feat: use new exchange session logic

Instead of manually creating a session and hoping the DAG we've been passed
implements the Session interface, add the session to the context in WalkDepth.
This should ensure that _any_ walk has an associated session.

go.mod

@@ -4,14 +4,15 @@ require (
 	github.com/gogo/protobuf v1.3.1
 	github.com/ipfs/go-block-format v0.0.2
 	github.com/ipfs/go-blockservice v0.1.0
-	github.com/ipfs/go-cid v0.0.3
+	github.com/ipfs/go-cid v0.0.5
 	github.com/ipfs/go-datastore v0.3.1
 	github.com/ipfs/go-ipfs-blockstore v0.1.0
+	github.com/ipfs/go-ipfs-exchange-interface v0.0.2-0.20200423055703-2e8ddd22ab43
 	github.com/ipfs/go-ipfs-exchange-offline v0.0.1
 	github.com/ipfs/go-ipfs-util v0.0.1
 	github.com/ipfs/go-ipld-cbor v0.0.3
 	github.com/ipfs/go-ipld-format v0.0.2
-	github.com/multiformats/go-multihash v0.0.10
+	github.com/multiformats/go-multihash v0.0.13
 )
 
 go 1.12

go.sum

@@ -70,8 +70,8 @@ github.com/ipfs/go-cid v0.0.1 h1:GBjWPktLnNyX0JiQCNFpUuUSoMw5KMyqrsejHYlILBE=
 github.com/ipfs/go-cid v0.0.1/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
 github.com/ipfs/go-cid v0.0.2 h1:tuuKaZPU1M6HcejsO3AcYWW8sZ8MTvyxfc4uqB4eFE8=
 github.com/ipfs/go-cid v0.0.2/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
-github.com/ipfs/go-cid v0.0.3 h1:UIAh32wymBpStoe83YCzwVQQ5Oy/H0FdxvUS6DJDzms=
-github.com/ipfs/go-cid v0.0.3/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
+github.com/ipfs/go-cid v0.0.5 h1:o0Ix8e/ql7Zb5UVUJEUfjsWCIY8t48++9lR8qi6oiJU=
+github.com/ipfs/go-cid v0.0.5/go.mod h1:plgt+Y5MnOey4vO4UlUazGqdbEXuFYitED67FexhXog=
 github.com/ipfs/go-datastore v0.0.1 h1:AW/KZCScnBWlSb5JbnEnLKFWXL224LBEh/9KXXOrUms=
 github.com/ipfs/go-datastore v0.0.1/go.mod h1:d4KVXhMt913cLBEI/PXAy6ko+W7e9AhyAKBGh803qeE=
 github.com/ipfs/go-datastore v0.0.5 h1:q3OfiOZV5rlsK1H5V8benjeUApRfMGs4Mrhmr6NriQo=
@@ -96,6 +96,8 @@ github.com/ipfs/go-ipfs-ds-help v0.0.1 h1:QBg+Ts2zgeemK/dB0saiF/ykzRGgfoFMT90Rzo
 github.com/ipfs/go-ipfs-ds-help v0.0.1/go.mod h1:gtP9xRaZXqIQRh1HRpp595KbBEdgqWFxefeVKOV8sxo=
 github.com/ipfs/go-ipfs-exchange-interface v0.0.1 h1:LJXIo9W7CAmugqI+uofioIpRb6rY30GUu7G6LUfpMvM=
 github.com/ipfs/go-ipfs-exchange-interface v0.0.1/go.mod h1:c8MwfHjtQjPoDyiy9cFquVtVHkO9b9Ob3FG91qJnWCM=
+github.com/ipfs/go-ipfs-exchange-interface v0.0.2-0.20200423055703-2e8ddd22ab43 h1:m6tthCWsKZHixR2WqO4O5Hq61nRIS13NVxPA/LsFWPE=
+github.com/ipfs/go-ipfs-exchange-interface v0.0.2-0.20200423055703-2e8ddd22ab43/go.mod h1:uChpHomshgrKU+8Uh6y1bh3SKn0jBRrdz4tHGKdDYao=
 github.com/ipfs/go-ipfs-exchange-offline v0.0.1 h1:P56jYKZF7lDDOLx5SotVh5KFxoY6C81I1NSHW1FxGew=
 github.com/ipfs/go-ipfs-exchange-offline v0.0.1/go.mod h1:WhHSFCVYX36H/anEKQboAzpUws3x7UeEGkzQc3iNkM0=
 github.com/ipfs/go-ipfs-pq v0.0.1 h1:zgUotX8dcAB/w/HidJh1zzc1yFq6Vm8J7T2F4itj/RU=
@@ -244,6 +246,8 @@ github.com/mr-tron/base58 v1.1.0/go.mod h1:xcD2VGqlgYjBdcBLw+TuYLr8afG+Hj8g2eTVq
 github.com/mr-tron/base58 v1.1.1/go.mod h1:xcD2VGqlgYjBdcBLw+TuYLr8afG+Hj8g2eTVqeSzSU8=
 github.com/mr-tron/base58 v1.1.2 h1:ZEw4I2EgPKDJ2iEw0cNmLB3ROrEmkOtXIkaG7wZg+78=
 github.com/mr-tron/base58 v1.1.2/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
+github.com/mr-tron/base58 v1.1.3 h1:v+sk57XuaCKGXpWtVBX8YJzO7hMGx4Aajh4TQbdEFdc=
+github.com/mr-tron/base58 v1.1.3/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
 github.com/multiformats/go-base32 v0.0.3 h1:tw5+NhuwaOjJCC5Pp82QuXbrmLzWg7uxlMFp8Nq/kkI=
 github.com/multiformats/go-base32 v0.0.3/go.mod h1:pLiuGC8y0QR3Ue4Zug5UzK9LjgbkL8NSQj0zQ5Nz/AA=
 github.com/multiformats/go-multiaddr v0.0.1 h1:/QUV3VBMDI6pi6xfiw7lr6xhDWWvQKn9udPn68kLSdY=
@@ -264,10 +268,12 @@ github.com/multiformats/go-multihash v0.0.1 h1:HHwN1K12I+XllBCrqKnhX949Orn4oawPk
 github.com/multiformats/go-multihash v0.0.1/go.mod h1:w/5tugSrLEbWqlcgJabL3oHFKTwfvkofsjW2Qa1ct4U=
 github.com/multiformats/go-multihash v0.0.5 h1:1wxmCvTXAifAepIMyF39vZinRw5sbqjPs/UIi93+uik=
 github.com/multiformats/go-multihash v0.0.5/go.mod h1:lt/HCbqlQwlPBz7lv0sQCdtfcMtlJvakRUn/0Ual8po=
-github.com/multiformats/go-multihash v0.0.10 h1:lMoNbh2Ssd9PUF74Nz008KGzGPlfeV6wH3rit5IIGCM=
-github.com/multiformats/go-multihash v0.0.10/go.mod h1:YSLudS+Pi8NHE7o6tb3D8vrpKa63epEDmG8nTduyAew=
+github.com/multiformats/go-multihash v0.0.13 h1:06x+mk/zj1FoMsgNejLpy6QTvJqlSt/BhLEy87zidlc=
+github.com/multiformats/go-multihash v0.0.13/go.mod h1:VdAWLKTwram9oKAatUcLxBNUjdtcVwxObEQBtRfuyjc=
 github.com/multiformats/go-multistream v0.1.0 h1:UpO6jrsjqs46mqAK3n6wKRYFhugss9ArzbyUzU+4wkQ=
 github.com/multiformats/go-multistream v0.1.0/go.mod h1:fJTiDfXJVmItycydCnNx4+wSzZ5NwG2FEVAI30fiovg=
+github.com/multiformats/go-varint v0.0.5 h1:XVZwSo04Cs3j/jS0uAEPpT3JY6DzMcVLLoWOSnCxOjg=
+github.com/multiformats/go-varint v0.0.5/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
 github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/ginkgo v1.7.0 h1:WSHQ+IS43OoUrWtD1/bbclrwK8TTH5hzp+umCiuxHgs=
 github.com/onsi/ginkgo v1.7.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=

