From 55d7226b06db5c2c025ad8ecc724741145e4f101 Mon Sep 17 00:00:00 2001
From: Haroon Qureshi <haroonq@google.com>
Date: Thu, 26 Feb 2026 06:58:06 -0800
Subject: [PATCH] Improve error handling of spec editor compilation.

PiperOrigin-RevId: 875703124
Change-Id: Idf4a90a48d75185ad03e4469cee9098104751d67
---
 src/experimental/platform/model_holder.cc |  2 +-
 src/experimental/studio/app.cc            | 12 +++++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/experimental/platform/model_holder.cc b/src/experimental/platform/model_holder.cc
index c62bfd83..a59105be 100644
--- a/src/experimental/platform/model_holder.cc
+++ b/src/experimental/platform/model_holder.cc
@@ -78,7 +78,7 @@ void ModelHolder::PostInit() {
   if (spec_ && !model_) {
     model_ = mj_compile(spec_, &vfs_);
     if (!model_) {
-      SetLoadError("Error compiling model from spec.");
+      SetLoadError(mjs_getError(spec_));
       return;
     }
   }
diff --git a/src/experimental/studio/app.cc b/src/experimental/studio/app.cc
index 66d71d34..12bce034 100644
--- a/src/experimental/studio/app.cc
+++ b/src/experimental/studio/app.cc
@@ -1287,9 +1287,15 @@ void App::SpecEditorGui() {
       ImGui::PushStyleColor(ImGuiCol_Button, ImColor(40, 180, 40, 255).Value);
       if (ImGui::Button("Compile and Reload", ImVec2(-1, 0))) {
         spec_op_ = [this]() {
-          model_holder_ = platform::ModelHolder::FromSpec(scratch_spec_);
-          scratch_spec_ = nullptr;
-          OnModelLoaded(model_name_, model_kind_);
+          auto tmp_holder = platform::ModelHolder::FromSpec(scratch_spec_);
+          if (tmp_holder->ok()) {
+            model_holder_ = std::move(tmp_holder);
+            scratch_spec_ = nullptr;
+            OnModelLoaded(model_name_, model_kind_);
+          } else {
+            scratch_spec_ = tmp_holder->ReleaseSpec();
+            load_error_ = std::move(tmp_holder->error());
+          }
         };
       }
       ImGui::PopStyleColor();