fix!: UnmarshalJSON is limited to the default Tree bug (#277)

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## Overview

Closed: #275 

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## Checklist

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- [x] New and updated code has appropriate documentation
- [x] New and updated code has new and/or updated testing
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---------

Co-authored-by: Rootul P <rootulp@gmail.com>
Co-authored-by: Sanaz Taheri <35961250+staheri14@users.noreply.github.com>

default_tree.go

@@ -0,0 +1,48 @@
+package rsmt2d
+
+import (
+	"crypto/sha256"
+	"fmt"
+
+	"github.com/celestiaorg/merkletree"
+)
+
+var DefaultTreeName = "default-tree"
+
+func init() {
+	err := RegisterTree(DefaultTreeName, NewDefaultTree)
+	if err != nil {
+		panic(fmt.Sprintf("%s already registered", DefaultTreeName))
+	}
+}
+
+var _ Tree = &DefaultTree{}
+
+type DefaultTree struct {
+	*merkletree.Tree
+	leaves [][]byte
+	root   []byte
+}
+
+func NewDefaultTree(_ Axis, _ uint) Tree {
+	return &DefaultTree{
+		Tree:   merkletree.New(sha256.New()),
+		leaves: make([][]byte, 0, 128),
+	}
+}
+
+func (d *DefaultTree) Push(data []byte) error {
+	// ignore the idx, as this implementation doesn't need that info
+	d.leaves = append(d.leaves, data)
+	return nil
+}
+
+func (d *DefaultTree) Root() ([]byte, error) {
+	if d.root == nil {
+		for _, l := range d.leaves {
+			d.Tree.Push(l)
+		}
+		d.root = d.Tree.Root()
+	}
+	return d.root, nil
+}

extendeddatacrossword_test.go

@@ -390,8 +390,14 @@ func TestCorruptedEdsReturnsErrByzantineData_UnorderedShares(t *testing.T) {
 
 	codec := NewLeoRSCodec()
 
+	edsWidth := 4            // number of shares per row/column in the extended data square
+	odsWidth := edsWidth / 2 // number of shares per row/column in the original data square
+	err := RegisterTree("testing-tree", newConstructor(uint64(odsWidth), nmt.NamespaceIDSize(namespaceSize)))
+	assert.NoError(t, err)
+
 	// create a DA header
 	eds := createTestEdsWithNMT(t, codec, shareSize, namespaceSize, 1, 2, 3, 4)
+
 	assert.NotNil(t, eds)
 	dAHeaderRoots, err := eds.getRowRoots()
 	assert.NoError(t, err)
@@ -436,10 +442,11 @@ func createTestEdsWithNMT(t *testing.T, codec Codec, shareSize, namespaceSize in
 	for i, shareValue := range sharesValue {
 		shares[i] = bytes.Repeat([]byte{byte(shareValue)}, shareSize)
 	}
-	edsWidth := 4            // number of shares per row/column in the extended data square
-	odsWidth := edsWidth / 2 // number of shares per row/column in the original data square
 
-	eds, err := ComputeExtendedDataSquare(shares, codec, newConstructor(uint64(odsWidth), nmt.NamespaceIDSize(namespaceSize)))
+	treeConstructorFn, err := TreeFn("testing-tree")
+	require.NoError(t, err)
+
+	eds, err := ComputeExtendedDataSquare(shares, codec, treeConstructorFn)
 	require.NoError(t, err)
 
 	return eds

extendeddatasquare.go

@@ -15,29 +15,45 @@ import (
 type ExtendedDataSquare struct {
 	*dataSquare
 	codec             Codec
+	treeName          string
 	originalDataWidth uint
 }
 
 func (eds *ExtendedDataSquare) MarshalJSON() ([]byte, error) {
 	return json.Marshal(&struct {
 		DataSquare [][]byte `json:"data_square"`
 		Codec      string   `json:"codec"`
+		Tree       string   `json:"tree"`
 	}{
 		DataSquare: eds.dataSquare.Flattened(),
 		Codec:      eds.codec.Name(),
+		Tree:       eds.treeName,
 	})
 }
 
 func (eds *ExtendedDataSquare) UnmarshalJSON(b []byte) error {
 	var aux struct {
 		DataSquare [][]byte `json:"data_square"`
 		Codec      string   `json:"codec"`
+		Tree       string   `json:"tree"`
 	}
 
