"""Rewrite assertion AST to produce nice error messages"""
import ast
import errno
import functools
import importlib.abc
import importlib.machinery
import importlib.util
import io
import itertools
import marshal
import os
import struct
import sys
import tokenize
import types
from typing import Dict
from typing import List
from typing import Optional
from typing import Set
from typing import Tuple
from _pytest._io.saferepr import safeformat
from _pytest._io.saferepr import saferepr
from _pytest._version import version
from _pytest.assertion import util
from _pytest.assertion.util import ( # noqa: F401
format_explanation as _format_explanation,
)
from _pytest.compat import fspath
from _pytest.pathlib import fnmatch_ex
from _pytest.pathlib import Path
from _pytest.pathlib import PurePath
# pytest caches rewritten pycs in pycache dirs
PYTEST_TAG = "{}-pytest-{}".format(sys.implementation.cache_tag, version)
PYC_EXT = ".py" + (__debug__ and "c" or "o")
PYC_TAIL = "." + PYTEST_TAG + PYC_EXT
[docs]class AssertionRewritingHook(importlib.abc.MetaPathFinder):
"""PEP302/PEP451 import hook which rewrites asserts."""
def __init__(self, config):
self.config = config
try:
self.fnpats = config.getini("python_files")
except ValueError:
self.fnpats = ["test_*.py", "*_test.py"]
self.session = None
self._rewritten_names = set() # type: Set[str]
self._must_rewrite = set() # type: Set[str]
# flag to guard against trying to rewrite a pyc file while we are already writing another pyc file,
# which might result in infinite recursion (#3506)
self._writing_pyc = False
self._basenames_to_check_rewrite = {"conftest"}
self._marked_for_rewrite_cache = {} # type: Dict[str, bool]
self._session_paths_checked = False
[docs] def set_session(self, session):
self.session = session
self._session_paths_checked = False
# Indirection so we can mock calls to find_spec originated from the hook during testing
_find_spec = importlib.machinery.PathFinder.find_spec
[docs] def find_spec(self, name, path=None, target=None):
if self._writing_pyc:
return None
state = self.config._assertstate
if self._early_rewrite_bailout(name, state):
return None
state.trace("find_module called for: %s" % name)
spec = self._find_spec(name, path)
if (
# the import machinery could not find a file to import
spec is None
# this is a namespace package (without `__init__.py`)
# there's nothing to rewrite there
# python3.5 - python3.6: `namespace`
# python3.7+: `None`
or spec.origin == "namespace"
or spec.origin is None
# we can only rewrite source files
or not isinstance(spec.loader, importlib.machinery.SourceFileLoader)
# if the file doesn't exist, we can't rewrite it
or not os.path.exists(spec.origin)
):
return None
else:
fn = spec.origin
if not self._should_rewrite(name, fn, state):
return None
return importlib.util.spec_from_file_location(
name,
fn,
loader=self,
submodule_search_locations=spec.submodule_search_locations,
)
[docs] def create_module(self, spec):
return None # default behaviour is fine
[docs] def exec_module(self, module):
fn = Path(module.__spec__.origin)
state = self.config._assertstate
self._rewritten_names.add(module.__name__)
# The requested module looks like a test file, so rewrite it. This is
# the most magical part of the process: load the source, rewrite the
# asserts, and load the rewritten source. We also cache the rewritten
# module code in a special pyc. We must be aware of the possibility of
# concurrent pytest processes rewriting and loading pycs. To avoid
# tricky race conditions, we maintain the following invariant: The
# cached pyc is always a complete, valid pyc. Operations on it must be
# atomic. POSIX's atomic rename comes in handy.
write = not sys.dont_write_bytecode
cache_dir = get_cache_dir(fn)
if write:
ok = try_makedirs(cache_dir)
if not ok:
write = False
state.trace("read only directory: {}".format(cache_dir))
cache_name = fn.name[:-3] + PYC_TAIL
pyc = cache_dir / cache_name
# Notice that even if we're in a read-only directory, I'm going
# to check for a cached pyc. This may not be optimal...
co = _read_pyc(fn, pyc, state.trace)
if co is None:
state.trace("rewriting {!r}".format(fn))
source_stat, co = _rewrite_test(fn, self.config)
if write:
self._writing_pyc = True
try:
_write_pyc(state, co, source_stat, pyc)
finally:
self._writing_pyc = False
else:
state.trace("found cached rewritten pyc for {}".format(fn))
exec(co, module.__dict__)
[docs] def _early_rewrite_bailout(self, name, state):
"""This is a fast way to get out of rewriting modules.
