[CI] Add /rerun-test --changed to rerun every test file a PR modifies (#37618)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-authored-by: Alison Shao <a.shao@wustl.edu>

docs/docs/developer_guide/contribution_guide.mdx

@@ -122,7 +122,7 @@ For CI to run on a pull request, it must have the "run-ci" label. Authorized use
 - `/tag-run-ci-label`: Adds the "run-ci" label. Only **future** commits trigger CI; the current commit is unaffected. Add the `extra` argument (`/tag-run-ci-label extra`) to additionally apply the "run-ci-extra" label, opting the PR into the extra test workflow (`pr-test-extra.yml`).
 - `/rerun-failed-ci`: Reruns workflows from the latest commit with conclusion **failed, skipped, cancelled, or timed out**.
 - `/tag-and-rerun-ci`: Runs both. Use this on a fresh PR to kick off CI on the current commit — `/tag-run-ci-label` alone won't. Accepts the same `extra` argument (`/tag-and-rerun-ci extra`).
-- `/rerun-test <test-spec> [<test-spec> ...]`: Reruns one or more specific tests directly. A spec may select a file, class, or method using `<file>::<TestClass>[.<test_method>]`. Multiple specs and file globs are supported. Examples: `/rerun-test test_srt_endpoint.py`, `/rerun-test registered/core/test_srt_endpoint.py::TestSRTEndpoint.test_simple_decode`, `/rerun-test test_a.py test_b.py`, or `/rerun-test test_*backend*.py`.
+- `/rerun-test <test-spec> [<test-spec> ...]`: Reruns one or more specific tests directly. A spec may select a file, class, or method using `<file>::<TestClass>[.<test_method>]`. Multiple specs and file globs are supported. `--changed` (short form `-c`) adds every test file the PR itself adds or modifies (under `test/registered/` or the multimodal test directory), so a PR that touches several tests can rerun them all without listing them. Examples: `/rerun-test test_srt_endpoint.py`, `/rerun-test registered/core/test_srt_endpoint.py::TestSRTEndpoint.test_simple_decode`, `/rerun-test test_a.py test_b.py`, `/rerun-test test_*backend*.py`, `/rerun-test --changed`, or `/rerun-test -c`.
 - `/rerun-group <group> [<group> ...]`: Expands one or more registered test groups (for example, `/rerun-group hicache`) and dispatches their tests through the same selective-rerun workflow.
 
 The rerun commands have the following permission rules:

scripts/ci/utils/slash_command_handler.py

@@ -30,6 +30,8 @@ PERMISSIONS_FILE_PATH = ".github/CI_PERMISSIONS.json"
 TEST_GROUPS_FILE_PATH = "scripts/ci/rerun_test_groups.json"
 PRECISION_BASELINE_TEST = "registered/debug_utils/test_nightly_precision_regression.py"
 PRECISION_BASELINE_REFRESH_FLAG = "--refresh-precision-baseline"
+CHANGED_TESTS_FLAG = "--changed"
+CHANGED_TESTS_SHORT_FLAG = "-c"
 
 
 MAINTENANCE_ISSUE_NUMBER = 21065
@@ -588,8 +590,8 @@ def expand_glob_spec(file_part):
     Globs are matched against the same locations resolve_test_file() searches
     — test/registered/ and the multimodal_gen test dir — so e.g.
     `test_*backend*.py` reruns every backend test without hand-enumerating
-    each file. Two constraints keep a broad pattern from pulling in non-tests:
+    each file. `_is_rerunnable_test_path` keeps a broad pattern from pulling in
-    a match must live under a known test root and be named `test_*.py`.
+    non-tests.
 
     glob's `*` matches path separators only via `**`, so a bare pattern is
     searched recursively under each root; a path-ful pattern is anchored.
@@ -628,19 +630,11 @@ def expand_glob_spec(file_part):
             expanded.add(p)
     matches = expanded
 
-    def _under_test_root(path):
-        return path.startswith("test/registered/") or path.startswith(
-            MULTIMODAL_TEST_DIR + "/"
-        )
-
     files = sorted(
         {
             os.path.normpath(p)
             for p in matches
-            if os.path.isfile(p)
+            if os.path.isfile(p) and _is_rerunnable_test_path(os.path.normpath(p))
-            and os.path.basename(p).startswith("test_")
-            and p.endswith(".py")
-            and _under_test_root(os.path.normpath(p))
         }
     )
     if not files:
@@ -652,6 +646,76 @@ def expand_glob_spec(file_part):
     return files, None
 
