From 9894e0386d0b0ae4139f3255a00d26629d42190e Mon Sep 17 00:00:00 2001
From: inciarmors <mors.jpg@gmail.com>
Date: Fri, 23 Oct 2026 15:07:05 +0200
Subject: [PATCH] fix(schema): preserve strict array length and uniqueness
 constraints

---
 deepseek-recipe/src/protocol/json_schema.rs   | 32 ++++++++
 .../tests/strict_array_constraints.rs         | 80 +++++++++++++++++++
 2 files changed, 112 insertions(+)
 create mode 100644 deepseek-recipe/tests/strict_array_constraints.rs

diff --git a/deepseek-recipe/src/protocol/json_schema.rs b/deepseek-recipe/src/protocol/json_schema.rs
index f00a97d..a6b8d6b 100644
--- a/deepseek-recipe/src/protocol/json_schema.rs
+++ b/deepseek-recipe/src/protocol/json_schema.rs
@@ -2,6 +2,7 @@
 //!
 //! Strict schemas are deserialized into this type and normalized: every object
 //! lists all of its properties as required and forbids additional properties.
+//! Array length and uniqueness constraints are preserved during normalization.
 //! Non-strict schemas are only validated; see [`validate_schema`].
 
 use deepseek_recipe_macros::UntaggedDeserialize;
@@ -127,6 +128,12 @@ pub(crate) enum JsonSchemaType {
         items: Box<JsonSchema>,
         #[serde(skip_serializing_if = "Option::is_none")]
         description: Option<String>,
+        #[serde(skip_serializing_if = "Option::is_none")]
+        min_items: Option<u64>,
+        #[serde(skip_serializing_if = "Option::is_none")]
+        max_items: Option<u64>,
+        #[serde(skip_serializing_if = "Option::is_none")]
+        unique_items: Option<bool>,
     },
     #[serde(rename_all = "camelCase")]
     Null {
@@ -316,6 +323,31 @@ mod tests {
         );
     }
 
+    #[test]
+    fn normalize_preserves_nested_array_constraints_and_normalizes_item_objects() {
+        let normalized = normalize(json!({
+            "type": "object",
+            "properties": {"groups": {
+                "type": "array", "minItems": 1, "maxItems": 2, "uniqueItems": true,
+                "items": {
+                    "type": "array", "minItems": 0, "maxItems": 0, "uniqueItems": false,
+                    "items": {"type": "object", "properties": {"name": {"type": "string"}}},
+                },
+            }},
+        }))
+        .expect("the schema normalizes");
+        let groups = &normalized["properties"]["groups"];
+        assert_eq!(groups["minItems"], 1);
+        assert_eq!(groups["maxItems"], 2);
+        assert_eq!(groups["uniqueItems"], true);
+        let items = &groups["items"];
+        assert_eq!(items["minItems"], 0);
+        assert_eq!(items["maxItems"], 0);
+        assert_eq!(items["uniqueItems"], false);
+        assert_eq!(items["items"]["required"], json!(["name"]));
+        assert_eq!(items["items"]["additionalProperties"], false);
+    }
+
     #[test]
     fn normalize_rejects_inconsistent_required_lists() {
         let base = json!({"type": "object", "properties": {"a": {"type": "string"}}});
diff --git a/deepseek-recipe/tests/strict_array_constraints.rs b/deepseek-recipe/tests/strict_array_constraints.rs
new file mode 100644
index 0000000..73c2ffd
--- /dev/null
+++ b/deepseek-recipe/tests/strict_array_constraints.rs
@@ -0,0 +1,80 @@
+use deepseek_recipe::openai::{ChatCompletionRequest, ResponsesRequest};
+use deepseek_recipe::request::{
+    ConversationRequest, ConversionOptions, OutputConstraint, ProtocolRequest,
+};
+use serde::de::DeserializeOwned;
+use serde_json::{Value, json};
+
+fn convert<T: ProtocolRequest + DeserializeOwned>(request: Value) -> ConversationRequest {
+    serde_json::from_value::<T>(request)
+        .expect("the request deserializes")
+        .convert(ConversionOptions::default())
+        .expect("the request converts")
+}
+
+#[test]
+fn strict_array_constraints_survive_protocol_conversion() {
+    let schema = json!({
+        "type": "object",
+        "properties": {
+            "labels": {
+                "type": "array", "items": {"type": "string"},
+                "minItems": 2, "maxItems": 3, "uniqueItems": true,
+            },
+        },
+    });
+    let model = "DeepSeek-V4.1-Flash";
+    let messages = json!([{"role": "user", "content": "Return JSON labels."}]);
+    let function = json!({"name": "label", "parameters": schema, "strict": true});
+    let requests = [
+        convert::<ChatCompletionRequest>(json!({
+            "model": model, "messages": messages,
+            "tools": [{"type": "function", "function": function}],
+        })),
+        convert::<ResponsesRequest>(json!({
+            "model": model, "input": "Return labels.",
+            "tools": [{"type": "function", "name": "label", "parameters": schema, "strict": true}],
+        })),
+        convert::<ChatCompletionRequest>(json!({
+            "model": model, "messages": messages,
+            "response_format": {"type": "json_schema", "json_schema": {
+                "name": "labels", "schema": schema, "strict": true,
+            }},
+        })),
+        convert::<ResponsesRequest>(json!({
+            "model": model, "input": "Return JSON labels.",
+            "text": {"format": {"type": "json_schema", "name": "labels", "schema": schema, "strict": true}},
+        })),
+    ];
+
+    for request in requests {
+        let normalized = match request.inference_options.output_constraint.unwrap() {
+            OutputConstraint::ToolCalls { tools, .. } => {
+                assert_eq!(
+                    request.conversation.tools[0].parameters,
+                    tools[0].parameters
+                );
+                tools[0].parameters.clone()
+            }
+            OutputConstraint::Json {
+                schema: Some(schema),
+            } => schema,
+            other => panic!("unexpected constraint: {other:?}"),
+        };
+        let validator = jsonschema::validator_for(&normalized).expect("valid normalized schema");
+        for labels in [json!(["a", "b"]), json!(["a", "b", "c"])] {
+            assert!(validator.is_valid(&json!({"labels": labels})));
+        }
+        for labels in [
+            json!([]),
+            json!(["a"]),
+            json!(["a", "b", "c", "d"]),
+            json!(["a", "a"]),
+        ] {
+            assert!(
+                !validator.is_valid(&json!({"labels": labels})),
+                "normalized schema accepted invalid labels {labels}: {normalized}"
+            );
+        }
+    }
+}