Profiling has shown that the call to PathFinder.find_spec (inside of
the find_spec from this class) is a major slowdown, so, this method
tries to filter what we're sure won't be rewritten before getting to
it.
"""
if self.session is not None and not self._session_paths_checked:
self._session_paths_checked = True
for path in self.session._initialpaths:
# Make something as c:/projects/my_project/path.py ->
# ['c:', 'projects', 'my_project', 'path.py']
parts = str(path).split(os.path.sep)
# add 'path' to basenames to be checked.
self._basenames_to_check_rewrite.add(os.path.splitext(parts[-1])[0])
# Note: conftest already by default in _basenames_to_check_rewrite.
parts = name.split(".")
if parts[-1] in self._basenames_to_check_rewrite:
return False
# For matching the name it must be as if it was a filename.
path = PurePath(os.path.sep.join(parts) + ".py")
for pat in self.fnpats:
# if the pattern contains subdirectories ("tests/**.py" for example) we can't bail out based
# on the name alone because we need to match against the full path
if os.path.dirname(pat):
return False
if fnmatch_ex(pat, path):
return False
if self._is_marked_for_rewrite(name, state):
return False
state.trace("early skip of rewriting module: {}".format(name))
return True
[docs] def _should_rewrite(self, name, fn, state):
# always rewrite conftest files
if os.path.basename(fn) == "conftest.py":
state.trace("rewriting conftest file: {!r}".format(fn))
return True
if self.session is not None:
if self.session.isinitpath(fn):
state.trace(
"matched test file (was specified on cmdline): {!r}".format(fn)
)
return True
# modules not passed explicitly on the command line are only
# rewritten if they match the naming convention for test files
fn_path = PurePath(fn)
for pat in self.fnpats:
if fnmatch_ex(pat, fn_path):
state.trace("matched test file {!r}".format(fn))
return True
return self._is_marked_for_rewrite(name, state)
[docs] def _is_marked_for_rewrite(self, name: str, state):
try:
return self._marked_for_rewrite_cache[name]
except KeyError:
for marked in self._must_rewrite:
if name == marked or name.startswith(marked + "."):
state.trace(
"matched marked file {!r} (from {!r})".format(name, marked)
)
self._marked_for_rewrite_cache[name] = True
return True
self._marked_for_rewrite_cache[name] = False
return False
[docs] def mark_rewrite(self, *names: str) -> None:
"""Mark import names as needing to be rewritten.
The named module or package as well as any nested modules will
be rewritten on import.
"""
already_imported = (
set(names).intersection(sys.modules).difference(self._rewritten_names)
)
for name in already_imported:
mod = sys.modules[name]
if not AssertionRewriter.is_rewrite_disabled(
mod.__doc__ or ""
) and not isinstance(mod.__loader__, type(self)):
self._warn_already_imported(name)
self._must_rewrite.update(names)
self._marked_for_rewrite_cache.clear()
[docs] def _warn_already_imported(self, name):
from _pytest.warning_types import PytestAssertRewriteWarning
from _pytest.warnings import _issue_warning_captured
_issue_warning_captured(
PytestAssertRewriteWarning(
"Module already imported so cannot be rewritten: %s" % name
),
self.config.hook,
stacklevel=5,
)
[docs] def get_data(self, pathname):
"""Optional PEP302 get_data API."""
