Fix MediaBag regressions.

With the 2.14 release `--extract-media` stopped working as before;
there could be mismatches between the paths in the rendered document and
the extracted media.

This patch makes several changes (while keeping the same API).

The `mediaPath` in 2.14 was always constructed from the SHA1 hash of
the media contents.  Now, we preserve the original path unless it's
an absolute path or contains `..` segments (in that case we use a path
based on the SHA1 hash of the contents).

When constructing a path from the SHA1 hash, we always use the
original extension, if there is one. Otherwise we look up an
appropriate extension for the mime type.

`mediaDirectory` and `mediaItems` now use the `mediaPath`, rather
than the mediabag key, for the first component of the tuple.
This makes more sense, I think, and fits with the documentation
of these functions; eventually, though, we should rework the API so that
`mediaItems` returns both the keys and the MediaItems.

Rewriting of source paths in `extractMedia` has been fixed.

`fillMediaBag` has been modified so that it doesn't modify
image paths (that was part of the problem in #7345).

We now do path normalization (e.g. `\` separators on Windows) only
in writing the media; the paths are left unchanged in the image
links (sensibly, since they might be URLs and not file paths).

These changes should restore the original behavior from before 2.14.

Closes #7345.

1 files changed, 21 insertions, 20 deletions

diff --git a/src/Text/Pandoc/Class/IO.hs b/src/Text/Pandoc/Class/IO.hs
index 6df39d4d0..169074860 100644
--- a/src/Text/Pandoc/Class/IO.hs
+++ b/src/Text/Pandoc/Class/IO.hs
@@ -62,7 +62,7 @@ import Text.Pandoc.Definition (Pandoc, Inline (Image))
 import Text.Pandoc.Error (PandocError (..))
 import Text.Pandoc.Logging (LogMessage (..), messageVerbosity, showLogMessage)
 import Text.Pandoc.MIME (MimeType)
-import Text.Pandoc.MediaBag (MediaBag, MediaItem(..), lookupMedia, mediaDirectory)
+import Text.Pandoc.MediaBag (MediaBag, MediaItem(..), lookupMedia, mediaItems)
 import Text.Pandoc.Walk (walk)
 import qualified Control.Exception as E
 import qualified Data.ByteString as B
@@ -200,31 +200,32 @@ alertIndent (l:ls) = do
 extractMedia :: (PandocMonad m, MonadIO m) => FilePath -> Pandoc -> m Pandoc
 extractMedia dir d = do
   media <- getMediaBag
-  case [fp | (fp, _, _) <- mediaDirectory media] of
-    []  -> return d
-    fps -> do
-      mapM_ (writeMedia dir media) fps
-      return $ walk (adjustImagePath dir fps) d
+  let items = mediaItems media
+  if null items
+    then return d
+    else do
+      mapM_ (writeMedia dir) items
+      return $ walk (adjustImagePath dir media) d
 
 -- | Write the contents of a media bag to a path.
 writeMedia :: (PandocMonad m, MonadIO m)
-           => FilePath -> MediaBag -> FilePath
+           => FilePath
+           -> (FilePath, MimeType, BL.ByteString)
            -> m ()
-writeMedia dir mediabag subpath = do
-  let mbcontents = lookupMedia subpath mediabag
-  case mbcontents of
-       Nothing -> throwError $ PandocResourceNotFound $ pack subpath
-       Just item -> do
-         -- we normalize to get proper path separators for the platform
-         let fullpath = dir </> normalise (mediaPath item)
-         liftIOError (createDirectoryIfMissing True) (takeDirectory fullpath)
-         logIOError $ BL.writeFile fullpath $ mediaContents item
+writeMedia dir (fp, _mt, bs) = do
+  -- we normalize to get proper path separators for the platform
+  let fullpath = normalise $ dir </> fp
+  liftIOError (createDirectoryIfMissing True) (takeDirectory fullpath)
+  logIOError $ BL.writeFile fullpath bs
 
 -- | If the given Inline element is an image with a @src@ path equal to
 -- one in the list of @paths@, then prepends @dir@ to the image source;
 -- returns the element unchanged otherwise.
-adjustImagePath :: FilePath -> [FilePath] -> Inline -> Inline
-adjustImagePath dir paths (Image attr lab (src, tit))
-   | unpack src `elem` paths
-     = Image attr lab (pack (normalise $ dir </> unpack src), tit)
+adjustImagePath :: FilePath -> MediaBag -> Inline -> Inline
+adjustImagePath dir mediabag (Image attr lab (src, tit)) =
+  case lookupMedia (T.unpack src) mediabag of
+    Nothing -> Image attr lab (src, tit)
+    Just item ->
+      let fullpath = dir </> mediaPath item
+      in  Image attr lab (T.pack fullpath, tit)
 adjustImagePath _ _ x = x