Docbook writer: Use correct id attribute consistently

DocBook5 should always use xml:id instead of id so let’s use it everywhere.

src/Text/Pandoc/Writers/Docbook.hs

@@ -53,6 +53,13 @@ getStartLvl opts =
        TopLevelSection -> 1
        TopLevelDefault -> 1
 
+-- | Get correct name for the id attribute based on DocBook version.
+-- DocBook 4 used custom id attribute but DocBook 5 adopted the xml:id specification.
+-- https://www.w3.org/TR/xml-id/
+idName :: DocBookVersion -> Text
+idName DocBook5 = "xml:id"
+idName DocBook4 = "id"
+
 -- | Convert list of authors to a docbook <author> section
 authorToDocbook :: PandocMonad m => WriterOptions -> [Inline] -> DB m B.Inlines
 authorToDocbook opts name' = do
@@ -174,10 +181,7 @@ blockToDocbook opts (Div (id',"section":_,_) (Header lvl _ ils : xs)) = do
                                               then "section"
                                               else "sect" <> tshow n
                  _                    -> "simplesect"
-      idName = if version == DocBook5
-                 then "xml:id"
-                 else "id"
-      idAttr = [(idName, writerIdentifierPrefix opts <> id') | not (T.null id')]
+      idAttr = [(idName version, writerIdentifierPrefix opts <> id') | not (T.null id')]
       -- We want to add namespaces to the root (top-level) element.
       nsAttr = if version == DocBook5 && lvl == getStartLvl opts && isNothing (writerTemplate opts)
       -- Though, DocBook 4 does not support namespaces and
@@ -188,11 +192,12 @@ blockToDocbook opts (Div (id',"section":_,_) (Header lvl _ ils : xs)) = do
   title' <- inlinesToDocbook opts ils
   contents <- blocksToDocbook opts bs
   return $ inTags True tag attribs $ inTagsSimple "title" title' $$ contents
-blockToDocbook opts (Div (ident,classes,_) bs) =
-  let identAttribs = [("id", ident) | not (T.null ident)]
+blockToDocbook opts (Div (ident,classes,_) bs) = do
+  version <- ask
+  let identAttribs = [(idName version, ident) | not (T.null ident)]
       admonitions = ["attention","caution","danger","error","hint",
                      "important","note","tip","warning"]
-  in case classes of
+  case classes of
     (l:_) | l `elem` admonitions -> do
         let (mTitleBs, bodyBs) =
                 case bs of
@@ -371,11 +376,12 @@ inlineToDocbook opts (Quoted _ lst) =
   inTagsSimple "quote" <$> inlinesToDocbook opts lst
 inlineToDocbook opts (Cite _ lst) =
   inlinesToDocbook opts lst
-inlineToDocbook opts (Span (ident,_,_) ils) =
+inlineToDocbook opts (Span (ident,_,_) ils) = do
+  version <- ask
   ((if T.null ident
        then mempty
-       else selfClosingTag "anchor" [("id", ident)]) <>) <$>
-  inlinesToDocbook opts ils
+       else selfClosingTag "anchor" [(idName version, ident)]) <>) <$>
+    inlinesToDocbook opts ils
 inlineToDocbook _ (Code _ str) =
   return $ inTagsSimple "literal" $ literal (escapeStringForXML str)
 inlineToDocbook opts (Math t str)