Refactor plugin and tests into multiple files (#78)

Author: lysnikolaou

src/pytest_run_parallel/cpu_detection.py

@@ -0,0 +1,36 @@
+def get_logical_cpus():
+    try:
+        import psutil
+    except ImportError:
+        pass
+    else:
+        process = psutil.Process()
+        try:
+            cpu_cores = process.cpu_affinity()
+            return len(cpu_cores)
+        except AttributeError:
+            cpu_cores = psutil.cpu_count()
+            if cpu_cores is not None:
+                return cpu_cores
+
+    try:
+        from os import process_cpu_count
+    except ImportError:
+        pass
+    else:
+        cpu_cores = process_cpu_count()
+        if cpu_cores is not None:
+            return cpu_cores
+
+    try:
+        from os import sched_getaffinity
+    except ImportError:
+        pass
+    else:
+        cpu_cores = sched_getaffinity(0)
+        if cpu_cores is not None:
+            return len(cpu_cores)
+
+    from os import cpu_count
+
+    return cpu_count()

src/pytest_run_parallel/plugin.py

@@ -7,12 +7,12 @@
 import _pytest.outcomes
 import pytest
 
-from pytest_run_parallel.utils import (
-    ThreadComparator,
-    get_configured_num_workers,
-    get_num_workers,
+from pytest_run_parallel.thread_comparator import ThreadComparator
+from pytest_run_parallel.thread_unsafe_detection import (
+    THREAD_UNSAFE_FIXTURES,
     identify_thread_unsafe_nodes,
 )
+from pytest_run_parallel.utils import get_configured_num_workers, get_num_workers
 
 
 def pytest_addoption(parser):
@@ -140,13 +140,6 @@ def closure(*args, **kwargs):
     return inner
 
 
-_thread_unsafe_fixtures = {
-    "capsys",
-    "monkeypatch",
-    "recwarn",
-}
-
-
 @pytest.hookimpl(trylast=True)
 def pytest_itemcollected(item):
     n_workers = get_num_workers(item.config, item)
@@ -207,7 +200,7 @@ def pytest_itemcollected(item):
             else:
                 item.add_marker(pytest.mark.parallel_threads(1))
 
-    unsafe_fixtures = _thread_unsafe_fixtures | set(
+    unsafe_fixtures = THREAD_UNSAFE_FIXTURES | set(
         item.config.getini("thread_unsafe_fixtures")
     )
 

src/pytest_run_parallel/thread_comparator.py

@@ -0,0 +1,73 @@
+import threading
+import types
+
+try:
+    import numpy as np
+
+    numpy_available = True
+except ImportError:
+    numpy_available = False
+
+
+class ThreadComparator:
+    def __init__(self, n_threads):
+        self._barrier = threading.Barrier(n_threads)
+        self._reset_evt = threading.Event()
+        self._entry_barrier = threading.Barrier(n_threads)
+
+        self._thread_ids = []
+        self._values = {}
+        self._entry_lock = threading.Lock()
+        self._entry_counter = 0
+
+    def __call__(self, **values):
+        """
+        Compares a set of values across threads.
+
+        For each value, type equality as well as comparison takes place. If any
+        of the values is a function, then address comparison is performed.
+        Also, if any of the values is a `numpy.ndarray`, then approximate
+        numerical comparison is performed.
+        """
+        tid = id(threading.current_thread())
+        self._entry_barrier.wait()
+        with self._entry_lock:
+            if self._entry_counter == 0:
+                # Reset state before comparison
+                self._barrier.reset()
+                self._reset_evt.clear()
+                self._thread_ids = []
+                self._values = {}
+                self._entry_barrier.reset()
+            self._entry_counter += 1
+
+        self._values[tid] = values
+        self._thread_ids.append(tid)
+        self._barrier.wait()
+
+        if tid == self._thread_ids[0]:
+            thread_ids = list(self._values)
+            try:
+                for value_name in values:
+                    for i in range(1, len(thread_ids)):
+                        tid_a = thread_ids[i - 1]
+                        tid_b = thread_ids[i]
+                        value_a = self._values[tid_a][value_name]
+                        value_b = self._values[tid_b][value_name]
+                        assert type(value_a) is type(value_b)
+                        if numpy_available and isinstance(value_a, np.ndarray):
+                            if len(value_a.shape) == 0:
+                                assert value_a == value_b
+                            else:
+                                assert np.allclose(value_a, value_b, equal_nan=True)
+                        elif isinstance(value_a, types.FunctionType):
+                            assert id(value_a) == id(value_b)
+                        elif value_a != value_a:
+                            assert value_b != value_b
+                        else:
+                            assert value_a == value_b
+            finally:
+                self._entry_counter = 0
+                self._reset_evt.set()
+        else:
+            self._reset_evt.wait()

