Improved fetching of external resources.

* In Shared, openURL and fetchItem now return an Either, for
  better error handling. (API change.)
* Better error message when fetching a URL fails with
  `--self-contained`.
* EPUB writer: If resource not found, skip it, as in Docx writer.
* Closes #916.

3 files changed, 12 insertions, 8 deletions

diff --git a/src/Text/Pandoc/Writers/Docx.hs b/src/Text/Pandoc/Writers/Docx.hs
index 1ed8c2fa5..611cddc65 100644
--- a/src/Text/Pandoc/Writers/Docx.hs
+++ b/src/Text/Pandoc/Writers/Docx.hs
@@ -726,7 +726,7 @@ inlineToOpenXML opts (Image alt (src, tit)) = do
     Just (_,_,_,elt,_) -> return [elt]
     Nothing -> do
       let sourceDir = writerSourceDirectory opts
-      res <- liftIO $ E.try $ fetchItem sourceDir src
+      res <- liftIO $ fetchItem sourceDir src
       case res of
         Left (_ :: E.SomeException) -> do
           liftIO $ warn $ "Could not find image `" ++ src ++ "', skipping..."
diff --git a/src/Text/Pandoc/Writers/EPUB.hs b/src/Text/Pandoc/Writers/EPUB.hs
index f171a2560..42863ef86 100644
--- a/src/Text/Pandoc/Writers/EPUB.hs
+++ b/src/Text/Pandoc/Writers/EPUB.hs
@@ -123,10 +123,15 @@ writeEPUB opts doc@(Pandoc meta _) = do
   Pandoc _ blocks <- bottomUpM
        (transformInline opts' sourceDir picsRef) doc
   pics <- readIORef picsRef
-  let readPicEntry (oldsrc, newsrc) = do
-        (img,_) <- fetchItem sourceDir oldsrc
-        return $ toEntry newsrc epochtime $ B.fromChunks . (:[]) $ img
-  picEntries <- mapM readPicEntry pics
+  let readPicEntry entries (oldsrc, newsrc) = do
+        res <- fetchItem sourceDir oldsrc
+        case res of
+             Left e        -> do
+              warn $ "Could not find image `" ++ oldsrc ++ "', skipping..."
+              return entries
+             Right (img,_) -> return $
+              (toEntry newsrc epochtime $ B.fromChunks . (:[]) $ img) : entries
+  picEntries <- foldM readPicEntry [] pics
 
   -- handle fonts
   let mkFontEntry f = mkEntry (takeFileName f) `fmap` B.readFile f
diff --git a/src/Text/Pandoc/Writers/ODT.hs b/src/Text/Pandoc/Writers/ODT.hs
index db27286e8..589010bb9 100644
--- a/src/Text/Pandoc/Writers/ODT.hs
+++ b/src/Text/Pandoc/Writers/ODT.hs
@@ -42,7 +42,6 @@ import Text.Pandoc.Definition
 import Text.Pandoc.Generic
 import Text.Pandoc.Writers.OpenDocument ( writeOpenDocument )
 import Control.Monad (liftM)
-import Control.Monad.Trans (liftIO)
 import Text.Pandoc.XML
 import Text.Pandoc.Pretty
 import qualified Control.Exception as E
@@ -114,10 +113,10 @@ writeODT opts doc@(Pandoc meta _) = do
 
 transformPic :: FilePath -> IORef [Entry] -> Inline -> IO Inline
 transformPic sourceDir entriesRef (Image lab (src,_)) = do
-  res <- liftIO $ E.try $ fetchItem sourceDir src
+  res <- fetchItem sourceDir src
   case res of
      Left (_ :: E.SomeException) -> do
-       liftIO $ warn $ "Could not find image `" ++ src ++ "', skipping..."
+       warn $ "Could not find image `" ++ src ++ "', skipping..."
        return $ Emph lab
      Right (img, _) -> do
        let size = imageSize img