Output a more useful resolve error

This outputs a missage that blames a specific sife for not having DNSLink record.  For example, the error message looks like:

`could not resolve name: bad.example.net is missing DNSLink record (https://docs.ipfs.io/concepts/dnslink/)`

The "could not resolve name" portion is still present because the returned error wraps the original ErrResolveFailed, allowing code to test if the error is an ErrorResolveFailed error.


This commit was moved from ipfs/go-namesys@4e753ad

Author: gammazero

namesys/base.go

@@ -2,6 +2,7 @@ package namesys
 
 import (
 	"context"
+	"fmt"
 	"strings"
 	"time"
 
@@ -36,6 +37,14 @@ func resolve(ctx context.Context, r resolver, name string, options opts.ResolveO
 		}
 	}
 
+	if err == ErrResolveFailed {
+		i := len(name) - 1
+		for i >= 0 && name[i] != '/' {
+			i--
+		}
+		// Wrap error so that it can be tested if it is a ErrResolveFailed
+		err = fmt.Errorf("%w: %s is missing DNSLink record (https://docs.ipfs.io/concepts/dnslink/)", ErrResolveFailed, name[i+1:])
+	}
 	return p, err
 }
 

namesys/namesys_test.go

@@ -2,6 +2,7 @@ package namesys
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"testing"
 	"time"
@@ -25,7 +26,7 @@ type mockResolver struct {
 func testResolution(t *testing.T, resolver Resolver, name string, depth uint, expected string, expError error) {
 	t.Helper()
 	p, err := resolver.Resolve(context.Background(), name, opts.Depth(depth))
-	if err != expError {
+	if !errors.Is(err, expError) {
 		t.Fatal(fmt.Errorf(
 			"expected %s with a depth of %d to have a '%s' error, but got '%s'",
 			name, depth, expError, err))