⚡️ Speed up function get_runner by 79%

[codeflash-ai]

📄 79% (0.79x) speedup for get_runner in django/test/utils.py

⏱️ Runtime : 813 microseconds → 455 microseconds (best of 71 runs)

📝 Explanation and details

The optimization adds a module caching check using sys.modules.get() before calling the expensive __import__() function.

Key changes:

• Added import sys at the top
• Check if test_module_name already exists in sys.modules cache
• Only call __import__() if the module isn't already loaded

Why this is faster:
The line profiler shows that __import__() was the bottleneck, consuming 73% of execution time in the original code. Python's __import__() function performs file system operations, module compilation, and initialization - even for already-loaded modules. By checking sys.modules first (a simple dictionary lookup), we avoid this expensive operation when the module is already in memory.

Performance impact by test case:

• Repeated calls with same modules (229% faster): Maximum benefit since modules stay cached
• Many modules scenarios (193-196% faster): High benefit as modules get reused across test runs
• Basic single calls (87-123% faster): Moderate benefit even on first import due to standard library modules already being cached
• Error cases (1-37% faster): Minimal benefit since errors occur regardless, but slight improvement from faster cache check

The optimization is most effective for Django test scenarios where the same test runner classes are imported repeatedly across multiple test runs.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 381 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Generated Regression Tests and Runtime

import sys
import types

# imports
import pytest  # used for our unit tests
from django.test.utils import get_runner

# unit tests

# Helper: create dummy modules/classes in sys.modules for testing
def make_dummy_module(module_name, class_name):
    """Create a dummy module with a class, and inject into sys.modules."""
    mod = types.ModuleType(module_name)
    dummy_class = type(class_name, (), {})
    setattr(mod, class_name, dummy_class)
    sys.modules[module_name] = mod
    return dummy_class

# Helper: settings object
class DummySettings:
    def __init__(self, test_runner):
        self.TEST_RUNNER = test_runner

# Basic Test Cases

def test_get_runner_basic_absolute_path():
    """Test basic case with absolute module path and class name."""
    dummy_class = make_dummy_module("foo.bar", "BazRunner")
    settings = DummySettings("foo.bar.BazRunner")
    codeflash_output = get_runner(settings); runner = codeflash_output # 3.29μs -> 1.66μs (98.4% faster)

def test_get_runner_basic_with_test_runner_class_arg():
    """Test providing test_runner_class argument overrides settings."""
    dummy_class = make_dummy_module("foo.bar2", "BazRunner2")
    settings = DummySettings("foo.bar.BazRunner")  # Should be ignored
    codeflash_output = get_runner(settings, test_runner_class="foo.bar2.BazRunner2"); runner = codeflash_output # 3.44μs -> 1.73μs (99.0% faster)


def test_get_runner_edge_nonexistent_module():
    """Test with a module that does not exist."""
    settings = DummySettings("doesnotexist.FakeRunner")
    with pytest.raises(ModuleNotFoundError):
        get_runner(settings) # 106μs -> 104μs (1.53% faster)

def test_get_runner_edge_nonexistent_class():
    """Test with a class that does not exist in the module."""
    mod = types.ModuleType("foo.missingclass")
    sys.modules["foo.missingclass"] = mod
    settings = DummySettings("foo.missingclass.NoSuchRunner")
    with pytest.raises(AttributeError):
        get_runner(settings) # 4.61μs -> 3.48μs (32.2% faster)

def test_get_runner_edge_empty_string():
    """Test with empty string as TEST_RUNNER."""
    settings = DummySettings("")
    with pytest.raises(ValueError):
        get_runner(settings) # 20.9μs -> 21.4μs (2.61% slower)

def test_get_runner_edge_module_with_multiple_classes():
    """Test module with multiple classes, ensure correct one is picked."""
    mod = types.ModuleType("foo.multi")
    class RunnerA: pass
    class RunnerB: pass
    setattr(mod, "RunnerA", RunnerA)
    setattr(mod, "RunnerB", RunnerB)
    sys.modules["foo.multi"] = mod
    settings = DummySettings("foo.multi.RunnerB")
    codeflash_output = get_runner(settings); runner = codeflash_output # 3.67μs -> 1.65μs (123% faster)


def test_get_runner_edge_test_runner_class_is_none_and_settings_missing_attr():
    """Test with test_runner_class=None and settings missing TEST_RUNNER attr."""
    class EmptySettings: pass
    settings = EmptySettings()
    with pytest.raises(AttributeError):
        get_runner(settings) # 1.53μs -> 1.51μs (1.19% faster)

