feat(test): add matcher/slice selector test cases

node/tests/byteSpecs.go

@@ -30,6 +30,5 @@ func SpecTestBytes(t *testing.T, np datamodel.NodePrototype) {
 			qt.Check(t, err, qt.IsNil)
 			qt.Check(t, bytes, qt.DeepEquals, []byte("asdf"))
 		}
-
 	})
 }

traversal/selector/matcher.go

@@ -40,11 +40,11 @@ func (s Slice) Slice(n datamodel.Node) (datamodel.Node, error) {
 			return nil, err
 		}
 		to = s.To
-		if len(str) < int(to) {
+		if int64(len(str)) < to {
 			to = int64(len(str))
 		}
 		from = s.From
-		if len(str) < int(from) {
+		if int64(len(str)) < from {
 			from = int64(len(str))
 		}
 		return basicnode.NewString(str[from:to]), nil
@@ -54,7 +54,6 @@ func (s Slice) Slice(n datamodel.Node) (datamodel.Node, error) {
 			if err != nil {
 				return nil, err
 			}
-
 			sr := io.NewSectionReader(&readerat{rdr, 0}, s.From, s.To-s.From)
 			return basicnode.NewBytesFromReader(sr), nil
 		}
@@ -63,14 +62,13 @@ func (s Slice) Slice(n datamodel.Node) (datamodel.Node, error) {
 			return nil, err
 		}
 		to = s.To
-		if len(bytes) < int(to) {
+		if int64(len(bytes)) < to {
 			to = int64(len(bytes))
 		}
 		from = s.From
-		if len(bytes) < int(from) {
+		if int64(len(bytes)) < from {
 			from = int64(len(bytes))
 		}
-
 		return basicnode.NewBytes(bytes[from:to]), nil
 	default:
 		return nil, nil

