About the worst job on any enterprise software project is the PDF output, they always end up doing it for emails or something else and its a never ending list of bugs. Text formatting is a never ending list of problems since its so got a lot of vague inputs and a relatively strict output. Far too many little details go wrong.
> That handful of code took me almost a year to write.
Formatting can be tough. See Knuth's extensive bug list for TEX from 1987 at https://yurichev.com/mirrors/knuth1989.pdf to see the kind of tarpit one can get trapped in.
In my brief experiments with Flutter, I must admit I didn't enjoy the experience of using the autoformatting. Not knocking the author of the tool at all, I can definitely see how absurdly hard it is to create something that does what it is trying to do. And I'm not against autoformatting in general either. I think gofmt works much better, and that's in large part because it tries to do less.
With dart, I felt that very often, when time I saved a file after editing (which activated the formatter), the code would jump around a lot, even for very small edits sometimes. I actually found myself saving less often, as I found the sudden reorganizing kind of jarring and disorienting.
Most of this, I felt like came from this wish of making the formatter keep lines inside a given width. While that's a goal I appreciate, I've come to think is one of those things that's better done manually. The same goes for the use of whitespace in general, other than trivial stuff like consistent indentation. There's actual, important meaning that can be conveyed in how you arrange things which I think is more important than having it always be exactly mathematically consistent.
It's one of the reasons I still prefer ESLint over Prettier in JS land, also, even for stylistic rules. The fact that Prettier always rewrites the entire file from scratch with the parsed AST often ends up mangling some deliberate way that I'd arrange the code.
> Note that “best” is a property of the entire statement being formatted. A line break changes the indentation of the remainder of the statement, which in turn affects which other line breaks are needed.
I really don't like formatters where changing one small part of a large expression results in the entire expression formatted very differently. It's simply not version control friendly. Especially if the language encourages large statements like the pro example. I would rather accept a little bit of code ugliness in this case. Sure this then means that the way the code is formatted is path dependent (depends on the history of the code), but I think it's a reasonable compromise.
For some time I tried to write a formatting tool for my programming language. After achieving first results I gave up. I have found that writing a formatter is surprisingly hard task. Operating on token-level can't provide good enough result, so a proper parser is necessary. Reusing existing parser isn't possible, since it ignores whitespaces and comments. Even more problems creates the necessity to preserve user-defined formatting in ambiguous cases.
So I thought, that there is no reason trying to solve all these problems, since it requires too much time investments. But without solving all this a semi-working formatter isn't good enough to be useful and not annoying.
Its funny when you have programmed long enough to see the same language/app names recycled. Two examples that come to mind: Dart, which was an RTL validation scripting language in the 80's/90's used by CPU designers, and Elm, which was a mail program in Unix/Aix/SunOS in the 80's/90's. Even weirder, when googling for the "old" Dart, it referred to RTL as right-to-left, and not register transfer level.
Most of the hardness of this program comes from a user-adjustable line length limit. The author on multiple occasions used a "blog-friendly 40-char line limit" which is of course insanely hard. The program can be made much much simpler if the line length is unlimited. And if that's not an option, the program can be made somewhat simpler by only allowing line limits that are reasonably large, such as 100 characters.
IMAP email parser for a ticket-like program. Even with abstractions and libraries, email can be such a pita...
I once wrote a formatter for powerquery that's still in use today. It's a much simpler language and I took a simpler approach. It was a really fun problem to solve.
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One can talk about about the technical side of writing a code formatter, but what about the ethical side? Automatically formatted code looks kind of okay but never great. Uniformity for the sake of uniformity. It is not a very humanistic.
Mine was an automated file transfer system that had to be 100% reliable on an insanely unreliable network (~95% uptime). Took about 9 months of bug squashing after development was done. So many edge cases. I would probably never mention this in a job interview because I doubt most people would understand why it was so hard.