fix: properly print tree for oras discover

cmd/oras/root/discover.go

@@ -22,7 +22,6 @@ import (
 	"os"
 	"strings"
 
-	"github.com/need-being/go-tree"
 	"github.com/opencontainers/image-spec/specs-go"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/spf13/cobra"
@@ -31,6 +30,7 @@ import (
 	"oras.land/oras-go/v2"
 	"oras.land/oras/cmd/oras/internal/option"
 	"oras.land/oras/internal/graph"
+	"oras.land/oras/internal/tree"
 )
 
 type discoverOptions struct {
@@ -153,7 +153,7 @@ func fetchAllReferrers(ctx context.Context, repo oras.ReadOnlyGraphTarget, desc
 				if err != nil {
 					return err
 				}
-				referrerNode.AddPathString(strings.TrimSpace(string(bytes)))
+				referrerNode.AddPath(strings.TrimSpace(string(bytes)))
 			}
 		}
 		err := fetchAllReferrers(

go.mod

@@ -3,7 +3,6 @@ module oras.land/oras
 go 1.20
 
 require (
-	github.com/need-being/go-tree v0.1.0
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/opencontainers/image-spec v1.1.0-rc2
 	github.com/oras-project/oras-credentials-go v0.2.0

go.sum

@@ -4,8 +4,6 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
-github.com/need-being/go-tree v0.1.0 h1:blQrtD006cFm97UDeMUfixwPc9o06A6c+uLaUskdNNw=
-github.com/need-being/go-tree v0.1.0/go.mod h1:UOHUchuOm+lxM+EtvQ9h/IO88hK/ke7FHai4oGhhEoI=
 github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
 github.com/opencontainers/image-spec v1.1.0-rc2 h1:2zx/Stx4Wc5pIPDvIxHXvXtQFW/7XWJGmnM7r3wg034=
@@ -36,7 +34,5 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-oras.land/oras-go/v2 v2.2.0 h1:E1fqITD56Eg5neZbxBtAdZVgDHD6wBabJo6xESTcQyo=
-oras.land/oras-go/v2 v2.2.0/go.mod h1:pXjn0+KfarspMHHNR3A56j3tgvr+mxArHuI8qVn59v8=
 oras.land/oras-go/v2 v2.2.1-0.20230531090906-7dd0378382c6 h1:2P1fjq1znGLo7tjy9PJsZrFF5L+qywbv28IgzKEX62E=
 oras.land/oras-go/v2 v2.2.1-0.20230531090906-7dd0378382c6/go.mod h1:pXjn0+KfarspMHHNR3A56j3tgvr+mxArHuI8qVn59v8=

internal/tree/node.go

@@ -0,0 +1,67 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package tree pretty prints trees
+package tree
+
+import "reflect"
+
+// Node represents a tree node.
+type Node struct {
+	Value any
+	Nodes []*Node
+}
+
+// New creates a new tree / root node.
+func New(value any) *Node {
+	return &Node{
+		Value: value,
+	}
+}
+
+// Add adds a leaf node.
+func (n *Node) Add(value any) *Node {
+	node := New(value)
+	n.Nodes = append(n.Nodes, node)
+	return node
+}
+
+// AddPath adds a chain of nodes.
+func (n *Node) AddPath(values ...any) *Node {
+	if len(values) == 0 {
+		return nil
+	}
+
+	current := n
+	for _, value := range values {
+		if node := current.Find(value); node == nil {
+			current = current.Add(value)
+		} else {
+			current = node
+		}
+	}
+	return current
+}
+
+// Find finds the child node with the target value.
+// Nil if not found.
+func (n *Node) Find(value any) *Node {
+	for _, node := range n.Nodes {
+		if reflect.DeepEqual(node.Value, value) {
+			return node
+		}
+	}
+	return nil
+}

