Only recheck useTickEffect memos when running effects modified state (#28)

Previously, when using `useTickEffect`, Hooks would re-evaluate after effects were run just in case the effects touched state that could have been a dependency for a tick effect. Now, we track a dirty flag in state and only re-evaluate hooks if an effect actually modified state.

Author: JordanMartinez

src/Halogen/Hooks/Component.purs

@@ -122,5 +122,6 @@ memoComponent eqInput inputHookFn = do
           , memoCells: { queue: [], index: 0 }
           , refCells: { queue: [], index: 0 }
           , evalQueue: []
+          , stateDirty: false
           }
       }

src/Halogen/Hooks/Internal/Eval.purs

@@ -70,18 +70,16 @@ mkEval inputEq runHookM runHook hookFn = case _ of
     _ <- runHook reason hookFn
     { evalQueue } <- getState
 
-    if Array.null evalQueue then
-      H.gets (_.result <<< unwrap)
-
-    else do
-      modifyState_ _ { evalQueue = [] }
+    when (not (Array.null evalQueue)) do
+      modifyState_ _ { evalQueue = [], stateDirty = false }
       sequence_ evalQueue
+      { stateDirty } <- getState
 
-      if (reason == Initialize || reason == Step) then
-        runHookAndEffects Step
+      let initializeOrStepReason = reason == Initialize || reason == Step
+      when (stateDirty && initializeOrStepReason) do
+        void $ runHookAndEffects Step
 
-      else
-        H.gets (_.result <<< unwrap)
+    H.gets (_.result <<< unwrap)
 
 interpretHook
   :: forall hooks q i m a
@@ -286,7 +284,10 @@ evalHookM runHooks (HookM evalUseHookF) = foldFree interpretHalogenHook evalUseH
       -- ensure calls to `get` don't trigger evaluations.
       unless (unsafeRefEq current next) do
         let newQueue = unsafeSetCell token next
-        putState $ state { stateCells { queue = newQueue state.stateCells.queue } }
+        putState $ state
+          { stateCells { queue = newQueue state.stateCells.queue }
+          , stateDirty = true
+          }
         void runHooks
 
       pure (reply next)

src/Halogen/Hooks/Internal/Eval/Types.purs

@@ -60,6 +60,7 @@ type InternalHookState q i m a =
   , effectCells :: QueueState ((Maybe MemoValues) /\ HookM m Unit)
   , memoCells :: QueueState (MemoValues /\ MemoValue)
   , refCells :: QueueState (Ref RefValue)
+  , stateDirty :: Boolean
   }
 
 type QueueState a =

test/Test/Hooks/UseEffect/UseLifecycleEffect.purs

@@ -63,7 +63,7 @@ lifecycleEffectHook = before initDriver $ describe "useLifecycleEffect" do
 
   where
   initializeSteps =
-    [ RunHooks Initialize, Render, RunEffect (EffectBody 0), RunHooks Step, Render ]
+    [ RunHooks Initialize, Render, RunEffect (EffectBody 0) ]
 
   finalizeSteps =
     [ RunHooks Finalize, Render, RunEffect (EffectCleanup 0) ]

test/Test/Hooks/UseEffect/UseTickEffect.purs

@@ -65,8 +65,6 @@ tickEffectHook = before initDriver $ describe "useTickEffect" do
           , Render
           , RunEffect (EffectCleanup 0)
           , RunEffect (EffectBody 0)
-          , RunHooks Step
-          , Render
           ]
       , finalizeSteps
       ]
@@ -91,7 +89,7 @@ tickEffectHook = before initDriver $ describe "useTickEffect" do
 
   where
   initializeSteps =
-    [ RunHooks Initialize, Render, RunEffect (EffectBody 0), RunHooks Step, Render ]
+    [ RunHooks Initialize, Render, RunEffect (EffectBody 0) ]
 
   finalizeSteps =
     [ RunHooks Finalize, Render, RunEffect (EffectCleanup 0) ]

test/Test/Setup/Eval.purs

@@ -146,6 +146,7 @@ initDriver = liftEffect do
     , memoCells: { queue: [], index: 0 }
     , refCells: { queue: [], index: 0 }
     , evalQueue: []
+    , stateDirty: false
     }
 
   lifecycleHandlers <- Ref.new mempty