EPUB reader: fix links to other files in the epub...

making them internal links to a fragment derived from the
filename.  There was already code to handle links like
`#foo`, but not to handle links like `ch0001.html#foo`.

Closes #10207.

Author: jgm

src/Text/Pandoc/Readers/EPUB.hs

@@ -29,7 +29,7 @@ import qualified Data.Map as M (Map, elems, fromList, lookup)
 import Data.Maybe (mapMaybe)
 import qualified Data.Text.Lazy as TL
 import qualified Data.Text.Lazy.Encoding as TL
-import Network.URI (unEscapeString)
+import Network.URI (unEscapeString, parseRelativeReference, URI(..))
 import System.FilePath (dropFileName, dropFileName, normalise, splitFileName,
                         takeFileName, (</>))
 import qualified Text.Pandoc.Builder as B
@@ -211,10 +211,17 @@ fixInlineIRs s (Span as v) =
   Span (fixAttrs s as) v
 fixInlineIRs s (Code as code) =
   Code (fixAttrs s as) code
-fixInlineIRs s (Link as is (T.uncons -> Just ('#', url), tit)) =
-  Link (fixAttrs s as) is (addHash s url, tit)
-fixInlineIRs s (Link as is t) =
-  Link (fixAttrs s as) is t
+fixInlineIRs s (Link as is (url, tit)) =
+  case parseRelativeReference (T.unpack url) of
+    Just URI{ uriScheme = ""
+            , uriAuthority = Nothing
+            , uriPath = upath
+            , uriQuery = ""
+            , uriFragment = '#':ufrag } ->
+         Link (fixAttrs s as) is (addHash (if null upath
+                                              then s
+                                              else upath) (T.pack ufrag), tit)
+    _ -> Link (fixAttrs s as) is (url, tit)
 fixInlineIRs _ v = v
 
 prependHash :: [Text] -> Inline -> Inline