basic implementation of object diff

License: MIT
Signed-off-by: Jeromy <jeromyj@gmail.com>

core/commands/object/diff.go

+package objectcmd
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	cmds "github.com/ipfs/go-ipfs/commands"
+	dagutils "github.com/ipfs/go-ipfs/merkledag/utils"
+	path "github.com/ipfs/go-ipfs/path"
+)
+
+var ObjectDiffCmd = &cmds.Command{
+	Helptext: cmds.HelpText{
+		Tagline: "takes a diff of the two given objects",
+		ShortDescription: `
+`,
+	},
+	Arguments: []cmds.Argument{
+		cmds.StringArg("obj_a", true, false, "object to diff against"),
+		cmds.StringArg("obj_b", true, false, "object to diff"),
+	},
+	Run: func(req cmds.Request, res cmds.Response) {
+		node, err := req.InvocContext().GetNode()
+		if err != nil {
+			res.SetError(err, cmds.ErrNormal)
+			return
+		}
+
+		a := req.Arguments()[0]
+		b := req.Arguments()[1]
+
+		pa, err := path.ParsePath(a)
+		if err != nil {
+			res.SetError(err, cmds.ErrNormal)
+			return
+		}
+
+		pb, err := path.ParsePath(b)
+		if err != nil {
+			res.SetError(err, cmds.ErrNormal)
+			return
+		}
+
+		ctx := req.Context()
+
+		obj_a, err := node.Resolver.ResolvePath(ctx, pa)
+		if err != nil {
+			res.SetError(err, cmds.ErrNormal)
+			return
+		}
+
+		obj_b, err := node.Resolver.ResolvePath(ctx, pb)
+		if err != nil {
+			res.SetError(err, cmds.ErrNormal)
+			return
+		}
+
+		changes, err := dagutils.Diff(ctx, node.DAG, obj_a, obj_b)
+		if err != nil {
+			res.SetError(err, cmds.ErrNormal)
+			return
+		}
+
+		res.SetOutput(changes)
+	},
+	Type: []*dagutils.Change{},
+	Marshalers: cmds.MarshalerMap{
+		cmds.Text: func(res cmds.Response) (io.Reader, error) {
+			changes := res.Output().([]*dagutils.Change)
+			buf := new(bytes.Buffer)
+			for _, change := range changes {
+				switch change.Type {
+				case dagutils.Add:
+					fmt.Fprintf(buf, "added new link %q pointing to %s\n", change.Path, change.After)
+				case dagutils.Mod:
+					fmt.Fprintf(buf, "changed %q from %s to %s\n", change.Path, change.Before, change.After)
+				case dagutils.Remove:
+					fmt.Fprintf(buf, "removed link %q (was %s)\n", change.Path, change.Before)
+				}
+			}
+			return buf, nil
+		},
+	},
+}

core/commands/object/object.go

@@ -48,13 +48,14 @@ var ObjectCmd = &cmds.Command{
 'ipfs object' is a plumbing command used to manipulate DAG objects
 directly.`,
 		Synopsis: `
-ipfs object data <key>      - Outputs raw bytes in an object
-ipfs object get <key>       - Get the DAG node named by <key>
-ipfs object links <key>     - Outputs links pointed to by object
-ipfs object new <template>  - Create new ipfs objects
-ipfs object patch <args>    - Create new object from old ones
-ipfs object put <data>      - Stores input, outputs its key
-ipfs object stat <key>      - Outputs statistics of object
+ipfs object data <key>           - Outputs raw bytes in an object
+ipfs object get <key>            - Get the DAG node named by <key>
+ipfs object links <key>          - Outputs links pointed to by object
+ipfs object new <template>       - Create new ipfs objects
+ipfs object patch <args>         - Create new object from old ones
+ipfs object put <data>           - Stores input, outputs its key
+ipfs object stat <key>           - Outputs statistics of object
+ipfs object diff <key1> <key2>   - Diffs two given objects
 `,
 	},
 
@@ -66,6 +67,7 @@ ipfs object stat <key>      - Outputs statistics of object
 		"patch": ObjectPatchCmd,
 		"put":   ObjectPutCmd,
 		"stat":  ObjectStatCmd,
+		"diff":  ObjectDiffCmd,
 	},
 }
 

merkledag/utils/diff.go

@@ -75,17 +75,25 @@ func ApplyChange(ctx context.Context, ds dag.DAGService, nd *dag.Node, cs []*Cha
 	return e.Finalize(ds)
 }
 
