fix(api): enhance OpenAI API compatibility for frontend integration (Issue #113) (#123)

- Add optional OpenAI-standard fields to Model struct: permission, root, parent
- Use skip_serializing_if to omit null fields for cleaner JSON responses
- Populate root field with model name for standard OpenAI compatibility
- Update regression tests to verify enhanced Model structure
- Improves compatibility with frontend tools that expect full OpenAI API format

Resolves Issue #113: OpenAI API compatibility for frontends

Signed-off-by: Michael A. Kuykendall <michaelallenkuykendall@gmail.com>

Author: Michael-A-Kuykendall

src/openai_compat.rs

@@ -77,6 +77,12 @@ pub struct Model {
     pub object: String,
     pub created: u64,
     pub owned_by: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub permission: Option<Vec<String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub root: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub parent: Option<String>,
 }
 
 pub async fn models(State(state): State<Arc<AppState>>) -> impl IntoResponse {
@@ -85,10 +91,13 @@ pub async fn models(State(state): State<Arc<AppState>>) -> impl IntoResponse {
         .list_all_available()
         .into_iter()
         .map(|name| Model {
-            id: name,
+            id: name.clone(),
             object: "model".to_string(),
             created: 0, // Fixed timestamp for simplicity
             owned_by: "shimmy".to_string(),
+            permission: None, // No fine-grained permissions for local models
+            root: Some(name), // The model itself is the root
+            parent: None, // Local models don't have parent models
         })
         .collect();
 

tests/regression_tests.rs

@@ -203,12 +203,18 @@ mod regression_tests {
                     object: "model".to_string(),
                     created: 0,
                     owned_by: "shimmy".to_string(),
+                    permission: None,
+                    root: Some("qwen3-4b-instruct".to_string()),
+                    parent: None,
                 },
                 Model {
                     id: "llama-7b".to_string(),
                     object: "model".to_string(),
                     created: 0,
                     owned_by: "shimmy".to_string(),
+                    permission: None,
+                    root: Some("llama-7b".to_string()),
+                    parent: None,
                 },
             ],
         };
@@ -316,12 +322,15 @@ mod regression_tests {
         // Test the fix for Issue #113 - OpenAI API compatibility for frontends
         use shimmy::openai_compat::{Model, ModelsResponse};
 
-        // Test basic Model structure (enhanced fields are on PR branch)
+        // Test enhanced Model structure with frontend compatibility fields
         let model = Model {
             id: "test-model".to_string(),
             object: "model".to_string(),
             created: 1640995200,
             owned_by: "shimmy".to_string(),
+            permission: None,
+            root: Some("test-model".to_string()),
+            parent: None,
         };
 
         // Test serialization works correctly
@@ -330,6 +339,10 @@ mod regression_tests {
         assert_eq!(json["owned_by"], "shimmy");
         assert_eq!(json["object"], "model");
         assert_eq!(json["created"], 1640995200);
+        assert_eq!(json["root"], "test-model");
+        // Optional fields should be omitted when None (due to skip_serializing_if)
+        assert!(json.get("permission").is_none());
+        assert!(json.get("parent").is_none());
 
         // Test ModelsResponse structure
         let response = ModelsResponse {