Add V2 of html extra attributes'

src/Nri/Ui/Html/Attributes/V2.elm

@@ -0,0 +1,40 @@
+module Nri.Ui.Html.Attributes.V2 exposing (includeIf, none)
+
+{-| Extras for working with Html.Attributes.
+
+This is the new version of Nri.Ui.Html.Attributes.Extra.
+
+@docs none, includeIf
+
+-}
+
+import Html.Styled exposing (Attribute)
+import Html.Styled.Attributes as Attributes
+import Json.Encode as Encode
+
+
+{-| Represents an attribute with no semantic meaning, useful for conditionals.
+
+This is implemented such that whenever Html.Attributes.Extra.none is encountered
+by VirtualDom it will set a meaningless property on the element object itself to
+null:
+
+    domNode['Html.Attributes.Extra.none'] = null
+
+It's totally safe and lets us clean up conditional and maybe attributes
+
+-}
+none : Attribute msg
+none =
+    Attributes.property "Html.Attributes.Extra.none" Encode.null
+
+
+{-| conditionally include an attribute. Useful for CSS classes generated with
+`UniqueClass`!
+-}
+includeIf : Bool -> Attribute msg -> Attribute msg
+includeIf cond attr =
+    if cond then
+        attr
+    else
+        none