fix: blanket impl GraphQLFields for Option<T> for nullable queries

crates/lineark-codegen/src/emit_queries.rs

@@ -138,12 +138,16 @@ fn emit_query(
     let is_connection =
         return_type_name.ends_with("Connection") || return_type_name.ends_with("Payload");
 
+    // Nullable return type: schema has `Type` (nullable) vs `Type!` (non-null).
+    let is_nullable = !is_connection && !matches!(field.ty, GqlType::NonNull(_));
+
     if has_optional {
         emit_builder_query(
             field,
             rename,
             &args,
             is_connection,
+            is_nullable,
             object_map,
             type_kind_map,
         )
@@ -153,6 +157,7 @@ fn emit_query(
             rename,
             &args,
             is_connection,
+            is_nullable,
             object_map,
             type_kind_map,
         )
@@ -166,6 +171,7 @@ fn emit_direct_query(
     rename: Option<&str>,
     args: &[ArgInfo],
     is_connection: bool,
+    is_nullable: bool,
     object_map: &HashMap<&str, &ObjectDef>,
     _type_kind_map: &HashMap<String, TypeKind>,
 ) -> QueryResult {
@@ -278,18 +284,30 @@ fn emit_direct_query(
             }
         };
 
+        let (return_type, execute_call) = if is_nullable {
+            (
+                quote! { Option<T> },
+                quote! { client.execute::<Option<T>>(&query, variables, #data_path).await },
+            )
+        } else {
+            (
+                quote! { T },
+                quote! { client.execute::<T>(&query, variables, #data_path).await },
+            )
+        };
+
         let standalone_fn = quote! {
             #doc
-            pub async fn #method_name<T: DeserializeOwned + GraphQLFields<FullType = super::types::#node_type_ident>>(client: &Client, #(#params),*) -> Result<T, LinearError> {
+            pub async fn #method_name<T: DeserializeOwned + GraphQLFields<FullType = super::types::#node_type_ident>>(client: &Client, #(#params),*) -> Result<#return_type, LinearError> {
                 let variables = serde_json::json!({ #(#variables_json),* });
                 #query_build
-                client.execute::<T>(&query, variables, #data_path).await
+                #execute_call
             }
         };
 
         let client_method = quote! {
             #doc
-            pub async fn #method_name<T: DeserializeOwned + GraphQLFields<FullType = super::types::#node_type_ident>>(&self, #(#params),*) -> Result<T, LinearError> {
+            pub async fn #method_name<T: DeserializeOwned + GraphQLFields<FullType = super::types::#node_type_ident>>(&self, #(#params),*) -> Result<#return_type, LinearError> {
                 crate::generated::queries::#method_name::<T>(self, #(#call_args),*).await
             }
         };
@@ -309,6 +327,7 @@ fn emit_builder_query(
     rename: Option<&str>,
     args: &[ArgInfo],
     is_connection: bool,
+    is_nullable: bool,
     object_map: &HashMap<&str, &ObjectDef>,
     _type_kind_map: &HashMap<String, TypeKind>,
 ) -> QueryResult {
@@ -456,12 +475,24 @@ fn emit_builder_query(
             }
         };
 
+        let (return_type, execute_call) = if is_nullable {
+            (
+                quote! { Option<T> },
+                quote! { self.client.execute::<Option<T>>(&query, variables, #data_path).await },
+            )
+        } else {
+            (
+                quote! { T },
+                quote! { self.client.execute::<T>(&query, variables, #data_path).await },
+            )
+        };
+
         (
-            quote! { T },
+            return_type,
             quote! {
                 #build_variables
                 #query_build
-                self.client.execute::<T>(&query, variables, #data_path).await
+                #execute_call
             },
         )
     };

