Preserve built-in styles in DOCX with custom style (#5670)

This commit prevents custom styles on divs and spans from overriding
styles on certain elements inside them, like headings, blockquotes,
and links. On those elements, the "native" style is required for the
element to display correctly. This change also allows nesting of
custom styles; in order to do so, it removes the default "Compact"
style applied to Plain blocks, except when inside a table.

6 files changed, 78 insertions, 24 deletions

diff --git a/MANUAL.txt b/MANUAL.txt
index 8b9e02da2..3c9f158ef 100644
--- a/MANUAL.txt
+++ b/MANUAL.txt
@@ -5255,8 +5255,10 @@ styles, pandoc allows you to define custom styles for blocks and text
 using `div`s and `span`s, respectively.
 
 If you define a `div` or `span` with the attribute `custom-style`,
-pandoc will apply your specified style to the contained elements. So,
-for example using the `bracketed_spans` syntax,
+pandoc will apply your specified style to the contained elements (with
+the exception of elements whose function depends on a style, like
+headings, code blocks, block quotes, or links). So, for example, using
+the `bracketed_spans` syntax,
 
     [Get out]{custom-style="Emphatically"}, he said.
 
diff --git a/src/Text/Pandoc/Writers/Docx.hs b/src/Text/Pandoc/Writers/Docx.hs
index b41b17ff9..02db23db5 100644
--- a/src/Text/Pandoc/Writers/Docx.hs
+++ b/src/Text/Pandoc/Writers/Docx.hs
@@ -81,8 +81,23 @@ listMarkerToId (NumberMarker sty delim n) =
                       OneParen     -> '2'
                       TwoParens    -> '3'
 
-data WriterEnv = WriterEnv{ envTextProperties :: [Element]
-                          , envParaProperties :: [Element]
+data EnvProps = EnvProps{ styleElement  :: Maybe Element
+                        , otherElements :: [Element]
+                        }
+
+instance Semigroup EnvProps where
+  EnvProps Nothing es <> EnvProps s es' = EnvProps s (es ++ es')
+  EnvProps s       es <> EnvProps _ es' = EnvProps s (es ++ es')
+
+instance Monoid EnvProps where
+  mempty = EnvProps Nothing []
+
+squashProps :: EnvProps -> [Element]
+squashProps (EnvProps Nothing es) = es
+squashProps (EnvProps (Just e) es) = e : es
+
+data WriterEnv = WriterEnv{ envTextProperties :: EnvProps
+                          , envParaProperties :: EnvProps
                           , envRTL            :: Bool
                           , envListLevel      :: Int
                           , envListNumId      :: Int
@@ -93,8 +108,8 @@ data WriterEnv = WriterEnv{ envTextProperties :: [Element]
                           }
 
