Upstream helper functions to Yesod.Form.Option.

yesod-form/ChangeLog.md

@@ -1,5 +1,12 @@
 # ChangeLog for yesod-form
 
+
+## 1.7.7
+
+* Added `optionsFromList'` to create an OptionList from a List, using the PathPiece instance for the external value and
+a custom function for the user-facing value. Also added `optionsEnum'` to create an OptionList from an enumeration
+[#1828](https://github.com/yesodweb/yesod/pull/1828)
+
 ## 1.7.6
 
 * Added `datetimeLocalField` for creating a html `<input type="datetime-local">` [#1817](https://github.com/yesodweb/yesod/pull/1817)

yesod-form/Yesod/Form/Option.hs

@@ -0,0 +1,37 @@
+{-# LANGUAGE FlexibleContexts #-}
+
+module Yesod.Form.Option where
+
+import Yesod.Core
+import Yesod.Form.Fields
+
+-- | Creates an 'OptionList' from a 'List', using the 'PathPiece' instance for
+-- the external value and a custom function for the user-facing value.
+-- NB: We choose PathPiece as the most suitable class for generating External
+-- Values. The motivation is to avoid Show/Read instances which could leak
+-- an internal representation to forms, query params, javascript etc.
+optionsFromList' ::
+     MonadHandler m
+  => RenderMessage (HandlerSite m) msg
+  => PathPiece a
+  => [a]
+  -> (a -> msg)
+  -> m (OptionList a)
+optionsFromList' lst toDisplay = do
+  mr <- getMessageRender
+  pure $ mkOptionList $ flip map lst $ \v -> Option
+    { optionDisplay = mr $ toDisplay v
+    , optionInternalValue = v
+    , optionExternalValue = toPathPiece v
+    }
+
+-- | Creates an 'OptionList' from an 'Enum'
+optionsEnum' ::
+     MonadHandler m
+  => RenderMessage (HandlerSite m) msg
+  => PathPiece a
+  => Enum a
+  => Bounded a
+  => (a -> msg)
+  -> m (OptionList a)
+optionsEnum' = optionsFromList' [minBound..maxBound]

yesod-form/yesod-form.cabal

@@ -1,6 +1,6 @@
 cabal-version:   >= 1.10
 name:            yesod-form
-version:         1.7.6
+version:         1.7.7
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <[email protected]>
@@ -46,6 +46,7 @@ library
       build-depends: network-uri >= 2.6
 
     exposed-modules: Yesod.Form
+                     Yesod.Form.Option
                      Yesod.Form.Types
                      Yesod.Form.Functions
                      Yesod.Form.Bootstrap3