AVOID lines longer than 80 characters
Readability studies show that long lines of text are harder to read because your eye has to travel farther when moving to the beginning of the next line. This is why newspapers and magazines use multiple columns of text.
If you really find yourself wanting lines longer than 80 characters, our
experience is that your code is likely too verbose and could be a little more
compact. The main offender is usually
yourself, “Does each word in that type name tell me something critical or
prevent a name collision?” If not, consider omitting it.
Note that dartfmt does 99% of this for you, but the last 1% is you. It does not split long string literals to fit in 80 columns, so you have to do that manually.
We make an exception for URIs and file paths. When those occur in comments or strings (usually in imports and exports), they may remain on a single line even if they go over the line limit. This makes it easier to search source files for a given path.