-	if err := json.Unmarshal(b, &aux); err != nil {
+	err := json.Unmarshal(b, &aux)
+	if err != nil {
+		return err
+	}
+
+	var treeConstructor TreeConstructorFn
+	if aux.Tree == "" {
+		aux.Tree = DefaultTreeName
+	}
+
+	treeConstructor, err = TreeFn(aux.Tree)
+	if err != nil {
 		return err
 	}
-	importedEds, err := ImportExtendedDataSquare(aux.DataSquare, codecs[aux.Codec], NewDefaultTree)
+
+	importedEds, err := ImportExtendedDataSquare(aux.DataSquare, codecs[aux.Codec], treeConstructor)
 	if err != nil {
 		return err
 	}
@@ -61,12 +77,18 @@ func ComputeExtendedDataSquare(
 	if err != nil {
 		return nil, err
 	}
+
 	ds, err := newDataSquare(data, treeCreatorFn, uint(chunkSize))
 	if err != nil {
 		return nil, err
 	}
 
-	eds := ExtendedDataSquare{dataSquare: ds, codec: codec}
+	treeName := getTreeNameFromConstructorFn(treeCreatorFn)
+	if treeName == "" {
+		return nil, errors.New("tree name not found")
+	}
+
+	eds := ExtendedDataSquare{dataSquare: ds, codec: codec, treeName: treeName}
 	err = eds.erasureExtendSquare(codec)
 	if err != nil {
 		return nil, err
@@ -90,12 +112,18 @@ func ImportExtendedDataSquare(
 	if err != nil {
 		return nil, err
 	}
+
 	ds, err := newDataSquare(data, treeCreatorFn, uint(chunkSize))
 	if err != nil {
 		return nil, err
 	}
 
-	eds := ExtendedDataSquare{dataSquare: ds, codec: codec}
+	treeName := getTreeNameFromConstructorFn(treeCreatorFn)
+	if treeName == "" {
+		return nil, errors.New("tree name not found")
+	}
+
+	eds := ExtendedDataSquare{dataSquare: ds, codec: codec, treeName: treeName}
 	err = validateEdsWidth(eds.width)
 	if err != nil {
 		return nil, err

extendeddatasquare_test.go

@@ -111,6 +111,69 @@ func TestMarshalJSON(t *testing.T) {
 	}
 }
 
+// TestUnmarshalJSON test the UnmarshalJSON function.
+func TestUnmarshalJSON(t *testing.T) {
+	treeName := "testing_unmarshalJSON_tree"
+	treeConstructorFn := sudoConstructorFn
+	err := RegisterTree(treeName, treeConstructorFn)
+	require.NoError(t, err)
+
+	codec := NewLeoRSCodec()
+	result, err := ComputeExtendedDataSquare([][]byte{
+		ones, twos,
+		threes, fours,
+	}, codec, treeConstructorFn)
+	if err != nil {
+		panic(err)
+	}
+
+	tests := []struct {
+		name             string
+		malleate         func()
+		expectedTreeName string
+		cleanUp          func()
+	}{
+		{
+			"Tree field exists",
+			func() {},
+			treeName,
+			func() {
+				cleanUp(treeName)
+			},
+		},
+		{
+			"Tree field missing",
+			func() {
+				// clear the tree name value in the eds before marshal
+				result.treeName = ""
+			},
+			DefaultTreeName,
+			func() {},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			test.malleate()
+			edsBytes, err := json.Marshal(result)
+			if err != nil {
+				t.Errorf("failed to marshal EDS: %v", err)
+			}
+
+			var eds ExtendedDataSquare
+			err = json.Unmarshal(edsBytes, &eds)
+			if err != nil {
+				t.Errorf("failed to unmarshal EDS: %v", err)
+			}
+			if !reflect.DeepEqual(result.squareRow, eds.squareRow) {
+				t.Errorf("eds not equal after json marshal/unmarshal")
+			}
+			require.Equal(t, test.expectedTreeName, eds.treeName)
+
+			test.cleanUp()
+		})
+	}
+}
+
 func TestNewExtendedDataSquare(t *testing.T) {
 	t.Run("returns an error if edsWidth is not even", func(t *testing.T) {
 		edsWidth := uint(1)

