Formatting code should be unnecessary

It’s tricky to find an objective optimum. Personally I’ve been happy with up to 100 chars per line (aim for 80 but some lines are just more readable without wrapping).

But someone will always have to either scroll horizontally or wrap the text. I’m speaking as someone who often views code on my phone, with a ~40 characters wide screen.

In typography, it’s well accepted that an average of ~66 chars per line increases readability of bulk text, with the theory being that short lines require you to mentally «jump» to the beginning of the next line frequently which interrupts flow, but long lines make it harder to mentally keep track of where you are in each line. There is however a difference between newspapers and books, since shorter ~40-char columns allows rapid skimming by moving your eyes down a column instead of zigzagging through the text.

But I don’t think these numbers translate directly to code, which is usually written with most lines indented (on the left) and most lines shorter than the maximum (few statements are so long). Depending on language, I could easily imagine a line length of 100 leading to an average of ~66 chars per line.

You're misunderstanding the idea I think.

You would use the format on disk for the grep. "Your format" only exists displayed in your editor.

I have to disagree with the premise. Formatting code is a critical communication channel. Well-formatted code should tell you:

1. The developer has enough experience to understand that formatting matters.

2. The developer has enough discipline to stick with their chosen formatting rules.

3. The developer has the taste necessary to choose good formatting rules.

4. The developer has the judgement necessary to identify when other concerns justify one-off violations of the rules.

These are really important attributes for a developer to have. They affect every aspect of the code, not just formatting. Formatting is just a very quick proxy to measure those by.

Unfortunately, things like autoformatting and linter rules are destroying the signal. Goodheart's law strikes again.

Formatters eliminating long lines is a pet peeve of mine.

About once every other project, some portion of the source benefits from source code being arranged in a tabular format. Long lines which are juxtaposed help make dissimilar values stand out. The following table is not unlike code I have written:

  setup_spi(&adc,    mode=SPI_01, rate=15, cs_control=CS_MUXED,  cs=0x01);
  setup_spi(&eeprom, mode=SPI_10, rate=13, cs_control=CS_MUXED,  cs=0x02);
  setup_spi(&mram,   mode=SPI_10, rate=50, cs_control=CS_DIRECT, cs=0x08);

Even if we add 4-5 more operational parameters, I find this arrangement much more readable than the short-line equivalent:

  setup_spi(&adc,
      mode=SPI_01,
      rate=15,
      cs_control=CS_MUXED,
      cs=0x01);
  setup_spi(&eeprom,
      mode=SPI_10,
      rate=13,
      cs_control=CS_MUXED,
      cs=0x02);
  setup_spi(&mram,
      mode=SPI_10,
      rate=50,
      cs_control=CS_DIRECT,
      cs=0x08);

Or worse, the formatter may keep the long lines but normalize the spaces, ruining the tabular alignment:

  setup_spi(&adc, mode=SPI_01, rate=15, cs_control=CS_MUXED, cs=0x01);
  setup_spi(&som_eeprom, mode=SPI_10, rate=13, cs_control=CS_MUXED, cs=0x02);
  setup_spi(&mram, mode=SPI_10, rate=50, cs_control=CS_DIRECT, cs=0x08);

Sometimes a neat, human-maintained block of 200 character lines brings order to chaos, even if you have to scroll a little.

Why is this flagged? I completely agree.

99% the linter is not enforcing correctness in my experience. It's just enforcing a bunch of subjective aesthetic constraints. Which import order, max number of empty lines between statement, what type of string literal to use, no trailing white space, etc. A non trivial part of my day is spent dealing with this giant catalog of dinner etiquette. Not all of it is auto fixable. Also, there are plenty of situations where everyone would agree that violating the rule is necessary (eg. "no use before define" but you need mutual recursion). Also sometimes rules are circularly in conflict (eg you have to change a line but there is no way to do it without violating the max-line-length rule).