refactor(createPngFallbacks): introduce PandocMonad.runConversion

This will be needed to run the conversion inside the PandocMonad,
where we know the desired image size.

[API change]

Signed-off-by: Edwin Török <[email protected]>

Author: edwintorok

pandoc-lua-engine/src/Text/Pandoc/Lua/PandocLua.hs

@@ -70,6 +70,7 @@ instance PandocMonad PandocLua where
   readFileLazy = IO.readFileLazy
   readFileStrict = IO.readFileStrict
   readStdinStrict = IO.readStdinStrict
+  runConversion = IO.runConversion
 
   glob = IO.glob
   fileExists = IO.fileExists

src/Text/Pandoc/App.hs

@@ -372,7 +372,7 @@ readAbbreviations mbfilepath =
     >>= fmap (Set.fromList . filter (not . T.null) . T.lines) .
          toTextM (fromMaybe mempty mbfilepath)
 
-createPngFallbacks :: (PandocMonad m, MonadIO m) => Int -> m ()
+createPngFallbacks :: (PandocMonad m) => Int -> m ()
 createPngFallbacks dpi = do
   -- create fallback pngs for svgs
   items <- mediaItems <$> getMediaBag

src/Text/Pandoc/Class/IO.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {- |
 Module      : Text.Pandoc.Class.IO
 Copyright   : Copyright (C) 2016-2020 Jesse Rosenthal, John MacFarlane
@@ -31,6 +32,7 @@ module Text.Pandoc.Class.IO
   , readFileLazy
   , readFileStrict
   , readStdinStrict
+  , runConversion
   , extractMedia
   , writeMedia
  ) where
@@ -60,7 +62,7 @@ import System.IO.Error
 import System.Random (StdGen)
 import Text.Pandoc.Class.CommonState (CommonState (..))
 import Text.Pandoc.Class.PandocMonad
-       (PandocMonad, getsCommonState, getMediaBag, report)
+       (PandocMonad (trace), getsCommonState, getMediaBag, report)
 import Text.Pandoc.Definition (Pandoc, Inline (Image))
 import Text.Pandoc.Error (PandocError (..))
 import Text.Pandoc.Logging (LogMessage (..), messageVerbosity, showLogMessage)
@@ -80,6 +82,9 @@ import qualified System.Environment as Env
 import qualified System.FilePath.Glob
 import qualified System.Random
 import qualified Text.Pandoc.UTF8 as UTF8
+import Text.Pandoc.Process (pipeProcess)
+import System.Exit (ExitCode(ExitSuccess))
+import Text.Pandoc.Shared (tshow)
 #ifndef EMBED_DATA_FILES
 import qualified Paths_pandoc as Paths
 #endif
@@ -170,6 +175,21 @@ readFileStrict s = liftIOError B.readFile s
 readStdinStrict :: (PandocMonad m, MonadIO m) => m B.ByteString
 readStdinStrict = liftIOError (const B.getContents) "stdin"
 
+-- | Runs an image conversion step, returning an error on failure.
+-- Not available when sandboxed.
+runConversion :: (PandocMonad m, MonadIO m) => (String, [String], BL.ByteString) -> m (Either T.Text BL.ByteString)  
+runConversion (cmd, args, bs) = do
+  trace (T.intercalate " " $ map T.pack $ cmd : args)
+  liftIO $ E.catch
+   (do (exit, out) <- pipeProcess Nothing cmd
+                      args
+                      bs
+       return $ if exit == ExitSuccess
+          then Right out
+          else Left "conversion from SVG failed")
+   (\(e :: E.SomeException) -> return $ Left $
+       "check that " <> T.pack cmd <> " is in path.\n" <> tshow e)
+
 -- | Return a list of paths that match a glob, relative to the working
 -- directory. See 'System.FilePath.Glob' for the glob syntax.
 glob :: (PandocMonad m, MonadIO m) => String -> m [FilePath]

