;lib: clarify/extend/refactor some line parsing helpers (#1580)

hledger-lib/Hledger/Read/Common.hs

@@ -95,9 +95,10 @@ module Hledger.Read.Common (
   rawnumberp,
 
   -- ** comments
+  isLineCommentStart,
+  isSameLineCommentStart,
   multilinecommentp,
   emptyorcommentlinep,
-
   followingcommentp,
   transactioncommentp,
   postingcommentp,
@@ -106,8 +107,11 @@ module Hledger.Read.Common (
   bracketeddatetagsp,
 
   -- ** misc
-  singlespacedtextp,
-  singlespacedtextsatisfyingp,
+  noncommenttextp,
+  noncommenttext1p,
+  singlespacedtext1p,
+  singlespacednoncommenttext1p,
+  singlespacedtextsatisfying1p,
   singlespacep,
   skipNonNewlineSpaces,
   skipNonNewlineSpaces1,
@@ -532,9 +536,11 @@ codep = option "" $ do
   char ')' <?> "closing bracket ')' for transaction code"
   pure code
 
+-- | Parse possibly empty text until a semicolon or newline.
+-- Whitespace is preserved (for now - perhaps helps preserve alignment 
+-- of same-line comments ?).
 descriptionp :: TextParser m Text
-descriptionp = takeWhileP Nothing (not . semicolonOrNewline)
-  where semicolonOrNewline c = c == ';' || c == '\n'
+descriptionp = noncommenttextp <?> "description"
 
 --- *** dates
 
@@ -694,19 +700,32 @@ modifiedaccountnamep = do
 -- It should have required parts to start with an alphanumeric;
 -- for now it remains as-is for backwards compatibility.
 accountnamep :: TextParser m AccountName
-accountnamep = singlespacedtextp
+accountnamep = singlespacedtext1p
 
+-- | Parse possibly empty text, including whitespace, 
+-- until a comment start (semicolon) or newline.
+noncommenttextp :: TextParser m T.Text
+noncommenttextp = takeWhileP Nothing (\c -> not $ isSameLineCommentStart c || isNewline c)
 
--- | Parse any text beginning with a non-whitespace character, until a
--- double space or the end of input.
--- TODO including characters which normally start a comment (;#) - exclude those ? 
-singlespacedtextp :: TextParser m T.Text
-singlespacedtextp = singlespacedtextsatisfyingp (const True)
+-- | Parse non-empty text, including whitespace, 
+-- until a comment start (semicolon) or newline.
+noncommenttext1p :: TextParser m T.Text
+noncommenttext1p = takeWhile1P Nothing (\c -> not $ isSameLineCommentStart c || isNewline c)
 
--- | Similar to 'singlespacedtextp', except that the text must only contain
--- characters satisfying the given predicate.
-singlespacedtextsatisfyingp :: (Char -> Bool) -> TextParser m T.Text
-singlespacedtextsatisfyingp pred = do
+-- | Parse non-empty, single-spaced text starting and ending with non-whitespace,
+-- until a double space or newline.
+singlespacedtext1p :: TextParser m T.Text
+singlespacedtext1p = singlespacedtextsatisfying1p (const True)
+
+-- | Parse non-empty, single-spaced text starting and ending with non-whitespace,
+-- until a comment start (semicolon), double space, or newline.
+singlespacednoncommenttext1p :: TextParser m T.Text
+singlespacednoncommenttext1p = singlespacedtextsatisfying1p (not . isSameLineCommentStart)
+
+-- | Parse non-empty, single-spaced text starting and ending with non-whitespace,
+-- where all characters satisfy the given predicate.
+singlespacedtextsatisfying1p :: (Char -> Bool) -> TextParser m T.Text
+singlespacedtextsatisfying1p pred = do
   firstPart <- partp
   otherParts <- many $ try $ singlespacep *> partp
   pure $! T.unwords $ firstPart : otherParts
@@ -1179,13 +1198,27 @@ emptyorcommentlinep = do
   where
     skiplinecommentp :: TextParser m ()
     skiplinecommentp = do
-      satisfy $ \c -> c == ';' || c == '#' || c == '*'
-      void $ takeWhileP Nothing (\c -> c /= '\n')
+      satisfy isLineCommentStart
+      void $ takeWhileP Nothing (/= '\n')
       optional newline
       pure ()
 
 {-# INLINABLE emptyorcommentlinep #-}
 
+-- | Is this a character that, as the first non-whitespace on a line,
+-- starts a comment line ?
+isLineCommentStart :: Char -> Bool
+isLineCommentStart '#' = True
+isLineCommentStart '*' = True
+isLineCommentStart ';' = True
+isLineCommentStart _   = False
+
+-- | Is this a character that, appearing anywhere within a line,
+-- starts a comment ?
+isSameLineCommentStart :: Char -> Bool
+isSameLineCommentStart ';' = True
+isSameLineCommentStart _   = False
+
 -- A parser combinator for parsing (possibly multiline) comments
 -- following journal items.
 --

hledger-lib/Hledger/Read/JournalReader.hs

@@ -620,7 +620,7 @@ periodictransactionp = do
                   Nothing -> today
                   Just y  -> fromGregorian y 1 1
   periodExcerpt <- lift $ excerpt_ $
-                    singlespacedtextsatisfyingp (\c -> c /= ';' && c /= '\n')
+                    singlespacedtextsatisfying1p (\c -> c /= ';' && c /= '\n')
   let periodtxt = T.strip $ getExcerptText periodExcerpt
 
   -- first parsing with 'singlespacedtextp', then "re-parsing" with

hledger-lib/Hledger/Utils/Parse.hs

@@ -19,6 +19,7 @@ module Hledger.Utils.Parse (
   parseerror,
   showDateParseError,
   nonspace,
+  isNewline,
   isNonNewlineSpace,
   restofline,
   eolof,
@@ -119,13 +120,15 @@ showDateParseError
   :: (Show t, Show (Token t), Show e) => ParseErrorBundle t e -> String
 showDateParseError e = printf "date parse error (%s)" (intercalate ", " $ tail $ lines $ show e)
 
+isNewline :: Char -> Bool 
+isNewline '\n' = True
+isNewline _    = False
+
 nonspace :: TextParser m Char
 nonspace = satisfy (not . isSpace)
 
 isNonNewlineSpace :: Char -> Bool
-isNonNewlineSpace c = c /= '\n' && isSpace c
--- XXX support \r\n ?
--- isNonNewlineSpace c = c /= '\n' && c /= '\r' && isSpace c
+isNonNewlineSpace c = not (isNewline c) && isSpace c
 
 spacenonewline :: (Stream s, Char ~ Token s) => ParsecT CustomErr s m Char
 spacenonewline = satisfy isNonNewlineSpace