traversal/selector/matcher_test.go

@@ -0,0 +1,307 @@
+package selector_test
+
+import (
+	"fmt"
+	"io"
+	"math"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+	"github.com/ipld/go-ipld-prime/traversal"
+	"github.com/ipld/go-ipld-prime/traversal/selector"
+)
+
+func TestSubsetMatch(t *testing.T) {
+	expectedString := "foobarbaz!"
+	nodes := []struct {
+		name string
+		node datamodel.Node
+	}{
+		{"stringNode", basicnode.NewString(expectedString)},
+		{"bytesNode", basicnode.NewBytes([]byte(expectedString))},
+		{"largeBytesNode", &MultiByteNode{
+			Bytes: [][]byte{
+				[]byte("foo"),
+				[]byte("bar"),
+				[]byte("baz"),
+				[]byte("!"),
+			},
+		}},
+	}
+
+	// selector for a slice of the value of the "bipbop" field within a map
+	mkRangeSelector := func(from int64, to int64) (datamodel.Node, error) {
+		return qp.BuildMap(basicnode.Prototype.Map, 1, func(na datamodel.MapAssembler) {
+			qp.MapEntry(na, selector.SelectorKey_ExploreFields, qp.Map(1, func(na datamodel.MapAssembler) {
+				qp.MapEntry(na, selector.SelectorKey_Fields, qp.Map(1, func(na datamodel.MapAssembler) {
+					qp.MapEntry(na, "bipbop", qp.Map(1, func(na datamodel.MapAssembler) {
+						qp.MapEntry(na, selector.SelectorKey_Matcher, qp.Map(1, func(na datamodel.MapAssembler) {
+							qp.MapEntry(na, selector.SelectorKey_Subset, qp.Map(1, func(na datamodel.MapAssembler) {
+								qp.MapEntry(na, selector.SelectorKey_From, qp.Int(from))
+								qp.MapEntry(na, selector.SelectorKey_To, qp.Int(to))
+							}))
+						}))
+					}))
+				}))
+			}))
+		})
+	}
+
+	for _, tc := range []struct {
+		from int64
+		to   int64
+		exp  string
+	}{
+		{0, math.MaxInt64, expectedString},
+		{0, int64(len(expectedString)), expectedString},
+		{0, 0, ""},
+		{0, 1, "f"},
+		{0, 2, "fo"},
+		{0, 3, "foo"},
+		{0, 4, "foob"},
+		{1, 4, "oob"},
+		{2, 4, "ob"},
+		{3, 4, "b"},
+		{4, 4, ""},
+		{4, math.MaxInt64, "arbaz!"},
+		{4, int64(len(expectedString)), "arbaz!"},
+		{4, int64(len(expectedString) - 1), "arbaz"},
+		{0, int64(len(expectedString) - 1), expectedString[0 : len(expectedString)-1]},
+		{0, int64(len(expectedString) - 2), expectedString[0 : len(expectedString)-2]},
+	} {
+		for _, variant := range nodes {
+			t.Run(fmt.Sprintf("%s[%d:%d]", variant.name, tc.from, tc.to), func(t *testing.T) {
+				selNode, err := mkRangeSelector(tc.from, tc.to)
+				qt.Assert(t, err, qt.IsNil)
+				ss, err := selector.ParseSelector(selNode)
+				qt.Assert(t, err, qt.IsNil)
+
+				// node that the selector will match, with our variant node embedded in the "bipbop" field
+				n, err := qp.BuildMap(basicnode.Prototype.Map, 1, func(na datamodel.MapAssembler) {
+					qp.MapEntry(na, "bipbop", qp.Node(variant.node))
+				})
+
+				var got datamodel.Node
+				qt.Assert(t, err, qt.IsNil)
+				err = traversal.WalkMatching(n, ss, func(prog traversal.Progress, n datamodel.Node) error {
+					qt.Assert(t, got, qt.IsNil)
+					got = n
+					return nil
+				})
+				qt.Assert(t, err, qt.IsNil)
+
+				qt.Assert(t, got, qt.IsNotNil)
+				qt.Assert(t, got.Kind(), qt.Equals, variant.node.Kind())
+				var gotString string
+				switch got.Kind() {
+				case datamodel.Kind_String:
+					gotString, err = got.AsString()
+					qt.Assert(t, err, qt.IsNil)
+				case datamodel.Kind_Bytes:
+					byts, err := got.AsBytes()
+					qt.Assert(t, err, qt.IsNil)
+					gotString = string(byts)
+				}
+				qt.Assert(t, gotString, qt.DeepEquals, tc.exp)
+			})
+		}
+	}
+}
+
+func TestMultiByteNode_Sanity(t *testing.T) {
+	mbn := &MultiByteNode{
+		Bytes: [][]byte{
+			[]byte("foo"),
+			[]byte("bar"),
+			[]byte("baz"),
+			[]byte("!"),
+		},
+	}
+	// Sanity check that the readseeker works.
+	// (This is a test of the test, not the code under test.)
+
+	for _, rl := range []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10} {
+		t.Run("readseeker works with read length "+qt.Format(rl), func(t *testing.T) {
+			rs, err := mbn.AsLargeBytes()
+			qt.Assert(t, err, qt.IsNil)
+			acc := make([]byte, 0, mbn.size())
+			buf := make([]byte, rl)
+			for {
+				n, err := rs.Read(buf)
+				if err == io.EOF {
+					qt.Check(t, n, qt.Equals, 0)
+					break
+				}
+				qt.Assert(t, err, qt.IsNil)
+				acc = append(acc, buf[0:n]...)
+			}
+			qt.Assert(t, string(acc), qt.DeepEquals, "foobarbaz!")
+		})
+	}
+
+	t.Run("readseeker can seek and read middle bytes", func(t *testing.T) {
+		rs, err := mbn.AsLargeBytes()
+		qt.Assert(t, err, qt.IsNil)
+		_, err = rs.Seek(2, io.SeekStart)
+		qt.Assert(t, err, qt.IsNil)
+		buf := make([]byte, 2)
+		acc := make([]byte, 0, 5)
+		for len(acc) < 5 {
+			n, err := rs.Read(buf)