with open(pathname, "rb") as f:
return f.read()
[docs]def _write_pyc_fp(fp, source_stat, co):
# Technically, we don't have to have the same pyc format as
# (C)Python, since these "pycs" should never be seen by builtin
# import. However, there's little reason deviate.
fp.write(importlib.util.MAGIC_NUMBER)
# as of now, bytecode header expects 32-bit numbers for size and mtime (#4903)
mtime = int(source_stat.st_mtime) & 0xFFFFFFFF
size = source_stat.st_size & 0xFFFFFFFF
# "<LL" stands for 2 unsigned longs, little-ending
fp.write(struct.pack("<LL", mtime, size))
fp.write(marshal.dumps(co))
if sys.platform == "win32":
from atomicwrites import atomic_write
def _write_pyc(state, co, source_stat, pyc):
try:
with atomic_write(fspath(pyc), mode="wb", overwrite=True) as fp:
_write_pyc_fp(fp, source_stat, co)
except EnvironmentError as e:
state.trace("error writing pyc file at {}: errno={}".format(pyc, e.errno))
# we ignore any failure to write the cache file
# there are many reasons, permission-denied, pycache dir being a
# file etc.
return False
return True
else:
[docs] def _write_pyc(state, co, source_stat, pyc):
proc_pyc = "{}.{}".format(pyc, os.getpid())
try:
fp = open(proc_pyc, "wb")
except EnvironmentError as e:
state.trace(
"error writing pyc file at {}: errno={}".format(proc_pyc, e.errno)
)
return False
try:
_write_pyc_fp(fp, source_stat, co)
os.rename(proc_pyc, fspath(pyc))
except BaseException as e:
state.trace("error writing pyc file at {}: errno={}".format(pyc, e.errno))
# we ignore any failure to write the cache file
# there are many reasons, permission-denied, pycache dir being a
# file etc.
return False
finally:
fp.close()
return True
[docs]def _rewrite_test(fn, config):
"""read and rewrite *fn* and return the code object."""
fn = fspath(fn)
stat = os.stat(fn)
with open(fn, "rb") as f:
source = f.read()
tree = ast.parse(source, filename=fn)
rewrite_asserts(tree, source, fn, config)
co = compile(tree, fn, "exec", dont_inherit=True)
return stat, co
[docs]def _read_pyc(source, pyc, trace=lambda x: None):
"""Possibly read a pytest pyc containing rewritten code.
Return rewritten code if successful or None if not.
"""
try:
fp = open(fspath(pyc), "rb")
except IOError:
return None
with fp:
try:
stat_result = os.stat(fspath(source))
mtime = int(stat_result.st_mtime)
size = stat_result.st_size
data = fp.read(12)
except EnvironmentError as e:
trace("_read_pyc({}): EnvironmentError {}".format(source, e))
return None
# Check for invalid or out of date pyc file.
if (
len(data) != 12
or data[:4] != importlib.util.MAGIC_NUMBER
or struct.unpack("<LL", data[4:]) != (mtime & 0xFFFFFFFF, size & 0xFFFFFFFF)
):
trace("_read_pyc(%s): invalid or out of date pyc" % source)
return None
try:
co = marshal.load(fp)
except Exception as e:
trace("_read_pyc({}): marshal.load error {}".format(source, e))
return None
if not isinstance(co, types.CodeType):
trace("_read_pyc(%s): not a code object" % source)
return None
return co
[docs]def rewrite_asserts(mod, source, module_path=None, config=None):
"""Rewrite the assert statements in mod."""
AssertionRewriter(module_path, config, source).run(mod)
[docs]def _saferepr(obj):
"""Get a safe repr of an object for assertion error messages.
The assertion formatting (util.format_explanation()) requires
newlines to be escaped since they are a special character for it.
Normally assertion.util.format_explanation() does this but for a
custom repr it is possible to contain one of the special escape
sequences, especially '\n{' and '\n}' are likely to be present in
JSON reprs.