crates/lineark-sdk/src/field_selection.rs

@@ -45,6 +45,16 @@ pub trait GraphQLFields {
     fn selection() -> String;
 }
 
+// Nullable queries: Option<T> delegates to T's selection.
+// This allows `client.some_nullable_query::<Option<MyType>>()` to work
+// when the GraphQL schema returns a nullable type (e.g. `Issue` vs `Issue!`).
+impl<T: GraphQLFields> GraphQLFields for Option<T> {
+    type FullType = T::FullType;
+    fn selection() -> String {
+        T::selection()
+    }
+}
+
 /// Marker trait for compile-time field type compatibility.
 ///
 /// Validates that a full type's field type `Self` is compatible with a custom
@@ -68,3 +78,62 @@ impl<T> FieldCompatible<Option<T>> for Option<Box<T>> {}
 impl FieldCompatible<String> for chrono::DateTime<chrono::Utc> {}
 impl FieldCompatible<Option<String>> for Option<chrono::DateTime<chrono::Utc>> {}
 impl FieldCompatible<String> for Option<chrono::DateTime<chrono::Utc>> {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct FakeFullType;
+
+    struct FakeIssue;
+    impl GraphQLFields for FakeIssue {
+        type FullType = FakeFullType;
+        fn selection() -> String {
+            "id title url".to_string()
+        }
+    }
+
+    #[test]
+    fn option_delegates_selection_to_inner_type() {
+        assert_eq!(
+            <Option<FakeIssue> as GraphQLFields>::selection(),
+            "id title url"
+        );
+    }
+
+    #[test]
+    fn option_preserves_full_type() {
+        // Compile-time proof: Option<FakeIssue>::FullType == FakeFullType
+        fn assert_full_type<T: GraphQLFields<FullType = FakeFullType>>() {}
+        assert_full_type::<FakeIssue>();
+        assert_full_type::<Option<FakeIssue>>();
+    }
+
+    #[test]
+    fn option_nullable_query_deserialization() {
+        // Proves the full chain: Option<T> with GraphQLFields + serde handles null
+        #[derive(serde::Deserialize)]
+        struct MyIssue {
+            id: String,
+        }
+        impl GraphQLFields for MyIssue {
+            type FullType = FakeFullType;
+            fn selection() -> String {
+                "id".to_string()
+            }
+        }
+
+        // Null → None
+        let null_val = serde_json::Value::Null;
+        let result: Option<MyIssue> = serde_json::from_value(null_val).unwrap();
+        assert!(result.is_none());
+
+        // Object → Some
+        let obj_val = serde_json::json!({"id": "abc-123"});
+        let result: Option<MyIssue> = serde_json::from_value(obj_val).unwrap();
+        assert_eq!(result.unwrap().id, "abc-123");
+
+        // Selection works through Option
+        assert_eq!(<Option<MyIssue> as GraphQLFields>::selection(), "id");
+    }
+}

crates/lineark-sdk/src/generated/client_impl.rs

@@ -101,6 +101,17 @@ impl Client {
     ) -> Result<T, LinearError> {
         crate::generated::queries::issue::<T>(self, id).await
     }
+    /// Find issue based on the VCS branch name.
+    ///
+    /// Full type: [`Issue`](super::types::Issue)
+    pub async fn issue_vcs_branch_search<
+        T: DeserializeOwned + GraphQLFields<FullType = super::types::Issue>,
+    >(
+        &self,
+        branch_name: String,
+    ) -> Result<Option<T>, LinearError> {
+        crate::generated::queries::issue_vcs_branch_search::<T>(self, branch_name).await
+    }
     /// All issue relationships.
     ///
     /// Full type: [`IssueRelation`](super::types::IssueRelation)

crates/lineark-sdk/src/generated/queries.rs

@@ -1208,6 +1208,29 @@ pub async fn issue<T: DeserializeOwned + GraphQLFields<FullType = super::types::
     );
     client.execute::<T>(&query, variables, "issue").await
 }
+/// Find issue based on the VCS branch name.
+///
+/// Full type: [`Issue`](super::types::Issue)
+pub async fn issue_vcs_branch_search<
+    T: DeserializeOwned + GraphQLFields<FullType = super::types::Issue>,
+>(
+    client: &Client,
+    branch_name: String,
+) -> Result<Option<T>, LinearError> {
+    let variables = serde_json::json!({ "branchName" : branch_name });
+    let selection = T::selection();
+    let query = format!(
+        "query {}({}) {{ {}({}) {{ {} }} }}",
+        "IssueVcsBranchSearch",
+        "$branchName: String!",
+        "issueVcsBranchSearch",
+        "branchName: $branchName",
+        selection
+    );
+    client
+        .execute::<Option<T>>(&query, variables, "issueVcsBranchSearch")
+        .await
+}
 /// All issue relationships.
 ///
 /// Full type: [`IssueRelation`](super::types::IssueRelation)

schema/operations.toml

@@ -12,6 +12,7 @@ cycles = true
 cycle = true
 issueLabels = true
 searchIssues = true
+issueVcsBranchSearch = true
 workflowStates = true
 
 # Phase 3 — Rich features