diff --git a/README.md b/README.md
index 18f64fd..ebf8392 100644
--- a/README.md
+++ b/README.md
@@ -45,7 +45,7 @@ pre-announce,
- CLI UX
- [x] opts
- [ ] logging
-- [ ] [deal with errors](https://github.com/srid/memoir/issues/1)
+- [x] [deal with errors](https://github.com/srid/memoir/issues/1)
- [ ] How to serve non-generated files (css, img, etc.)
- [ ] Publish Data.LVar to Hackage
- [ ] documentation ([guide](https://documentation.divio.com/))
diff --git a/docs/concepts/hot-reload.md b/docs/concepts/hot-reload.md
index 9382d9c..41ac955 100644
--- a/docs/concepts/hot-reload.md
+++ b/docs/concepts/hot-reload.md
@@ -13,5 +13,5 @@ TODO
- data reload (filesystem.md)
- HTML templates implications
- link to tailwind (for shim trick)
-- exceptions
+- exception handling in browser view
- can run in production?
\ No newline at end of file
diff --git a/src/Ema/Server.hs b/src/Ema/Server.hs
index a2cee2a..5534117 100644
--- a/src/Ema/Server.hs
+++ b/src/Ema/Server.hs
@@ -5,11 +5,12 @@
module Ema.Server where
import Control.Concurrent.Async (race)
-import Control.Exception (try)
+import Control.Exception (catch, try)
import Data.LVar (LVar)
import qualified Data.LVar as LVar
import qualified Data.Text as T
import Ema.Class (Ema (decodeRoute))
+import GHC.IO.Unsafe (unsafePerformIO)
import NeatInterpolation (text)
import qualified Network.HTTP.Types as H
import qualified Network.Wai as Wai
@@ -83,14 +84,21 @@ runServerWithWebSocketHotReload port model render = do
pure (H.status404, "No route")
Just r -> do
val <- LVar.get model
- pure (H.status200, renderWithEmaShims val r)
+ let html = renderCatchingErrors val r
+ pure (H.status200, html <> emaStatusHtml <> wsClientShim)
f $ Wai.responseLBS status [(H.hContentType, "text/html")] v
- renderWithEmaShims m r =
- render m r <> emaStatusHtml <> wsClientShim
renderWithEmaHtmlShims m r =
- render m r <> emaStatusHtml
+ renderCatchingErrors m r <> emaStatusHtml
+ renderCatchingErrors m r =
+ unsafeCatch (render m r) $ \(err :: SomeException) ->
+ encodeUtf8 $
+ "Ema App threw an exception
"
+ <> show @Text err
+ <> "
Once you fix your code this page will automatically update."
routeFromPathInfo =
decodeRoute @model . fmap (fromString . toString)
+ unsafeCatch :: Exception e => a -> (e -> a) -> a
+ unsafeCatch x f = unsafePerformIO $ catch (seq x $ pure x) (pure . f)
-- | Return the equivalent of WAI's @pathInfo@, from the raw path string
-- (`document.location.pathname`) the browser sends us.