editor: Use better error types

Author: a-kenji

src/app.rs

@@ -344,19 +344,17 @@ impl App {
         print_progress(&format!("Opening {} in {}...", file_path.display(), editor));
 
         let status = Command::new(&editor).arg(file_path).status().map_err(|e| {
-            SizelintError::config_invalid(
-                "editor".to_string(),
-                editor.clone(),
-                format!("Failed to start editor: {e}"),
-            )
+            SizelintError::EditorExec {
+                editor: editor.clone(),
+                source: e,
+            }
         })?;
 
         if !status.success() {
-            return Err(SizelintError::config_invalid(
-                "editor".to_string(),
+            return Err(SizelintError::EditorFailed {
                 editor,
-                "Editor exited with error".to_string(),
-            ));
+                exit_code: status.code().unwrap_or(-1),
+            });
         }
 
         print_success("Configuration saved");

src/error.rs

@@ -69,6 +69,21 @@ pub enum SizelintError {
         source: std::io::Error,
     },
 
+    #[error("Failed to start editor '{editor}'")]
+    #[diagnostic(
+        code(sizelint::editor::exec),
+        help("Check that the editor is installed and on your PATH, or set $VISUAL / $EDITOR")
+    )]
+    EditorExec {
+        editor: String,
+        #[source]
+        source: std::io::Error,
+    },
+
+    #[error("Editor '{editor}' exited with status {exit_code}")]
+    #[diagnostic(code(sizelint::editor::failed))]
+    EditorFailed { editor: String, exit_code: i32 },
+
     #[error("Invalid size format '{input}': {reason}")]
     #[diagnostic(
         code(sizelint::rule::invalid_size_format),