Use KeyDID() method instead of signer string representation in errors

[bajtos]

Summary

Updated error messages in the PEM encoding function to use the KeyDID() method for more consistent and meaningful signer identification instead of relying on the signer's string representation.

Changes

• Modified error messages in EncodeSignerToPEM() to call signer.KeyDID() instead of passing the signer object directly to fmt.Errorf()
• Applied to two error cases:
  • Private key marshaling error
  • Private key PEM encoding error

Details

This change improves error messages by using the signer's DID (Decentralized Identifier) as a stable, meaningful identifier rather than the default string representation of the signer object. This makes debugging and error tracking more reliable and user-friendly.

https://claude.ai/code/session_017uKN5QJLWhCX6jTTJ8t6FV

[Copilot]

Pull request overview

This PR updates identity.EncodeSignerToPEM() error messages to identify the signer using KeyDID() (a stable DID) rather than relying on the signer's default string representation, improving consistency and debuggability across error reports.

Changes:

• Updated the private-key marshaling error to include signer.KeyDID().
• Updated the PEM encoding error to include signer.KeyDID().

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[frrist]

My preference would be to define String() string on the interface embedded in a multikey, then implement it on all its implementations over in ucantone. This will fix all instances in dependencies where a signer operand is passeed to fmt.*. Here's a diff of the change that can be applied in ucantone:

diff --git a/multikey/ed25519/signer.go b/multikey/ed25519/signer.go
index 2a398c8..3e114e8 100644
--- a/multikey/ed25519/signer.go
+++ b/multikey/ed25519/signer.go
@@ -5,15 +5,16 @@ import (
        "crypto/rand"
        "fmt"
 
+       "github.com/multiformats/go-multibase"
+       "github.com/multiformats/go-multicodec"
+       "github.com/multiformats/go-varint"
+
        "github.com/fil-forge/ucantone/did"
        "github.com/fil-forge/ucantone/multikey"
        "github.com/fil-forge/ucantone/multikey/ed25519/verifier"
        "github.com/fil-forge/ucantone/ucan"
        "github.com/fil-forge/ucantone/varsig"
        "github.com/fil-forge/ucantone/varsig/algorithm/eddsa"
-       "github.com/multiformats/go-multibase"
-       "github.com/multiformats/go-multicodec"
-       "github.com/multiformats/go-varint"
 )
 
 const Code = multicodec.Ed25519Priv
@@ -94,6 +95,10 @@ func FromRaw(b []byte) (Signer, error) {
 
 type Signer []byte
 
+func (s Signer) String() string {
+       return s.verifier().KeyDID().String()
+}
+
 var _ multikey.Signer = (Signer)(nil)
 
 func (s Signer) Code() multicodec.Code {
diff --git a/multikey/secp256k1/signer.go b/multikey/secp256k1/signer.go
index 7c2224d..c9c3236 100644
--- a/multikey/secp256k1/signer.go
+++ b/multikey/secp256k1/signer.go
@@ -5,16 +5,17 @@ import (
        "crypto/sha256"
        "fmt"
 
+       "github.com/multiformats/go-multibase"
+       "github.com/multiformats/go-multicodec"
+       "github.com/multiformats/go-varint"
+       "gitlab.com/yawning/secp256k1-voi/secec"
+
        "github.com/fil-forge/ucantone/did"
        "github.com/fil-forge/ucantone/multikey"
        "github.com/fil-forge/ucantone/multikey/secp256k1/verifier"
        "github.com/fil-forge/ucantone/ucan"
        "github.com/fil-forge/ucantone/varsig"
        "github.com/fil-forge/ucantone/varsig/algorithm/ecdsa"
-       "github.com/multiformats/go-multibase"
-       "github.com/multiformats/go-multicodec"
-       "github.com/multiformats/go-varint"
-       "gitlab.com/yawning/secp256k1-voi/secec"
 )
 
 const Code = multicodec.Secp256k1Priv
@@ -99,6 +100,10 @@ func FromRaw(b []byte) (Signer, error) {
 
 type Signer []byte
 
+func (s Signer) String() string {
+       return s.verifier().KeyDID().String()
+}
+
 var _ multikey.Signer = (Signer)(nil)
 
 func (s Signer) SignatureAlgorithm() varsig.Algorithm {
diff --git a/ucan/ucan.go b/ucan/ucan.go
index 106c047..80b7437 100644
--- a/ucan/ucan.go
+++ b/ucan/ucan.go
@@ -43,6 +43,8 @@ type Signer interface {
 
        // Verifier returns a Verifier that can verify signatures from this Signer.
        Verifier() Verifier
+
+       String() string
 }
 
 // Signature encapsulates the bytes that comprise the signature as well as the

Approved in the event:

• you feel strongly about the current design in this PR.
• this bug is blocking your work.

[bajtos]

Great suggestion!

[bajtos]

Closing in favour of fil-forge/ucantone#48