LaTeX reader: improve \def and implement \newif.

- Improve parsing of `\def` macros.  We previously set "verbatim mode"
  even for parsing the initial `\def`; this caused problems for things
  like
  ```
  \def\foo{\def\bar{BAR}}
  \foo
  \bar
  ```
- Implement `\newif`.
- Add tests.

src/Text/Pandoc/Readers/LaTeX/Macro.hs

@@ -14,6 +14,7 @@ import Text.Pandoc.Parsing hiding (blankline, mathDisplay, mathInline,
 import Control.Applicative ((<|>), optional)
 import qualified Data.Map as M
 import Data.Text (Text)
+import qualified Data.Text as T
 
 macroDef :: (PandocMonad m, Monoid a) => (Text -> a) -> LP m a
 macroDef constructor = do
@@ -22,9 +23,11 @@ macroDef constructor = do
       guardDisabled Ext_latex_macros)
      <|> return mempty
   where commandDef = do
-          (name, macro') <- newcommand <|> letmacro <|> defmacro
+          nameMacroPairs <- newcommand <|> letmacro <|> defmacro <|> newif
           guardDisabled Ext_latex_macros <|>
-           updateState (\s -> s{ sMacros = M.insert name macro' (sMacros s) })
+           mapM_ (\(name, macro') ->
+                   updateState (\s -> s{ sMacros = M.insert name macro'
+                                          (sMacros s) })) nameMacroPairs
         environmentDef = do
           mbenv <- newenvironment
           case mbenv of
@@ -40,7 +43,7 @@ macroDef constructor = do
         -- @\newcommand{\envname}[n-args][default]{begin}@
         -- @\newcommand{\endenvname}@
 
-letmacro :: PandocMonad m => LP m (Text, Macro)
+letmacro :: PandocMonad m => LP m [(Text, Macro)]
 letmacro = do
   controlSeq "let"
   (name, contents) <- withVerbatimMode $ do
@@ -53,18 +56,47 @@ letmacro = do
     contents <- bracedOrToken
     return (name, contents)
   contents' <- doMacros' 0 contents
-  return (name, Macro ExpandWhenDefined [] Nothing contents')
+  return [(name, Macro ExpandWhenDefined [] Nothing contents')]
 
-defmacro :: PandocMonad m => LP m (Text, Macro)
-defmacro = try $
+defmacro :: PandocMonad m => LP m [(Text, Macro)]
+defmacro = do
   -- we use withVerbatimMode, because macros are to be expanded
   -- at point of use, not point of definition
+  controlSeq "def"
   withVerbatimMode $ do
-    controlSeq "def"
     Tok _ (CtrlSeq name) _ <- anyControlSeq
     argspecs <- many (argspecArg <|> argspecPattern)
     contents <- bracedOrToken
-    return (name, Macro ExpandWhenUsed argspecs Nothing contents)
+    return [(name, Macro ExpandWhenUsed argspecs Nothing contents)]
+
+-- \newif\iffoo' defines:
+-- \iffoo to be \iffalse
+-- \footrue to be a command that defines \iffoo to be \iftrue
+-- \foofalse to be a command that defines \iffoo to be \iffalse
+newif :: PandocMonad m => LP m [(Text, Macro)]
+newif = do
+  controlSeq "newif"
+  withVerbatimMode $ do
+    Tok pos (CtrlSeq name) _ <- anyControlSeq
+    -- \def\iffoo\iffalse
+    -- \def\footrue{\def\iffoo\iftrue}
+    -- \def\foofalse{\def\iffoo\iffalse}
+    let base = T.drop 2 name
+    return [ (name, Macro ExpandWhenUsed [] Nothing
+                    [Tok pos (CtrlSeq "iffalse") "\\iffalse"])
+           , (base <> "true",
+                   Macro ExpandWhenUsed [] Nothing
+                   [ Tok pos (CtrlSeq "def") "\\def"
+                   , Tok pos (CtrlSeq name) ("\\" <> name)
+                   , Tok pos (CtrlSeq "iftrue") "\\iftrue"
+                   ])
+           , (base <> "false",
+                   Macro ExpandWhenUsed [] Nothing
+                   [ Tok pos (CtrlSeq "def") "\\def"
+                   , Tok pos (CtrlSeq name) ("\\" <> name)
+                   , Tok pos (CtrlSeq "iffalse") "\\iffalse"
+                   ])
+           ]
 
 argspecArg :: PandocMonad m => LP m ArgSpec
 argspecArg = do
@@ -77,10 +109,9 @@ argspecPattern =
                               (toktype' == Symbol || toktype' == Word) &&
                               (txt /= "{" && txt /= "\\" && txt /= "}")))
 