merkledag.go

@@ -9,6 +9,7 @@ import (
 	blocks "github.com/ipfs/go-block-format"
 	bserv "github.com/ipfs/go-blockservice"
 	cid "github.com/ipfs/go-cid"
+	exchange "github.com/ipfs/go-ipfs-exchange-interface"
 	ipldcbor "github.com/ipfs/go-ipld-cbor"
 	ipld "github.com/ipfs/go-ipld-format"
 )
@@ -157,17 +158,15 @@ func (n *dagService) Session(ctx context.Context) ipld.NodeGetter {
 }
 
 // FetchGraph fetches all nodes that are children of the given node
-func FetchGraph(ctx context.Context, root cid.Cid, serv ipld.DAGService) error {
-	return FetchGraphWithDepthLimit(ctx, root, -1, serv)
+func FetchGraph(ctx context.Context, root cid.Cid, ng ipld.NodeGetter) error {
+	return FetchGraphWithDepthLimit(ctx, root, -1, ng)
 }
 
 // FetchGraphWithDepthLimit fetches all nodes that are children to the given
 // node down to the given depth. maxDepth=0 means "only fetch root",
 // maxDepth=1 means "fetch root and its direct children" and so on...
 // maxDepth=-1 means unlimited.
-func FetchGraphWithDepthLimit(ctx context.Context, root cid.Cid, depthLim int, serv ipld.DAGService) error {
-	var ng ipld.NodeGetter = NewSession(ctx, serv)
-
+func FetchGraphWithDepthLimit(ctx context.Context, root cid.Cid, depthLim int, ng ipld.NodeGetter) error {
 	set := make(map[cid.Cid]int)
 
 	// Visit function returns true when:
@@ -386,6 +385,11 @@ func Walk(ctx context.Context, getLinks GetLinks, c cid.Cid, visit func(cid.Cid)
 // depth to a given visit function. The visit function can be used to limit DAG
 // exploration.
 func WalkDepth(ctx context.Context, getLinks GetLinks, c cid.Cid, visit func(cid.Cid, int) bool, options ...WalkOption) error {
+	// Make sure we have an exchange session.
+	ctx, cancel := context.WithCancel(ctx)
+	ctx = exchange.NewSession(ctx)
+	defer cancel()
+
 	opts := &walkOptions{}
 	for _, opt := range options {
 		opt(opts)

session.go

@@ -13,6 +13,10 @@ type SessionMaker interface {
 
 // NewSession returns a session backed NodeGetter if the given NodeGetter
 // implements SessionMaker.
+//
+// Deprecated: Use exchange.NewSession to wrap your context. This function only
+// works if the NodeGetter happens to implement the session interface. If it has
+// been wrapped in some way, it won't work.
 func NewSession(ctx context.Context, g ipld.NodeGetter) ipld.NodeGetter {
 	if sm, ok := g.(SessionMaker); ok {
 		return sm.Session(ctx)