From 91b28d610962efe8794bdfc74ff9d1243b7fed1d Mon Sep 17 00:00:00 2001
From: Ali Farhadi <a.farhadi@gmail.com>
Date: Sat, 13 Feb 2021 23:14:42 +0100
Subject: [PATCH] Exit with required error when checking a constrait and key
 does not exist.

---
 src/cowboy_req.erl | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/cowboy_req.erl b/src/cowboy_req.erl
index 90c5a3a0..30afd2cb 100644
--- a/src/cowboy_req.erl
+++ b/src/cowboy_req.erl
@@ -991,7 +991,12 @@ filter([], Map, Errors) ->
 		_ -> {error, Errors}
 	end;
 filter([{Key, Constraints}|Tail], Map, Errors) ->
-	filter_constraints(Tail, Map, Errors, Key, maps:get(Key, Map), Constraints);
+	case maps:find(Key, Map) of
+		{ok, Value} ->
+			filter_constraints(Tail, Map, Errors, Key, Value, Constraints);
+		error ->
+			filter(Tail, Map, Errors#{Key => required})
+	end;
 filter([{Key, Constraints, Default}|Tail], Map, Errors) ->
 	case maps:find(Key, Map) of
 		{ok, Value} ->