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1# This file is part of Hypothesis, which may be found at
2# https://github.com/HypothesisWorks/hypothesis/
3#
4# Copyright the Hypothesis Authors.
5# Individual contributors are listed in AUTHORS.rst and the git log.
6#
7# This Source Code Form is subject to the terms of the Mozilla Public License,
8# v. 2.0. If a copy of the MPL was not distributed with this file, You can
9# obtain one at https://mozilla.org/MPL/2.0/.
11import functools
12import os
13import re
14import subprocess
15import sys
16import sysconfig
17import types
18from collections import defaultdict
19from collections.abc import Iterable
20from enum import IntEnum
21from functools import lru_cache, reduce
22from os import sep
23from pathlib import Path
24from typing import TYPE_CHECKING, Optional
26from hypothesis._settings import Phase, Verbosity
27from hypothesis.internal.compat import PYPY
28from hypothesis.internal.escalation import is_hypothesis_file
30if TYPE_CHECKING:
31 from typing import TypeAlias
33Location: "TypeAlias" = tuple[str, int]
34Branch: "TypeAlias" = tuple[Optional[Location], Location]
35Trace: "TypeAlias" = set[Branch]
38@functools.cache
39def should_trace_file(fname: str) -> bool:
40 # fname.startswith("<") indicates runtime code-generation via compile,
41 # e.g. compile("def ...", "<string>", "exec") in e.g. attrs methods.
42 return not (is_hypothesis_file(fname) or fname.startswith("<"))
45# where possible, we'll use 3.12's new sys.monitoring module for low-overhead
46# coverage instrumentation; on older python versions we'll use sys.settrace.
47# tool_id = 1 is designated for coverage, but we intentionally choose a
48# non-reserved tool id so we can co-exist with coverage tools.
49MONITORING_TOOL_ID = 3
50if sys.version_info[:2] >= (3, 12):
51 MONITORING_EVENTS = {sys.monitoring.events.LINE: "trace_line"}
54class Tracer:
55 """A super-simple branch coverage tracer."""
57 __slots__ = ("_previous_location", "_should_trace", "branches")
59 def __init__(self, *, should_trace: bool) -> None:
60 self.branches: Trace = set()
61 self._previous_location: Optional[Location] = None
62 self._should_trace = should_trace and self.can_trace()
64 @staticmethod
65 def can_trace() -> bool:
66 return (
67 (sys.version_info[:2] < (3, 12) and sys.gettrace() is None)
68 or (
69 sys.version_info[:2] >= (3, 12)
70 and sys.monitoring.get_tool(MONITORING_TOOL_ID) is None
71 )
72 ) and not PYPY
74 def trace(self, frame, event, arg):
75 try:
76 if event == "call":
77 return self.trace
78 elif event == "line":
79 fname = frame.f_code.co_filename
80 if should_trace_file(fname):
81 current_location = (fname, frame.f_lineno)
82 self.branches.add((self._previous_location, current_location))
83 self._previous_location = current_location
84 except RecursionError:
85 pass
87 def trace_line(self, code: types.CodeType, line_number: int) -> None:
88 fname = code.co_filename
89 if not should_trace_file(fname):
90 # this function is only called on 3.12+, but we want to avoid an
91 # assertion to that effect for performance.
92 return sys.monitoring.DISABLE # type: ignore
94 current_location = (fname, line_number)
95 self.branches.add((self._previous_location, current_location))
96 self._previous_location = current_location
98 def __enter__(self):
99 if not self._should_trace:
100 return self
102 if sys.version_info[:2] < (3, 12):
103 sys.settrace(self.trace)
104 return self
106 sys.monitoring.use_tool_id(MONITORING_TOOL_ID, "scrutineer")
107 for event, callback_name in MONITORING_EVENTS.items():
108 sys.monitoring.set_events(MONITORING_TOOL_ID, event)
109 callback = getattr(self, callback_name)
110 sys.monitoring.register_callback(MONITORING_TOOL_ID, event, callback)
112 return self
114 def __exit__(self, *args, **kwargs):
115 if not self._should_trace:
116 return
118 if sys.version_info[:2] < (3, 12):
119 sys.settrace(None)
120 return
122 sys.monitoring.free_tool_id(MONITORING_TOOL_ID)
123 for event in MONITORING_EVENTS:
124 sys.monitoring.register_callback(MONITORING_TOOL_ID, event, None)
127UNHELPFUL_LOCATIONS = (
128 # There's a branch which is only taken when an exception is active while exiting
129 # a contextmanager; this is probably after the fault has been triggered.