src/Text/Pandoc/Class/PandocIO.hs

@@ -63,6 +63,7 @@ instance PandocMonad PandocIO where
   readFileLazy = IO.readFileLazy
   readFileStrict = IO.readFileStrict
   readStdinStrict = IO.readStdinStrict
+  runConversion = IO.runConversion
 
   glob = IO.glob
   fileExists = IO.fileExists

src/Text/Pandoc/Class/PandocMonad.hs

@@ -8,6 +8,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE ViewPatterns #-}
+
 {- |
 Module      : Text.Pandoc.Class.PandocMonad
 Copyright   : Copyright (C) 2016-2020 Jesse Rosenthal, John MacFarlane
@@ -116,6 +117,9 @@ class (Functor m, Applicative m, Monad m, MonadError PandocError m)
   -- | Read the contents of stdin as a strict ByteString, raising
   -- an error on failure.
   readStdinStrict :: m B.ByteString
+  -- | Runs an image conversion step, returning an error on failure.
+  -- Not called when sandboxed.
+  runConversion :: (String, [String], BL.ByteString) -> m (Either T.Text BL.ByteString)
   -- | Return a list of paths that match a glob, relative to
   -- the working directory.  See 'System.FilePath.Glob' for
   -- the glob syntax.
@@ -505,6 +509,7 @@ instance (MonadTrans t, PandocMonad m, Functor (t m),
   readFileLazy = lift . readFileLazy
   readFileStrict = lift . readFileStrict
   readStdinStrict = lift readStdinStrict
+  runConversion = lift . runConversion
   glob = lift . glob
   fileExists = lift . fileExists
   getDataFileName = lift . getDataFileName
@@ -523,6 +528,7 @@ instance {-# OVERLAPS #-} PandocMonad m => PandocMonad (ParsecT s st m) where
   readFileLazy = lift . readFileLazy
   readFileStrict = lift . readFileStrict
   readStdinStrict = lift readStdinStrict
+  runConversion = lift . runConversion
   glob = lift . glob
   fileExists = lift . fileExists
   getDataFileName = lift . getDataFileName

src/Text/Pandoc/Class/PandocPure.hs

@@ -205,6 +205,8 @@ instance PandocMonad PandocPure where
       Nothing -> throwError $ PandocResourceNotFound $ T.pack fp
 
   readStdinStrict = getsPureState stStdin
+  
+  runConversion _ = return $ Left "Conversion not available in PandocPure"
 
   glob s = do
     FileTree ftmap <- getsPureState stFiles

src/Text/Pandoc/Image.hs

@@ -11,32 +11,17 @@ Portability : portable
 Functions for converting images.
 -}
 module Text.Pandoc.Image ( svgToPng ) where
-import Text.Pandoc.Process (pipeProcess)
 import qualified Data.ByteString.Lazy as L
-import System.Exit
 import Data.Text (Text)
-import Text.Pandoc.Shared (tshow)
-import qualified Control.Exception as E
-import Control.Monad.IO.Class (MonadIO(liftIO))
 import Text.Pandoc.Class.PandocMonad
-import qualified Data.Text as T
 
 -- | Convert svg image to png. rsvg-convert
 -- is used and must be available on the path.
-svgToPng :: (PandocMonad m, MonadIO m)
+svgToPng :: (PandocMonad m)
          => Int           -- ^ DPI
          -> L.ByteString  -- ^ Input image as bytestring
          -> m (Either Text L.ByteString)
 svgToPng dpi bs = do
   let dpi' = show dpi
   let args = ["-f","png","-a","--dpi-x",dpi',"--dpi-y",dpi']
-  trace (T.intercalate " " $ map T.pack $ "rsvg-convert" : args)
-  liftIO $ E.catch
-       (do (exit, out) <- pipeProcess Nothing "rsvg-convert"
-                          args
-                          bs
-           return $ if exit == ExitSuccess
-              then Right out
-              else Left "conversion from SVG failed")
-       (\(e :: E.SomeException) -> return $ Left $
-           "check that rsvg-convert is in path.\n" <> tshow e)
+  runConversion ("rsvg-convert", args, bs)