fix: improved error message on broken CIDv0

.travis.yml

@@ -4,7 +4,8 @@ os:
 language: go
 
 go:
-  - 1.11.x
+  - 1.14.x
+  - 1.15.x
 
 env:
   global:

go.mod

@@ -1,5 +1,7 @@
 module github.com/ipfs/go-path
 
+go 1.14
+
 require (
 	github.com/ipfs/go-cid v0.0.2
 	github.com/ipfs/go-ipld-format v0.0.2

path.go

@@ -96,7 +96,7 @@ func ParsePath(txt string) (Path, error) {
 	// if the path doesnt begin with a '/'
 	// we expect this to start with a hash, and be an 'ipfs' path
 	if parts[0] != "" {
-		if _, err := cid.Decode(parts[0]); err != nil {
+		if _, err := decodeCid(parts[0]); err != nil {
 			return "", &pathError{error: err, path: txt}
 		}
 		// The case when the path starts with hash without a protocol prefix
@@ -114,7 +114,7 @@ func ParsePath(txt string) (Path, error) {
 			return "", &pathError{error: fmt.Errorf("not enough path components"), path: txt}
 		}
 		// Validate Cid.
-		_, err := cid.Decode(parts[2])
+		_, err := decodeCid(parts[2])
 		if err != nil {
 			return "", &pathError{error: fmt.Errorf("invalid CID: %s", err), path: txt}
 		}
@@ -135,7 +135,7 @@ func ParseCidToPath(txt string) (Path, error) {
 		return "", &pathError{error: fmt.Errorf("empty"), path: txt}
 	}
 
-	c, err := cid.Decode(txt)
+	c, err := decodeCid(txt)
 	if err != nil {
 		return "", &pathError{error: err, path: txt}
 	}
@@ -172,11 +172,19 @@ func SplitAbsPath(fpath Path) (cid.Cid, []string, error) {
 		return cid.Cid{}, nil, &pathError{error: fmt.Errorf("empty"), path: string(fpath)}
 	}
 
-	c, err := cid.Decode(parts[0])
+	c, err := decodeCid(parts[0])
 	// first element in the path is a cid
 	if err != nil {
 		return cid.Cid{}, nil, &pathError{error: fmt.Errorf("invalid CID: %s", err), path: string(fpath)}
 	}
 
 	return c, parts[1:], nil
 }
+
+func decodeCid(cstr string) (cid.Cid, error) {
+	c, err := cid.Decode(cstr)
+	if err != nil && len(cstr) == 46 && cstr[:2] == "qm" { // https://github.com/ipfs/go-ipfs/issues/7792
+		return cid.Cid{}, fmt.Errorf("%v (possible lowercased CIDv0; consider converting to a case-agnostic CIDv1, such as base32)", err)
+	}
+	return c, err
+}

path_test.go

@@ -102,3 +102,14 @@ func TestPopLastSegment(t *testing.T) {
 		}
 	}
 }
+
+func TestV0ErrorDueToLowercase(t *testing.T) {
+	badb58 := "/ipfs/qmbwqxbekc3p8tqskc98xmwnzrzdtrlmimpl8wbutgsmnr"
+	_, err := ParsePath(badb58)
+	if err == nil {
+		t.Fatal("should have failed to decode")
+	}
+	if !strings.HasSuffix(err.Error(), "(possible lowercased CIDv0; consider converting to a case-agnostic CIDv1, such as base32)") {
+		t.Fatal("should have meaningful info about case-insensitive fix")
+	}
+}

resolver/resolver.go

@@ -89,6 +89,10 @@ func (r *Resolver) ResolveToLastNode(ctx context.Context, fpath path.Path) (cid.
 			return cid.Cid{}, nil, err
 		}
 
+		if len(rest) == 0 {
+			return lnk.Cid, nil, nil
+		}
+
 		next, err := lnk.GetNode(ctx, r.DAG)
 		if err != nil {
 			return cid.Cid{}, nil, err

resolver/resolver_test.go

@@ -105,3 +105,43 @@ func TestRecurivePathResolution(t *testing.T) {
 			p.String(), rCid.String(), cKey.String()))
 	}
 }
+
+func TestResolveToLastNode_NoUnnecessaryFetching(t *testing.T) {
+	ctx := context.Background()
+	dagService := dagmock.Mock()
+
+	a := randNode()
+	b := randNode()
+
+	err := a.AddNodeLink("child", b)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = dagService.Add(ctx, a)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	aKey := a.Cid()
+
+	segments := []string{aKey.String(), "child"}
+	p, err := path.FromSegments("/ipfs/", segments...)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	resolver := resolver.NewBasicResolver(dagService)
+	resolvedCID, remainingPath, err := resolver.ResolveToLastNode(ctx, p)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(remainingPath) > 0 {
+		t.Fatal("cannot have remaining path")
+	}
+
+	if !resolvedCID.Equals(b.Cid()) {
+		t.Fatal("resolved to the wrong CID")
+	}
+}