adds empty animation (#26)

Author: andrewMacmurray

src/Internal/Animation.elm

@@ -174,8 +174,15 @@ renderIteration i =
 
 
 name_ : Animation -> String
-name_ (Animation d options frames) =
-    "anim-" ++ String.fromInt d ++ optionNames options ++ framesNames frames
+name_ anim =
+    if isEmpty anim then
+        "anim-empty"
+
+    else
+        "anim-"
+            ++ String.fromInt (duration_ anim)
+            ++ optionNames (rawOptions_ anim)
+            ++ framesNames (frames_ anim)
 
 
 optionNames : List Option -> String
@@ -231,6 +238,11 @@ iterationName i =
 -- Helpers
 
 
+isEmpty : Animation -> Bool
+isEmpty anim =
+    duration_ anim == 0
+
+
 options_ : Animation -> Options
 options_ =
     rawOptions_

src/Simple/Animation.elm

@@ -1,5 +1,5 @@
 module Simple.Animation exposing
-    ( Animation, Millis, fromTo, steps
+    ( Animation, Millis, fromTo, steps, empty
     , Step, step, set, wait, waitTillComplete
     , Option, loop, count, delay, reverse, yoyo
     , linear, easeIn, easeOut, easeInOut, cubic
@@ -12,7 +12,7 @@ module Simple.Animation exposing
 
 # Create an Animation
 
-@docs Animation, Millis, fromTo, steps
+@docs Animation, Millis, fromTo, steps, empty
 
 
 # Steps
@@ -152,6 +152,29 @@ steps { options, startAt } steps_ =
         )
 
 
+{-| Create an Empty Animation - Useful when you want to conditionally animate something
+
+    fadeIf : Bool -> Animation
+    fadeIf shouldFade =
+        if shouldFade then
+            Animation.fromTo
+                { duration = 1000
+                , options = []
+                }
+                [ P.opacity 0 ]
+                [ P.opacity 1 ]
+
+        else
+            Animation.empty
+
+`Animation.empty` is equivalent to an animation with `0` duration
+
+-}
+empty : Animation
+empty =
+    fromTo { duration = 0, options = [] } [] []
+
+
 
 -- Step
 

tests/FromToTest.elm

@@ -1,5 +1,7 @@
 module FromToTest exposing (suite)
 
+import Expect
+import Internal.Animation as Animation
 import Simple.Animation as Animation exposing (Animation)
 import Simple.Animation.Property as P
 import Test exposing (..)
@@ -47,4 +49,12 @@ suite =
                         , "animation-duration: 1000ms"
                         , "animation-timing-function: linear"
                         ]
+        , test "Empty Animations have formatted name" <|
+            \_ ->
+                [ Animation.empty
+                , Animation.fromTo { duration = 0, options = [] } [] []
+                , Animation.steps { startAt = [], options = [] } []
+                ]
+                    |> List.map Animation.name_
+                    |> Expect.equal (List.repeat 3 "anim-empty")
         ]