feat(narrated): global footer and related diagnostics support

src/handlers/narratable.rs

@@ -58,6 +58,10 @@ impl NarratableReportHandler {
         self.render_causes(f, diagnostic)?;
         self.render_snippets(f, diagnostic)?;
         self.render_footer(f, diagnostic)?;
+        self.render_related(f, diagnostic)?;
+        if let Some(footer) = &self.footer {
+            writeln!(f, "{}", footer)?;
+        }
         Ok(())
     }
 
@@ -95,6 +99,26 @@ impl NarratableReportHandler {
         Ok(())
     }
 
+    fn render_related(
+        &self,
+        f: &mut impl fmt::Write,
+        diagnostic: &(dyn Diagnostic),
+    ) -> fmt::Result {
+        if let Some(related) = diagnostic.related() {
+            writeln!(f)?;
+            for rel in related {
+                write!(f, "Error: ")?;
+                self.render_header(f, rel)?;
+                writeln!(f)?;
+                self.render_causes(f, rel)?;
+                self.render_snippets(f, rel)?;
+                self.render_footer(f, rel)?;
+                self.render_related(f, rel)?;
+            }
+        }
+        Ok(())
+    }
+
     fn render_snippets(
         &self,
         f: &mut impl fmt::Write,