The idea is nice and simple we replace:
fn placeholder() -> Self;
with
fn message_formats() -> &'static [&'static str];
So e.g. if a Violation implementation defines:
fn message(&self) -> String {
format!("Local variable `{name}` is assigned to but never used")
}
it would also have to define:
fn message_formats() -> &'static [&'static str] {
&["Local variable `{name}` is assigned to but never used"]
}
Since we however obviously do not want to duplicate all of our format
strings we simply introduce a new procedural macro attribute
#[derive_message_formats] that can be added to the message method
declaration in order to automatically derive the message_formats
implementation.
This commit implements the macro. The following and final commit
updates violations.rs to use the macro. (The changes have been separated
because the next commit is autogenerated via a Python script.)
ruff_dev::generate_rules_table previously documented which rules are
autofixable via DiagnosticKind::fixable ... since the DiagnosticKind was
obtained via Rule::kind (and Violation::placeholder) which we both want
to get rid of we have to obtain the autofixability via another way.
This commit implements such another way by adding an AUTOFIX
associated constant to the Violation trait. The constant is of the type
Option<AutoFixkind>, AutofixKind is a new struct containing an
Availability enum { Sometimes, Always}, letting us additionally document
that some autofixes are only available sometimes (which previously
wasn't documented). We intentionally introduce this information in a
struct so that we can easily introduce further autofix metadata in the
future such as autofix applicability[1].
[1]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_errors/enum.Applicability.html
While ruff displays the string returned by Violation::message in its
output for detected violations the messages displayed in the README
and in the `--explain <code>` output previously used the
DiagnosticKind::summary() function which for some verbose messages
provided shorter descriptions.
This commit removes DiagnosticKind::summary, and moves the more
extensive documentation into doc comments ... these are not displayed
yet to the user but doing that is very much planned.
This commit series removes the following associated
function from the Violation trait:
fn placeholder() -> Self;
ruff previously used this placeholder approach for the messages it
listed in the README and displayed when invoked with --explain <code>.
This approach is suboptimal for three reasons:
1. The placeholder implementations are completely boring code since they
just initialize the struct with some dummy values.
2. Displaying concrete error messages with arbitrary interpolated values
can be confusing for the user since they might not recognize that the
values are interpolated.
3. Some violations have varying format strings depending on the
violation which could not be documented with the previous approach
(while we could have changed the signature to return Vec<Self> this
would still very much suffer from the previous two points).
We therefore drop Violation::placeholder in favor of a new macro-based
approach, explained in commit 4/5.
Violation::placeholder is only invoked via Rule::kind, so we firstly
have to get rid of all Rule::kind invocations ... this commit starts
removing the trivial cases.
This makes it easier to see which rules you're enabling when selecting
one of the pylint codes (like `PLC`). This also makes it clearer what
those abbreviations stand for. When I first saw the pylint section, I
was very confused by that, so other might be as well.
See it rendered here:
https://github.com/thomkeh/ruff/blob/patch-1/README.md#pylint-plc-ple-plr-plw
