From 8557ee55f598ab5cb58ae2fbaa8b4ecd49a08c90 Mon Sep 17 00:00:00 2001
From: Marios Koulakis <mariosco100@gmail.com>
Date: Fri, 7 Apr 2017 23:21:50 -0400
Subject: [PATCH] Update with empty json (#852)

---
 CHANGELOG.md               |  2 +-
 src/PostgREST/App.hs       | 10 ++++++----
 test/Feature/InsertSpec.hs | 24 ++++++++++++++++++++++++
 3 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5b93645ec..cae35f7a3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,9 +8,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 - Allow requesting binary output on GET - @steve-chavez
 - Accept clients requesting `Content-Type: application/json` from / - @feynmanliang
+- #493, Updating with empty JSON object makes zero updates @koulakis
 
 ### Fixed
-
 - #827, Avoid Warp reaper, extend socket timeout to 1 hour - @majorcode
 - #791, malformed nested JSON error - @diogob
 - Resource embedding in views referencing tables in public schema - @fab1an
diff --git a/src/PostgREST/App.hs b/src/PostgREST/App.hs
index c60335699..b2ef314eb 100644
--- a/src/PostgREST/App.hs
+++ b/src/PostgREST/App.hs
@@ -165,10 +165,12 @@ app dbStructure conf apiRequest =
                     if iPreferRepresentation apiRequest == Full
                       then toS body else ""
 
-        (ActionUpdate, TargetIdent _, Just payload) ->
-          case mutateSqlParts of
-            Left errorResponse -> return errorResponse
-            Right (sq, mq) -> do
+        (ActionUpdate, TargetIdent _, Just payload@(PayloadJSON rows)) ->
+          case (mutateSqlParts, null <$> rows V.!? 0, iPreferRepresentation apiRequest == Full) of
+            (Left errorResponse, _, _) -> return errorResponse
+            (_, Just True, True) -> return $ responseLBS status200 [contentRangeH 1 0 Nothing] "[]"
+            (_, Just True, False) -> return $ responseLBS status204 [contentRangeH 1 0 Nothing] ""
+            (Right (sq, mq), _, _) -> do
               let stm = createWriteStatement sq mq
                     (contentType == CTSingularJSON) False (contentType == CTTextCSV)
                     (iPreferRepresentation apiRequest) []
diff --git a/test/Feature/InsertSpec.hs b/test/Feature/InsertSpec.hs
index a8c69ec9b..60b770465 100644
--- a/test/Feature/InsertSpec.hs
+++ b/test/Feature/InsertSpec.hs
@@ -413,6 +413,30 @@ spec = do
           [json| { id: 99 } |]
           `shouldRespondWith` [json| [{id:99}] |]
           { matchHeaders = [matchContentTypeJson] }
+        -- put value back for other tests
+        void $ request methodPatch "/items?id=eq.99" [] [json| { "id":1 } |]
+
+      it "makes no updates and returns 204, when patching with an empty json object" $ do
+        request methodPatch "/items" [] [json| {} |]
+          `shouldRespondWith` ""
+          {
+            matchStatus  = 204,
+            matchHeaders = ["Content-Range" <:> "*/*"]
+          }
+
+        g <- get "/items"
+        liftIO $ simpleBody g `shouldBe` [json| [{"id":3},{"id":4},{"id":5},{"id":6},{"id":7},{"id":8},{"id":9},{"id":10},{"id":11},{"id":12},{"id":13},{"id":14},{"id":15},{id:16},{"id":2},{"id":1}] |]
+
+      it "makes no updates and and returns 200, when patching with an empty json object and return=rep" $ do
+        request methodPatch "/items" [("Prefer", "return=representation")] [json| {} |]
+          `shouldRespondWith` "[]"
+          {
+            matchStatus  = 200,
+            matchHeaders = ["Content-Range" <:> "*/*"]
+          }
+
+        g <- get "/items"
+        liftIO $ simpleBody g `shouldBe` [json| [{"id":3},{"id":4},{"id":5},{"id":6},{"id":7},{"id":8},{"id":9},{"id":10},{"id":11},{"id":12},{"id":13},{"id":14},{"id":15},{id:16},{"id":2},{"id":1}] |]
 
     context "with unicode values" $
       it "succeeds and returns values intact" $ do