Unify OldDiagnostic and Message (#18391)

Summary
--

This PR unifies the remaining differences between `OldDiagnostic` and
`Message` (`OldDiagnostic` was only missing an optional `noqa_offset`
field) and
replaces `Message` with `OldDiagnostic`.

The biggest functional difference is that the combined `OldDiagnostic`
kind no
longer implements `AsRule` for an infallible conversion to `Rule`. This
was
pretty easy to work around with `is_some_and` and `is_none_or` in the
few places
it was needed. In `LintContext::report_diagnostic_if_enabled` we can
just use
the new `Violation::rule` method, which takes care of most cases.

Most of the interesting changes are in [this
range](8156992540)
before I started renaming.

Test Plan
--

Existing tests

Future Work
--

I think it's time to start shifting some of these fields to the new
`Diagnostic`
kind. I believe we want `Fix` for sure, but I'm less sure about the
others. We
may want to keep a thin wrapper type here anyway to implement a `rule`
method,
so we could leave some of these fields on that too.

crates/ruff_linter/src/test.rs

@@ -23,7 +23,7 @@ use ruff_source_file::SourceFileBuilder;
 use crate::codes::Rule;
 use crate::fix::{FixResult, fix_file};
 use crate::linter::check_path;
-use crate::message::{Emitter, EmitterContext, Message, TextEmitter};
+use crate::message::{Emitter, EmitterContext, OldDiagnostic, TextEmitter};
 use crate::package::PackageRoot;
 use crate::packaging::detect_package_root;
 use crate::settings::types::UnsafeFixes;
@@ -39,7 +39,10 @@ pub(crate) fn test_resource_path(path: impl AsRef<Path>) -> std::path::PathBuf {
 
 /// Run [`check_path`] on a Python file in the `resources/test/fixtures` directory.
 #[cfg(not(fuzzing))]
-pub(crate) fn test_path(path: impl AsRef<Path>, settings: &LinterSettings) -> Result<Vec<Message>> {
+pub(crate) fn test_path(
+    path: impl AsRef<Path>,
+    settings: &LinterSettings,
+) -> Result<Vec<OldDiagnostic>> {
     let path = test_resource_path("fixtures").join(path);
     let source_type = PySourceType::from(&path);
     let source_kind = SourceKind::from_path(path.as_ref(), source_type)?.expect("valid source");
@@ -48,7 +51,7 @@ pub(crate) fn test_path(path: impl AsRef<Path>, settings: &LinterSettings) -> Re
 
 #[cfg(not(fuzzing))]
 pub(crate) struct TestedNotebook {
-    pub(crate) messages: Vec<Message>,
+    pub(crate) diagnostics: Vec<OldDiagnostic>,
     pub(crate) source_notebook: Notebook,
     pub(crate) linted_notebook: Notebook,
 }
@@ -77,14 +80,14 @@ pub(crate) fn assert_notebook_path(
     );
 
     Ok(TestedNotebook {
-        messages,
+        diagnostics: messages,
         source_notebook: source_kind.expect_ipy_notebook(),
         linted_notebook,
     })
 }
 
 /// Run [`check_path`] on a snippet of Python code.
-pub fn test_snippet(contents: &str, settings: &LinterSettings) -> Vec<Message> {
+pub fn test_snippet(contents: &str, settings: &LinterSettings) -> Vec<OldDiagnostic> {
     let path = Path::new("<filename>");
     let contents = dedent(contents);
     test_contents(&SourceKind::Python(contents.into_owned()), path, settings).0
@@ -108,7 +111,7 @@ pub(crate) fn test_contents<'a>(
     source_kind: &'a SourceKind,
     path: &Path,
     settings: &LinterSettings,
-) -> (Vec<Message>, Cow<'a, SourceKind>) {
+) -> (Vec<OldDiagnostic>, Cow<'a, SourceKind>) {
     let source_type = PySourceType::from(path);
     let target_version = settings.resolve_target_version(path);
     let options =
@@ -288,7 +291,7 @@ Either ensure you always emit a fix or change `Violation::FIX_AVAILABILITY` to e
             diagnostic
         })
         .chain(parsed.errors().iter().map(|parse_error| {
-            Message::from_parse_error(parse_error, &locator, source_code.clone())
+            OldDiagnostic::from_parse_error(parse_error, &locator, source_code.clone())
         }))
         .sorted()
         .collect();
@@ -306,7 +309,9 @@ fn print_syntax_errors(
 
     let messages: Vec<_> = errors
         .iter()
-        .map(|parse_error| Message::from_parse_error(parse_error, locator, source_file.clone()))
+        .map(|parse_error| {
+            OldDiagnostic::from_parse_error(parse_error, locator, source_file.clone())
+        })
         .collect();
 
     if let Some(notebook) = source.as_ipy_notebook() {
@@ -317,18 +322,22 @@ fn print_syntax_errors(
 }
 
 /// Print the [`Message::Diagnostic`]s in `messages`.
-fn print_diagnostics(mut messages: Vec<Message>, path: &Path, source: &SourceKind) -> String {
-    messages.retain(|msg| !msg.is_syntax_error());
+fn print_diagnostics(
+    mut diagnostics: Vec<OldDiagnostic>,
+    path: &Path,
+    source: &SourceKind,
+) -> String {
+    diagnostics.retain(|msg| !msg.is_syntax_error());
 
     if let Some(notebook) = source.as_ipy_notebook() {
-        print_jupyter_messages(&messages, path, notebook)
+        print_jupyter_messages(&diagnostics, path, notebook)
     } else {
-        print_messages(&messages)
+        print_messages(&diagnostics)
     }
 }
 
 pub(crate) fn print_jupyter_messages(
-    messages: &[Message],
+    diagnostics: &[OldDiagnostic],
     path: &Path,
     notebook: &Notebook,
 ) -> String {
@@ -341,7 +350,7 @@ pub(crate) fn print_jupyter_messages(
         .with_unsafe_fixes(UnsafeFixes::Enabled)
         .emit(
             &mut output,
-            messages,
+            diagnostics,
             &EmitterContext::new(&FxHashMap::from_iter([(
                 path.file_name().unwrap().to_string_lossy().to_string(),
                 notebook.index().clone(),
@@ -352,7 +361,7 @@ pub(crate) fn print_jupyter_messages(
     String::from_utf8(output).unwrap()
 }
 
-pub(crate) fn print_messages(messages: &[Message]) -> String {
+pub(crate) fn print_messages(diagnostics: &[OldDiagnostic]) -> String {
     let mut output = Vec::new();
 
     TextEmitter::default()
@@ -362,7 +371,7 @@ pub(crate) fn print_messages(messages: &[Message]) -> String {
         .with_unsafe_fixes(UnsafeFixes::Enabled)
         .emit(
             &mut output,
-            messages,
+            diagnostics,
             &EmitterContext::new(&FxHashMap::default()),
         )
         .unwrap();
@@ -371,7 +380,7 @@ pub(crate) fn print_messages(messages: &[Message]) -> String {
 }
 
 #[macro_export]
-macro_rules! assert_messages {
+macro_rules! assert_diagnostics {
     ($value:expr, $path:expr, $notebook:expr) => {{
         insta::with_settings!({ omit_expression => true }, {
             insta::assert_snapshot!(