fix runLayer safety for open rows

Prevent runLayer from accepting open requirement rows so missing dependencies fail at compile time instead of crashing at runtime. Add regression coverage for the bad case and preserve support for running closed-row layers with superset contexts.

Author: i-am-the-slime

compile-fail-tests/RunLayerOpenRowMissingDep.purs

@@ -0,0 +1,19 @@
+-- EXPECT: Prim.RowList.RowToList
+module Yoga.Om.Layer.CompileFailTest where
+
+import Prelude
+
+import Yoga.Om as Om
+import Yoga.Om.Layer (OmLayer, makeLayer, runLayer)
+
+type Fastify = String
+type Connection = String
+
+apiLayer :: forall r. OmLayer (fastify :: Fastify, sqlite :: Connection | r) () {}
+apiLayer = makeLayer do
+  { fastify, sqlite } <- Om.ask
+  let _ = fastify <> sqlite
+  pure {}
+
+bad :: Om.Om { fastify :: Fastify } () {}
+bad = runLayer { fastify: "server" } apiLayer

src/Yoga/Om/Layer.purs

@@ -340,9 +340,13 @@ else instance
 -- =============================================================================
 
 -- | Run a layer with a given context, with custom error if requirements aren't met.
+-- | `runLayer` requires a closed requirement row. If you have an open layer like
+-- | `OmLayer (db :: Db | r) err a`, specialize it to a closed row before running
+-- | it directly.
 runLayer
   :: forall req err a available
    . CheckAllProvided req available
+  => Keys req
   => Record available
   -> OmLayer req err a
   -> Om (Record available) err a

test/Test/Yoga/Om/Layer/InstancesSpec.purs

@@ -46,6 +46,18 @@ spec = do
       result <- Om.runOm {} { exception: \_ -> pure { result: 0 } } (runLayer {} layer)
       result.result `shouldEqual` 15
 
+    it "runs layers against a superset context" do
+      let
+        layer :: OmLayer (a :: Int) () { out :: Int }
+        layer = makeLayer do
+          { a } <- Om.ask
+          pure { out: a + 1 }
+
+        ctx = { a: 41, extra: "ok" }
+
+      result <- Om.runOm ctx { exception: \_ -> pure { out: 0 } } (runLayer ctx layer)
+      result.out `shouldEqual` 42
+
   describe "Parallel" do
 
     it "runs layers in parallel via parApply" do