From 3af63cb94ce68f49b7dcd2ee19df20318d7cff44 Mon Sep 17 00:00:00 2001
From: steve-chavez <stevechavezast@gmail.com>
Date: Tue, 19 Dec 2023 16:46:56 -0500
Subject: [PATCH] fix: empty row on handler function

Closes https://github.com/PostgREST/postgrest/issues/3126
---
 CHANGELOG.md                               | 1 +
 src/PostgREST/Query/Statements.hs          | 3 ++-
 test/spec/Feature/Query/CustomMediaSpec.hs | 7 +++++++
 test/spec/fixtures/schema.sql              | 5 +++++
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 138f054ff0..aa1eb5bfd3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
   - #3124, Fix table's media type handlers not working for all schemas - @steve-chavez
+  - #3126, Fix empty row on media type handler function - @steve-chavez
 
 ## [12.0.1] - 2023-12-12
 
diff --git a/src/PostgREST/Query/Statements.hs b/src/PostgREST/Query/Statements.hs
index 2c6d7d28e3..77947d04cd 100644
--- a/src/PostgREST/Query/Statements.hs
+++ b/src/PostgREST/Query/Statements.hs
@@ -157,7 +157,8 @@ preparePlanRows countQuery =
 standardRow :: Bool -> HD.Row ResultSet
 standardRow noLocation =
   RSStandard <$> nullableColumn HD.int8 <*> column HD.int8
-             <*> (if noLocation then pure mempty else fmap splitKeyValue <$> arrayColumn HD.bytea) <*> column HD.bytea
+             <*> (if noLocation then pure mempty else fmap splitKeyValue <$> arrayColumn HD.bytea)
+             <*> (fromMaybe mempty <$> nullableColumn HD.bytea)
              <*> nullableColumn HD.bytea
              <*> nullableColumn HD.text
              <*> nullableColumn HD.int8
diff --git a/test/spec/Feature/Query/CustomMediaSpec.hs b/test/spec/Feature/Query/CustomMediaSpec.hs
index 0c4de99cdd..c5c1786040 100644
--- a/test/spec/Feature/Query/CustomMediaSpec.hs
+++ b/test/spec/Feature/Query/CustomMediaSpec.hs
@@ -119,6 +119,13 @@ spec = describe "custom media types" $ do
         , matchHeaders = ["Content-Type" <:> "application/json; charset=utf-8"]
         }
 
+    it "should not fail when the function doesn't return a row" $ do
+      request methodGet "/rpc/get_line?id=777" (acceptHdrs "application/vnd.twkb") ""
+        `shouldRespondWith` ""
+        { matchStatus = 200
+        , matchHeaders = ["Content-Type" <:> "application/vnd.twkb"]
+        }
+
   context "Proc that returns scalar based on a table" $ do
     it "can get an image with Accept: image/png" $ do
       r <- request methodGet "/rpc/ret_image" (acceptHdrs "image/png") ""
diff --git a/test/spec/fixtures/schema.sql b/test/spec/fixtures/schema.sql
index 8d268dcc5a..33f2eefc5b 100644
--- a/test/spec/fixtures/schema.sql
+++ b/test/spec/fixtures/schema.sql
@@ -3517,6 +3517,11 @@ returns setof test.lines as $$
   select * from lines;
 $$ language sql;
 
+create or replace function test.get_line (id int)
+returns "application/vnd.twkb" as $$
+  select extensions.st_astwkb(geom)::"application/vnd.twkb" from lines where id = get_line.id;
+$$ language sql;
+
 create or replace function test.get_shop_bles ()
 returns setof test.shop_bles as $$
   select * from shop_bles;