 defaultWriterEnv :: WriterEnv
-defaultWriterEnv = WriterEnv{ envTextProperties = []
-                            , envParaProperties = []
+defaultWriterEnv = WriterEnv{ envTextProperties = mempty
+                            , envParaProperties = mempty
                             , envRTL = False
                             , envListLevel = -1
                             , envListNumId = 1
@@ -115,6 +130,7 @@ data WriterState = WriterState{
        , stDelId          :: Int
        , stStyleMaps      :: StyleMaps
        , stFirstPara      :: Bool
+       , stInTable        :: Bool
        , stTocTitle       :: [Inline]
        , stDynamicParaProps :: Set.Set String
        , stDynamicTextProps :: Set.Set String
@@ -133,6 +149,7 @@ defaultWriterState = WriterState{
       , stDelId          = 1
       , stStyleMaps      = defaultStyleMaps
       , stFirstPara      = False
+      , stInTable        = False
       , stTocTitle       = [Str "Table of Contents"]
       , stDynamicParaProps = Set.empty
       , stDynamicTextProps = Set.empty
@@ -496,7 +513,7 @@ writeDocx opts doc@(Pandoc meta _) = do
         case key' of
              "description"    -> intercalate "_x000d_\n" (map stringify $ lookupMetaBlocks "description" meta')
              _                -> lookupMetaString key' meta'
-  
+
   let docProps = mknode "cp:coreProperties"
           [("xmlns:cp","http://schemas.openxmlformats.org/package/2006/metadata/core-properties")
           ,("xmlns:dc","http://purl.org/dc/elements/1.1/")
@@ -901,8 +918,12 @@ blockToOpenXML' opts (Header lev (ident,_,_) lst) = do
                                       $ stSectionIds s }
        bookmarkedContents <- wrapBookmark bookmarkName contents
        return [mknode "w:p" [] (paraProps ++ bookmarkedContents)]
-blockToOpenXML' opts (Plain lst) = withParaProp (pCustomStyle "Compact")
-  $ blockToOpenXML opts (Para lst)
+blockToOpenXML' opts (Plain lst) = do
+  isInTable <- gets stInTable
+  let block = blockToOpenXML opts (Para lst)
+  para <- if isInTable then withParaProp (pCustomStyle "Compact") block else block
+  return $ para
+
 -- title beginning with fig: indicates that the image is a figure
 blockToOpenXML' opts (Para [Image attr alt (src,'f':'i':'g':':':tit)]) = do
   setFirstPara
@@ -910,7 +931,7 @@ blockToOpenXML' opts (Para [Image attr alt (src,'f':'i':'g':':':tit)]) = do
         if null alt
         then "Figure"
         else "CaptionedFigure"
-  paraProps <- local (\env -> env { envParaProperties = prop : envParaProperties env }) (getParaProps False)
+  paraProps <- local (\env -> env { envParaProperties = EnvProps (Just prop) [] <> envParaProperties env }) (getParaProps False)
   contents <- inlinesToOpenXML opts [Image attr alt (src,tit)]
   captionNode <- withParaProp (pCustomStyle "ImageCaption")
                  $ blockToOpenXML opts (Para alt)
@@ -939,7 +960,8 @@ blockToOpenXML' _ b@(RawBlock format str)
       report $ BlockNotRendered b
       return []
 blockToOpenXML' opts (BlockQuote blocks) = do
-  p <- withParaPropM (pStyleM "Block Text") $ blocksToOpenXML opts blocks
+  p <- withParaPropM (pStyleM "Block Text")
+       $ blocksToOpenXML opts blocks
   setFirstPara
   return p
 blockToOpenXML' opts (CodeBlock attrs@(ident, _, _) str) = do
@@ -955,6 +977,7 @@ blockToOpenXML' _ HorizontalRule = do
                        ("o:hrstd","t"),("o:hr","t")] () ]
 blockToOpenXML' opts (Table caption aligns widths headers rows) = do
   setFirstPara
+  modify $ \s -> s { stInTable = True }
   let captionStr = stringify caption
   caption' <- if null caption
                  then return []
@@ -990,6 +1013,7 @@ blockToOpenXML' opts (Table caption aligns widths headers rows) = do
   let mkgridcol w = mknode "w:gridCol"
                        [("w:w", show (floor (textwidth * w) :: Integer))] ()
   let hasHeader = not (all null headers)
+  modify $ \s -> s { stInTable = False }
   return $
     caption' ++
     [mknode "w:tbl" []
@@ -1063,16 +1087,22 @@ withNumId numid = local $ \env -> env{ envListNumId = numid }
 asList :: (PandocMonad m) => WS m a -> WS m a
 asList = local $ \env -> env{ envListLevel = envListLevel env + 1 }
 
+isStyle :: Element -> Bool
+isStyle e = isElem [] "w" "rStyle" e ||
+            isElem [] "w" "pStyle" e
+
 getTextProps :: (PandocMonad m) => WS m [Element]
 getTextProps = do
   props <- asks envTextProperties
-  return $ if null props
+  let squashed = squashProps props
+  return $ if null squashed
               then []
-              else [mknode "w:rPr" [] props]
+              else [mknode "w:rPr" [] squashed]
 
 withTextProp :: PandocMonad m => Element -> WS m a -> WS m a
 withTextProp d p =
-  local (\env -> env {envTextProperties = d : envTextProperties env}) p
+  local (\env -> env {envTextProperties = ep <> envTextProperties env}) p
+  where ep = if isStyle d then EnvProps (Just d) [] else EnvProps Nothing [d]
 
