fix: error not as pointer

cid.go

@@ -37,10 +37,32 @@ import (
 // UnsupportedVersionString just holds an error message
 const UnsupportedVersionString = "<unsupported cid version>"
 
+// ErrInvalidCid is an error that indicates that a CID is invalid.
+type ErrInvalidCid struct {
+	Err error
+}
+
+func (e ErrInvalidCid) Error() string {
+	return fmt.Sprintf("invalid cid: %s", e.Err)
+}
+
+func (e ErrInvalidCid) Unwrap() error {
+	return e.Err
+}
+
+func (e ErrInvalidCid) Is(err error) bool {
+	switch err.(type) {
+	case ErrInvalidCid, *ErrInvalidCid:
+		return true
+	default:
+		return false
+	}
+}
+
 var (
 	// ErrCidTooShort means that the cid passed to decode was not long
 	// enough to be a valid Cid
-	ErrCidTooShort = errors.New("cid too short")
+	ErrCidTooShort = ErrInvalidCid{errors.New("cid too short")}
 
 	// ErrInvalidEncoding means that selected encoding is not supported
 	// by this Cid version
@@ -90,10 +112,10 @@ func tryNewCidV0(mhash mh.Multihash) (Cid, error) {
 	// incorrectly detect it as CidV1 in the Version() method
 	dec, err := mh.Decode(mhash)
 	if err != nil {
-		return Undef, err
+		return Undef, ErrInvalidCid{err}
 	}
 	if dec.Code != mh.SHA2_256 || dec.Length != 32 {
-		return Undef, fmt.Errorf("invalid hash for cidv0 %d-%d", dec.Code, dec.Length)
+		return Undef, ErrInvalidCid{fmt.Errorf("invalid hash for cidv0 %d-%d", dec.Code, dec.Length)}
 	}
 	return Cid{string(mhash)}, nil
 }
@@ -177,7 +199,7 @@ func Parse(v interface{}) (Cid, error) {
 	case Cid:
 		return v2, nil
 	default:
-		return Undef, fmt.Errorf("can't parse %+v as Cid", v2)
+		return Undef, ErrInvalidCid{fmt.Errorf("can't parse %+v as Cid", v2)}
 	}
 }
 
@@ -210,7 +232,7 @@ func Decode(v string) (Cid, error) {
 	if len(v) == 46 && v[:2] == "Qm" {
 		hash, err := mh.FromB58String(v)
 		if err != nil {
-			return Undef, err
+			return Undef, ErrInvalidCid{err}
 		}
 
 		return tryNewCidV0(hash)
@@ -218,7 +240,7 @@ func Decode(v string) (Cid, error) {
 
 	_, data, err := mbase.Decode(v)
 	if err != nil {
-		return Undef, err
+		return Undef, ErrInvalidCid{err}
 	}
 
 	return Cast(data)
@@ -240,7 +262,7 @@ func ExtractEncoding(v string) (mbase.Encoding, error) {
 	// check encoding is valid
 	_, err := mbase.NewEncoder(encoding)
 	if err != nil {
-		return -1, err
+		return -1, ErrInvalidCid{err}
 	}
 
 	return encoding, nil
@@ -260,11 +282,11 @@ func ExtractEncoding(v string) (mbase.Encoding, error) {
 func Cast(data []byte) (Cid, error) {
 	nr, c, err := CidFromBytes(data)
 	if err != nil {
-		return Undef, err
+		return Undef, ErrInvalidCid{err}
 	}
 
 	if nr != len(data) {
-		return Undef, fmt.Errorf("trailing bytes in data buffer passed to cid Cast")
+		return Undef, ErrInvalidCid{fmt.Errorf("trailing bytes in data buffer passed to cid Cast")}
 	}
 
 	return c, nil
@@ -615,12 +637,12 @@ func PrefixFromBytes(buf []byte) (Prefix, error) {
 func CidFromBytes(data []byte) (int, Cid, error) {
 	if len(data) > 2 && data[0] == mh.SHA2_256 && data[1] == 32 {
 		if len(data) < 34 {
-			return 0, Undef, fmt.Errorf("not enough bytes for cid v0")
+			return 0, Undef, ErrInvalidCid{fmt.Errorf("not enough bytes for cid v0")}
 		}
 
 		h, err := mh.Cast(data[:34])
 		if err != nil {
-			return 0, Undef, err
+			return 0, Undef, ErrInvalidCid{err}
 		}
 
 		return 34, Cid{string(h)}, nil
@@ -628,21 +650,21 @@ func CidFromBytes(data []byte) (int, Cid, error) {
 
 	vers, n, err := varint.FromUvarint(data)
 	if err != nil {
-		return 0, Undef, err
+		return 0, Undef, ErrInvalidCid{err}
 	}
 
 	if vers != 1 {
-		return 0, Undef, fmt.Errorf("expected 1 as the cid version number, got: %d", vers)
+		return 0, Undef, ErrInvalidCid{fmt.Errorf("expected 1 as the cid version number, got: %d", vers)}
 	}
 
 	_, cn, err := varint.FromUvarint(data[n:])
 	if err != nil {
-		return 0, Undef, err
+		return 0, Undef, ErrInvalidCid{err}
 	}
 
 	mhnr, _, err := mh.MHFromBytes(data[n+cn:])
 	if err != nil {
-		return 0, Undef, err
+		return 0, Undef, ErrInvalidCid{err}
 	}
 
 	l := n + cn + mhnr
@@ -705,32 +727,32 @@ func CidFromReader(r io.Reader) (int, Cid, error) {
 	// The varint package wants a io.ByteReader, so we must wrap our io.Reader.
 	vers, err := varint.ReadUvarint(br)
 	if err != nil {
-		return len(br.dst), Undef, err
+		return len(br.dst), Undef, ErrInvalidCid{err}
 	}
 
