json: fix negative min (w/ more than 1 digit)

common/json-schema-to-grammar.cpp

@@ -276,9 +276,9 @@ static void _generate_min_max_int(int min_value, int max_value, std::stringstrea
 
     if (has_min) {
         if (min_value < 0) {
-            out << "\"-\" ";
+            out << "\"-\" (";
             _generate_min_max_int(std::numeric_limits<int>::min(), -min_value, out, decimals_left, /* top_level= */ false);
-            out << " | [0] | [1-9] ";
+            out << ") | [0] | [1-9] ";
             more_digits(0, decimals_left - 1);
         } else if (min_value == 0) {
             if (top_level) {

tests/test-grammar-integration.cpp

@@ -199,6 +199,30 @@ static void test_simple_grammar() {
             "123",
         }
     );
+    test_schema(
+        "simple min -123",
+        R"""({
+            "type": "integer",
+            "minimum": -123
+        })""",
+        // Passing strings
+        {
+            "-123",
+            "-122",
+            "-11",
+            "-1",
+            "0",
+            "1",
+            "123",
+            "1234",
+            "2345",
+        },
+        // Failing strings
+        {
+            "-1234",
+            "-124",
+        }
+    );
 
     // Test case for a simple grammar
     test_grammar(

tests/test-json-schema-to-grammar.cpp

@@ -179,7 +179,21 @@ static void test_all(const std::string & lang, std::function<void(const TestCase
             "minimum": -5
         })""",
         R"""(
-            root ::= ("-" [0-5] | [0] | [1-9] [0-9]{0,15}) space
+            root ::= ("-" ([0-5]) | [0] | [1-9] [0-9]{0,15}) space
+            space ::= " "?
+        )"""
+    });
+
+    test({
+        SUCCESS,
+        "min -123",
+        R"""({
+            "type": "integer",
+            "minimum": -123
+        })""",
+        R"""(
+            root ::= ("-" ([0-9] | ([1-8] [0-9] | [9] [0-9]) | "1" ([0-1] [0-9] | [2] [0-3])) | [0] | [1-9] [0-9]{0,15}) space
+            space ::= " "?
         )"""
     });