def test_get_runner_edge_test_runner_class_is_not_string():
    """Test with test_runner_class not a string."""
    settings = DummySettings("foo.bar.BazRunner")
    with pytest.raises(AttributeError):
        get_runner(settings, test_runner_class=123) # 1.44μs -> 1.43μs (0.280% faster)


def test_get_runner_large_scale_many_modules():
    """Test with many dummy modules/classes to check scalability."""
    # Create 100 dummy modules/classes
    for i in range(100):
        module_name = f"bulkmod{i}"
        class_name = f"BulkRunner{i}"
        make_dummy_module(module_name, class_name)
        settings = DummySettings(f"{module_name}.{class_name}")
        codeflash_output = get_runner(settings); runner = codeflash_output # 142μs -> 47.9μs (196% faster)

def test_get_runner_large_scale_long_module_path():
    """Test with a long module path (depth 10)."""
    # Create a chain of modules: mod0.mod1.mod2....mod9
    # We'll inject the deepest module into sys.modules
    module_path = ".".join([f"mod{i}" for i in range(10)])
    class_name = "DeepRunner"
    make_dummy_module(module_path, class_name)
    settings = DummySettings(f"{module_path}.{class_name}")
    codeflash_output = get_runner(settings); runner = codeflash_output # 3.50μs -> 1.87μs (87.4% faster)

def test_get_runner_large_scale_long_class_name():
    """Test with a very long class name."""
    module_name = "longclassmod"
    class_name = "Runner" + "X" * 200
    make_dummy_module(module_name, class_name)
    settings = DummySettings(f"{module_name}.{class_name}")
    codeflash_output = get_runner(settings); runner = codeflash_output # 3.15μs -> 1.49μs (111% faster)

def test_get_runner_large_scale_repeated_calls():
    """Test repeated calls for same module/class to check for caching/side effects."""
    module_name = "repeatmod"
    class_name = "RepeatRunner"
    dummy_class = make_dummy_module(module_name, class_name)
    settings = DummySettings(f"{module_name}.{class_name}")
    for _ in range(100):
        codeflash_output = get_runner(settings); runner = codeflash_output # 127μs -> 38.9μs (229% faster)

def test_get_runner_large_scale_with_similar_names():
    """Test with modules/classes with similar names to check correct resolution."""
    for i in range(10):
        module_name = f"simmod{i}"
        class_name = f"SimRunner{i}"
        make_dummy_module(module_name, class_name)
    # Now test picking correct class from correct module
    for i in range(10):
        settings = DummySettings(f"simmod{i}.SimRunner{i}")
        codeflash_output = get_runner(settings); runner = codeflash_output # 15.3μs -> 5.35μs (187% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
import sys
import types

# imports
import pytest  # used for our unit tests
from django.test.utils import get_runner


# helper: dummy settings object
class DummySettings:
    def __init__(self, test_runner):
        self.TEST_RUNNER = test_runner

# helper: dynamically create modules/classes for testing
def create_module_with_class(module_name, class_name):
    mod = types.ModuleType(module_name)
    cls = type(class_name, (), {})
    setattr(mod, class_name, cls)
    sys.modules[module_name] = mod
    return mod, cls

def remove_module(module_name):
    sys.modules.pop(module_name, None)

# Basic Test Cases

def test_get_runner_basic_absolute_import():
    """Test absolute import path with module and class."""
    module_name = "mytestmodule"
    class_name = "MyTestRunner"
    create_module_with_class(module_name, class_name)
    settings = DummySettings(f"{module_name}.{class_name}")
    codeflash_output = get_runner(settings); runner_cls = codeflash_output # 2.93μs -> 1.41μs (108% faster)
    remove_module(module_name)

def test_get_runner_basic_with_explicit_test_runner_class():
    """Test providing test_runner_class argument explicitly."""
    module_name = "othermodule"
    class_name = "OtherRunner"
    create_module_with_class(module_name, class_name)
    settings = DummySettings("unused.module.Class")
    codeflash_output = get_runner(settings, f"{module_name}.{class_name}"); runner_cls = codeflash_output # 2.83μs -> 1.36μs (108% faster)
    remove_module(module_name)


def test_get_runner_edge_nonexistent_module():
    """Test when module does not exist, should raise ImportError."""
    settings = DummySettings("nonexistent.module.Runner")
    with pytest.raises(ImportError):
        get_runner(settings) # 114μs -> 111μs (2.32% faster)