 
+def _collects_pytest_tests(path):
+    """Whether a test file defines anything pytest would collect."""
+    if not os.path.isfile(path):
+        # Fork-added file, absent from the handler's main checkout; leave it for
+        # resolve_test_file() to report as `File not found`.
+        return True
+    with open(path, "r", encoding="utf-8", errors="replace") as f:
+        content = f.read()
+    return (
+        re.search(r"^\s*((async )?def test_|class Test)", content, re.MULTILINE)
+        is not None
+    )
+
+
+def _is_rerunnable_test_path(path):
+    """A repo-relative test file /rerun-test may select on its own (glob or --changed)."""
+    under_test_root = path.startswith("test/registered/") or path.startswith(
+        MULTIMODAL_TEST_DIR + "/"
+    )
+    if (
+        not under_test_root
+        or not os.path.basename(path).startswith("test_")
+        or not path.endswith(".py")
+    ):
+        return False
+    if not path.startswith(MULTIMODAL_TEST_DIR + "/"):
+        # detect_suite() rejects an unregistered file, and a registered one may
+        # expose its cases through load_tests() rather than `def test_`.
+        return True
+    # Nothing downstream rejects a multimodal path, so a `test_*.py` helper that
+    # collects nothing reaches `pytest -x` and exits 5. manual/ is hand-run.
+    return "manual" not in path.split("/") and _collects_pytest_tests(path)
+
+
+def _move_changes_dispatch(previous_filename, filename):
+    """Whether a content-free move still changes how `filename` dispatches."""
+    previous_filename = previous_filename or ""
+    is_mm = filename.startswith(MULTIMODAL_TEST_DIR + "/")
+    if is_mm != previous_filename.startswith(MULTIMODAL_TEST_DIR + "/"):
+        return True
+    if not _is_rerunnable_test_path(previous_filename):
+        return True
+    return is_mm and (
+        detect_multimodal_suite(previous_filename)[0]
+        != detect_multimodal_suite(filename)[0]
+    )
+
+
+def changed_test_files(pr):
+    """Rerunnable test files the PR adds or edits, as repo-relative paths.
+
+    A pure move reports `renamed` with an empty diff and is dropped, unless the
+    move itself changes dispatch: into a CI root, across the multimodal
+    boundary, or onto a different multimodal pool.
+    """
+    return sorted(
+        f.filename
+        for f in pr.get_files()
+        if f.status != "removed"
+        and _is_rerunnable_test_path(f.filename)
+        and (
+            f.changes > 0
+            or (
+                f.status == "renamed"
+                and _move_changes_dispatch(f.previous_filename, f.filename)
+            )
+        )
+    )
+
+
 def resolve_test_file(file_part):
     """
     Resolve a user-provided file path to a path relative to test/ or full path for multimodal.
@@ -1196,6 +1260,7 @@ def handle_rerun_test(
     skip_permission_check=False,
     command_label=None,
     refresh_precision_baseline=False,
+    include_changed_tests=False,
 ):
     """
     Handles the /rerun-test command. Resolves all test specs, groups them by
@@ -1212,7 +1277,7 @@ def handle_rerun_test(
     ):
         return False
 
-    if not test_specs:
+    if not test_specs and not include_changed_tests:
         comment.create_reaction("confused")
         pr.create_issue_comment(
             "⛔ Please specify a test: `/rerun-test <file>::<TestClass.test_method>`\n\n"
@@ -1222,7 +1287,9 @@ def handle_rerun_test(
             "- `/rerun-test test_srt_endpoint.py`\n"
             "- `/rerun-test test_a.py test_b.py test_c.py` (multiple tests)\n"
             "- `/rerun-test test_*backend*.py` (wildcard — reruns every matching "
-            "file; wrap the pattern in backticks so GitHub keeps the `*` literal)"
+            "file; wrap the pattern in backticks so GitHub keeps the `*` literal)\n"
+            f"- `/rerun-test {CHANGED_TESTS_FLAG}` (or `{CHANGED_TESTS_SHORT_FLAG}`; "
+            "every test file this PR adds or modifies)"
         )
         return False
 
@@ -1232,6 +1299,17 @@ def handle_rerun_test(
         pr.create_issue_comment(gate_msg)
         return False
 
+    if include_changed_tests:
+        changed = changed_test_files(pr)
+        if not changed and not test_specs:
+            comment.create_reaction("confused")
+            pr.create_issue_comment(
+                f"⛔ `{CHANGED_TESTS_FLAG}`: this PR adds or modifies no runnable test files "
+                f"under `test/registered/` or `{MULTIMODAL_TEST_DIR}/`."
+            )
+            return False
+        test_specs = list(test_specs or []) + changed
+
     # Phase 0: Expand wildcard specs into concrete test files. A spec whose
     # file part contains a glob metacharacter (* ? [) expands to every
     # matching file; plain specs pass through to single-file resolution.
@@ -1542,9 +1620,10 @@ def main():
     elif first_line.startswith("/rerun-test"):
         rerun_args = first_line.split()[1:]
         refresh_precision_baseline = PRECISION_BASELINE_REFRESH_FLAG in rerun_args
-        test_specs = [
+        changed_flags = {CHANGED_TESTS_FLAG, CHANGED_TESTS_SHORT_FLAG}
-            arg for arg in rerun_args if arg != PRECISION_BASELINE_REFRESH_FLAG
+        include_changed_tests = bool(changed_flags & set(rerun_args))
-        ]
+        flags = changed_flags | {PRECISION_BASELINE_REFRESH_FLAG}
+        test_specs = [arg for arg in rerun_args if arg not in flags]
         handle_rerun_test(
             repo,
             pr,
@@ -1554,6 +1633,7 @@ def main():
             token,
             command_label=first_line,
             refresh_precision_baseline=refresh_precision_baseline,
+            include_changed_tests=include_changed_tests,
         )
 
     else:

test/registered/unit/tools/test_slash_command_handler.py

@@ -1,4 +1,4 @@
-"""Tests for declarative slash-command test groups."""
+"""Tests for slash-command test selection: declarative groups and `--changed`."""
 
