Templates: use filename to search for default template of custom writers

The default template of a custom writer `/path/to/my-writer.lua` is
expected in the `templates/default.my-writer.lua` data file. Note that
templates are *not* applied automatically to the output of custom
writers; custom writer authors must ensure that the template is applied
if one is present in the writer options.

Closes: #8137

1 files changed, 3 insertions, 1 deletions

diff --git a/src/Text/Pandoc/App/OutputSettings.hs b/src/Text/Pandoc/App/OutputSettings.hs
index ab224cd7f..537def363 100644
--- a/src/Text/Pandoc/App/OutputSettings.hs
+++ b/src/Text/Pandoc/App/OutputSettings.hs
@@ -188,7 +188,9 @@ optToOutputSettings scriptingEngine opts = do
 
   templ <- case optTemplate opts of
                   _ | not standalone -> return Nothing
-                  Nothing -> Just <$> compileDefaultTemplate format
+                  Nothing ->
+                    let filename = T.pack . takeFileName . T.unpack
+                    in Just <$> compileDefaultTemplate (filename format)
                   Just tp -> do
                     -- strip off extensions
                     let tp' = case takeExtension tp of