Show diagnostic codes (#29296)

Closes #28135
Closes #4388
Closes #28136

Release Notes:

- diagnostics: Show the diagnostic code if available

---------

Co-authored-by: Neo Nie <nihgwu@live.com>
Co-authored-by: Zed AI <ai+claude-3.7@zed.dev>

crates/language/src/buffer.rs

@@ -208,6 +208,7 @@ pub struct Diagnostic {
     pub source: Option<String>,
     /// A machine-readable code that identifies this diagnostic.
     pub code: Option<NumberOrString>,
+    pub code_description: Option<lsp::Url>,
     /// Whether this diagnostic is a hint, warning, or error.
     pub severity: DiagnosticSeverity,
     /// The human-readable message associated with this diagnostic.
@@ -4612,6 +4613,7 @@ impl Default for Diagnostic {
         Self {
             source: Default::default(),
             code: None,
+            code_description: None,
             severity: DiagnosticSeverity::ERROR,
             message: Default::default(),
             group_id: 0,

crates/language/src/proto.rs

@@ -213,6 +213,11 @@ pub fn serialize_diagnostics<'a>(
             group_id: entry.diagnostic.group_id as u64,
             is_primary: entry.diagnostic.is_primary,
             code: entry.diagnostic.code.as_ref().map(|s| s.to_string()),
+            code_description: entry
+                .diagnostic
+                .code_description
+                .as_ref()
+                .map(|s| s.to_string()),
             is_disk_based: entry.diagnostic.is_disk_based,
             is_unnecessary: entry.diagnostic.is_unnecessary,
             data: entry.diagnostic.data.as_ref().map(|data| data.to_string()),
@@ -419,6 +424,9 @@ pub fn deserialize_diagnostics(
                     message: diagnostic.message,
                     group_id: diagnostic.group_id as usize,
                     code: diagnostic.code.map(lsp::NumberOrString::from_string),
+                    code_description: diagnostic
+                        .code_description
+                        .and_then(|s| lsp::Url::parse(&s).ok()),
                     is_primary: diagnostic.is_primary,
                     is_disk_based: diagnostic.is_disk_based,
                     is_unnecessary: diagnostic.is_unnecessary,