[Feature] support regex strings as a stopping condition (#10635)

test/srt/openai_server/validation/test_matched_stop.py

@@ -3,6 +3,7 @@ import unittest
 
 import requests
 
+from sglang.srt.sampling.sampling_params import MAX_LEN, get_max_seq_length
 from sglang.srt.utils import kill_process_tree
 from sglang.test.test_utils import (
     DEFAULT_MODEL_NAME_FOR_TEST,
@@ -40,6 +41,7 @@ class TestMatchedStop(CustomTestCase):
         prompt=MANY_NEW_TOKENS_PROMPT,
         max_tokens=1,
         stop=None,
+        stop_regex=None,
         finish_reason=None,
         matched_stop=None,
     ):
@@ -54,6 +56,9 @@ class TestMatchedStop(CustomTestCase):
         if stop is not None:
             payload["stop"] = stop
 
+        if stop_regex is not None:
+            payload["stop_regex"] = stop_regex
+
         response_completions = requests.post(
             self.base_url + "/v1/completions",
             json=payload,
@@ -71,6 +76,7 @@ class TestMatchedStop(CustomTestCase):
         prompt=MANY_NEW_TOKENS_PROMPT,
         max_tokens=1,
         stop=None,
+        stop_regex=None,
         finish_reason=None,
         matched_stop=None,
     ):
@@ -88,6 +94,9 @@ class TestMatchedStop(CustomTestCase):
         if stop is not None:
             chat_payload["stop"] = stop
 
+        if stop_regex is not None:
+            chat_payload["stop_regex"] = stop_regex
+
         response_chat = requests.post(
             self.base_url + "/v1/chat/completions",
             json=chat_payload,
@@ -106,6 +115,30 @@ class TestMatchedStop(CustomTestCase):
             max_tokens=1000, stop="\n", finish_reason="stop", matched_stop="\n"
         )
 
+    def test_finish_stop_regex_str(self):
+        STOP_REGEX_STR = r"and|or"
+        self.run_completions_generation(
+            max_tokens=1000,
+            stop_regex=STOP_REGEX_STR,
+            finish_reason="stop",
+            matched_stop=STOP_REGEX_STR,
+        )
+        self.run_chat_completions_generation(
+            max_tokens=1000,
+            stop_regex=STOP_REGEX_STR,
+            finish_reason="stop",
+            matched_stop=STOP_REGEX_STR,
+        )
+
+        # Match a complete sentence
+        STOP_REGEX_STR_SENTENCE = r"[.!?]\s*$"
+        self.run_chat_completions_generation(
+            max_tokens=1000,
+            stop_regex=STOP_REGEX_STR_SENTENCE,
+            finish_reason="stop",
+            matched_stop=STOP_REGEX_STR_SENTENCE,
+        )
+
     def test_finish_stop_eos(self):
         llama_format_prompt = """
         <|begin_of_text|><|start_header_id|>system<|end_header_id|>
@@ -136,5 +169,53 @@ class TestMatchedStop(CustomTestCase):
         )
 
 
+class TestRegexPatternMaxLength(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.regex_str_to_max_len = {
+            "((ab|cd(e|f){2}){3,5}g|hij)*k": MAX_LEN,
+            # - '*' → infinite tokens need to be stored
+            "abc*?k": MAX_LEN,
+            # - '*?' → infinite tokens still need to be stored even if lazy matching used
+            "^spec(foo|at)$": 7,
+            # - '^' and '$' don't add any characters to the max length
+            # "spec" → 4
+            # "(foo|at)" → max(3, 2) = 3
+            # Whole regex = 7
+            "(a(bca|de(fg|hi){2,3})j){2}kl": 22,
+            # - Innermost alt: "fg" vs "hi" → 2
+            # - Repeat {2,3}: max = 3 * 2 = 6
+            # - Inner group "de(...)": 2 (for "de") + 6 = 8.
+            # - "bca" or "de(...)" → max(3, 8) = 8
+            # - Whole group: "a" (1) + group (8) + "j"(1) = 10
+            # - Repeat {2} → 20
+            # - Add "kl"(2) → 22
+            "(foo(bar|baz(qux){1,2}))|(x(yz){5,10})": 21,
+            # Branch 1:
+            #   "foo"(3) + max("bar"(3), "baz"(3)+"qux"{2} = 3 + 6 = 9) = 3 + 9 = 12
+            # Branch 2:
+            #   "x"(1) + "yz"{10} = 1 + 20 =21
+            # Whole regex = max(12, 21) = 21
+            "(((a|bc){1,3}(d(e|f){2}|gh){2,4})|(ijk|lmp(no|p){3})){5}": 90,
+            # Branch A:
+            #   (a|bc){1,3} → max = 3 * 2 = 6
+            #   Inside: d(e|f){2} = 1 + 2 * 1 = 3 vs gh = 2 → max = 3
+            #   Repeat {2,4} → 4 * 3 = 12
+            #   Branch A total = 18
+            # Branch B:
+            #   "ijk"(3) vs "lmp(no|p){3}" = 3 + 3 * max(2, 1) = 3 + 6 = 9 → max = 9
+            #   Branch B total = 9
+            # Whole outer alt = max(18, 9) = 18
+            # Repeat {5} → 90
+        }
+
+    def test_get_max_length(self):
+        for regex_str, max_len in self.regex_str_to_max_len.items():
+            if max_len == MAX_LEN:
+                self.assertGreaterEqual(get_max_seq_length(regex_str), MAX_LEN)
+            else:
+                self.assertEqual(get_max_seq_length(regex_str), max_len)
+
+
 if __name__ == "__main__":
     unittest.main()