refactor: diagnostics server — replace manual JSON write! with serde_json #2627

Activity

1. strawgate

   added

   enhancementNew feature or requestNew feature or request

   P2: mediumMinor bug, missing validation, metric inaccuracyMinor bug, missing validation, metric inaccuracy

   component:diagnosticsDiagnostics endpoints, dashboard, health, probes, and trace explorerDiagnostics endpoints, dashboard, health, probes, and trace explorer

   on Apr 25, 2026
2. strawgate commented on Apr 27, 2026

   

   strawgate

   on Apr 27, 2026

   OwnerAuthor

   More actions

   Verification (2026-04-27)

   CONFIRMED: Issue still exists on main.

   Verified on current main:

   • ffwd-diagnostics/src/diagnostics/server.rs:737 - build_traces_body() still uses manual String + write!
   • ffwd-diagnostics/src/diagnostics/server.rs:964 - build_logs_body() same pattern

   Current Code:

   fn build_traces_body(state: &DiagnosticsState) -> String {
       // ...
       let mut out = String::with_capacity(64 * 1024);
       out.push_str(r#"{"traces":["#);
       // ... manual write! chain continues
   }

   Reproduction:

   No test needed - code is clearly visible at lines 737-900+ and 964+

   Fix Plan:

   1. Replace manual JSON with serde_json::to_string()
   2. Create struct for traces response:

   #[derive(Serialize)]
   struct TracesResponse {
       traces: Vec<TraceData>,
   }

   3. Use serde_json::to_string(&response)

   Priority: MEDIUM - Technical debt, but low risk

   ---

   Verified by code inspection of server.rs:737 and 964
3. strawgate commented on Apr 27, 2026

   

   strawgate

   on Apr 27, 2026

   OwnerAuthor

   More actions

   Verification (2026-04-27)

   STATUS: CONFIRMED OPEN

   Manual JSON construction found in ffwd-diagnostics/src/diagnostics/server.rs:

   • Line 758: build_traces_body uses out.push_str(r#"{"traces":["#)
   • Line 844, 914: write! macros for JSON string building
   • Line 967: build_lines_body uses body.push_str(r#"{"lines":["#)
   • Line 977: manual string building for stderr state

   42 serde_json usages found, but these manual string operations are error-prone and hard to maintain.

   Fix needed:

   Replace manual write!/push_str JSON building with serde_json serialization to struct types.

   Priority: MEDIUM (code quality, maintainability)