namesys: select on output

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

namesys/base.go

@@ -49,6 +49,11 @@ func resolveAsync(ctx context.Context, r resolver, name string, options opts.Res
 		defer close(outCh)
 		var subCh <-chan Result
 		var cancelSub context.CancelFunc
+		defer func() {
+			if cancelSub != nil {
+				cancelSub()
+			}
+		}()
 
 		for {
 			select {
@@ -59,20 +64,17 @@ func resolveAsync(ctx context.Context, r resolver, name string, options opts.Res
 				}
 
 				if res.err != nil {
-					outCh <- Result{Err: res.err}
+					emitResult(ctx, outCh, Result{Err: res.err})
-					if cancelSub != nil {
-						cancelSub()
-					}
 					return
 				}
 				log.Debugf("resolved %s to %s", name, res.value.String())
 				if !strings.HasPrefix(res.value.String(), ipnsPrefix) {
-					outCh <- Result{Path: res.value}
+					emitResult(ctx, outCh, Result{Path: res.value})
 					break
 				}
 
 				if depth == 1 {
-					outCh <- Result{Path: res.value, Err: ErrResolveRecursion}
+					emitResult(ctx, outCh, Result{Path: res.value, Err: ErrResolveRecursion})
 					break
 				}
 
@@ -87,6 +89,7 @@ func resolveAsync(ctx context.Context, r resolver, name string, options opts.Res
 					cancelSub()
 				}
 				subCtx, cancelSub = context.WithCancel(ctx)
+				_ = cancelSub
 
 				p := strings.TrimPrefix(res.value.String(), ipnsPrefix)
 				subCh = resolveAsync(subCtx, r, p, subopts)
@@ -96,27 +99,21 @@ func resolveAsync(ctx context.Context, r resolver, name string, options opts.Res
 					break
 				}
 
-				select {
+				emitResult(ctx, outCh, res)
-				case outCh <- res:
-				case <-ctx.Done():
-					if cancelSub != nil {
-						cancelSub()
-					}
-					return
-				}
 			case <-ctx.Done():
-				if cancelSub != nil {
-					cancelSub()
-				}
 				return
 			}
 			if resCh == nil && subCh == nil {
-				if cancelSub != nil {
-					cancelSub()
-				}
 				return
 			}
 		}
 	}()
 	return outCh
 }
+
+func emitResult(ctx context.Context, outCh chan<- Result, r Result) {
+	select {
+	case outCh <- r:
+	case <-ctx.Done():
+	}
+}

namesys/dns.go

@@ -80,10 +80,7 @@ func (r *DNSResolver) resolveOnceAsync(ctx context.Context, name string, options
 				}
 				if subRes.error == nil {
 					p, err := appendPath(subRes.path)
-					select {
+					emitOnceResult(ctx, out, onceResult{value: p, err: err})
-					case out <- onceResult{value: p, err: err}:
-					case <-ctx.Done():
-					}
 					return
 				}
 			case rootRes, ok := <-rootChan:
@@ -93,10 +90,7 @@ func (r *DNSResolver) resolveOnceAsync(ctx context.Context, name string, options
 				}
 				if rootRes.error == nil {
 					p, err := appendPath(rootRes.path)
-					select {
+					emitOnceResult(ctx, out, onceResult{value: p, err: err})
-					case out <- onceResult{value: p, err: err}:
-					case <-ctx.Done():
-					}
 				}
 			case <-ctx.Done():
 				return

namesys/namesys.go

@@ -141,19 +141,11 @@ func (ns *mpns) resolveOnceAsync(ctx context.Context, name string, options opts.
 				if len(segments) > 3 {
 					p, err := path.FromSegments("", strings.TrimRight(p.String(), "/"), segments[3])
 					if err != nil {
-						select {
+						emitOnceResult(ctx, out, onceResult{value: p, ttl: res.ttl, err: err})
-						case out <- onceResult{value: p, err: err}:
-						case <-ctx.Done():
-						}
-						return
 					}
 				}
 
-				select {
+				emitOnceResult(ctx, out, onceResult{value: p, ttl: res.ttl, err: res.err})
-				case out <- onceResult{value: p, ttl: res.ttl, err: res.err}:
-				case <-ctx.Done():
-					return
-				}
 			case <-ctx.Done():
 				return
 			}
@@ -163,6 +155,13 @@ func (ns *mpns) resolveOnceAsync(ctx context.Context, name string, options opts.
 	return out
 }
 
+func emitOnceResult(ctx context.Context, outCh chan<- onceResult, r onceResult) {
+	select {
+	case outCh <- r:
+	case <-ctx.Done():
+	}
+}
+
 // Publish implements Publisher
 func (ns *mpns) Publish(ctx context.Context, name ci.PrivKey, value path.Path) error {
 	return ns.PublishWithEOL(ctx, name, value, time.Now().Add(DefaultRecordTTL))

namesys/routing.go

@@ -112,10 +112,7 @@ func (r *IpnsResolver) resolveOnceAsync(ctx context.Context, name string, option
 				err = proto.Unmarshal(val, entry)
 				if err != nil {
 					log.Debugf("RoutingResolver: could not unmarshal value for name %s: %s", name, err)
-					select {
+					emitOnceResult(ctx, out, onceResult{err: err})
-					case out <- onceResult{err: err}:
-					case <-ctx.Done():
-					}
 					return
 				}
 
@@ -129,10 +126,7 @@ func (r *IpnsResolver) resolveOnceAsync(ctx context.Context, name string, option
 					// Not a multihash, probably a new style record
 					p, err = path.ParsePath(string(entry.GetValue()))
 					if err != nil {
-						select {
+						emitOnceResult(ctx, out, onceResult{err: err})
-						case out <- onceResult{err: err}:
-						case <-ctx.Done():
-						}
 						return
 					}
 				}
@@ -154,17 +148,11 @@ func (r *IpnsResolver) resolveOnceAsync(ctx context.Context, name string, option
 					}
 				default:
 					log.Errorf("encountered error when parsing EOL: %s", err)
-					select {
+					emitOnceResult(ctx, out, onceResult{err: err})
-					case out <- onceResult{err: err}:
-					case <-ctx.Done():
-					}
 					return
 				}
 
-				select {
+				emitOnceResult(ctx, out, onceResult{value: p, ttl: ttl})
-				case out <- onceResult{value: p, ttl: ttl}:
-				case <-ctx.Done():
-				}
 			case <-ctx.Done():
 				return
 			}