jinja : add missing 'in' test to template engine (#19004) (#19239)

* jinja : add missing 'in' test to template engine (#19004)

The jinja template parser was missing the 'in' test from
global_builtins(), causing templates using reject("in", ...),
select("in", ...), or 'x is in(y)' to fail with
"selectattr: unknown test 'in'".

This broke tool-calling for Qwen3-Coder and any other model
whose chat template uses the 'in' test.

Added test_is_in supporting array, string, and object containment
checks, mirroring the existing 'in' operator logic in runtime.cpp.

Includes test cases for all three containment types plus
reject/select filter usage.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* reuse test_is_in in binary op

---------

Co-authored-by: Sid Mohan <sidmohan0@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

tests/test-jinja.cpp

@@ -189,12 +189,24 @@ static void test_conditionals(testing & t) {
         "negated"
     );
 
-    test_template(t, "in operator",
+    test_template(t, "in operator (element in array)",
         "{% if 'x' in items %}found{% endif %}",
         {{"items", json::array({"x", "y"})}},
         "found"
     );
 
+    test_template(t, "in operator (substring)",
+        "{% if 'bc' in 'abcd' %}found{% endif %}",
+        json::object(),
+        "found"
+    );
+
+    test_template(t, "in operator (object key)",
+        "{% if 'key' in obj %}found{% endif %}",
+        {{"obj", {{"key", 1}, {"other", 2}}}},
+        "found"
+    );
+
     test_template(t, "is defined",
         "{% if x is defined %}yes{% else %}no{% endif %}",
         {{"x", 1}},
@@ -1036,6 +1048,42 @@ static void test_tests(testing & t) {
         json::object(),
         "yes"
     );
+
+    test_template(t, "is in (array, true)",
+        "{{ 'yes' if 2 is in([1, 2, 3]) }}",
+        json::object(),
+        "yes"
+    );
+
+    test_template(t, "is in (array, false)",
+        "{{ 'yes' if 5 is in([1, 2, 3]) else 'no' }}",
+        json::object(),
+        "no"
+    );
+
+    test_template(t, "is in (string)",
+        "{{ 'yes' if 'bc' is in('abcde') }}",
+        json::object(),
+        "yes"
+    );
+
+    test_template(t, "is in (object keys)",
+        "{{ 'yes' if 'a' is in(obj) }}",
+        {{"obj", {{"a", 1}, {"b", 2}}}},
+        "yes"
+    );
+
+    test_template(t, "reject with in test",
+        "{{ items | reject('in', skip) | join(', ') }}",
+        {{"items", json::array({"a", "b", "c", "d"})}, {"skip", json::array({"b", "d"})}},
+        "a, c"
+    );
+
+    test_template(t, "select with in test",
+        "{{ items | select('in', keep) | join(', ') }}",
+        {{"items", json::array({"a", "b", "c", "d"})}, {"keep", json::array({"b", "c"})}},
+        "b, c"
+    );
 }
 
 static void test_string_methods(testing & t) {