internal/tree/node_test.go

@@ -0,0 +1,171 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package tree
+
+import (
+	"bytes"
+	"reflect"
+	"testing"
+)
+
+func TestNode_Add(t *testing.T) {
+	root := &Node{
+		Value: "root",
+	}
+
+	nodeNil := root.Add(nil)
+	want := &Node{}
+	if !reflect.DeepEqual(nodeNil, want) {
+		t.Errorf("Node.Add() = %v, want %v", nodeNil, want)
+	}
+
+	nodeFoo := root.Add("foo")
+	want = &Node{
+		Value: "foo",
+	}
+	if !reflect.DeepEqual(nodeFoo, want) {
+		t.Errorf("Node.Add() = %v, want %v", nodeFoo, want)
+	}
+	nodeBar := nodeFoo.Add("bar")
+	want = &Node{
+		Value: "bar",
+	}
+	if !reflect.DeepEqual(nodeBar, want) {
+		t.Errorf("Node.Add() = %v, want %v", nodeBar, want)
+	}
+
+	node42 := root.Add(42)
+	want = &Node{
+		Value: 42,
+	}
+	if !reflect.DeepEqual(node42, want) {
+		t.Errorf("Node.Add() = %v, want %v", node42, want)
+	}
+
+	buf := bytes.NewBuffer(nil)
+	printer := NewPrinter(buf)
+	if err := printer.Print(root); err != nil {
+		t.Fatalf("Printer.Print() error = %v", err)
+	}
+	gotPrint := buf.String()
+	// root
+	// ├── <nil>
+	// ├── foo
+	// │   └── bar
+	// └── 42
+	wantPrint := "root\n├── <nil>\n├── foo\n│   └── bar\n└── 42\n"
+	if gotPrint != wantPrint {
+		t.Errorf("Node = %s, want %s", gotPrint, wantPrint)
+	}
+}
+
+func TestNode_AddPath(t *testing.T) {
+	root := &Node{
+		Value: "root",
+	}
+
+	nodeNil := root.AddPath()
+	var want *Node
+	if !reflect.DeepEqual(nodeNil, want) {
+		t.Errorf("Node.AddPath() = %v, want %v", nodeNil, want)
+	}
+
+	nodeBar := root.AddPath("foo", "bar")
+	want = &Node{
+		Value: "bar",
+	}
+	if !reflect.DeepEqual(nodeBar, want) {
+		t.Errorf("Node.AddPath() = %v, want %v", nodeBar, want)
+	}
+	nodeBar2 := root.AddPath("foo", "bar2")
+	want = &Node{
+		Value: "bar2",
+	}
+	if !reflect.DeepEqual(nodeBar2, want) {
+		t.Errorf("Node.AddPath() = %v, want %v", nodeBar2, want)
+	}
+
+	node42 := root.AddPath(42)
+	want = &Node{
+		Value: 42,
+	}
+	if !reflect.DeepEqual(node42, want) {
+		t.Errorf("Node.AddPath() = %v, want %v", node42, want)
+	}
+
+	buf := bytes.NewBuffer(nil)
+	printer := NewPrinter(buf)
+	if err := printer.Print(root); err != nil {
+		t.Fatalf("Printer.Print() error = %v", err)
+	}
+	gotPrint := buf.String()
+	// root
+	// ├── foo
+	// │   ├── bar
+	// │   └── bar2
+	// └── 42
+	wantPrint := "root\n├── foo\n│   ├── bar\n│   └── bar2\n└── 42\n"
+	if gotPrint != wantPrint {
+		t.Errorf("Node = %s, want %s", gotPrint, wantPrint)
+	}
+}
+
+func TestNode_Find(t *testing.T) {
+	root := &Node{
+		Value: "root",
+		Nodes: []*Node{
+			{
+				Value: "foo",
+				Nodes: []*Node{
+					{
+						Value: "bar",
+					},
+				},
+			},
+			{
+				Value: 42,
+			},
+		},
+	}
+	tests := []struct {
+		name  string
+		value any
+		want  *Node
+	}{
+		{
+			name:  "find existing node",
+			value: 42,
+			want:  root.Nodes[1],
+		},
+		{
+			name:  "find non-existing node",
+			value: "hello",
+			want:  nil,
+		},
+		{
+			name:  "find non-existing node but it is a grand child",
+			value: "bar",
+			want:  nil,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := root.Find(tt.value); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Node.Find() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

internal/tree/printer.go

@@ -0,0 +1,82 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package tree
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+// Box-drawing symbols
+const (
+	EdgeEmpty = "    "
+	EdgePipe  = "│   "
+	EdgeItem  = "├── "
+	EdgeLast  = "└── "
+)
+
+// DefaultPrinter prints the tree to the stdout with default settings.
+var DefaultPrinter = NewPrinter(os.Stdout)
+
+// Printer prints the tree.
+type Printer struct {
+	writer io.Writer
+}
+
+// NewPrinter create s a new printer.
+func NewPrinter(writer io.Writer) *Printer {
+	return &Printer{
+		writer: writer,
+	}
+}
+
+// Print prints a tree.
+func (p *Printer) Print(root *Node) error {
+	return p.print("", root)
+}
+
+// print prints a tree recursively.
+func (p *Printer) print(prefix string, n *Node) error {
+	if _, err := fmt.Fprintln(p.writer, n.Value); err != nil {
+		return err
+	}
+	size := len(n.Nodes)
+	if size == 0 {
+		return nil
+	}
+
+	prefixItem := prefix + EdgeItem
+	prefixPipe := prefix + EdgePipe
+	last := size - 1
+	for _, n := range n.Nodes[:last] {
+		if _, err := io.WriteString(p.writer, prefixItem); err != nil {
+			return err
+		}
+		if err := p.print(prefixPipe, n); err != nil {
+			return nil
+		}
+	}
+	if _, err := io.WriteString(p.writer, prefix+EdgeLast); err != nil {
+		return err
+	}
+	return p.print(prefix+EdgeEmpty, n.Nodes[last])
+}
+
+// Print prints the tree using the default printer.
+func Print(root *Node) error {
+	return DefaultPrinter.Print(root)
+}