130 # Similar reasoning applies to a few other standard-library modules: even
131 # if the fault was later, these still aren't useful locations to report!
132 # Note: The list is post-processed, so use plain "/" for separator here.
133 "/contextlib.py",
134 "/inspect.py",
135 "/re.py",
136 "/re/__init__.py", # refactored in Python 3.11
137 "/warnings.py",
138 # Quite rarely, the first AFNP line is in Pytest's internals.
139 "/_pytest/**",
140 "/pluggy/_*.py",
141 # used by pytest for failure formatting in the terminal
142 "/pygments/lexer.py",
143 # used by pytest for failure formatting
144 "/difflib.py",
145 "/reprlib.py",
146 "/typing.py",
147 "/conftest.py",
148 "/pprint.py",
149)
152def _glob_to_re(locs: Iterable[str]) -> str:
153 """Translate a list of glob patterns to a combined regular expression.
154 Only the * and ** wildcards are supported, and patterns including special
155 characters will only work by chance."""
156 # fnmatch.translate is not an option since its "*" consumes path sep
157 return "|".join(
158 loc.replace(".", re.escape("."))
159 .replace("**", r".+")
160 .replace("*", r"[^/]+")
161 .replace("/", re.escape(sep))
162 + r"\Z" # right anchored
163 for loc in locs
164 )
167def get_explaining_locations(traces):
168 # Traces is a dict[interesting_origin | None, set[frozenset[tuple[str, int]]]]
169 # Each trace in the set might later become a Counter instead of frozenset.
170 if not traces:
171 return {}
173 unions = {origin: set().union(*values) for origin, values in traces.items()}
174 seen_passing = {None}.union(*unions.pop(None, set()))
176 always_failing_never_passing = {
177 origin: reduce(set.intersection, [set().union(*v) for v in values])
178 - seen_passing
179 for origin, values in traces.items()
180 if origin is not None
181 }
183 # Build the observed parts of the control-flow graph for each origin
184 cf_graphs = {origin: defaultdict(set) for origin in unions}
185 for origin, seen_arcs in unions.items():
186 for src, dst in seen_arcs:
187 cf_graphs[origin][src].add(dst)
188 assert cf_graphs[origin][None], "Expected start node with >=1 successor"
190 # For each origin, our explanation is the always_failing_never_passing lines
191 # which are reachable from the start node (None) without passing through another
192 # AFNP line. So here's a whatever-first search with early stopping:
193 explanations = defaultdict(set)
194 for origin in unions:
195 queue = {None}
196 seen = set()
197 while queue:
198 assert queue.isdisjoint(seen), f"Intersection: {queue & seen}"
199 src = queue.pop()
200 seen.add(src)
201 if src in always_failing_never_passing[origin]:
202 explanations[origin].add(src)
203 else:
204 queue.update(cf_graphs[origin][src] - seen)
206 # The last step is to filter out explanations that we know would be uninformative.
207 # When this is the first AFNP location, we conclude that Scrutineer missed the
208 # real divergence (earlier in the trace) and drop that unhelpful explanation.
