When deciding on style guidelines, the style team tried to be guided by the following principles (in rough priority order):
-
readability
- scan-ability
- avoiding misleading formatting
- accessibility - readable and editable by users using the the widest variety of hardware, including non-visual accessibility interfaces
- readability of code when quoted in rustc error messages
-
aesthetics
- sense of 'beauty'
- consistent with other languages/tools
-
specifics
- compatibility with version control practices - preserving diffs, merge-friendliness, etc.
- preventing right-ward drift
- minimising vertical space
-
application
- ease of manual application
- ease of implementation (in Rustfmt, and in other tools/editors/code generators)
- internal consistency
- simplicity of formatting rules
Prefer block indent over visual indent. E.g.,
// Block indent
a_function_call(
foo,
bar,
);
// Visual indent
a_function_call(foo,
bar);
This makes for smaller diffs (e.g., if a_function_call
is renamed in the above
example) and less rightward drift.
Lists should have a trailing comma when followed by a newline, see the block indent example above. This choice makes moving code (e.g., by copy and paste) easier and makes smaller diffs.