refactor(oxlint/lsp): prefill FixedContent.message and remove Option wrapper (#16515)

> This PR refactors the linter's fix message handling by removing the Option wrapper from FixedContent.message and prefilling messages earlier in the processing pipeline. The change simplifies code action generation by moving the fallback message logic from fix_content_to_code_action into message_to_lsp_diagnostic, where fix messages are now populated before being converted to FixedContent.

The goal in the next PR is that the alternative message (from diagnostic) is no longer be stored in memory. So the title should be updated beforehand.

Author: Sysix

crates/oxc_language_server/src/linter/code_actions.rs

@@ -9,25 +9,10 @@ pub const CODE_ACTION_KIND_SOURCE_FIX_ALL_OXC: CodeActionKind =
 fn fix_content_to_code_action(
     fixed_content: &FixedContent,
     uri: &Uri,
-    alternative_message: &str,
     is_preferred: bool,
 ) -> CodeAction {
-    // 1) Use `fixed_content.message` if it exists
-    // 2) Try to parse the report diagnostic message
-    // 3) Fallback to "Fix this problem"
-    let title = match fixed_content.message.clone() {
-        Some(msg) => msg,
-        None => {
-            if let Some(code) = alternative_message.split(':').next() {
-                format!("Fix this {code} problem")
-            } else {
-                "Fix this problem".to_string()
-            }
-        }
-    };
-
     CodeAction {
-        title,
+        title: fixed_content.message.clone(),
         kind: Some(CodeActionKind::QUICKFIX),
         is_preferred: Some(is_preferred),
         edit: Some(WorkspaceEdit {
@@ -45,17 +30,13 @@ fn fix_content_to_code_action(
     }
 }
 
-pub fn apply_fix_code_actions(
-    report: &LinterCodeAction,
-    alternative_message: &str,
-    uri: &Uri,
-) -> Vec<CodeAction> {
+pub fn apply_fix_code_actions(report: &LinterCodeAction, uri: &Uri) -> Vec<CodeAction> {
     let mut code_actions = vec![];
 
     // only the first code action is preferred
     let mut preferred = true;
     for fixed in &report.fixed_content {
-        let action = fix_content_to_code_action(fixed, uri, alternative_message, preferred);
+        let action = fix_content_to_code_action(fixed, uri, preferred);
         preferred = false;
         code_actions.push(action);
     }
@@ -104,13 +85,8 @@ pub fn fix_all_text_edit<'a>(reports: impl Iterator<Item = &'a LinterCodeAction>
             debug!("Multiple fixes found, but only ignore fixes available");
             #[cfg(debug_assertions)]
             {
-                debug_assert!(report.fixed_content[0].message.as_ref().is_some());
-                debug_assert!(
-                    report.fixed_content[0].message.as_ref().unwrap().starts_with("Disable")
-                );
-                debug_assert!(
-                    report.fixed_content[0].message.as_ref().unwrap().ends_with("for this line")
-                );
+                debug_assert!(report.fixed_content[0].message.starts_with("Disable"));
+                debug_assert!(report.fixed_content[0].message.ends_with("for this line"));
             }
             continue;
         }

crates/oxc_language_server/src/linter/error_with_position.rs

@@ -1,4 +1,4 @@
-use std::str::FromStr;
+use std::{borrow::Cow, str::FromStr};
 
 use tower_lsp_server::lsp_types::{
     self, CodeDescription, Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity,
@@ -23,7 +23,7 @@ pub struct LinterCodeAction {
 
 #[derive(Debug, Clone, Default)]
 pub struct FixedContent {
-    pub message: Option<String>,
+    pub message: String,
     pub code: String,
     pub range: Range,
 }
@@ -32,7 +32,7 @@ pub struct FixedContent {
 // we assume that the fix offset will not exceed 2GB in either direction
 #[expect(clippy::cast_possible_truncation)]
 pub fn message_to_lsp_diagnostic(
-    message: &Message,
+    mut message: Message,
     uri: &Uri,
     source_text: &str,
     rope: &Rope,
@@ -87,6 +87,16 @@ pub fn message_to_lsp_diagnostic(
         None => message.error.message.to_string(),
     };
 
