Test JSON decoding and fix implentation

Add a test that decodes a JSON object, and detect links in it. Then encode
it again and it must match the original file. The test failed (because the
link was a map[string]interface{} instead of a Node). The fix post-process
the result of the JSON decoder to convert map[string]interface{} to Node.

Author: mildred

coding/Makefile

@@ -9,3 +9,9 @@ pb/testfile:
 pb/bin/multicodec:
 	$(MAKE) -C pb bin/multicodec
 
+json.testfile: pb/bin/multicodec Makefile
+	: >$@
+	pb/bin/multicodec header /multicodec >>$@
+	pb/bin/multicodec header /json >>$@
+	echo '{"@codec":"/json","abc":{"mlink":"QmXg9Pp2ytZ14xgmQjYEiHjVjMFXzCVVEcRTWJBmLgR39V"}}' >>$@
+

coding/coding.go

@@ -3,7 +3,6 @@ package ipfsld
 import (
 	mc "github.com/jbenet/go-multicodec"
 	mccbor "github.com/jbenet/go-multicodec/cbor"
-	mcjson "github.com/jbenet/go-multicodec/json"
 	mcmux "github.com/jbenet/go-multicodec/mux"
 
 	ipld "github.com/ipfs/go-ipld"
@@ -24,7 +23,7 @@ func init() {
 	defaultCodec = string(mc.HeaderPath(mccbor.Header))
 	muxCodec = mcmux.MuxMulticodec([]mc.Multicodec{
 		mccbor.Multicodec(),
-		mcjson.Multicodec(false),
+		jsonMulticodec(),
 		pb.Multicodec(),
 	}, selectCodec)
 }
@@ -61,8 +60,6 @@ func codecKey(n ipld.Node) (string, error) {
 	if !ok {
 		// if no codec is defined, use our default codec
 		chdr = defaultCodec
-
-		// except, if it looks like an old, style protobuf object
 	}
 
 	chdrs, ok := chdr.(string)

coding/coding_test.go

@@ -3,6 +3,7 @@ package ipfsld
 import (
 	"bytes"
 	"testing"
+	"reflect"
 	"io/ioutil"
 
 	ipld "github.com/ipfs/go-ipld"
@@ -11,14 +12,18 @@ import (
 	mctest "github.com/jbenet/go-multicodec/test"
 )
 
-var testfile []byte
+var testfile, json_testfile []byte
 
 func init() {
 	var err error
 	testfile, err = ioutil.ReadFile("testfile")
 	if err != nil {
 		panic("could not read testfile. please run: make testfile")
 	}
+	json_testfile, err = ioutil.ReadFile("json.testfile")
+	if err != nil {
+		panic("could not read json.testfile. please run: make json.testfile")
+	}
 }
 
 type TC struct {
@@ -125,3 +130,42 @@ func TestPbDecodeEncode(t *testing.T) {
 		t.Log(encoded)
 	}
 }
+
+// Test decoding and encoding a json file
+func TestJsonDecodeEncode(t *testing.T) {
+	var n ipld.Node
+	codec := Multicodec()
+
+	if err := mc.Unmarshal(codec, json_testfile, &n); err != nil {
+		t.Log(json_testfile)
+		t.Error(err)
+		return
+	}
+
+	linksExpected := map[string]ipld.Link{
+		"abc": ipld.Link {
+			"mlink": "QmXg9Pp2ytZ14xgmQjYEiHjVjMFXzCVVEcRTWJBmLgR39V",
+		},
+	}
+	linksActual := ipld.Links(n)
+	if !reflect.DeepEqual(linksExpected, linksActual) {
+		t.Log(linksExpected)
+		t.Log(linksActual)
+		t.Logf("node: %#v\n", n)
+		t.Fatalf("Links are not expected")
+	}
+
+	encoded, err := mc.Marshal(codec, &n)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	if !bytes.Equal(json_testfile, encoded) {
+		t.Error("marshalled values not equal")
+		t.Log(string(json_testfile))
+		t.Log(string(encoded))
+		t.Log(json_testfile)
+		t.Log(encoded)
+	}
+}

coding/json.go

@@ -0,0 +1,71 @@
+package ipfsld
+
+import (
+	"io"
+
+	mc "github.com/jbenet/go-multicodec"
+	mcjson "github.com/jbenet/go-multicodec/json"
+	ipld "github.com/ipfs/go-ipld"
+)
+
+type codec struct {
+	mc.Multicodec
+}
+
+type decoder struct {
+	mc.Decoder
+}
+
+func jsonMulticodec() mc.Multicodec {
+	return &codec{mcjson.Multicodec(false)}
+}
+
+func (c *codec) Decoder(r io.Reader) mc.Decoder {
+	return &decoder{ c.Multicodec.Decoder(r) }
+}
+
+func (c *decoder) Decode(v interface{}) error {
+	err := c.Decoder.Decode(v)
+	if err == nil {
+		convert(v)
+	}
+	return err
+}
+
+func convert(val interface{}) interface{} {
+	switch val.(type) {
+	case *map[string]interface{}:
+		vmi := val.(*map[string]interface{})
+		n := ipld.Node{}
+		for k, v := range *vmi {
+			n[k] = convert(v)
+			(*vmi)[k] = convert(v)
+		}
+		return &n
+	case map[string]interface{}:
+		vmi := val.(map[string]interface{})
+		n := ipld.Node{}
+		for k, v := range vmi {
+			n[k] = convert(v)
+			vmi[k] = convert(v)
+		}
+		return n
+	case *[]interface{}:
+		convert(*val.(*[]interface{}))
+	case []interface{}:
+		slice := val.([]interface{})
+		for k, v := range slice {
+			slice[k] = convert(v)
+		}
+	case *ipld.Node:
+		convert(*val.(*ipld.Node))
+	case ipld.Node:
+		n := val.(ipld.Node)
+		for k, v := range n {
+			n[k] = convert(v)
+		}
+	default:
+	}
+	return val
+}
+

coding/json.testfile

@@ -0,0 +1,3 @@
+/multicodec
+/json
+{"@codec":"/json","abc":{"mlink":"QmXg9Pp2ytZ14xgmQjYEiHjVjMFXzCVVEcRTWJBmLgR39V"}}