Org reader: improve sub- and superscript parsing.

Sub- and superscript must be preceded by a string in Org mode. Some text
preceded by space or at the start of a paragraph was previously parsed
incorrectly as sub- or superscript.

3 files changed, 33 insertions, 6 deletions

diff --git a/src/Text/Pandoc/Readers/Org/Inlines.hs b/src/Text/Pandoc/Readers/Org/Inlines.hs
index be8813e5c..f9e38124f 100644
--- a/src/Text/Pandoc/Readers/Org/Inlines.hs
+++ b/src/Text/Pandoc/Readers/Org/Inlines.hs
@@ -2,8 +2,8 @@
 {-# LANGUAGE OverloadedStrings #-}
 {- |
    Module      : Text.Pandoc.Readers.Org.Inlines
-   Copyright   : Copyright (C) 2014-2024 Albert Krewinkel
-   License     : GNU GPL, version 2 or above
+   Copyright   : Copyright (C) 2014-2025 Albert Krewinkel
+   License     : GPL-2.0-or-later
 
    Maintainer  : Albert Krewinkel <[email protected]>
 
@@ -88,13 +88,13 @@ inline =
          , inlineCodeBlock
          , str
          , endline
+         , subscript   -- takes precedence over underlined text
+         , superscript
          , emphasizedText
          , code
          , math
          , displayMath
          , verbatim
-         , subscript
-         , superscript
          , inlineLaTeX
          , exportSnippet
          , macro
@@ -594,11 +594,25 @@ verbatim  = return . B.codeWith ("", ["verbatim"], []) <$> verbatimBetween '='
 code      :: PandocMonad m => OrgParser m (F Inlines)
 code      = return . B.code     <$> verbatimBetween '~'
 
+-- | Returns 'True' if the parser position right after a string, and 'False'
+-- otherwise.
+isAfterString :: PandocMonad m => OrgParser m Bool
+isAfterString = do
+  pos <- getPosition
+  st  <- getState
+  pure $ getLastStrPos st == Just pos
+
+-- | Parses subscript markup. Subscripts must be preceded by a string.
 subscript   :: PandocMonad m => OrgParser m (F Inlines)
-subscript   = fmap B.subscript   <$> try (char '_' *> subOrSuperExpr)
+subscript   = do
+  guard =<< isAfterString
+  fmap B.subscript   <$> try (char '_' *> subOrSuperExpr)
 
+-- | Parses superscript markup. Superscript must be preceded by a string.
 superscript :: PandocMonad m => OrgParser m (F Inlines)
-superscript = fmap B.superscript <$> try (char '^' *> subOrSuperExpr)
+superscript = do
+  guard =<< isAfterString
+  fmap B.superscript <$> try (char '^' *> subOrSuperExpr)
 
 math      :: PandocMonad m => OrgParser m (F Inlines)
 math      = return . B.math      <$> choice [ math1CharBetween '$'
diff --git a/src/Text/Pandoc/Readers/Org/Parsing.hs b/src/Text/Pandoc/Readers/Org/Parsing.hs
index 4f5b38311..3adf9f227 100644
--- a/src/Text/Pandoc/Readers/Org/Parsing.hs
+++ b/src/Text/Pandoc/Readers/Org/Parsing.hs
@@ -54,6 +54,7 @@ module Text.Pandoc.Readers.Org.Parsing
   , guardEnabled
   , updateLastStrPos
   , notAfterString
+  , getLastStrPos
   , ParserState (..)
   , registerHeader
   , QuoteContext (..)
diff --git a/test/Tests/Readers/Org/Inline.hs b/test/Tests/Readers/Org/Inline.hs
index 00956e1ce..10cd9c214 100644
--- a/test/Tests/Readers/Org/Inline.hs
+++ b/test/Tests/Readers/Org/Inline.hs
@@ -88,6 +88,10 @@ tests =
       "2^{n-1}" =?>
       para (str "2" <> superscript "n-1")
 
+  , "Superscript-like, but not after string" =:
+      "a ^caret" =?>
+      para "a ^caret"
+
   , "Subscript simple expression" =:
       "a_n" =?>
       para (str "a" <> subscript "n")
@@ -96,6 +100,14 @@ tests =
       "a_{n+1}" =?>
       para (str "a" <> subscript "n+1")
 
+  , "Subscript-like, but not after string" =:
+      "_underscore" =?>
+      para "_underscore"
+
+  , "Subscript takes precedence before underline" =:
+      "text_subscript_" =?>
+      para (str "text" <> subscript "subscript" <> str "_")
+
   , "Linebreak" =:
       "line \\\\ \nbreak" =?>
       para ("line" <> linebreak <> "break")