100 lines
2.9 KiB
Haskell
100 lines
2.9 KiB
Haskell
-- | Running your app inside GHCi.
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--
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-- To start up GHCi for usage with Yesod, first make sure you are in dev mode:
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--
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-- > cabal configure -fdev
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--
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-- Note that @yesod devel@ automatically sets the dev flag.
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-- Now launch the repl:
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--
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-- > cabal repl --ghc-options="-O0 -fobject-code"
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--
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-- To start your app, run:
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--
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-- > :l DevelMain
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-- > DevelMain.update
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--
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-- You can also call @DevelMain.shutdown@ to stop the app
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--
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-- You will need to add the foreign-store package to your .cabal file.
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-- It is very light-weight.
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--
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-- If you don't use cabal repl, you will need
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-- to run the following in GHCi or to add it to
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-- your .ghci file.
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--
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-- :set -DDEVELOPMENT
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--
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-- There is more information about this approach,
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-- on the wiki: https://github.com/yesodweb/yesod/wiki/ghci
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module DevelMain where
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import Prelude
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import Application (getApplicationRepl, shutdownApp)
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import Control.Exception (finally)
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import Control.Monad ((>=>))
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import Control.Concurrent
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import Data.IORef
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import Foreign.Store
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import Network.Wai.Handler.Warp
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import GHC.Word
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-- | Start or restart the server.
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-- newStore is from foreign-store.
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-- A Store holds onto some data across ghci reloads
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update :: IO ()
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update = do
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mtidStore <- lookupStore tidStoreNum
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case mtidStore of
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-- no server running
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Nothing -> do
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done <- storeAction doneStore newEmptyMVar
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tid <- start done
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_ <- storeAction (Store tidStoreNum) (newIORef tid)
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return ()
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-- server is already running
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Just tidStore -> restartAppInNewThread tidStore
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where
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doneStore :: Store (MVar ())
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doneStore = Store 0
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-- shut the server down with killThread and wait for the done signal
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restartAppInNewThread :: Store (IORef ThreadId) -> IO ()
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restartAppInNewThread tidStore = modifyStoredIORef tidStore $ \tid -> do
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killThread tid
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withStore doneStore takeMVar
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readStore doneStore >>= start
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-- | Start the server in a separate thread.
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start :: MVar () -- ^ Written to when the thread is killed.
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-> IO ThreadId
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start done = do
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(port, site, app) <- getApplicationRepl
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forkIO (finally (runSettings (setPort port defaultSettings) app)
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-- Note that this implies concurrency
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-- between shutdownApp and the next app that is starting.
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-- Normally this should be fine
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(putMVar done () >> shutdownApp site))
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-- | kill the server
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shutdown :: IO ()
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shutdown = do
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mtidStore <- lookupStore tidStoreNum
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case mtidStore of
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-- no server running
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Nothing -> putStrLn "no Yesod app running"
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Just tidStore -> do
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withStore tidStore $ readIORef >=> killThread
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putStrLn "Yesod app is shutdown"
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tidStoreNum :: Word32
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tidStoreNum = 1
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modifyStoredIORef :: Store (IORef a) -> (a -> IO a) -> IO ()
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modifyStoredIORef store f = withStore store $ \ref -> do
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v <- readIORef ref
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f v >>= writeIORef ref
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