Revert "Fully preserve indented strings and match Nix parser"

This reverts commit ea74366.

src/Nixfmt/Parser.hs

@@ -193,50 +193,17 @@ indentedStringPart :: Parser StringPart
 indentedStringPart =
   TextPart
     <$> someText
-      ( {-
-          This should match https://github.com/NixOS/nix/blob/052f1320ddf72d617e337479ff1bf22cb4ee682a/src/libexpr/lexer.l#L182-L205
-          To understand that file, [this](https://westes.github.io/flex/manual/Matching.html#Matching) is important:
-          > If it finds more than one match, it takes the one matching the most text.
-          > If it finds two or more matches of the same length, the rule listed first in the flex input file is chosen.
-
-          There are some inconsequential differences though:
-          - We only parse one line at a time here, so we make sure to not process any newlines
-          - We don't want to transform the input in any way, e.g. don't turn ''' into ''
-            This is to preserve the input string as-is
-        -}
-
-        -- <IND_STRING>([^\$\']|\$[^\{\']|\'[^\'\$])+
-        -- While this rule doesn't have a fixed length, it's non-conflicting with the rules below,
-        -- so we can do it first without worrying about the length matching
-        someText
-          ( Text.singleton
-              <$> satisfy (\t -> t /= '$' && t /= '\'' && t /= '\n')
-                <|> try (Text.snoc <$> chunk "$" <*> satisfy (\t -> t /= '{' && t /= '\'' && t /= '\n'))
-                <|> try (Text.snoc <$> chunk "'" <*> satisfy (\t -> t /= '\'' && t /= '$' && t /= '\n'))
-          )
-          -- These rules are of length 3, they need to come before shorter ones
-          -- <IND_STRING>\'\'\$
-          <|> chunk "''$"
-          -- <IND_STRING>\'\'\'
-          <|> chunk "'''"
-          -- <IND_STRING>\'\'\\{ANY} -> Note that ANY can match newlines as well, but we need to ignore those
-          <|> do
-            prefix <- chunk "''\\"
-            -- If we do have a newline
-            rest <-
-              -- If there's no newline, take the next character
-              (notFollowedBy (char '\n') *> (Text.singleton <$> anySingle))
-                -- Otherwise there's an unconsumed newline, which we don't need to handle,
-                -- it's consumed elsewhere
-                <|> pure ""
-            pure $ prefix <> rest
-          -- These are rules with length 2 and 1
-          -- <IND_STRING>\$\{ -> don't match, this will be an interpolation
-          -- <IND_STRING>\$ -> do match, just a dollar
-          <|> try (chunk "$" <* notFollowedBy (char '{'))
-          -- <IND_STRING>\'\' -> don't match, indented string ends
-          -- <IND_STRING>\' -> do match, just a quote
-          <|> try (chunk "'" <* notFollowedBy (char '\''))
+      ( chunk "''\\n"
+          <|> chunk "''\\r"
+          <|> chunk "''\\t"
+          <|> chunk "''\\"
+          *> (Text.singleton <$> anySingle)
+            <|> chunk "''$"
+            <|> chunk "'''"
+            <|> chunk "$$"
+            <|> try (chunk "$" <* notFollowedBy (char '{'))
+            <|> try (chunk "'" <* notFollowedBy (char '\''))
+            <|> someP (\t -> t /= '\'' && t /= '$' && t /= '\n')
       )
 
 indentedLine :: Parser [StringPart]