 withTextPropM :: PandocMonad m => WS m Element -> WS m a -> WS m a
 withTextPropM = (. flip withTextProp) . (>>=)
@@ -1085,13 +1115,14 @@ getParaProps displayMathPara = do
   let listPr = [mknode "w:numPr" []
                 [ mknode "w:ilvl" [("w:val",show listLevel)] ()
                 , mknode "w:numId" [("w:val",show numid)] () ] | listLevel >= 0 && not displayMathPara]
-  return $ case listPr ++ props of
+  return $ case listPr ++ squashProps props of
                 [] -> []
                 ps -> [mknode "w:pPr" [] ps]
 
 withParaProp :: PandocMonad m => Element -> WS m a -> WS m a
 withParaProp d p =
-  local (\env -> env {envParaProperties = d : envParaProperties env}) p
+  local (\env -> env {envParaProperties = ep <> envParaProperties env}) p
+  where ep = if isStyle d then EnvProps (Just d) [] else EnvProps Nothing [d]
 
 withParaPropM :: PandocMonad m => WS m Element -> WS m a -> WS m a
 withParaPropM = (. flip withParaProp) . (>>=)
@@ -1264,8 +1295,8 @@ inlineToOpenXML' opts (Note bs) = do
       insertNoteRef xs               = Para [notemarkerXml] : xs
 
   contents <- local (\env -> env{ envListLevel = -1
-                                , envParaProperties = []
-                                , envTextProperties = [] })
+                                , envParaProperties = mempty
+                                , envTextProperties = mempty })
               (withParaPropM (pStyleM "Footnote Text") $ blocksToOpenXML opts
                 $ insertNoteRef bs)
   let newnote = mknode "w:footnote" [("w:id", notenum)] contents
@@ -1417,16 +1448,18 @@ withDirection x = do
   -- We want to clean all bidirection (bidi) and right-to-left (rtl)
   -- properties from the props first. This is because we don't want
   -- them to stack up.
-  let paraProps' = filter (\e -> (qName . elName) e /= "bidi") paraProps
-      textProps' = filter (\e -> (qName . elName) e /= "rtl") textProps
+  let paraProps' = filter (\e -> (qName . elName) e /= "bidi") (otherElements paraProps)
+      textProps' = filter (\e -> (qName . elName) e /= "rtl") (otherElements textProps)
+      paraStyle = styleElement paraProps
+      textStyle = styleElement textProps
   if isRTL
     -- if we are going right-to-left, we (re?)add the properties.
     then flip local x $
-         \env -> env { envParaProperties = mknode "w:bidi" [] () : paraProps'
-                     , envTextProperties = mknode "w:rtl" [] () : textProps'
+         \env -> env { envParaProperties = EnvProps paraStyle $ mknode "w:bidi" [] () : paraProps'
+                     , envTextProperties = EnvProps textStyle $ mknode "w:rtl" [] () : textProps'
                      }
-    else flip local x $ \env -> env { envParaProperties = paraProps'
-                                    , envTextProperties = textProps'
+    else flip local x $ \env -> env { envParaProperties = EnvProps paraStyle paraProps'
+                                    , envTextProperties = EnvProps textStyle textProps'
                                     }
 