"""
return saferepr(obj).replace("\n", "\\n")
[docs]def _should_repr_global_name(obj):
if callable(obj):
return False
try:
return not hasattr(obj, "__name__")
except Exception:
return True
[docs]def _call_reprcompare(ops, results, expls, each_obj):
# type: (Tuple[str, ...], Tuple[bool, ...], Tuple[str, ...], Tuple[object, ...]) -> str
for i, res, expl in zip(range(len(ops)), results, expls):
try:
done = not res
except Exception:
done = True
if done:
break
if util._reprcompare is not None:
custom = util._reprcompare(ops[i], each_obj[i], each_obj[i + 1])
if custom is not None:
return custom
return expl
[docs]def _call_assertion_pass(lineno, orig, expl):
# type: (int, str, str) -> None
if util._assertion_pass is not None:
util._assertion_pass(lineno, orig, expl)
[docs]def _check_if_assertion_pass_impl():
# type: () -> bool
"""Checks if any plugins implement the pytest_assertion_pass hook
in order not to generate explanation unecessarily (might be expensive)"""
return True if util._assertion_pass else False
UNARY_MAP = {ast.Not: "not %s", ast.Invert: "~%s", ast.USub: "-%s", ast.UAdd: "+%s"}
BINOP_MAP = {
ast.BitOr: "|",
ast.BitXor: "^",
ast.BitAnd: "&",
ast.LShift: "<<",
ast.RShift: ">>",
ast.Add: "+",
ast.Sub: "-",
ast.Mult: "*",
ast.Div: "/",
ast.FloorDiv: "//",
ast.Mod: "%%", # escaped for string formatting
ast.Eq: "==",
ast.NotEq: "!=",
ast.Lt: "<",
ast.LtE: "<=",
ast.Gt: ">",
ast.GtE: ">=",
ast.Pow: "**",
ast.Is: "is",
ast.IsNot: "is not",
ast.In: "in",
ast.NotIn: "not in",
ast.MatMult: "@",
}
[docs]def set_location(node, lineno, col_offset):
"""Set node location information recursively."""
def _fix(node, lineno, col_offset):
if "lineno" in node._attributes:
node.lineno = lineno
if "col_offset" in node._attributes:
node.col_offset = col_offset
for child in ast.iter_child_nodes(node):
_fix(child, lineno, col_offset)
_fix(node, lineno, col_offset)
return node
[docs]def _get_assertion_exprs(src: bytes) -> Dict[int, str]:
"""Returns a mapping from {lineno: "assertion test expression"}"""
ret = {} # type: Dict[int, str]
depth = 0
lines = [] # type: List[str]
assert_lineno = None # type: Optional[int]
seen_lines = set() # type: Set[int]
def _write_and_reset() -> None:
nonlocal depth, lines, assert_lineno, seen_lines
assert assert_lineno is not None
ret[assert_lineno] = "".join(lines).rstrip().rstrip("\\")
depth = 0
lines = []
assert_lineno = None
seen_lines = set()
tokens = tokenize.tokenize(io.BytesIO(src).readline)
for tp, source, (lineno, offset), _, line in tokens:
if tp == tokenize.NAME and source == "assert":
assert_lineno = lineno
elif assert_lineno is not None:
# keep track of depth for the assert-message `,` lookup
if tp == tokenize.OP and source in "([{":
depth += 1
elif tp == tokenize.OP and source in ")]}":
depth -= 1
if not lines:
lines.append(line[offset:])
seen_lines.add(lineno)
# a non-nested comma separates the expression from the message
elif depth == 0 and tp == tokenize.OP and source == ",":
# one line assert with message
if lineno in seen_lines and len(lines) == 1:
offset_in_trimmed = offset + len(lines[-1]) - len(line)
lines[-1] = lines[-1][:offset_in_trimmed]
# multi-line assert with message
elif lineno in seen_lines:
lines[-1] = lines[-1][:offset]
# multi line assert with escapd newline before message
else:
lines.append(line[:offset])
_write_and_reset()
elif tp in {tokenize.NEWLINE, tokenize.ENDMARKER}:
_write_and_reset()
elif lines and lineno not in seen_lines:
lines.append(line)
seen_lines.add(lineno)
return ret
[docs]class AssertionRewriter(ast.NodeVisitor):
"""Assertion rewriting implementation.
The main entrypoint is to call .run() with an ast.Module instance,
this will then find all the assert statements and rewrite them to
provide intermediate values and a detailed assertion error. See
http://pybites.blogspot.be/2011/07/behind-scenes-of-pytests-new-assertion.html
for an overview of how this works.
The entry point here is .run() which will iterate over all the
statements in an ast.Module and for each ast.Assert statement it
finds call .visit() with it. Then .visit_Assert() takes over and
is responsible for creating new ast statements to replace the
original assert statement: it rewrites the test of an assertion
to provide intermediate values and replace it with an if statement
which raises an assertion error with a detailed explanation in
case the expression is false and calls pytest_assertion_pass hook
if expression is true.
For this .visit_Assert() uses the visitor pattern to visit all the
AST nodes of the ast.Assert.test field, each visit call returning
an AST node and the corresponding explanation string. During this
state is kept in several instance attributes:
:statements: All the AST statements which will replace the assert
statement.