src/pytest_run_parallel/thread_unsafe_detection.py

@@ -0,0 +1,138 @@
+import ast
+import functools
+import inspect
+from textwrap import dedent
+
+try:
+    # added in hypothesis 6.131.0
+    from hypothesis import is_hypothesis_test
+except ImportError:
+    try:
+        # hypothesis versions < 6.131.0
+        from hypothesis.internal.detection import is_hypothesis_test
+    except ImportError:
+        # hypothesis isn't installed
+        def is_hypothesis_test(fn):
+            return False
+
+
+THREAD_UNSAFE_FIXTURES = {
+    "capsys",
+    "monkeypatch",
+    "recwarn",
+}
+
+
+class ThreadUnsafeNodeVisitor(ast.NodeVisitor):
+    def __init__(self, fn, skip_set, level=0):
+        self.thread_unsafe = False
+        self.thread_unsafe_reason = None
+        self.blacklist = {
+            ("pytest", "warns"),
+            ("pytest", "deprecated_call"),
+            ("_pytest.recwarn", "warns"),
+            ("_pytest.recwarn", "deprecated_call"),
+            ("warnings", "catch_warnings"),
+            ("mock", "patch"),  # unittest.mock
+        } | set(skip_set)
+        modules = {mod.split(".")[0] for mod, _ in self.blacklist}
+        modules |= {mod for mod, _ in self.blacklist}
+
+        self.fn = fn
+        self.skip_set = skip_set
+        self.level = level
+        self.modules_aliases = {}
+        self.func_aliases = {}
+        for var_name in getattr(fn, "__globals__", {}):
+            value = fn.__globals__[var_name]
+            if inspect.ismodule(value) and value.__name__ in modules:
+                self.modules_aliases[var_name] = value.__name__
+            elif inspect.isfunction(value):
+                real_name = value.__name__
+                for mod in modules:
+                    if mod == value.__module__:
+                        self.func_aliases[var_name] = (mod, real_name)
+                        break
+
+        super().__init__()
+
+    def visit_Call(self, node):
+        if self.thread_unsafe:
+            return
+
+        if isinstance(node.func, ast.Attribute):
+            if isinstance(node.func.value, ast.Name):
+                real_mod = node.func.value.id
+                if real_mod in self.modules_aliases:
+                    real_mod = self.modules_aliases[real_mod]
+                if (real_mod, node.func.attr) in self.blacklist:
+                    self.thread_unsafe = True
+                    self.thread_unsafe_reason = (
+                        "calls thread-unsafe function: " f"{real_mod}.{node.func.attr}"
+                    )
+                elif self.level < 2:
+                    if node.func.value.id in getattr(self.fn, "__globals__", {}):
+                        mod = self.fn.__globals__[node.func.value.id]
+                        child_fn = getattr(mod, node.func.attr, None)
+                        if child_fn is not None:
+                            self.thread_unsafe, self.thread_unsafe_reason = (
+                                identify_thread_unsafe_nodes(
+                                    child_fn, self.skip_set, self.level + 1
+                                )
+                            )
+        elif isinstance(node.func, ast.Name):
+            recurse = True
+            if node.func.id in self.func_aliases:
+                if self.func_aliases[node.func.id] in self.blacklist:
+                    self.thread_unsafe = True
+                    self.thread_unsafe_reason = (
+                        f"calls thread-unsafe function: {node.func.id}"
+                    )
+                    recurse = False
+            if recurse and self.level < 2:
+                if node.func.id in getattr(self.fn, "__globals__", {}):
+                    child_fn = self.fn.__globals__[node.func.id]
+                    self.thread_unsafe, self.thread_unsafe_reason = (
+                        identify_thread_unsafe_nodes(
+                            child_fn, self.skip_set, self.level + 1
+                        )
+                    )
+
+    def visit_Assign(self, node):
+        if self.thread_unsafe:
+            return
+
+        if len(node.targets) == 1:
+            name_node = node.targets[0]
+            value_node = node.value
+            if getattr(name_node, "id", None) == "__thread_safe__":
+                self.thread_unsafe = not bool(value_node.value)
+                self.thread_unsafe_reason = (
+                    f"calls thread-unsafe function: f{name_node} "
+                    "(inferred via func.__thread_safe__ == False)"
+                )
+            else:
+                self.generic_visit(node)
+
+
+def _identify_thread_unsafe_nodes(fn, skip_set, level=0):
+    if is_hypothesis_test(fn):
+        return True, "uses hypothesis"
+    try:
+        src = inspect.getsource(fn)
+        tree = ast.parse(dedent(src))
+    except Exception:
+        return False, None
+    visitor = ThreadUnsafeNodeVisitor(fn, skip_set, level=level)
+    visitor.visit(tree)
+    return visitor.thread_unsafe, visitor.thread_unsafe_reason
+
+
+cached_thread_unsafe_identify = functools.lru_cache(_identify_thread_unsafe_nodes)
+
+
+def identify_thread_unsafe_nodes(fn, skip_set, level=0):
+    try:
+        return cached_thread_unsafe_identify(fn, skip_set, level=level)
+    except TypeError:
+        return _identify_thread_unsafe_nodes(fn, skip_set, level=level)