+			qt.Assert(t, err, qt.IsNil)
+			acc = append(acc, buf[0:n]...)
+		}
+		qt.Assert(t, string(acc), qt.DeepEquals, "obarba")
+	})
+
+	t.Run("readseeker can seek and read last byte", func(t *testing.T) {
+		rs, err := mbn.AsLargeBytes()
+		qt.Assert(t, err, qt.IsNil)
+		_, err = rs.Seek(-1, io.SeekEnd)
+		qt.Assert(t, err, qt.IsNil)
+		buf := make([]byte, 1)
+		n, err := rs.Read(buf)
+		qt.Assert(t, err, qt.IsNil)
+		qt.Check(t, n, qt.Equals, 1)
+		qt.Check(t, string(buf[0]), qt.Equals, "!")
+	})
+}
+
+var _ datamodel.Node = (*MultiByteNode)(nil)
+var _ datamodel.LargeBytesNode = (*MultiByteNode)(nil)
+
+// MultiByteNode is a node that is a concatenation of multiple byte slices.
+// It's not particularly sophisticated but lets us exercise LargeBytesNode as a
+// path through the selectors. The novel behaviour of Read() and Seek() on the
+// AsLargeBytes is similar to that which would be expected from a LBN ADL, such
+// as UnixFS sharded files.
+type MultiByteNode struct {
+	Bytes [][]byte
+}
+
+func (mbn *MultiByteNode) Kind() datamodel.Kind {
+	return datamodel.Kind_Bytes
+}
+
+func (mbn *MultiByteNode) AsBytes() ([]byte, error) {
+	ret := make([]byte, 0, mbn.size())
+	for _, b := range mbn.Bytes {
+		ret = append(ret, b...)
+	}
+	return ret, nil
+}
+
+func (mbn *MultiByteNode) size() int {
+	var size int
+	for _, b := range mbn.Bytes {
+		size += len(b)
+	}
+	return size
+}
+
+func (mbn *MultiByteNode) AsLargeBytes() (io.ReadSeeker, error) {
+	return &mbnReadSeeker{node: mbn}, nil
+}
+
+func (mbn *MultiByteNode) AsBool() (bool, error) {
+	return false, datamodel.ErrWrongKind{TypeName: "bool", MethodName: "AsBool", AppropriateKind: datamodel.KindSet_JustBytes}
+}
+
+func (mbn *MultiByteNode) AsInt() (int64, error) {
+	return 0, datamodel.ErrWrongKind{TypeName: "int", MethodName: "AsInt", AppropriateKind: datamodel.KindSet_JustBytes}
+}
+
+func (mbn *MultiByteNode) AsFloat() (float64, error) {
+	return 0, datamodel.ErrWrongKind{TypeName: "float", MethodName: "AsFloat", AppropriateKind: datamodel.KindSet_JustBytes}
+}
+
+func (mbn *MultiByteNode) AsString() (string, error) {
+	return "", datamodel.ErrWrongKind{TypeName: "string", MethodName: "AsString", AppropriateKind: datamodel.KindSet_JustBytes}
+}
+
+func (mbn *MultiByteNode) AsLink() (datamodel.Link, error) {
+	return nil, datamodel.ErrWrongKind{TypeName: "link", MethodName: "AsLink", AppropriateKind: datamodel.KindSet_JustBytes}
+}
+
+func (mbn *MultiByteNode) AsNode() (datamodel.Node, error) {
+	return nil, nil
+}
+
+func (mbn *MultiByteNode) Size() int {
+	return 0
+}
+
+func (mbn *MultiByteNode) IsAbsent() bool {
+	return false
+}
+
+func (mbn *MultiByteNode) IsNull() bool {
+	return false
+}
+
+func (mbn *MultiByteNode) Length() int64 {
+	return 0
+}
+
+func (mbn *MultiByteNode) ListIterator() datamodel.ListIterator {
+	return nil
+}
+
+func (mbn *MultiByteNode) MapIterator() datamodel.MapIterator {
+	return nil
+}
+
+func (mbn *MultiByteNode) LookupByIndex(idx int64) (datamodel.Node, error) {
+	return nil, datamodel.ErrWrongKind{}
+}
+
+func (mbn *MultiByteNode) LookupByString(key string) (datamodel.Node, error) {
+	return nil, datamodel.ErrWrongKind{}
+}
+
+func (mbn *MultiByteNode) LookupByNode(key datamodel.Node) (datamodel.Node, error) {
+	return nil, datamodel.ErrWrongKind{}
+}
+
+func (mbn *MultiByteNode) LookupBySegment(seg datamodel.PathSegment) (datamodel.Node, error) {
+	return nil, datamodel.ErrWrongKind{}
+}
+
+func (mbn *MultiByteNode) Prototype() datamodel.NodePrototype {
+	return basicnode.Prototype.Bytes // not really ... but it'll do for this test
+}
+
+type mbnReadSeeker struct {
+	node   *MultiByteNode
+	offset int
+}
+
+func (mbnrs *mbnReadSeeker) Read(p []byte) (int, error) {
+	var acc int
+	for _, byts := range mbnrs.node.Bytes {
+		if mbnrs.offset-acc >= len(byts) {
+			acc += len(byts)
+			continue
+		}
+		n := copy(p, byts[mbnrs.offset-acc:])
+		mbnrs.offset += n
+		return n, nil
+	}
+	return 0, io.EOF
+}
+
+func (mbnrs *mbnReadSeeker) Seek(offset int64, whence int) (int64, error) {
+	switch whence {
+	case io.SeekStart:
+		mbnrs.offset = int(offset)
+	case io.SeekCurrent:
+		mbnrs.offset += int(offset)
+	case io.SeekEnd:
+		mbnrs.offset = mbnrs.node.size() + int(offset)
+	}
+	return int64(mbnrs.offset), nil
+}

traversal/selector/matcher_util.go

@@ -13,8 +13,7 @@ type readerat struct {
 // current offset and seek if necessary.
 func (r *readerat) ReadAt(p []byte, off int64) (n int, err error) {
 	if off != r.off {
-		_, err = r.rs.Seek(off, 0)
-		if err != nil {
+		if _, err = r.rs.Seek(off, io.SeekStart); err != nil {
 			return 0, err
 		}
 		r.off = off