-func Diff(ctx context.Context, ds dag.DAGService, a, b *dag.Node) []*Change {
+func Diff(ctx context.Context, ds dag.DAGService, a, b *dag.Node) ([]*Change, error) {
 	if len(a.Links) == 0 && len(b.Links) == 0 {
-		ak, _ := a.Key()
-		bk, _ := b.Key()
+		ak, err := a.Key()
+		if err != nil {
+			return nil, err
+		}
+
+		bk, err := b.Key()
+		if err != nil {
+			return nil, err
+		}
+
 		return []*Change{
 			&Change{
 				Type:   Mod,
 				Before: ak,
 				After:  bk,
 			},
-		}
+		}, nil
 	}
 
 	var out []*Change
@@ -99,9 +107,20 @@ func Diff(ctx context.Context, ds dag.DAGService, a, b *dag.Node) []*Change {
 			if bytes.Equal(l.Hash, lnk.Hash) {
 				// no change... ignore it
 			} else {
-				anode, _ := lnk.GetNode(ctx, ds)
-				bnode, _ := l.GetNode(ctx, ds)
-				sub := Diff(ctx, ds, anode, bnode)
+				anode, err := lnk.GetNode(ctx, ds)
+				if err != nil {
+					return nil, err
+				}
+
+				bnode, err := l.GetNode(ctx, ds)
+				if err != nil {
+					return nil, err
+				}
+
+				sub, err := Diff(ctx, ds, anode, bnode)
+				if err != nil {
+					return nil, err
+				}
 
 				for _, subc := range sub {
 					subc.Path = path.Join(lnk.Name, subc.Path)
@@ -128,7 +147,7 @@ func Diff(ctx context.Context, ds dag.DAGService, a, b *dag.Node) []*Change {
 		})
 	}
 
-	return out
+	return out, nil
 }
 
 type Conflict struct {

test/sharness/t0052-object-diff.sh

+#!/bin/sh
+#
+# Copyright (c) 2016 Jeromy Johnson
+# MIT Licensed; see the LICENSE file in this repository.
+#
+
+test_description="Test object diff command"
+
+. lib/test-lib.sh
+
+test_init_ipfs
+
+test_expect_success "create some objects for testing diffs" '
+	mkdir foo &&
+	echo "stuff" > foo/bar &&
+	mkdir foo/baz &&
+	A=$(ipfs add -r -q foo | tail -n1) &&
+	echo "more things" > foo/cat &&
+	B=$(ipfs add -r -q foo | tail -n1) &&
+	echo "nested" > foo/baz/dog &&
+	C=$(ipfs add -r -q foo | tail -n1)
+	echo "changed" > foo/bar &&
+	D=$(ipfs add -r -q foo | tail -n1)
+'
+
+test_expect_success "diff against self is empty" '
+	ipfs object diff $A $A > diff_out
+'
+
+test_expect_success "identity diff output looks good" '
+	printf "" > diff_exp &&
+	test_cmp diff_exp diff_out
+'
+
+test_expect_success "diff added link works" '
+	ipfs object diff $A $B > diff_out
+'
+
+test_expect_success "diff added link looks right" '
+	echo added new link \"cat\" pointing to QmUSvcqzhdfYM1KLDbM76eLPdS9ANFtkJvFuPYeZt73d7A > diff_exp &&
+	test_cmp diff_exp diff_out
+'
+
+test_expect_success "diff removed link works" '
+	ipfs object diff $B $A > diff_out
+'
+
+test_expect_success "diff removed link looks right" '
+	echo removed link \"cat\" \(was QmUSvcqzhdfYM1KLDbM76eLPdS9ANFtkJvFuPYeZt73d7A\) > diff_exp &&
+	test_cmp diff_exp diff_out
+'
+
+test_expect_success "diff nested add works" '
+	ipfs object diff $B $C > diff_out
+'
+
+test_expect_success "diff looks right" '
+	echo added new link \"baz/dog\" pointing to QmdNJQUTZuDpsUcec7YDuCfRfvw1w4J13DCm7YcU4VMZdS > diff_exp &&
+	test_cmp diff_exp diff_out
+'
+
+test_expect_success "diff changed link works" '
+	ipfs object diff $C $D > diff_out
+'
+
+test_expect_success "diff looks right" '
+	echo changed \"bar\" from QmNgd5cz2jNftnAHBhcRUGdtiaMzb5Rhjqd4etondHHST8 to QmRfFVsjSXkhFxrfWnLpMae2M4GBVsry6VAuYYcji5MiZb > diff_exp &&
+	test_cmp diff_exp diff_out
+'
+
+test_done