From 8d880ac012003de6fcddff0e9108e75703e68d8a Mon Sep 17 00:00:00 2001
From: Ray Xu <22774575+RayXu14@users.noreply.github.com>
Date: Tue, 10 Mar 2026 21:38:18 +0800
Subject: [PATCH] examples : fix empty items in json_schema_to_grammar.py [no
 ci] (#19968)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Fix logic for retrieving schema items in `json_schema_to_grammar.py`

If `schema['items']` is `{}` and `prefixItems not in schema', as `{}` is Falsy, the original code here will raise an error.

I think if `schema['items']` is `{}`, them items should just be `{}`

* Apply suggestion from @CISC

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Add tests for arrays with empty items

Add two unit tests to `tests/test-json-schema-to-grammar.cpp` that validate handling of arrays when 'items' is an empty schema and when 'prefixItems' is present alongside an empty 'items'. Both tests expect the same generated grammar, ensuring the JSON Schema->grammar conversion treats an empty 'items' schema (and the presence of 'prefixItems') correctly and covering this edge case.

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>
---
 examples/json_schema_to_grammar.py    |  2 +-
 tests/test-json-schema-to-grammar.cpp | 49 +++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/examples/json_schema_to_grammar.py b/examples/json_schema_to_grammar.py
index 35f7d47f3c..018ba49b24 100755
--- a/examples/json_schema_to_grammar.py
+++ b/examples/json_schema_to_grammar.py
@@ -633,7 +633,7 @@ class SchemaConverter:
             return self._add_rule(rule_name, self._build_object_rule(properties, required, hybrid_name, additional_properties=None))
 
         elif schema_type in (None, 'array') and ('items' in schema or 'prefixItems' in schema):
-            items = schema.get('items') or schema['prefixItems']
+            items = schema.get('items', schema.get('prefixItems'))
             if isinstance(items, list):
                 return self._add_rule(
                     rule_name,
diff --git a/tests/test-json-schema-to-grammar.cpp b/tests/test-json-schema-to-grammar.cpp
index eb33804c9a..ac697c4d24 100755
--- a/tests/test-json-schema-to-grammar.cpp
+++ b/tests/test-json-schema-to-grammar.cpp
@@ -569,6 +569,55 @@ static void test_all(const std::string & lang, std::function<void(const TestCase
         )"""
     });
 
+    test({
+        SUCCESS,
+        "array with empty items",
+        R"""({
+            "type": "array",
+            "items": {}
+        })""",
+        R"""(
+            array ::= "[" space ( value ("," space value)* )? "]" space
+            boolean ::= ("true" | "false") space
+            char ::= [^"\\\x7F\x00-\x1F] | [\\] (["\\bfnrt] | "u" [0-9a-fA-F]{4})
+            decimal-part ::= [0-9]{1,16}
+            integral-part ::= [0] | [1-9] [0-9]{0,15}
+            item ::= object
+            null ::= "null" space
+            number ::= ("-"? integral-part) ("." decimal-part)? ([eE] [-+]? integral-part)? space
+            object ::= "{" space ( string ":" space value ("," space string ":" space value)* )? "}" space
+            root ::= "[" space (item ("," space item)*)? "]" space
+            space ::= | " " | "\n"{1,2} [ \t]{0,20}
+            string ::= "\"" char* "\"" space
+            value ::= object | array | string | number | boolean | null
+        )"""
+    });
+
+    test({
+        SUCCESS,
+        "array with empty items and prefixItems",
+        R"""({
+            "type": "array",
+            "items": {},
+            "prefixItems": { "type": "string" }
+        })""",
+        R"""(
+            array ::= "[" space ( value ("," space value)* )? "]" space
+            boolean ::= ("true" | "false") space
+            char ::= [^"\\\x7F\x00-\x1F] | [\\] (["\\bfnrt] | "u" [0-9a-fA-F]{4})
+            decimal-part ::= [0-9]{1,16}
+            integral-part ::= [0] | [1-9] [0-9]{0,15}
+            item ::= object
+            null ::= "null" space
+            number ::= ("-"? integral-part) ("." decimal-part)? ([eE] [-+]? integral-part)? space
+            object ::= "{" space ( string ":" space value ("," space string ":" space value)* )? "}" space
+            root ::= "[" space (item ("," space item)*)? "]" space
+            space ::= | " " | "\n"{1,2} [ \t]{0,20}
+            string ::= "\"" char* "\"" space
+            value ::= object | array | string | number | boolean | null
+        )"""
+    });
+
     test({
         SUCCESS,
         "number",