:variables: This is populated by .variable() with each variable
used by the statements so that they can all be set to None at
the end of the statements.
:variable_counter: Counter to create new unique variables needed
by statements. Variables are created using .variable() and
have the form of "@py_assert0".
:expl_stmts: The AST statements which will be executed to get
data from the assertion. This is the code which will construct
the detailed assertion message that is used in the AssertionError
or for the pytest_assertion_pass hook.
:explanation_specifiers: A dict filled by .explanation_param()
with %-formatting placeholders and their corresponding
expressions to use in the building of an assertion message.
This is used by .pop_format_context() to build a message.
:stack: A stack of the explanation_specifiers dicts maintained by
.push_format_context() and .pop_format_context() which allows
to build another %-formatted string while already building one.
This state is reset on every new assert statement visited and used
by the other visitors.
"""
def __init__(self, module_path, config, source):
super().__init__()
self.module_path = module_path
self.config = config
if config is not None:
self.enable_assertion_pass_hook = config.getini(
"enable_assertion_pass_hook"
)
else:
self.enable_assertion_pass_hook = False
self.source = source
[docs] @functools.lru_cache(maxsize=1)
def _assert_expr_to_lineno(self):
return _get_assertion_exprs(self.source)
[docs] def run(self, mod: ast.Module) -> None:
"""Find all assert statements in *mod* and rewrite them."""
if not mod.body:
# Nothing to do.
return
# Insert some special imports at the top of the module but after any
# docstrings and __future__ imports.
aliases = [
ast.alias("builtins", "@py_builtins"),
ast.alias("_pytest.assertion.rewrite", "@pytest_ar"),
]
doc = getattr(mod, "docstring", None)
expect_docstring = doc is None
if doc is not None and self.is_rewrite_disabled(doc):
return
pos = 0
lineno = 1
for item in mod.body:
if (
expect_docstring
and isinstance(item, ast.Expr)
and isinstance(item.value, ast.Str)
):
doc = item.value.s
if self.is_rewrite_disabled(doc):
return
expect_docstring = False
elif (
not isinstance(item, ast.ImportFrom)
or item.level > 0
or item.module != "__future__"
):
lineno = item.lineno
break
pos += 1
else:
lineno = item.lineno
imports = [
ast.Import([alias], lineno=lineno, col_offset=0) for alias in aliases
]
mod.body[pos:pos] = imports
# Collect asserts.
nodes = [mod] # type: List[ast.AST]
while nodes:
node = nodes.pop()
for name, field in ast.iter_fields(node):
if isinstance(field, list):
new = [] # type: List
for i, child in enumerate(field):
if isinstance(child, ast.Assert):
# Transform assert.
new.extend(self.visit(child))
else:
new.append(child)
if isinstance(child, ast.AST):
nodes.append(child)
setattr(node, name, new)
elif (
isinstance(field, ast.AST)
# Don't recurse into expressions as they can't contain
# asserts.
and not isinstance(field, ast.expr)
):
nodes.append(field)
[docs] @staticmethod
def is_rewrite_disabled(docstring):
return "PYTEST_DONT_REWRITE" in docstring
[docs] def variable(self):
"""Get a new variable."""
# Use a character invalid in python identifiers to avoid clashing.
name = "@py_assert" + str(next(self.variable_counter))
self.variables.append(name)
return name
[docs] def assign(self, expr):
"""Give *expr* a name."""
name = self.variable()
self.statements.append(ast.Assign([ast.Name(name, ast.Store())], expr))
return ast.Name(name, ast.Load())
[docs] def display(self, expr):
"""Call saferepr on the expression."""
return self.helper("_saferepr", expr)
[docs] def helper(self, name, *args):
"""Call a helper in this module."""
py_name = ast.Name("@pytest_ar", ast.Load())
attr = ast.Attribute(py_name, name, ast.Load())
return ast.Call(attr, list(args), [])
[docs] def builtin(self, name):
"""Return the builtin called *name*."""
builtin_name = ast.Name("@py_builtins", ast.Load())
return ast.Attribute(builtin_name, name, ast.Load())
[docs] def explanation_param(self, expr):
"""Return a new named %-formatting placeholder for expr.
