Add server config to filter out syntax error diagnostics (#12059)

## Summary

Follow-up from #11901 

This PR adds a new server setting to show / hide syntax errors.

## Test Plan

### VS Code

Using astral-sh/ruff-vscode#504 with the
following config:

```json
{
  "ruff.nativeServer": true,
  "ruff.path": ["/Users/dhruv/work/astral/ruff/target/debug/ruff"],
  "ruff.showSyntaxErrors": true
}
```

First, set `ruff.showSyntaxErrors` to `true`:
<img width="1177" alt="Screenshot 2024-06-27 at 08 34 58"
src="https://github.com/astral-sh/ruff/assets/67177269/5d77547a-a908-4a00-8714-7c00784e8679">

And then set it to `false`:
<img width="1185" alt="Screenshot 2024-06-27 at 08 35 19"
src="https://github.com/astral-sh/ruff/assets/67177269/9720f089-f10c-420b-a2c1-2bbb2245be35">

### Neovim

Using the following Ruff server config:

```lua
require('lspconfig').ruff.setup {
  init_options = {
    settings = {
      showSyntaxErrors = false,
    },
  },
}
```

First, set `showSyntaxErrors` to `true`:
<img width="1279" alt="Screenshot 2024-06-27 at 08 28 03"
src="https://github.com/astral-sh/ruff/assets/67177269/e694e231-91ba-47f8-8e8a-ad2e82b85a45">

And then set it to `false`:
<img width="1284" alt="Screenshot 2024-06-27 at 08 28 20"
src="https://github.com/astral-sh/ruff/assets/67177269/25b86a57-02b1-44f7-9f65-cf5fdde93b0c">

crates/ruff_server/src/lint.rs

@@ -60,7 +60,11 @@ pub(crate) struct DiagnosticFix {
 /// A series of diagnostics across a single text document or an arbitrary number of notebook cells.
 pub(crate) type DiagnosticsMap = FxHashMap<lsp_types::Url, Vec<lsp_types::Diagnostic>>;
 
-pub(crate) fn check(query: &DocumentQuery, encoding: PositionEncoding) -> DiagnosticsMap {
+pub(crate) fn check(
+    query: &DocumentQuery,
+    encoding: PositionEncoding,
+    show_syntax_errors: bool,
+) -> DiagnosticsMap {
     let source_kind = query.make_source_kind();
     let file_resolver_settings = query.settings().file_resolver();
     let linter_settings = query.settings().linter();
@@ -156,10 +160,18 @@ pub(crate) fn check(query: &DocumentQuery, encoding: PositionEncoding) -> Diagno
         .zip(noqa_edits)
         .map(|(diagnostic, noqa_edit)| {
             to_lsp_diagnostic(diagnostic, &noqa_edit, &source_kind, &index, encoding)
-        })
-        .chain(parsed.errors().iter().map(|parse_error| {
-            parse_error_to_lsp_diagnostic(parse_error, &source_kind, &index, encoding)
-        }));
+        });
+
+    let lsp_diagnostics = lsp_diagnostics.chain(
+        show_syntax_errors
+            .then(|| {
+                parsed.errors().iter().map(|parse_error| {
+                    parse_error_to_lsp_diagnostic(parse_error, &source_kind, &index, encoding)
+                })
+            })
+            .into_iter()
+            .flatten(),
+    );
 
     if let Some(notebook) = query.as_notebook() {
         for (index, diagnostic) in lsp_diagnostics {
@@ -173,12 +185,10 @@ pub(crate) fn check(query: &DocumentQuery, encoding: PositionEncoding) -> Diagno
                 .push(diagnostic);
         }
     } else {
-        for (_, diagnostic) in lsp_diagnostics {
-            diagnostics_map
-                .entry(query.make_key().into_url())
-                .or_default()
-                .push(diagnostic);
-        }
+        diagnostics_map
+            .entry(query.make_key().into_url())
+            .or_default()
+            .extend(lsp_diagnostics.map(|(_, diagnostic)| diagnostic));
     }
 