 wrapBookmark :: (PandocMonad m) => String -> [Element] -> WS m [Element]
diff --git a/test/Tests/Writers/Docx.hs b/test/Tests/Writers/Docx.hs
index c958ddf7d..9e1414c40 100644
--- a/test/Tests/Writers/Docx.hs
+++ b/test/Tests/Writers/Docx.hs
@@ -155,6 +155,10 @@ tests = [ testGroup "inlines"
             def{writerReferenceDoc = Just "docx/custom-style-reference.docx"}
             "docx/custom_style.native"
             "docx/golden/custom_style_reference.docx"
+          , docxTest "suppress custom style for headers and blockquotes"
+            def
+            "docx/custom-style-preserve.native"
+            "docx/golden/custom_style_preserve.docx"
           ]
         , testGroup "metadata"
           [ docxTest "document properties (core, custom)"
diff --git a/test/docx/custom-style-preserve.native b/test/docx/custom-style-preserve.native
new file mode 100644
index 000000000..859f71c20
--- /dev/null
+++ b/test/docx/custom-style-preserve.native
@@ -0,0 +1,15 @@
+[Para [Span ("",[],[("custom-style","MyStyle")]) [Str "This",Space,Str "span",Note [Para [Str "Neither",Space,Str "footnote",Space,Str "nor",Space,Str "footnote",Space,Str "reference",Space,Str "should",Space,Str "get",Space,Str "a",Space,Str "custom",Space,Str "style",Space,Str "from",Space,Str "its",Space,Str "span."]],Space,Str "should",Space,Str "have",Space,Str "a",Space,Str "custom",Space,Str "style",Space,Str "(",Link ("",[],[]) [Str "link"] ("http://example.com/",""),Str "),"],Space,Str "but",Space,Str "the",Space,Str "text",Space,Str "after",Space,Str "the",Space,Str "comma",Space,Str "shouldn\8217t,",Space,Str "nor",Space,Str "should",Space,Str "the",Space,Str "link."]
+,Div ("",[],[("custom-style","MyOtherStyle")])
+ [Para [Str "The",Space,Str "contents",Space,Str "of",Space,Str "this",Space,Str "div",Space,Str "should",Space,Str "have",Space,Str "a",Space,Str "custom",Space,Str "style,",Space,Str "but",Space,Link ("",[],[]) [Str "this",Space,Str "link",Space,Str "should",Space,Str "not"] ("http://example.com/",""),Str "."]
+ ,Header 2 ("this-header-should-not-have-the-divs-custom-style",[],[]) [Str "This",Space,Str "header",Space,Str "should",Space,Str "not",Space,Str "have",Space,Str "the",Space,Str "div\8217s",Space,Str "custom",Space,Str "style"]
+ ,BlockQuote
+  [Para [Str "This",Space,Str "blockquote",Space,Str "should",Space,Str "not."]]
+ ,CodeBlock ("",[],[]) "# This code block should not."
+ ,Para [Str "But",Space,Str "this",Space,Str "paragraph",Space,Str "should.",Note [Para [Str "Neither",Space,Str "footnote",Space,Str "nor",Space,Str "footnote",Space,Str "reference",Space,Str "should",Space,Str "get",Space,Str "a",Space,Str "custom",Space,Str "style",Space,Str "from",Space,Str "its",Space,Str "div."]]]]
+,Div ("",[],[("custom-style","MyOuterStyle")])
+ [Div ("",[],[("custom-style","MyInnerStyle")])
+  [Para [Str "This",Space,Str "should",Space,Str "have",Space,Str "MyInnerStyle."]
+  ,Header 3 ("this-heading-should-not",[],[]) [Str "This",Space,Str "heading",Space,Str "should",Space,Str "not"]]
+ ,Para [Str "This",Space,Str "should",Space,Str "have",Space,Str "MyOuterStyle,",Space,Str "but",Space,Str "the",Space,Str "following",Space,Str "elision",Space,Str "should",Space,Str "have",Space,Str "its",SoftBreak,Str "own",Space,Str "style.",Space,Span ("",[],[("custom-style","Elision")]) [Str "..."]]
+ ,BlockQuote
+  [Para [Str "This",Space,Str "blockquote",Space,Str "should",Space,Str "include",Space,Strong [Str "bold",Space,Str "text",Space,Str "with",Space,Str "an",Space,Str "elision:",SoftBreak,Span ("",[],[("custom-style","Elision")]) [Str "..."]]]]]]
diff --git a/test/docx/golden/custom_style_preserve.docx b/test/docx/golden/custom_style_preserve.docx
new file mode 100644
index 000000000..06371d51e
--- /dev/null
+++ b/test/docx/golden/custom_style_preserve.docx
diff --git a/test/docx/golden/document-properties.docx b/test/docx/golden/document-properties.docx
index 00c78bc0f..8bb498e02 100644
--- a/test/docx/golden/document-properties.docx
+++ b/test/docx/golden/document-properties.docx