This creates a %-formatting placeholder for expr in the
current formatting context, e.g. ``%(py0)s``. The placeholder
and expr are placed in the current format context so that it
can be used on the next call to .pop_format_context().
"""
specifier = "py" + str(next(self.variable_counter))
self.explanation_specifiers[specifier] = expr
return "%(" + specifier + ")s"
[docs] def push_format_context(self):
"""Create a new formatting context.
The format context is used for when an explanation wants to
have a variable value formatted in the assertion message. In
this case the value required can be added using
.explanation_param(). Finally .pop_format_context() is used
to format a string of %-formatted values as added by
.explanation_param().
"""
self.explanation_specifiers = {} # type: Dict[str, ast.expr]
self.stack.append(self.explanation_specifiers)
[docs] def pop_format_context(self, expl_expr):
"""Format the %-formatted string with current format context.
The expl_expr should be an ast.Str instance constructed from
the %-placeholders created by .explanation_param(). This will
add the required code to format said string to .expl_stmts and
return the ast.Name instance of the formatted string.
"""
current = self.stack.pop()
if self.stack:
self.explanation_specifiers = self.stack[-1]
keys = [ast.Str(key) for key in current.keys()]
format_dict = ast.Dict(keys, list(current.values()))
form = ast.BinOp(expl_expr, ast.Mod(), format_dict)
name = "@py_format" + str(next(self.variable_counter))
if self.enable_assertion_pass_hook:
self.format_variables.append(name)
self.expl_stmts.append(ast.Assign([ast.Name(name, ast.Store())], form))
return ast.Name(name, ast.Load())
[docs] def generic_visit(self, node):
"""Handle expressions we don't have custom code for."""
assert isinstance(node, ast.expr)
res = self.assign(node)
return res, self.explanation_param(self.display(res))
[docs] def visit_Assert(self, assert_):
"""Return the AST statements to replace the ast.Assert instance.
This rewrites the test of an assertion to provide
intermediate values and replace it with an if statement which
raises an assertion error with a detailed explanation in case
the expression is false.
"""
if isinstance(assert_.test, ast.Tuple) and len(assert_.test.elts) >= 1:
from _pytest.warning_types import PytestAssertRewriteWarning
import warnings
warnings.warn_explicit(
PytestAssertRewriteWarning(
"assertion is always true, perhaps remove parentheses?"
),
category=None,
filename=fspath(self.module_path),
lineno=assert_.lineno,
)
self.statements = [] # type: List[ast.stmt]
self.variables = [] # type: List[str]
self.variable_counter = itertools.count()
if self.enable_assertion_pass_hook:
self.format_variables = [] # type: List[str]
self.stack = [] # type: List[Dict[str, ast.expr]]
self.expl_stmts = [] # type: List[ast.stmt]
self.push_format_context()
# Rewrite assert into a bunch of statements.
top_condition, explanation = self.visit(assert_.test)
negation = ast.UnaryOp(ast.Not(), top_condition)
if self.enable_assertion_pass_hook: # Experimental pytest_assertion_pass hook
msg = self.pop_format_context(ast.Str(explanation))
# Failed
if assert_.msg:
assertmsg = self.helper("_format_assertmsg", assert_.msg)
gluestr = "\n>assert "
else:
assertmsg = ast.Str("")
gluestr = "assert "
err_explanation = ast.BinOp(ast.Str(gluestr), ast.Add(), msg)
err_msg = ast.BinOp(assertmsg, ast.Add(), err_explanation)
err_name = ast.Name("AssertionError", ast.Load())
fmt = self.helper("_format_explanation", err_msg)
exc = ast.Call(err_name, [fmt], [])
raise_ = ast.Raise(exc, None)
statements_fail = []
statements_fail.extend(self.expl_stmts)
statements_fail.append(raise_)
# Passed
fmt_pass = self.helper("_format_explanation", msg)
orig = self._assert_expr_to_lineno()[assert_.lineno]
hook_call_pass = ast.Expr(
self.helper(
"_call_assertion_pass",
ast.Num(assert_.lineno),
ast.Str(orig),
fmt_pass,
)
)
# If any hooks implement assert_pass hook
hook_impl_test = ast.If(
self.helper("_check_if_assertion_pass_impl"),
self.expl_stmts + [hook_call_pass],
[],
)
statements_pass = [hook_impl_test]
# Test for assertion condition
main_test = ast.If(negation, statements_fail, statements_pass)
self.statements.append(main_test)
if self.format_variables:
variables = [
ast.Name(name, ast.Store()) for name in self.format_variables
]
clear_format = ast.Assign(variables, ast.NameConstant(None))
self.statements.append(clear_format)
