Move Pylint rendering to ruff_db (#19340)

Summary
--

This is a very simple output format, the only decision is what to do if
the file
is missing from the diagnostic. For now, I opted to `unwrap_or_default`
both the
path and the `OneIndexed` row number, giving `:1: main diagnostic
message` in
the test without a file.

Another quirk here is that the path is relativized. I just pasted in the
`relativize_path` and `get_cwd` implementations from `ruff_linter::fs`
for now,
but maybe there's a better place for them.

I didn't see any details about why this needs to be relativized in the
original
[issue](https://github.com/astral-sh/ruff/issues/1953),
[PR](https://github.com/astral-sh/ruff/pull/1995), or in the pylint

[docs](https://flake8.pycqa.org/en/latest/internal/formatters.html#pylint-formatter),
but it did change the results of the CLI integration test when I tried
deleting
it. I haven't been able to reproduce that in the CLI, though, so it may
only
happen with `Command::current_dir`.

Test Plan
--

Tests ported from `ruff_linter` and a new test for the case with no file

---------

Co-authored-by: Micha Reiser <micha@reiser.io>

crates/ruff_linter/src/message/mod.rs

@@ -15,7 +15,6 @@ pub use github::GithubEmitter;
 pub use gitlab::GitlabEmitter;
 pub use grouped::GroupedEmitter;
 pub use junit::JunitEmitter;
-pub use pylint::PylintEmitter;
 use ruff_notebook::NotebookIndex;
 use ruff_source_file::{LineColumn, SourceFile};
 use ruff_text_size::{Ranged, TextRange, TextSize};
@@ -30,7 +29,6 @@ mod github;
 mod gitlab;
 mod grouped;
 mod junit;
-mod pylint;
 mod sarif;
 mod text;
 
@@ -128,6 +126,10 @@ impl FileResolver for EmitterContext<'_> {
             UnifiedFile::Ruff(file) => self.notebook_indexes.get(file.name()).is_some(),
         }
     }
+
+    fn current_directory(&self) -> &std::path::Path {
+        crate::fs::get_cwd()
+    }
 }
 
 struct MessageWithLocation<'a> {

crates/ruff_linter/src/message/pylint.rs

@@ -1,72 +0,0 @@
-use std::io::Write;
-
-use ruff_db::diagnostic::Diagnostic;
-use ruff_source_file::OneIndexed;
-
-use crate::fs::relativize_path;
-use crate::message::{Emitter, EmitterContext};
-
-/// Generate violations in Pylint format.
-/// See: [Flake8 documentation](https://flake8.pycqa.org/en/latest/internal/formatters.html#pylint-formatter)
-#[derive(Default)]
-pub struct PylintEmitter;
-
-impl Emitter for PylintEmitter {
-    fn emit(
-        &mut self,
-        writer: &mut dyn Write,
-        diagnostics: &[Diagnostic],
-        context: &EmitterContext,
-    ) -> anyhow::Result<()> {
-        for diagnostic in diagnostics {
-            let filename = diagnostic.expect_ruff_filename();
-            let row = if context.is_notebook(&filename) {
-                // We can't give a reasonable location for the structured formats,
-                // so we show one that's clearly a fallback
-                OneIndexed::from_zero_indexed(0)
-            } else {
-                diagnostic.expect_ruff_start_location().line
-            };
-
-            let body = if let Some(code) = diagnostic.secondary_code() {
-                format!("[{code}] {body}", body = diagnostic.body())
-            } else {
-                diagnostic.body().to_string()
-            };
-
-            writeln!(
-                writer,
-                "{path}:{row}: {body}",
-                path = relativize_path(&filename),
-            )?;
-        }
-
-        Ok(())
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use insta::assert_snapshot;
-
-    use crate::message::PylintEmitter;
-    use crate::message::tests::{
-        capture_emitter_output, create_diagnostics, create_syntax_error_diagnostics,
-    };
-
-    #[test]
-    fn output() {
-        let mut emitter = PylintEmitter;
-        let content = capture_emitter_output(&mut emitter, &create_diagnostics());
-
-        assert_snapshot!(content);
-    }
-
-    #[test]
-    fn syntax_errors() {
-        let mut emitter = PylintEmitter;
-        let content = capture_emitter_output(&mut emitter, &create_syntax_error_diagnostics());
-
-        assert_snapshot!(content);
-    }
-}

crates/ruff_linter/src/message/snapshots/ruff_linter__message__pylint__tests__output.snap

@@ -1,8 +0,0 @@
----
-source: crates/ruff_linter/src/message/pylint.rs
-expression: content
-snapshot_kind: text
----
-fib.py:1: [F401] `os` imported but unused
-fib.py:6: [F841] Local variable `x` is assigned to but never used
-undef.py:1: [F821] Undefined name `a`

crates/ruff_linter/src/message/snapshots/ruff_linter__message__pylint__tests__syntax_errors.snap

@@ -1,7 +0,0 @@
----
-source: crates/ruff_linter/src/message/pylint.rs
-expression: content
-snapshot_kind: text
----
-syntax_errors.py:1: SyntaxError: Expected one or more symbol names after import
-syntax_errors.py:3: SyntaxError: Expected ')', found newline