},
+		{"$[1:-1]", `["b","c"]`},
+		{"$[-3:-1]", `["b","c"]`},
+		{"$[-3:3]", `["b","c"]`},
+		{"$[:3]", `["a","b","c"]`},
+		{"$[:100]", `["a","b","c","d"]`},
+		{"$[1:]", `["b","c","d"]`},
+		{"$[2:1]", `[]`},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path, func(t *testing.T) {
+			tc.testUnmarshalGet(t, js)
+		})
+	}
+
+	t.Run("big depth", func(t *testing.T) {
+		js := `[[[[[[[1]]]]]]]`
+		t.Run("single index", func(t *testing.T) {
+			t.Run("max", func(t *testing.T) {
+				p := pathTestCase{"$[0][0][0][0][0][0]", "[[1]]"}
+				p.testUnmarshalGet(t, js)
+			})
+
+			_, ok := unmarshalGet(t, js, "$[0][0][0][0][0][0][0]")
+			require.False(t, ok)
+		})
+		t.Run("slice", func(t *testing.T) {
+			t.Run("max", func(t *testing.T) {
+				p := pathTestCase{"$[0:][0:][0:][0:][0:][0:]", "[[1]]"}
+				p.testUnmarshalGet(t, js)
+			})
+
+			_, ok := unmarshalGet(t, js, "$[0:][0:][0:][0:][0:][0:][0:]")
+			require.False(t, ok)
+		})
+	})
+
+	t.Run("$[:][1], skip wrong types", func(t *testing.T) {
+		js := `[[1,2],{"1":"4"},[5,6]]`
+		p := pathTestCase{"$[:][1]", "[2,6]"}
+		p.testUnmarshalGet(t, js)
+	})
+
+	t.Run("$[*].*, flatten", func(t *testing.T) {
+		js := `[[1,2],{"1":"4"},[5,6]]`
+		p := pathTestCase{"$[*].*", "[1,2,\"4\",5,6]"}
+		p.testUnmarshalGet(t, js)
+	})
+
+	t.Run("$[*].[1:], skip wrong types", func(t *testing.T) {
+		js := `[[1,2],3,{"1":"4"},[5,6]]`
+		p := pathTestCase{"$[*][1:]", "[2,6]"}
+		p.testUnmarshalGet(t, js)
+	})
+}
+
+func TestUnion(t *testing.T) {
+	js := `["a",{"x":1,"y":2,"z":3},"c","d"]`
+
+	testCases := []pathTestCase{
+		{"$[0,2]", `["a","c"]`},
+		{"$[1]['x','z']", `[1,3]`},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path, func(t *testing.T) {
+			tc.testUnmarshalGet(t, js)
+		})
+	}
+}
+
+// These tests are taken directly from C# code.
+func TestCSharpCompat(t *testing.T) {
+	js := `{
+    "store": {
+        "book": [
+            {
+                "category": "reference",
+                "author": "Nigel Rees",
+                "title": "Sayings of the Century",
+                "price": 8.95
+            },
+            {
+                "category": "fiction",
+                "author": "Evelyn Waugh",
+                "title": "Sword of Honour",
+                "price": 12.99
+            },
+            {
+                "category": "fiction",
+                "author": "Herman Melville",
+                "title": "Moby Dick",
+                "isbn": "0-553-21311-3",
+                "price": 8.99
+            },
+            {
+                "category": "fiction",
+                "author": "J. R. R. Tolkien",
+                "title": "The Lord of the Rings",
+                "isbn": "0-395-19395-8",
+                "price": 22.99
+            }
+        ],
+        "bicycle": {
+                "color": "red",
+            "price": 19.95
+        }
+        },
+    "expensive": 10
+}`
+
+	testCases := []pathTestCase{
+		{"$.store.book[*].author", `["Nigel Rees","Evelyn Waugh","Herman Melville","J. R. R. Tolkien"]`},
+		{"$..author", `["Nigel Rees","Evelyn Waugh","Herman Melville","J. R. R. Tolkien"]`},
+		{"$.store.*", `[[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}],{"color":"red","price":19.95}]`},
+		{"$.store..price", `[19.95,8.95,12.99,8.99,22.99]`},
+		{"$..book[2]", `[{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99}]`},
+		{"$..book[-2]", `[{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99}]`},
+		{"$..book[0,1]", `[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99}]`},
+		{"$..book[:2]", `[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99}]`},
+		{"$..book[1:2]", `[{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99}]`},
+		{"$..book[-2:]", `[{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}]`},
+		{"$..book[2:]", `[{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}]`},
+		{"", `[{"store":{"book":[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}],"bicycle":{"color":"red","price":19.95}},"expensive":10}]`},
+		{"$.*", `[{"book":[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}],"bicycle":{"color":"red","price":19.95}},10]`},
+		{"$..invalidfield", `[]`},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path, func(t *testing.T) {
+			tc.testUnmarshalGet(t, js)
+		})
+	}
+
+	t.Run("bad cases", func(t *testing.T) {
+		_, ok := unmarshalGet(t, js, `$..book[*].author"`)
+		require.False(t, ok)
+	})
+}