 	// If we have a CIDv0, read the rest of the bytes and cast the buffer.
 	if vers == mh.SHA2_256 {
 		if n, err := io.ReadFull(r, br.dst[1:34]); err != nil {
-			return len(br.dst) + n, Undef, err
+			return len(br.dst) + n, Undef, ErrInvalidCid{err}
 		}
 
 		br.dst = br.dst[:34]
 		h, err := mh.Cast(br.dst)
 		if err != nil {
-			return len(br.dst), Undef, err
+			return len(br.dst), Undef, ErrInvalidCid{err}
 		}
 
 		return len(br.dst), Cid{string(h)}, nil
 	}
 
 	if vers != 1 {
-		return len(br.dst), Undef, fmt.Errorf("expected 1 as the cid version number, got: %d", vers)
+		return len(br.dst), Undef, ErrInvalidCid{fmt.Errorf("expected 1 as the cid version number, got: %d", vers)}
 	}
 
 	// CID block encoding multicodec.
 	_, err = varint.ReadUvarint(br)
 	if err != nil {
-		return len(br.dst), Undef, err
+		return len(br.dst), Undef, ErrInvalidCid{err}
 	}
 
 	// We could replace most of the code below with go-multihash's ReadMultihash.
@@ -741,19 +763,19 @@ func CidFromReader(r io.Reader) (int, Cid, error) {
 	// Multihash hash function code.
 	_, err = varint.ReadUvarint(br)
 	if err != nil {
-		return len(br.dst), Undef, err
+		return len(br.dst), Undef, ErrInvalidCid{err}
 	}
 
 	// Multihash digest length.
 	mhl, err := varint.ReadUvarint(br)
 	if err != nil {
-		return len(br.dst), Undef, err
+		return len(br.dst), Undef, ErrInvalidCid{err}
 	}
 
 	// Refuse to make large allocations to prevent OOMs due to bugs.
 	const maxDigestAlloc = 32 << 20 // 32MiB
 	if mhl > maxDigestAlloc {
-		return len(br.dst), Undef, fmt.Errorf("refusing to allocate %d bytes for a digest", mhl)
+		return len(br.dst), Undef, ErrInvalidCid{fmt.Errorf("refusing to allocate %d bytes for a digest", mhl)}
 	}
 
 	// Fine to convert mhl to int, given maxDigestAlloc.
@@ -772,7 +794,7 @@ func CidFromReader(r io.Reader) (int, Cid, error) {
 	if n, err := io.ReadFull(r, br.dst[prefixLength:cidLength]); err != nil {
 		// We can't use len(br.dst) here,
 		// as we've only read n bytes past prefixLength.
-		return prefixLength + n, Undef, err
+		return prefixLength + n, Undef, ErrInvalidCid{err}
 	}
 
 	// This simply ensures the multihash is valid.
@@ -780,7 +802,7 @@ func CidFromReader(r io.Reader) (int, Cid, error) {
 	// for now, it helps ensure consistency with CidFromBytes.
 	_, _, err = mh.MHFromBytes(br.dst[mhStart:])
 	if err != nil {
-		return len(br.dst), Undef, err
+		return len(br.dst), Undef, ErrInvalidCid{err}
 	}
 
 	return len(br.dst), Cid{string(br.dst)}, nil

cid_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	crand "crypto/rand"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"math/rand"
@@ -227,6 +228,9 @@ func TestEmptyString(t *testing.T) {
 	if err == nil {
 		t.Fatal("shouldnt be able to parse an empty cid")
 	}
+	if !errors.Is(err, ErrInvalidCid{}) {
+		t.Fatal("error must be ErrInvalidCid")
+	}
 }
 
 func TestV0Handling(t *testing.T) {
@@ -282,6 +286,9 @@ func TestV0ErrorCases(t *testing.T) {
 	if err == nil {
 		t.Fatal("should have failed to decode that ref")
 	}
+	if !errors.Is(err, ErrInvalidCid{}) {
+		t.Fatal("error must be ErrInvalidCid")
+	}
 }
 
 func TestNewPrefixV1(t *testing.T) {
@@ -455,6 +462,9 @@ func TestParse(t *testing.T) {
 	if !strings.Contains(err.Error(), "can't parse 123 as Cid") {
 		t.Fatalf("expected int error, got %s", err.Error())
 	}
+	if !errors.Is(err, ErrInvalidCid{}) {
+		t.Fatalf("expected ErrInvalidCid, got %s", err.Error())
+	}
 
 	theHash := "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n"
 	h, err := mh.FromB58String(theHash)
@@ -749,6 +759,9 @@ func TestBadParse(t *testing.T) {
 	if err == nil {
 		t.Fatal("expected to fail to parse an invalid CIDv1 CID")
 	}
+	if !errors.Is(err, ErrInvalidCid{}) {
+		t.Fatal("error must be ErrInvalidCid")
+	}
 }
 
 func TestLoggable(t *testing.T) {
@@ -763,3 +776,15 @@ func TestLoggable(t *testing.T) {
 		t.Fatalf("did not get expected loggable form (got %v)", actual)
 	}
 }
+
+func TestErrInvalidCid(t *testing.T) {
+	_, err := Decode("not-a-cid")
+	if err == nil {
+		t.Fatal("expected error")
+	}
+
+	is := errors.Is(err, ErrInvalidCid{})
+	if !is {
+		t.Fatal("expected error to be ErrInvalidCid")
+	}
+}