assistant2: Encourage diagnostics check (#27510)

Release Notes:

- N/A

crates/assistant_tools/src/diagnostics_tool.rs

@@ -25,9 +25,19 @@ pub struct DiagnosticsToolInput {
     ///
     /// If you wanna access diagnostics for `dolor.txt` in `ipsum`, you should use the path `ipsum/dolor.txt`.
     /// </example>
+    #[serde(deserialize_with = "deserialize_path")]
     pub path: Option<String>,
 }
 
+fn deserialize_path<'de, D>(deserializer: D) -> Result<Option<String>, D::Error>
+where
+    D: serde::Deserializer<'de>,
+{
+    let opt = Option::<String>::deserialize(deserializer)?;
+    // The model passes an empty string sometimes
+    Ok(opt.filter(|s| !s.is_empty()))
+}
+
 pub struct DiagnosticsTool;
 
 impl Tool for DiagnosticsTool {
@@ -71,7 +81,7 @@ impl Tool for DiagnosticsTool {
         input: serde_json::Value,
         _messages: &[LanguageModelRequestMessage],
         project: Entity<Project>,
-        _action_log: Entity<ActionLog>,
+        action_log: Entity<ActionLog>,
         cx: &mut App,
     ) -> Task<Result<String>> {
         match serde_json::from_value::<DiagnosticsToolInput>(input)
@@ -140,6 +150,10 @@ impl Tool for DiagnosticsTool {
                     }
                 }
 
+                action_log.update(cx, |action_log, _cx| {
+                    action_log.checked_project_diagnostics();
+                });
+
                 if has_diagnostics {
                     Task::ready(Ok(output))
                 } else {

crates/assistant_tools/src/diagnostics_tool/description.md

@@ -14,3 +14,5 @@ To get diagnostics for a specific file:
 To get a project-wide diagnostic summary:
 {}
 </example>
+
+IMPORTANT: When you're done making changes, you **MUST** get the **project** diagnostics (input: `{}`) at the end of your edits so you can fix any problems you might have introduced. **DO NOT** tell the user you're done before doing this!