Handle Clipboard being undefined in insecure contexts (#15)

* Handle Clipboard being undefined in insecure contexts

* Add changelog entry for Maybeness of window.clipboard

* Add explicit export list

* Use double quotes for string literal

Author: ysangkok

CHANGELOG.md

@@ -6,6 +6,10 @@ Notable changes to this project are documented in this file. The format is based
 
 Breaking changes:
 
+- `clipboard` now returns `Effect (Maybe Clipboard)` instead of `Effect Clipboard`.
+  This is because insecure contexts don't have the clipboard available, see
+  [MDN](https://developer.mozilla.org/en-US/docs/Web/API/Navigator/clipboard).
+
 New features:
 
 Bugfixes:

src/Web/Clipboard/Clipboard.js

@@ -1,6 +1,12 @@
-export function clipboard(navigator) {
+export function clipboardWrapper(just, nothing, navigator) {
   return function () {
-    return navigator.clipboard;
+    var clp = navigator.clipboard;
+    if (typeof clp === "undefined") {
+      // This is expected if we don't have a SecureContext (see w3 spec).
+      return nothing;
+    } else {
+      return just(clp);
+    }
   };
 }
 

src/Web/Clipboard/Clipboard.purs

@@ -1,16 +1,27 @@
-module Web.Clipboard where
+module Web.Clipboard
+  ( clipboard
+  , Clipboard
+  , toEventTarget
+  , fromEventTarget
+  , readText
+  , writeText
+  ) where
 
 import Prelude
 
-import Data.Maybe (Maybe)
+import Data.Function.Uncurried (Fn3, runFn3)
+import Data.Maybe (Maybe(..))
 import Effect (Effect)
 import Promise (Promise)
 import Unsafe.Coerce (unsafeCoerce)
 import Web.Event.Internal.Types (EventTarget)
 import Web.HTML (Navigator)
 import Web.Internal.FFI (unsafeReadProtoTagged)
 
-foreign import clipboard :: Navigator -> Effect Clipboard
+foreign import clipboardWrapper :: Fn3 (forall a. a -> Maybe a) (forall a. Maybe a) Navigator (Effect (Maybe Clipboard))
+
+clipboard :: Navigator -> Effect (Maybe Clipboard)
+clipboard = runFn3 clipboardWrapper Just Nothing
 
 foreign import data Clipboard :: Type