 import importlib.util
 import json
@@ -7,7 +7,7 @@ import sys
 import tempfile
 import unittest
 from pathlib import Path
-from types import ModuleType
+from types import ModuleType, SimpleNamespace
 from unittest.mock import patch
 
 from sglang.test.ci.ci_register import register_cpu_ci
@@ -95,5 +95,105 @@ class TestConfiguredTestGroups(CustomTestCase):
             os.chdir(previous_cwd)
 
 
+class TestChangedTestFiles(CustomTestCase):
+    def test_only_dispatchable_changed_test_files_are_selected(self):
+        """`--changed` feeds the dispatcher directly, so every path it returns must
+        be runnable: no deleted tests, helpers, source, `manual/` files, or
+        multimodal `test_*.py` that collect nothing. A pure move is dropped only
+        when it leaves dispatch alone."""
+        handler = _load_handler()
+        mm = handler.MULTIMODAL_TEST_DIR
+        pr = SimpleNamespace(
+            get_files=lambda: [
+                SimpleNamespace(
+                    filename=name,
+                    status=status,
+                    changes=changes,
+                    previous_filename=previous,
+                )
+                for name, status, changes, previous in [
+                    (
+                        "test/registered/unit/mem_cache/test_radix_cache_unit.py",
+                        "modified",
+                        4,
+                        None,
+                    ),
+                    ("test/registered/core/test_srt_endpoint.py", "removed", 12, None),
+                    ("test/registered/unit/mem_cache/helpers.py", "modified", 2, None),
+                    ("python/sglang/srt/mem_cache/radix_cache.py", "modified", 7, None),
+                    ("test/manual/test_not_registered.py", "added", 20, None),
+                    (
+                        "test/registered/spec/test_moved_untouched.py",
+                        "renamed",
+                        0,
+                        "test/registered/core/test_moved_untouched.py",
+                    ),
+                    (
+                        "test/registered/spec/test_moved_into_ci.py",
+                        "renamed",
+                        0,
+                        "test/manual/test_moved_into_ci.py",
+                    ),
+                    (
+                        f"{mm}/2_gpu/test_moved_pool.py",
+                        "renamed",
+                        0,
+                        f"{mm}/unit/test_moved_pool.py",
+                    ),
+                    (
+                        "test/registered/spec/test_moved_and_edited.py",
+                        "renamed",
+                        9,
+                        "test/registered/core/test_moved_and_edited.py",
+                    ),
+                    (f"{mm}/server/test_server_common.py", "modified", 3, None),
+                    (f"{mm}/server/test_server_utils.py", "modified", 3, None),
+                    (f"{mm}/unit/manual/test_fp4_linear.py", "modified", 3, None),
+                    # Absent from the checkout, as a fork-added file is; kept so
+                    # resolve_test_file() reports `File not found` for it.
+                    (
+                        f"{mm}/server/test_server_added_by_fork.py",
+                        "added",
+                        30,
+                        None,
+                    ),
+                ]
+            ]
+        )
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp) / mm
+            (root / "server").mkdir(parents=True)
+            (root / "unit" / "manual").mkdir(parents=True)
+            (root / "2_gpu").mkdir(parents=True)
+            (root / "server" / "test_server_common.py").write_text(
+                "def test_diffusion_generation():\n    pass\n"
+            )
+            (root / "server" / "test_server_utils.py").write_text(
+                "def build_server():\n    return None\n"
+            )
+            (root / "unit" / "manual" / "test_fp4_linear.py").write_text(
+                "class TestFp4Linear:\n    def test_it(self):\n        pass\n"
+            )
+            (root / "2_gpu" / "test_moved_pool.py").write_text(
+                "def test_two_gpu():\n    pass\n"
+            )
+            previous_cwd = os.getcwd()
+            try:
+                os.chdir(tmp)
+                self.assertEqual(
+                    handler.changed_test_files(pr),
+                    [
+                        f"{mm}/2_gpu/test_moved_pool.py",
+                        f"{mm}/server/test_server_added_by_fork.py",
+                        f"{mm}/server/test_server_common.py",
+                        "test/registered/spec/test_moved_and_edited.py",
+                        "test/registered/spec/test_moved_into_ci.py",
+                        "test/registered/unit/mem_cache/test_radix_cache_unit.py",
+                    ],
+                )
+            finally:
+                os.chdir(previous_cwd)
+
+
 if __name__ == "__main__":
     unittest.main()