From be7f23bde7ec5d7d52c58269ba66148bca9e613f Mon Sep 17 00:00:00 2001
From: Cory Slep <coryslep1@mac.com>
Date: Sun, 13 Dec 2020 23:32:23 +0100
Subject: [PATCH] Return ErrNotFound when handler retrieves no data

---
 pub/handlers.go | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/pub/handlers.go b/pub/handlers.go
index a2ad2b2..e77d025 100644
--- a/pub/handlers.go
+++ b/pub/handlers.go
@@ -3,11 +3,15 @@ package pub
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
-	"github.com/go-fed/activity/streams"
 	"net/http"
+
+	"github.com/go-fed/activity/streams"
 )
 
+var ErrNotFound = errors.New("go-fed/activity: ActivityStreams data not found")
+
 // HandlerFunc determines whether an incoming HTTP request is an ActivityStreams
 // GET request, and if so attempts to serve ActivityStreams data.
 //
@@ -49,6 +53,9 @@ func NewActivityStreamsHandler(db Database, clock Clock) HandlerFunc {
 //
 // Specifying the "scheme" allows for retrieving ActivityStreams content with
 // identifiers such as HTTP, HTTPS, or other protocol schemes.
+//
+// Returns ErrNotFound when the database does not retrieve any data and no
+// errors occurred during retrieval.
 func NewActivityStreamsHandlerScheme(db Database, clock Clock, scheme string) HandlerFunc {
 	return func(c context.Context, w http.ResponseWriter, r *http.Request) (isASRequest bool, err error) {
 		// Do nothing if it is not an ActivityPub GET request
@@ -71,7 +78,10 @@ func NewActivityStreamsHandlerScheme(db Database, clock Clock, scheme string) Ha
 		db.Unlock(c, id)
 		// Unlock must have been called by this point and in every
 		// branch above
-		//
+		if t == nil {
+			err = ErrNotFound
+			return
+		}
 		// Remove sensitive fields.
 		clearSensitiveFields(t)
 		// Serialize the fetched value.