else: # Original assertion rewriting
# Create failure message.
body = self.expl_stmts
self.statements.append(ast.If(negation, body, []))
if assert_.msg:
assertmsg = self.helper("_format_assertmsg", assert_.msg)
explanation = "\n>assert " + explanation
else:
assertmsg = ast.Str("")
explanation = "assert " + explanation
template = ast.BinOp(assertmsg, ast.Add(), ast.Str(explanation))
msg = self.pop_format_context(template)
fmt = self.helper("_format_explanation", msg)
err_name = ast.Name("AssertionError", ast.Load())
exc = ast.Call(err_name, [fmt], [])
raise_ = ast.Raise(exc, None)
body.append(raise_)
# Clear temporary variables by setting them to None.
if self.variables:
variables = [ast.Name(name, ast.Store()) for name in self.variables]
clear = ast.Assign(variables, ast.NameConstant(None))
self.statements.append(clear)
# Fix line numbers.
for stmt in self.statements:
set_location(stmt, assert_.lineno, assert_.col_offset)
return self.statements
[docs] def visit_Name(self, name):
# Display the repr of the name if it's a local variable or
# _should_repr_global_name() thinks it's acceptable.
locs = ast.Call(self.builtin("locals"), [], [])
inlocs = ast.Compare(ast.Str(name.id), [ast.In()], [locs])
dorepr = self.helper("_should_repr_global_name", name)
test = ast.BoolOp(ast.Or(), [inlocs, dorepr])
expr = ast.IfExp(test, self.display(name), ast.Str(name.id))
return name, self.explanation_param(expr)
[docs] def visit_BoolOp(self, boolop):
res_var = self.variable()
expl_list = self.assign(ast.List([], ast.Load()))
app = ast.Attribute(expl_list, "append", ast.Load())
is_or = int(isinstance(boolop.op, ast.Or))
body = save = self.statements
fail_save = self.expl_stmts
levels = len(boolop.values) - 1
self.push_format_context()
# Process each operand, short-circuiting if needed.
for i, v in enumerate(boolop.values):
if i:
fail_inner = [] # type: List[ast.stmt]
# cond is set in a prior loop iteration below
self.expl_stmts.append(ast.If(cond, fail_inner, [])) # noqa
self.expl_stmts = fail_inner
self.push_format_context()
res, expl = self.visit(v)
body.append(ast.Assign([ast.Name(res_var, ast.Store())], res))
expl_format = self.pop_format_context(ast.Str(expl))
call = ast.Call(app, [expl_format], [])
self.expl_stmts.append(ast.Expr(call))
if i < levels:
cond = res # type: ast.expr
if is_or:
cond = ast.UnaryOp(ast.Not(), cond)
inner = [] # type: List[ast.stmt]
self.statements.append(ast.If(cond, inner, []))
self.statements = body = inner
self.statements = save
self.expl_stmts = fail_save
expl_template = self.helper("_format_boolop", expl_list, ast.Num(is_or))
expl = self.pop_format_context(expl_template)
return ast.Name(res_var, ast.Load()), self.explanation_param(expl)
[docs] def visit_UnaryOp(self, unary):
pattern = UNARY_MAP[unary.op.__class__]
operand_res, operand_expl = self.visit(unary.operand)
res = self.assign(ast.UnaryOp(unary.op, operand_res))
return res, pattern % (operand_expl,)
[docs] def visit_BinOp(self, binop):
symbol = BINOP_MAP[binop.op.__class__]
left_expr, left_expl = self.visit(binop.left)
right_expr, right_expl = self.visit(binop.right)
explanation = "({} {} {})".format(left_expl, symbol, right_expl)
res = self.assign(ast.BinOp(left_expr, binop.op, right_expr))
return res, explanation
[docs] def visit_Call(self, call):
"""
visit `ast.Call` nodes
"""
new_func, func_expl = self.visit(call.func)
arg_expls = []
new_args = []
new_kwargs = []
for arg in call.args:
res, expl = self.visit(arg)
arg_expls.append(expl)
new_args.append(res)