def test_get_runner_edge_nonexistent_class():
    """Test when class does not exist in module, should raise AttributeError."""
    module_name = "modwithnoclass"
    class_name = "NoSuchClass"
    mod = types.ModuleType(module_name)
    sys.modules[module_name] = mod
    settings = DummySettings(f"{module_name}.{class_name}")
    with pytest.raises(AttributeError):
        get_runner(settings) # 4.97μs -> 3.61μs (37.9% faster)
    remove_module(module_name)

def test_get_runner_edge_empty_test_runner_class():
    """Test when test_runner_class is empty string."""
    settings = DummySettings("")
    with pytest.raises(ValueError):
        # __import__ with '.' and empty class will fail
        get_runner(settings) # 20.2μs -> 21.0μs (3.78% slower)

def test_get_runner_edge_none_test_runner_class():
    """Test when test_runner_class is None and settings.TEST_RUNNER is also None."""
    settings = DummySettings(None)
    with pytest.raises(AttributeError):
        get_runner(settings) # 1.09μs -> 1.20μs (8.70% slower)

def test_get_runner_edge_module_with_dot_in_name():
    """Test module with dot in name (submodule)."""
    # Create a package and submodule
    pkg_name = "pkg"
    submodule_name = "pkg.submod"
    class_name = "SubRunner"
    pkg = types.ModuleType(pkg_name)
    submod = types.ModuleType(submodule_name)
    setattr(submod, class_name, type(class_name, (), {}))
    sys.modules[pkg_name] = pkg
    sys.modules[submodule_name] = submod
    settings = DummySettings(f"{submodule_name}.{class_name}")
    codeflash_output = get_runner(settings); runner_cls = codeflash_output # 3.86μs -> 1.70μs (128% faster)
    remove_module(submodule_name)
    remove_module(pkg_name)


def test_get_runner_edge_module_is_builtin():
    """Test importing a builtin module and getting a builtin class."""
    settings = DummySettings("builtins.str")
    codeflash_output = get_runner(settings); runner_cls = codeflash_output # 4.19μs -> 1.94μs (117% faster)


def test_get_runner_large_scale_many_modules():
    """Test with many dynamically created modules and classes."""
    num_modules = 100
    for i in range(num_modules):
        module_name = f"mod{i}"
        class_name = f"Runner{i}"
        create_module_with_class(module_name, class_name)
        settings = DummySettings(f"{module_name}.{class_name}")
        codeflash_output = get_runner(settings); runner_cls = codeflash_output # 142μs -> 48.6μs (193% faster)
        remove_module(module_name)

def test_get_runner_large_scale_long_module_path():
    """Test with long module path (deeply nested)."""
    # Simulate package.subpackage.subsubpackage.module.Class
    base = "pkg"
    num_levels = 10
    module_path = ".".join([base] + [f"sub{i}" for i in range(num_levels)]) + ".mod"
    class_name = "DeepRunner"
    # Create all parent packages
    full_module_name = module_path
    mod = types.ModuleType(full_module_name)
    setattr(mod, class_name, type(class_name, (), {}))
    sys.modules[full_module_name] = mod
    settings = DummySettings(f"{full_module_name}.{class_name}")
    codeflash_output = get_runner(settings); runner_cls = codeflash_output # 3.73μs -> 2.10μs (77.3% faster)
    remove_module(full_module_name)

def test_get_runner_large_scale_long_class_name():
    """Test with very long class name."""
    module_name = "longmod"
    class_name = "Runner" + "X" * 500
    create_module_with_class(module_name, class_name)
    settings = DummySettings(f"{module_name}.{class_name}")
    codeflash_output = get_runner(settings); runner_cls = codeflash_output # 3.39μs -> 1.84μs (84.0% faster)
    remove_module(module_name)

def test_get_runner_large_scale_multiple_calls():
    """Test calling get_runner repeatedly with different modules/classes."""
    modules = []
    for i in range(50):
        module_name = f"multi{i}"
        class_name = f"MultiRunner{i}"
        create_module_with_class(module_name, class_name)
        modules.append((module_name, class_name))
    for module_name, class_name in modules:
        settings = DummySettings(f"{module_name}.{class_name}")
        codeflash_output = get_runner(settings); runner_cls = codeflash_output # 69.4μs -> 23.6μs (194% faster)
        remove_module(module_name)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-get_runner-mh6jwhvj and push.