209 filter_regex = re.compile(_glob_to_re(UNHELPFUL_LOCATIONS))
210 return {
211 origin: {loc for loc in afnp_locs if not filter_regex.search(loc[0])}
212 for origin, afnp_locs in explanations.items()
213 }
216# see e.g. https://docs.python.org/3/library/sysconfig.html#posix-user
217# for examples of these path schemes
218STDLIB_DIRS = {
219 Path(sysconfig.get_path("platstdlib")).resolve(),
220 Path(sysconfig.get_path("stdlib")).resolve(),
221}
222SITE_PACKAGES_DIRS = {
223 Path(sysconfig.get_path("purelib")).resolve(),
224 Path(sysconfig.get_path("platlib")).resolve(),
225}
227EXPLANATION_STUB = (
228 "Explanation:",
229 " These lines were always and only run by failing examples:",
230)
233class ModuleLocation(IntEnum):
234 LOCAL = 0
235 SITE_PACKAGES = 1
236 STDLIB = 2
238 @classmethod
239 @lru_cache(1024)
240 def from_path(cls, path: str) -> "ModuleLocation":
241 path = Path(path).resolve()
242 # site-packages may be a subdir of stdlib or platlib, so it's important to
243 # check is_relative_to for this before the stdlib.
244 if any(path.is_relative_to(p) for p in SITE_PACKAGES_DIRS):
245 return cls.SITE_PACKAGES
246 if any(path.is_relative_to(p) for p in STDLIB_DIRS):
247 return cls.STDLIB
248 return cls.LOCAL
251# show local files first, then site-packages, then stdlib
252def _sort_key(path: str, lineno: int) -> tuple[int, str, int]:
253 return (ModuleLocation.from_path(path), path, lineno)
256def make_report(explanations, *, cap_lines_at=5):
257 report = defaultdict(list)
258 for origin, locations in explanations.items():
259 locations = list(locations)
260 locations.sort(key=lambda v: _sort_key(v[0], v[1]))
261 report_lines = [f" {fname}:{lineno}" for fname, lineno in locations]
262 if len(report_lines) > cap_lines_at + 1:
263 msg = " (and {} more with settings.verbosity >= verbose)"
264 report_lines[cap_lines_at:] = [msg.format(len(report_lines[cap_lines_at:]))]
265 if report_lines: # We might have filtered out every location as uninformative.
266 report[origin] = list(EXPLANATION_STUB) + report_lines
267 return report
270def explanatory_lines(traces, settings):
271 if Phase.explain in settings.phases and sys.gettrace() and not traces:
272 return defaultdict(list)
273 # Return human-readable report lines summarising the traces
274 explanations = get_explaining_locations(traces)
275 max_lines = 5 if settings.verbosity <= Verbosity.normal else float("inf")
276 return make_report(explanations, cap_lines_at=max_lines)
279# beware the code below; we're using some heuristics to make a nicer report...
282@functools.lru_cache
283def _get_git_repo_root() -> Path:
284 try:
285 where = subprocess.run(
286 ["git", "rev-parse", "--show-toplevel"],
287 check=True,
288 timeout=10,
289 capture_output=True,
290 text=True,
291 encoding="utf-8",
292 ).stdout.strip()
293 except Exception: # pragma: no cover
294 return Path().absolute().parents[-1]
295 else:
296 return Path(where)
299def tractable_coverage_report(trace: Trace) -> dict[str, list[int]]:
300 """Report a simple coverage map which is (probably most) of the user's code."""
301 coverage: dict = {}
302 t = dict(trace)
303 for file, line in set(t.keys()).union(t.values()) - {None}: # type: ignore
304 # On Python <= 3.11, we can use coverage.py xor Hypothesis' tracer,
305 # so the trace will be empty and this line never run under coverage.
306 coverage.setdefault(file, set()).add(line) # pragma: no cover
307 stdlib_fragment = f"{os.sep}lib{os.sep}python3.{sys.version_info.minor}{os.sep}"
308 return {
309 k: sorted(v)
310 for k, v in coverage.items()
311 if stdlib_fragment not in k
312 and (p := Path(k)).is_relative_to(_get_git_repo_root())
313 and "site-packages" not in p.parts
314 }