-newcommand :: PandocMonad m => LP m (Text, Macro)
+newcommand :: PandocMonad m => LP m [(Text, Macro)]
 newcommand = do
-  pos <- getPosition
-  Tok _ (CtrlSeq mtype) _ <- controlSeq "newcommand" <|>
+  Tok pos (CtrlSeq mtype) _ <- controlSeq "newcommand" <|>
                              controlSeq "renewcommand" <|>
                              controlSeq "providecommand" <|>
                              controlSeq "DeclareMathOperator" <|>
@@ -112,9 +143,9 @@ newcommand = do
         Just macro
           | mtype == "newcommand" -> do
               report $ MacroAlreadyDefined txt pos
-              return (name, macro)
-          | mtype == "providecommand" -> return (name, macro)
-        _ -> return (name, Macro ExpandWhenUsed argspecs optarg contents)
+              return [(name, macro)]
+          | mtype == "providecommand" -> return [(name, macro)]
+        _ -> return [(name, Macro ExpandWhenUsed argspecs optarg contents)]
 
 newenvironment :: PandocMonad m => LP m (Maybe (Text, Macro, Macro))
 newenvironment = do

src/Text/Pandoc/Readers/LaTeX/Parsing.hs

@@ -113,7 +113,6 @@ import Text.Pandoc.Readers.LaTeX.Types (ExpansionPoint (..), Macro (..),
                                         ArgSpec (..), Tok (..), TokType (..))
 import Text.Pandoc.Shared
 import Text.Parsec.Pos
--- import Debug.Trace
 
 newtype DottedNum = DottedNum [Int]
   deriving (Show, Eq)
@@ -563,8 +562,26 @@ trySpecialMacro "xspace" ts = do
     Tok pos Word t : _
       | startsWithAlphaNum t -> return $ Tok pos Spaces " " : ts'
     _ -> return ts'
+trySpecialMacro "iftrue" ts = handleIf True ts
+trySpecialMacro "iffalse" ts = handleIf False ts
 trySpecialMacro _ _ = mzero
 
+handleIf :: PandocMonad m => Bool -> [Tok] -> LP m [Tok]
+handleIf b ts = do
+  res' <- lift $ runParserT (ifParser b) defaultLaTeXState "tokens" ts
+  case res' of
+    Left _ -> Prelude.fail "Could not parse conditional"
+    Right ts' -> return ts'
+
+ifParser :: PandocMonad m => Bool -> LP m [Tok]
+ifParser b = do
+  ifToks <- many (notFollowedBy (controlSeq "else" <|> controlSeq "fi")
+                    *> anyTok)
+  elseToks <- (controlSeq "else" >> manyTill anyTok (controlSeq "fi"))
+                 <|> ([] <$ controlSeq "fi")
+  rest <- getInput
+  return $ (if b then ifToks else elseToks) ++ rest
+
 startsWithAlphaNum :: Text -> Bool
 startsWithAlphaNum t =
   case T.uncons t of

test/command/newif.md

@@ -0,0 +1,55 @@
+```
+% pandoc -f latex -t plain
+\iftrue
+should print
+\iftrue
+should print
+\else
+should not print
+\fi
+\else
+should not print
+\fi
+
+\iffalse
+should not print
+\else
+\iftrue
+should print
+\else
+should not print
+\fi
+\fi
+
+\newif\ifepub
+
+\ifepub
+should not print
+\fi
+
+\epubtrue
+
+\ifepub
+should print
+\else
+should not print
+\fi
+
+\epubfalse
+
+\ifepub
+should not print
+\else
+should print
+\fi
+^D
+should print
+
+should print
+
+should print
+
+should print
+
+should print
+```