From f9291b64bce3d93ee00473aa7d284b728473c85b Mon Sep 17 00:00:00 2001
From: Henrique Dias <hacdias@gmail.com>
Date: Thu, 23 Feb 2023 13:43:25 +0100
Subject: [PATCH 1/2] feat: expose ErrInvalidPath

---
 error.go | 16 ++++++++++------
 path.go  | 20 ++++++++++----------
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/error.go b/error.go
index ca2e841..dafc446 100644
--- a/error.go
+++ b/error.go
@@ -4,20 +4,24 @@ import (
 	"fmt"
 )
 
-// helper type so path parsing errors include the path
-type pathError struct {
+type ErrInvalidPath struct {
 	error error
 	path  string
 }
 
-func (e *pathError) Error() string {
+func (e ErrInvalidPath) Error() string {
 	return fmt.Sprintf("invalid path %q: %s", e.path, e.error)
 }
 
-func (e *pathError) Unwrap() error {
+func (e ErrInvalidPath) Unwrap() error {
 	return e.error
 }
 
-func (e *pathError) Path() string {
-	return e.path
+func (e ErrInvalidPath) Is(err error) bool {
+	switch err.(type) {
+	case ErrInvalidPath:
+		return true
+	default:
+		return false
+	}
 }
diff --git a/path.go b/path.go
index e70d963..6d53ade 100644
--- a/path.go
+++ b/path.go
@@ -97,33 +97,33 @@ func ParsePath(txt string) (Path, error) {
 	// we expect this to start with a hash, and be an 'ipfs' path
 	if parts[0] != "" {
 		if _, err := decodeCid(parts[0]); err != nil {
-			return "", &pathError{error: err, path: txt}
+			return "", &ErrInvalidPath{error: err, path: txt}
 		}
 		// The case when the path starts with hash without a protocol prefix
 		return Path("/ipfs/" + txt), nil
 	}
 
 	if len(parts) < 3 {
-		return "", &pathError{error: fmt.Errorf("invalid ipfs path"), path: txt}
+		return "", &ErrInvalidPath{error: fmt.Errorf("invalid ipfs path"), path: txt}
 	}
 
 	//TODO: make this smarter
 	switch parts[1] {
 	case "ipfs", "ipld":
 		if parts[2] == "" {
-			return "", &pathError{error: fmt.Errorf("not enough path components"), path: txt}
+			return "", &ErrInvalidPath{error: fmt.Errorf("not enough path components"), path: txt}
 		}
 		// Validate Cid.
 		_, err := decodeCid(parts[2])
 		if err != nil {
-			return "", &pathError{error: fmt.Errorf("invalid CID: %s", err), path: txt}
+			return "", &ErrInvalidPath{error: fmt.Errorf("invalid CID: %w", err), path: txt}
 		}
 	case "ipns":
 		if parts[2] == "" {
-			return "", &pathError{error: fmt.Errorf("not enough path components"), path: txt}
+			return "", &ErrInvalidPath{error: fmt.Errorf("not enough path components"), path: txt}
 		}
 	default:
-		return "", &pathError{error: fmt.Errorf("unknown namespace %q", parts[1]), path: txt}
+		return "", &ErrInvalidPath{error: fmt.Errorf("unknown namespace %q", parts[1]), path: txt}
 	}
 
 	return Path(txt), nil
@@ -132,12 +132,12 @@ func ParsePath(txt string) (Path, error) {
 // ParseCidToPath takes a CID in string form and returns a valid ipfs Path.
 func ParseCidToPath(txt string) (Path, error) {
 	if txt == "" {
-		return "", &pathError{error: fmt.Errorf("empty"), path: txt}
+		return "", &ErrInvalidPath{error: fmt.Errorf("empty"), path: txt}
 	}
 
 	c, err := decodeCid(txt)
 	if err != nil {
-		return "", &pathError{error: err, path: txt}
+		return "", &ErrInvalidPath{error: err, path: txt}
 	}
 
 	return FromCid(c), nil
@@ -169,13 +169,13 @@ func SplitAbsPath(fpath Path) (cid.Cid, []string, error) {
 
 	// if nothing, bail.
 	if len(parts) == 0 {
-		return cid.Cid{}, nil, &pathError{error: fmt.Errorf("empty"), path: string(fpath)}
+		return cid.Cid{}, nil, &ErrInvalidPath{error: fmt.Errorf("empty"), path: string(fpath)}
 	}
 
 	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 cid.Cid{}, nil, &ErrInvalidPath{error: fmt.Errorf("invalid CID: %w", err), path: string(fpath)}
 	}
 
 	return c, parts[1:], nil

From 986db2269d7d78de09c9595f3f88e536948d979c Mon Sep 17 00:00:00 2001
From: Henrique Dias <hacdias@gmail.com>
Date: Thu, 23 Feb 2023 13:49:33 +0100
Subject: [PATCH 2/2] feat: add test to ensure error.Is works

---
 error_test.go | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 error_test.go

diff --git a/error_test.go b/error_test.go
new file mode 100644
index 0000000..07aab64
--- /dev/null
+++ b/error_test.go
@@ -0,0 +1,16 @@
+package path
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestErrorIs(t *testing.T) {
+	if !errors.Is(ErrInvalidPath{path: "foo", error: errors.New("bar")}, ErrInvalidPath{}) {
+		t.Fatal("error must be error")
+	}
+
+	if !errors.Is(&ErrInvalidPath{path: "foo", error: errors.New("bar")}, ErrInvalidPath{}) {
+		t.Fatal("pointer to error must be error")
+	}
+}