+    // 1) Use `fixed_content.message` if it exists
+    // 2) Try to parse the report diagnostic message
+    // 3) Fallback to "Fix this problem"
+    let alternative_fix_title: Cow<'static, str> =
+        if let Some(code) = diagnostic_message.split(':').next() {
+            format!("Fix this {code} problem").into()
+        } else {
+            std::borrow::Cow::Borrowed("Fix this problem")
+        };
+
     let diagnostic = Diagnostic {
         range,
         severity,
@@ -101,14 +111,21 @@ pub fn message_to_lsp_diagnostic(
 
     let mut fixed_content = vec![];
     // Convert PossibleFixes directly to PossibleFixContent
-    match &message.fixes {
+    match &mut message.fixes {
         PossibleFixes::None => {}
         PossibleFixes::Single(fix) => {
+            if fix.message.is_none() {
+                fix.message = Some(alternative_fix_title);
+            }
             fixed_content.push(fix_to_fixed_content(fix, rope, source_text));
         }
         PossibleFixes::Multiple(fixes) => {
-            fixed_content
-                .extend(fixes.iter().map(|fix| fix_to_fixed_content(fix, rope, source_text)));
+            fixed_content.extend(fixes.iter_mut().map(|fix| {
+                if fix.message.is_none() {
+                    fix.message = Some(alternative_fix_title.clone());
+                }
+                fix_to_fixed_content(fix, rope, source_text)
+            }));
         }
     }
 
@@ -154,8 +171,13 @@ fn fix_to_fixed_content(fix: &Fix, rope: &Rope, source_text: &str) -> FixedConte
     let start_position = offset_to_position(rope, fix.span.start, source_text);
     let end_position = offset_to_position(rope, fix.span.end, source_text);
 
+    debug_assert!(
+        fix.message.is_some(),
+        "Fix message should be present. `message_to_lsp_diagnostic` should modify fixes to include messages."
+    );
+
     FixedContent {
-        message: fix.message.as_ref().map(std::string::ToString::to_string),
+        message: fix.message.as_ref().map(std::string::ToString::to_string).unwrap_or_default(),
         code: fix.content.to_string(),
         range: Range::new(start_position, end_position),
     }
@@ -220,12 +242,7 @@ fn add_ignore_fixes(
     source_text: &str,
 ) {
     // do not append ignore code actions when the error is the ignore action
-    if fixes.len() == 1
-        && fixes[0]
-            .message
-            .as_ref()
-            .is_some_and(|message| message.starts_with("remove unused disable directive"))
-    {
+    if fixes.len() == 1 && fixes[0].message.starts_with("remove unused disable directive") {
         return;
     }
 
@@ -281,7 +298,7 @@ fn disable_for_this_line(
 
     let position = offset_to_position(rope, insert_offset, source_text);
     FixedContent {
-        message: Some(format!("Disable {rule_name} for this line")),
+        message: format!("Disable {rule_name} for this line"),
         code: format!(
             "{content_prefix}{whitespace_string}// oxlint-disable-next-line {rule_name}\n"
         ),
@@ -304,7 +321,7 @@ fn disable_for_this_section(
     let position = offset_to_position(rope, insert_offset, source_text);
 
     FixedContent {
-        message: Some(format!("Disable {rule_name} for this whole file")),
+        message: format!("Disable {rule_name} for this whole file"),
         code: content,
         range: Range::new(position, position),
     }

crates/oxc_language_server/src/linter/isolated_lint_handler.rs

@@ -126,7 +126,7 @@ impl IsolatedLintHandler {
         let mut messages: Vec<DiagnosticReport> = self
             .runner
             .run_source(&Arc::from(path.as_os_str()), source_text.to_string(), &fs)
-            .iter()
+            .into_iter()
             .map(|message| message_to_lsp_diagnostic(message, uri, source_text, rope))
             .collect();
 
@@ -136,7 +136,7 @@ impl IsolatedLintHandler {
         {
             messages.extend(
                 create_unused_directives_messages(&directives, severity, source_text)
-                    .iter()
+                    .into_iter()
                     .map(|message| message_to_lsp_diagnostic(message, uri, source_text, rope)),
             );
         }

crates/oxc_language_server/src/linter/server_linter.rs

@@ -496,7 +496,7 @@ impl Tool for ServerLinter {
             let Some(ref code_action) = report.code_action else {
                 continue;
             };
-            let fix_actions = apply_fix_code_actions(code_action, &report.diagnostic.message, uri);
+            let fix_actions = apply_fix_code_actions(code_action, uri);
             code_actions_vec.extend(fix_actions.into_iter().map(CodeActionOrCommand::CodeAction));
         }