for keyword in call.keywords:
res, expl = self.visit(keyword.value)
new_kwargs.append(ast.keyword(keyword.arg, res))
if keyword.arg:
arg_expls.append(keyword.arg + "=" + expl)
else: # **args have `arg` keywords with an .arg of None
arg_expls.append("**" + expl)
expl = "{}({})".format(func_expl, ", ".join(arg_expls))
new_call = ast.Call(new_func, new_args, new_kwargs)
res = self.assign(new_call)
res_expl = self.explanation_param(self.display(res))
outer_expl = "{}\n{{{} = {}\n}}".format(res_expl, res_expl, expl)
return res, outer_expl
[docs] def visit_Starred(self, starred):
# From Python 3.5, a Starred node can appear in a function call
res, expl = self.visit(starred.value)
new_starred = ast.Starred(res, starred.ctx)
return new_starred, "*" + expl
[docs] def visit_Attribute(self, attr):
if not isinstance(attr.ctx, ast.Load):
return self.generic_visit(attr)
value, value_expl = self.visit(attr.value)
res = self.assign(ast.Attribute(value, attr.attr, ast.Load()))
res_expl = self.explanation_param(self.display(res))
pat = "%s\n{%s = %s.%s\n}"
expl = pat % (res_expl, res_expl, value_expl, attr.attr)
return res, expl
[docs] def visit_Compare(self, comp: ast.Compare):
self.push_format_context()
left_res, left_expl = self.visit(comp.left)
if isinstance(comp.left, (ast.Compare, ast.BoolOp)):
left_expl = "({})".format(left_expl)
res_variables = [self.variable() for i in range(len(comp.ops))]
load_names = [ast.Name(v, ast.Load()) for v in res_variables]
store_names = [ast.Name(v, ast.Store()) for v in res_variables]
it = zip(range(len(comp.ops)), comp.ops, comp.comparators)
expls = []
syms = []
results = [left_res]
for i, op, next_operand in it:
next_res, next_expl = self.visit(next_operand)
if isinstance(next_operand, (ast.Compare, ast.BoolOp)):
next_expl = "({})".format(next_expl)
results.append(next_res)
sym = BINOP_MAP[op.__class__]
syms.append(ast.Str(sym))
expl = "{} {} {}".format(left_expl, sym, next_expl)
expls.append(ast.Str(expl))
res_expr = ast.Compare(left_res, [op], [next_res])
self.statements.append(ast.Assign([store_names[i]], res_expr))
left_res, left_expl = next_res, next_expl
# Use pytest.assertion.util._reprcompare if that's available.
expl_call = self.helper(
"_call_reprcompare",
ast.Tuple(syms, ast.Load()),
ast.Tuple(load_names, ast.Load()),
ast.Tuple(expls, ast.Load()),
ast.Tuple(results, ast.Load()),
)
if len(comp.ops) > 1:
res = ast.BoolOp(ast.And(), load_names) # type: ast.expr
else:
res = load_names[0]
return res, self.explanation_param(self.pop_format_context(expl_call))
[docs]def try_makedirs(cache_dir) -> bool:
"""Attempts to create the given directory and sub-directories exist, returns True if
successful or it already exists"""
try:
os.makedirs(fspath(cache_dir), exist_ok=True)
except (FileNotFoundError, NotADirectoryError, FileExistsError):
# One of the path components was not a directory:
# - we're in a zip file
# - it is a file
return False
except PermissionError:
return False
except OSError as e:
# as of now, EROFS doesn't have an equivalent OSError-subclass
if e.errno == errno.EROFS:
return False
raise
return True
[docs]def get_cache_dir(file_path: Path) -> Path:
"""Returns the cache directory to write .pyc files for the given .py file path"""
if sys.version_info >= (3, 8) and sys.pycache_prefix:
# given:
# prefix = '/tmp/pycs'
# path = '/home/user/proj/test_app.py'
# we want:
# '/tmp/pycs/home/user/proj'
return Path(sys.pycache_prefix) / Path(*file_path.parts[1:-1])
else:
# classic pycache directory
return file_path.parent / "__pycache__"