yary/docs/flow-logic.md

Flow scalar line joining

Forward

These are notes are from my investigation of how to do line joins in flow scalars. They are preserved for posterity, but are largely incorrect

Notes

leading_blanks->false
string->String::new()
whitespaces->String::new()
trailing_breaks->String::new()
leading_break->String::new()

while parser[0]->!isBlankZ!
    // <...>
    if scalar_double && parser[0]->'\\' && parser[1]->'\n' // if double quoted and escaped newline
        leading_blanks = true
        break
    // <...>

while parser[0]->isBlank! || parser[0]->isBreak!
    if isBlank!:                                      // current byte is a space or newline
        if leading_blanks:
            parser->skip(1)
        else
            parser->read(1)->whitespaces
    else if isBreak!:                                 // current byte is a yaml line break
        if leading_blanks:                            // this looks like an initialization clause, either
            parser->read_line(1)->trailing_breaks     // A. we are already in state "leading_blanks", in which case append to trailing_breaks
        else                                          // B. we're not in that state yet, put a line end in leading_break and set "leading_blanks" to true
            clear(whitespaces)                        //    clearing any stuff from whitespaces
            parser->read_line(1)->leading_break
            leadings_blanks = true

    if leading_blanks:
        if leading_break[0]->'\n':
            if trailing_breaks.is_empty():
                string += ' '
            else
                string += trailing_breaks
                clear(trailing_breaks)

            clear(leading_break)
        else
            string += leading_break
            string += trailing_breaks
            clear(leading_break)
            clear(trailing_breaks)
    else
        string += whitespaces
        clear(whitespaces)

return string

Paths

1. leading_blanks is false the entire loop

   This looks like the path that is taken when eating spaces between words, but NOT between a word and an EOL

2. leading_blanks is BEING SET TRUE this loop

   This paths looks the start of handling a line break. We need to encounter a YAML break (not blank), in which case we clear any whitespaces since the last word was read, set leading_break to a '\n' and set leading_blanks to true.

   Next we check if leading_blanks is true (it is) and leading_break has a '\n' (it does) and trailing_breaks is empty (it is) and we append a single space to the output string.

Flow style line join rules (double quoted)

IF double_quoted AND $line ENDS WITH ['\\', isBreak!]
        KEEP ALL trailing whitespace
    AND
        REMOVE ALL leading whitespace on $line+1
ELSE
        REMOVE ALL trailing whitespace
    AND
        REMOVE ALL leading whitespace on $line+1

AND THEN

IF $line+1 IS ONLY WHITESPACE
        ADD ONE '\n'
ELSE
        ADD ONE ' '