Pin Blender for CI asset processing (#58)

Reviewed-on: #58
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/blend_asset.rs

@@ -84,10 +84,11 @@ impl AssetLoader for BlendSourceLoader {
             .arg(&blend_path)
             .arg("--python")
             .arg(&script)
-        .arg("--")
-        .arg(&output)
-        .arg(&actions_path)
-        .output()
+            .arg("--")
+            .arg(&output)
+            .arg(&actions_path)
+            .arg(&blend_path)
+            .output()
             .map_err(|error| io::Error::other(format!("failed to start Blender: {error}")))?;
         if !result.status.success() {
             return Err(io::Error::other(format!(
@@ -106,6 +107,7 @@ impl AssetLoader for BlendSourceLoader {
         let mut dependencies = manifest.dependencies;
         let document: serde_json::Value = serde_json::from_slice(&fs::read(&output)?)
             .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
+        validate_export(&document, &output)?;
         if let Some(images) = document.get("images").and_then(serde_json::Value::as_array) {
             for image in images {
                 if let Some(uri) = image.get("uri").and_then(serde_json::Value::as_str) {
@@ -142,6 +144,22 @@ impl AssetLoader for BlendSourceLoader {
     }
 }
 
+fn validate_export(document: &serde_json::Value, output: &Path) -> io::Result<()> {
+    for key in ["scenes", "nodes", "meshes"] {
+        let count = document
+            .get(key)
+            .and_then(serde_json::Value::as_array)
+            .map_or(0, Vec::len);
+        if count == 0 {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!("Blender export {} contains no {key}", output.display()),
+            ));
+        }
+    }
+    Ok(())
+}
+
 async fn referenced_actions(
     load_context: &mut LoadContext<'_>,
     root: &Path,