     diagnostics_map

crates/ruff_server/src/server/api/diagnostics.rs

@@ -9,7 +9,11 @@ use super::LSPResult;
 pub(super) fn generate_diagnostics(snapshot: &DocumentSnapshot) -> DiagnosticsMap {
     if snapshot.client_settings().lint() {
         let document = snapshot.query();
-        crate::lint::check(document, snapshot.encoding())
+        crate::lint::check(
+            document,
+            snapshot.encoding(),
+            snapshot.client_settings().show_syntax_errors(),
+        )
     } else {
         DiagnosticsMap::default()
     }

crates/ruff_server/src/session/settings.rs

@@ -21,6 +21,7 @@ pub(crate) struct ResolvedClientSettings {
     lint_enable: bool,
     disable_rule_comment_enable: bool,
     fix_violation_enable: bool,
+    show_syntax_errors: bool,
     editor_settings: ResolvedEditorSettings,
 }
 
@@ -70,6 +71,13 @@ pub struct ClientSettings {
     exclude: Option<Vec<String>>,
     line_length: Option<LineLength>,
     configuration_preference: Option<ConfigurationPreference>,
+
+    /// If `true` or [`None`], show syntax errors as diagnostics.
+    ///
+    /// This is useful when using Ruff with other language servers, allowing the user to refer
+    /// to syntax errors from only one source.
+    show_syntax_errors: Option<bool>,
+
     // These settings are only needed for tracing, and are only read from the global configuration.
     // These will not be in the resolved settings.
     #[serde(flatten)]
@@ -244,6 +252,11 @@ impl ResolvedClientSettings {
                 },
                 true,
             ),
+            show_syntax_errors: Self::resolve_or(
+                all_settings,
+                |settings| settings.show_syntax_errors,
+                true,
+            ),
             editor_settings: ResolvedEditorSettings {
                 configuration: Self::resolve_optional(all_settings, |settings| {
                     settings
@@ -345,6 +358,10 @@ impl ResolvedClientSettings {
         self.fix_violation_enable
     }
 
+    pub(crate) fn show_syntax_errors(&self) -> bool {
+        self.show_syntax_errors
+    }
+
     pub(crate) fn editor_settings(&self) -> &ResolvedEditorSettings {
         &self.editor_settings
     }
@@ -439,6 +456,7 @@ mod tests {
                 exclude: None,
                 line_length: None,
                 configuration_preference: None,
+                show_syntax_errors: None,
                 tracing: TracingSettings {
                     log_level: None,
                     log_file: None,
@@ -491,6 +509,7 @@ mod tests {
                         exclude: None,
                         line_length: None,
                         configuration_preference: None,
+                        show_syntax_errors: None,
                         tracing: TracingSettings {
                             log_level: None,
                             log_file: None,
@@ -556,6 +575,7 @@ mod tests {
                         exclude: None,
                         line_length: None,
                         configuration_preference: None,
+                        show_syntax_errors: None,
                         tracing: TracingSettings {
                             log_level: None,
                             log_file: None,
@@ -602,6 +622,7 @@ mod tests {
                 lint_enable: true,
                 disable_rule_comment_enable: false,
                 fix_violation_enable: false,
+                show_syntax_errors: true,
                 editor_settings: ResolvedEditorSettings {
                     configuration: None,
                     lint_preview: Some(true),
@@ -633,6 +654,7 @@ mod tests {
                 lint_enable: true,
                 disable_rule_comment_enable: true,
                 fix_violation_enable: false,
+                show_syntax_errors: true,
                 editor_settings: ResolvedEditorSettings {
                     configuration: None,
                     lint_preview: Some(false),
@@ -700,6 +722,7 @@ mod tests {
                     ),
                 ),
                 configuration_preference: None,
+                show_syntax_errors: None,
                 tracing: TracingSettings {
                     log_level: Some(
                         Warn,
@@ -726,6 +749,7 @@ mod tests {
                 lint_enable: true,
                 disable_rule_comment_enable: false,
                 fix_violation_enable: true,
+                show_syntax_errors: true,
                 editor_settings: ResolvedEditorSettings {
                     configuration: None,
                     lint_preview: None,