From 75802e6ee4e94604b379ed64b422c8fc254bf8a4 Mon Sep 17 00:00:00 2001
From: Jesse Brault <jbrault@mac.com>
Date: Thu, 12 Mar 2026 16:15:03 -0500
Subject: [PATCH] Expand diagnostic API.

---
 dm/src/run.rs             | 38 +++++++++++++++++--
 dmc-lib/src/diagnostic.rs | 80 +++++++++++++++++++++++++++++++++++----
 2 files changed, 107 insertions(+), 11 deletions(-)

diff --git a/dm/src/run.rs b/dm/src/run.rs
index df4414e..5c273a2 100644
--- a/dm/src/run.rs
+++ b/dm/src/run.rs
@@ -125,12 +125,42 @@ fn report_and_exit(
     let writer = StandardStream::stderr(ColorChoice::Always);
     let config = term::Config::default();
     for diagnostic in diagnostics {
-        let csr_diagnostic = codespan_reporting::diagnostic::Diagnostic::error()
+        let mut primary_label =
+            Label::primary(script_file_id, diagnostic.start()..diagnostic.end());
+        if let Some(primary_label_message) = diagnostic.primary_label_message() {
+            primary_label = primary_label.with_message(primary_label_message);
+        }
+
+        let secondary_labels: Vec<Label<usize>> = diagnostic
+            .secondary_labels()
+            .iter()
+            .map(|secondary_label| {
+                let mut label = Label::secondary(
+                    script_file_id,
+                    secondary_label.start()..secondary_label.end(),
+                );
+                if let Some(message) = secondary_label.message() {
+                    label = label.with_message(message);
+                }
+                label
+            })
+            .collect();
+
+        let mut csr_diagnostic = codespan_reporting::diagnostic::Diagnostic::error()
             .with_message(diagnostic.message())
-            .with_label(Label::primary(
-                script_file_id,
-                diagnostic.start()..diagnostic.end(),
+            .with_label(primary_label)
+            .with_labels(secondary_labels);
+
+        if let Some(error_code) = diagnostic.error_code() {
+            csr_diagnostic = csr_diagnostic.with_code(format!("E{}", error_code));
+        }
+
+        if let Some((reporter_file, reporter_line)) = diagnostic.reporter() {
+            csr_diagnostic = csr_diagnostic.with_note(format!(
+                "Reported by (Rust) source: {}, line {}",
+                reporter_file, reporter_line
             ));
+        }
 
         term::emit_to_write_style(&mut writer.lock(), &config, files, &csr_diagnostic).unwrap();
     }
diff --git a/dmc-lib/src/diagnostic.rs b/dmc-lib/src/diagnostic.rs
index 06ee3f8..4044c2f 100644
--- a/dmc-lib/src/diagnostic.rs
+++ b/dmc-lib/src/diagnostic.rs
@@ -1,20 +1,26 @@
 #[derive(Debug)]
 pub struct Diagnostic {
     message: String,
+    primary_label_message: Option<String>,
+    error_code: Option<usize>,
     start: usize,
     end: usize,
     reporter_file: Option<&'static str>,
     reporter_line: Option<u32>,
+    secondary_labels: Vec<SecondaryLabel>,
 }
 
 impl Diagnostic {
     pub fn new(message: &str, start: usize, end: usize) -> Self {
         Self {
             message: message.into(),
+            primary_label_message: None,
+            error_code: None,
             start,
             end,
             reporter_line: None,
             reporter_file: None,
+            secondary_labels: vec![],
         }
     }
 
@@ -22,6 +28,14 @@ impl Diagnostic {
         &self.message
     }
 
+    pub fn primary_label_message(&self) -> Option<&str> {
+        self.primary_label_message.as_deref()
+    }
+
+    pub fn error_code(&self) -> Option<usize> {
+        self.error_code
+    }
+
     pub fn start(&self) -> usize {
         self.start
     }
@@ -30,13 +44,65 @@ impl Diagnostic {
         self.end
     }
 
-    pub fn with_reporter(&self, file: &'static str, line: u32) -> Self {
-        Self {
-            message: self.message.clone(),
-            start: self.start,
-            end: self.end,
-            reporter_file: Some(file),
-            reporter_line: Some(line),
+    pub fn reporter(&self) -> Option<(&'static str, u32)> {
+        if let Some(file) = self.reporter_file {
+            Some((file, self.reporter_line.unwrap()))
+        } else {
+            None
         }
     }
+
+    pub fn secondary_labels(&self) -> &[SecondaryLabel] {
+        &self.secondary_labels
+    }
+
+    pub fn with_error_code(mut self, code: usize) -> Self {
+        self.error_code = Some(code);
+        self
+    }
+
+    pub fn with_primary_label_message(mut self, message: &str) -> Self {
+        self.primary_label_message = Some(message.into());
+        self
+    }
+
+    pub fn with_reporter(mut self, file: &'static str, line: u32) -> Self {
+        self.reporter_file = Some(file);
+        self.reporter_line = Some(line);
+        self
+    }
+
+    pub fn with_secondary_labels(mut self, labels: &[SecondaryLabel]) -> Self {
+        self.secondary_labels.extend_from_slice(labels);
+        self
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct SecondaryLabel {
+    start: usize,
+    end: usize,
+    message: Option<String>,
+}
+
+impl SecondaryLabel {
+    pub fn new(start: usize, end: usize, message: Option<String>) -> Self {
+        Self {
+            start,
+            end,
+            message,
+        }
+    }
+
+    pub fn start(&self) -> usize {
+        self.start
+    }
+
+    pub fn end(&self) -> usize {
+        self.end
+    }
+
+    pub fn message(&self) -> Option<&str> {
+        self.message.as_deref()
+    }
 }