tree.go

@@ -1,9 +1,9 @@
 package rsmt2d
 
 import (
-	"crypto/sha256"
-
-	"github.com/celestiaorg/merkletree"
+	"fmt"
+	"reflect"
+	"sync"
 )
 
 // TreeConstructorFn creates a fresh Tree instance to be used as the Merkle tree
@@ -22,33 +22,65 @@ type Tree interface {
 	Root() ([]byte, error)
 }
 
-var _ Tree = &DefaultTree{}
+// treeFns is a global map used for keeping track of registered tree constructors for JSON serialization
+// The keys of this map should be kebab cased. E.g. "default-tree"
+var treeFns = sync.Map{}
+
+// RegisterTree must be called in the init function
+func RegisterTree(treeName string, treeConstructor TreeConstructorFn) error {
+	if _, ok := treeFns.Load(treeName); ok {
+		return fmt.Errorf("%s already registered", treeName)
+	}
+
+	treeFns.Store(treeName, treeConstructor)
 
-type DefaultTree struct {
-	*merkletree.Tree
-	leaves [][]byte
-	root   []byte
+	return nil
 }
 
-func NewDefaultTree(_ Axis, _ uint) Tree {
-	return &DefaultTree{
-		Tree:   merkletree.New(sha256.New()),
-		leaves: make([][]byte, 0, 128),
+// TreeFn get tree constructor function by tree name from the global map registry
+func TreeFn(treeName string) (TreeConstructorFn, error) {
+	var treeFn TreeConstructorFn
+	v, ok := treeFns.Load(treeName)
+	if !ok {
+		return nil, fmt.Errorf("%s not registered yet", treeName)
+	}
+	treeFn, ok = v.(TreeConstructorFn)
+	if !ok {
+		return nil, fmt.Errorf("key %s has invalid interface", treeName)
 	}
+
+	return treeFn, nil
 }
 
-func (d *DefaultTree) Push(data []byte) error {
-	// ignore the idx, as this implementation doesn't need that info
-	d.leaves = append(d.leaves, data)
-	return nil
+// removeTreeFn removes a treeConstructorFn by treeName.
+// Only use for test cleanup. Proceed with caution.
+func removeTreeFn(treeName string) {
+	treeFns.Delete(treeName)
 }
 
-func (d *DefaultTree) Root() ([]byte, error) {
-	if d.root == nil {
-		for _, l := range d.leaves {
-			d.Tree.Push(l)
+// Get the tree name by the tree constructor function from the global map registry
+// TODO: this code is temporary until all breaking changes is handle here: https://github.com/celestiaorg/rsmt2d/pull/278
+func getTreeNameFromConstructorFn(treeConstructor TreeConstructorFn) string {
+	key := ""
+	treeFns.Range(func(k, v interface{}) bool {
+		keyString, ok := k.(string)
+		if !ok {
+			// continue checking other key, value
+			return true
 		}
-		d.root = d.Tree.Root()
-	}
-	return d.root, nil
+		treeFn, ok := v.(TreeConstructorFn)
+		if !ok {
+			// continue checking other key, value
+			return true
+		}
+
+		if reflect.DeepEqual(reflect.ValueOf(treeFn), reflect.ValueOf(treeConstructor)) {
+			key = keyString
+			return false
+		}
+
+		return true
+	})
+
+	return key
 }