From a6e4587281cb91a63d6901a1282c21739877283f Mon Sep 17 00:00:00 2001
From: fr33domlover <fr33domlover@riseup.net>
Date: Sun, 26 Jun 2022 13:54:37 +0000
Subject: [PATCH] Raise build-time error on incomplete patterns

I realized I never intend to leave patterns (e.g. pattern matching in a 'case'
clause) incomplete, i.e. some cases left missing. When I do that it means I
forgot, and I'd like GHC to highlight it by raising an error instead of just
warning. Vervis has lots of warnings so it's hard to detect among them.

I suppose in other kinds of software people sometimes leave incomplete patterns
intentionally / are okay with a runtime exception being thrown? In a web
application, I definitely want to handle all cases, and be in control of how
errors are handled and displayed in UI.
---
 src/Vervis/API.hs         | 2 ++
 src/Vervis/ActivityPub.hs | 1 +
 vervis.cabal              | 2 +-
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Vervis/API.hs b/src/Vervis/API.hs
index 6a8b47f..0c0dbcc 100644
--- a/src/Vervis/API.hs
+++ b/src/Vervis/API.hs
@@ -922,6 +922,8 @@ createNoteC (Entity pidUser personUser) sharerUser summary audience note muTarge
                 if u == u'
                     then Nothing
                     else Just $ Right u'
+        checkParent _            _                           =
+            error "A situation I missed in pattern matching, fix it?"
     checkFederation remoteRecips = do
         federation <- asksSite $ appFederation . appSettings
         unless (federation || null remoteRecips) $
diff --git a/src/Vervis/ActivityPub.hs b/src/Vervis/ActivityPub.hs
index 569fcd2..73c69cb 100644
--- a/src/Vervis/ActivityPub.hs
+++ b/src/Vervis/ActivityPub.hs
@@ -1302,6 +1302,7 @@ getOutboxActorEntity obid = do
         (Just p, Nothing, Nothing) -> return $ ActorPerson p
         (Nothing, Just j, Nothing) -> return $ ActorProject j
         (Nothing, Nothing, Just r) -> return $ ActorRepo r
+        _ -> error "obid used by multiple actors"
 
 actorEntityPath (ActorPerson (Entity _ p)) =
     LocalActorSharer . sharerIdent <$> getJust (personIdent p)
diff --git a/vervis.cabal b/vervis.cabal
index 356c3ca..7657ab0 100644
--- a/vervis.cabal
+++ b/vervis.cabal
@@ -399,7 +399,7 @@ library
 
   if flag(dev) || flag(library-only)
     cpp-options:       -DDEVELOPMENT
-    ghc-options:       -Wall -fwarn-tabs -O0
+    ghc-options:       -Wall -fwarn-tabs -O0 -Werror=incomplete-patterns
   else
     ghc-options:       -Wall -fwarn-tabs -O2