From df46a438b8a641fffb11a1d72e774b7059499762 Mon Sep 17 00:00:00 2001
From: Ettore Di Giacinto <mudler@users.noreply.github.com>
Date: Wed, 8 Oct 2025 19:13:40 +0200
Subject: [PATCH] fix(grammars): handle empty parameters on object types
 (#6409)

fix: handle empty parameters on object types

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
---
 core/http/endpoints/openai/chat.go         |  6 ++++
 pkg/functions/grammars/json_schema.go      |  6 +++-
 pkg/functions/grammars/json_schema_test.go | 34 ++++++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/core/http/endpoints/openai/chat.go b/core/http/endpoints/openai/chat.go
index a19828450..4e91a5329 100644
--- a/core/http/endpoints/openai/chat.go
+++ b/core/http/endpoints/openai/chat.go
@@ -247,6 +247,8 @@ func ChatEndpoint(cl *config.ModelConfigLoader, ml *model.ModelLoader, evaluator
 				g, err := fs.Grammar(config.FunctionsConfig.GrammarOptions()...)
 				if err == nil {
 					input.Grammar = g
+				} else {
+					log.Error().Err(err).Msg("Failed generating grammar")
 				}
 			}
 		}
@@ -286,11 +288,15 @@ func ChatEndpoint(cl *config.ModelConfigLoader, ml *model.ModelLoader, evaluator
 			g, err := jsStruct.Grammar(config.FunctionsConfig.GrammarOptions()...)
 			if err == nil {
 				config.Grammar = g
+			} else {
+				log.Error().Err(err).Msg("Failed generating grammar")
 			}
 		case input.JSONFunctionGrammarObject != nil:
 			g, err := input.JSONFunctionGrammarObject.Grammar(config.FunctionsConfig.GrammarOptions()...)
 			if err == nil {
 				config.Grammar = g
+			} else {
+				log.Error().Err(err).Msg("Failed generating grammar")
 			}
 		default:
 			// Force picking one of the functions by the request
diff --git a/pkg/functions/grammars/json_schema.go b/pkg/functions/grammars/json_schema.go
index df4ca6a13..df05a914d 100644
--- a/pkg/functions/grammars/json_schema.go
+++ b/pkg/functions/grammars/json_schema.go
@@ -171,10 +171,14 @@ func (sc *JSONSchemaConverter) visit(schema map[string]interface{}, name string,
 		}
 		rule := fmt.Sprintf(`"[" space (%s ("," space %s)*)? "]" space`, itemRuleName, itemRuleName)
 		return sc.addRule(ruleName, rule), nil
+	} else if properties, _ := schema["properties"].(map[string]interface{}); (schemaType == "object" || schemaType == "") && len(properties) == 0 {
+		// Handle empty object schema (no properties)
+		rule := `"{" space "}" space`
+		return sc.addRule(ruleName, rule), nil
 	} else {
 		primitiveRule, exists := PRIMITIVE_RULES[schemaType]
 		if !exists {
-			return "", fmt.Errorf("unrecognized schema: %v", schema)
+			return "", fmt.Errorf("unrecognized schema: %v (type: %s)", schema, schemaType)
 		}
 		if ruleName == "root" {
 			schemaType = "root"
diff --git a/pkg/functions/grammars/json_schema_test.go b/pkg/functions/grammars/json_schema_test.go
index 5fc4a6029..2b2c5d22b 100644
--- a/pkg/functions/grammars/json_schema_test.go
+++ b/pkg/functions/grammars/json_schema_test.go
@@ -442,5 +442,39 @@ realvalue
 				}
 			}
 		})
+
+		It("handles empty object schema without properties", func() {
+			// Test case for the bug fix: schema with empty properties map
+			emptyObjectSchema := `{
+				"type": "object",
+				"properties": {}
+			}`
+
+			grammar, err := NewJSONSchemaConverter("").GrammarFromBytes([]byte(emptyObjectSchema))
+			Expect(err).To(BeNil())
+			Expect(grammar).To(ContainSubstring(`root ::= "{" space "}" space`))
+		})
+
+		It("handles object schema without properties field", func() {
+			// Test case for object schema without properties field at all
+			objectWithoutProperties := `{
+				"type": "object"
+			}`
+
+			grammar, err := NewJSONSchemaConverter("").GrammarFromBytes([]byte(objectWithoutProperties))
+			Expect(err).To(BeNil())
+			Expect(grammar).To(ContainSubstring(`root ::= "{" space "}" space`))
+		})
+
+		It("handles schema with properties but no type field", func() {
+			// Test case for the exact scenario causing the panic: schema with properties but no type
+			schemaWithPropertiesNoType := `{
+				"properties": {}
+			}`
+
+			grammar, err := NewJSONSchemaConverter("").GrammarFromBytes([]byte(schemaWithPropertiesNoType))
+			Expect(err).To(BeNil())
+			Expect(grammar).To(ContainSubstring(`root ::= "{" space "}" space`))
+		})
 	})
 })