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"""Rewrite assertion AST to produce nice error messages""" 

 

import ast 

import errno 

import itertools 

import imp 

import marshal 

import os 

import re 

import struct 

import sys 

import types 

 

import py 

from _pytest.assertion import util 

 

 

# pytest caches rewritten pycs in __pycache__. 

20if hasattr(imp, "get_tag"): 

    PYTEST_TAG = imp.get_tag() + "-PYTEST" 

else: 

23    if hasattr(sys, "pypy_version_info"): 

        impl = "pypy" 

25    elif sys.platform == "java": 

        impl = "jython" 

    else: 

        impl = "cpython" 

    ver = sys.version_info 

    PYTEST_TAG = "%s-%s%s-PYTEST" % (impl, ver[0], ver[1]) 

    del ver, impl 

 

PYC_EXT = ".py" + (__debug__ and "c" or "o") 

PYC_TAIL = "." + PYTEST_TAG + PYC_EXT 

 

REWRITE_NEWLINES = sys.version_info[:2] != (2, 7) and sys.version_info < (3, 2) 

ASCII_IS_DEFAULT_ENCODING = sys.version_info[0] < 3 

 

39if sys.version_info >= (3,5): 

    ast_Call = ast.Call 

else: 

exit    ast_Call = lambda a,b,c: ast.Call(a, b, c, None, None) 

 

 

class AssertionRewritingHook(object): 

    """PEP302 Import hook which rewrites asserts.""" 

 

    def __init__(self): 

        self.session = None 

        self.modules = {} 

        self._register_with_pkg_resources() 

 

    def set_session(self, session): 

        self.fnpats = session.config.getini("python_files") 

        self.session = session 

 

    def find_module(self, name, path=None): 

        if self.session is None: 

            return None 

        sess = self.session 

        state = sess.config._assertstate 

        state.trace("find_module called for: %s" % name) 

        names = name.rsplit(".", 1) 

        lastname = names[-1] 

        pth = None 

        if path is not None: 

            # Starting with Python 3.3, path is a _NamespacePath(), which 

            # causes problems if not converted to list. 

            path = list(path) 

            if len(path) == 1: 

                pth = path[0] 

        if pth is None: 

            try: 

                fd, fn, desc = imp.find_module(lastname, path) 

            except ImportError: 

                return None 

            if fd is not None: 

                fd.close() 

            tp = desc[2] 

80            if tp == imp.PY_COMPILED: 

                if hasattr(imp, "source_from_cache"): 

                    fn = imp.source_from_cache(fn) 

                else: 

                    fn = fn[:-1] 

            elif tp != imp.PY_SOURCE: 

                # Don't know what this is. 

                return None 

        else: 

            fn = os.path.join(pth, name.rpartition(".")[2] + ".py") 

        fn_pypath = py.path.local(fn) 

        # Is this a test file? 

105        if not sess.isinitpath(fn): 

            # We have to be very careful here because imports in this code can 

            # trigger a cycle. 

            self.session = None 

            try: 

                for pat in self.fnpats: 

                    if fn_pypath.fnmatch(pat): 

                        state.trace("matched test file %r" % (fn,)) 

                        break 

                else: 

                    return None 

            finally: 

                self.session = sess 

        else: 

            state.trace("matched test file (was specified on cmdline): %r" % 

                        (fn,)) 

        # 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 = os.path.join(fn_pypath.dirname, "__pycache__") 

136        if write: 

            try: 

                os.mkdir(cache_dir) 

            except OSError: 

                e = sys.exc_info()[1].errno 

127                if e == errno.EEXIST: 

                    # Either the __pycache__ directory already exists (the 

                    # common case) or it's blocked by a non-dir node. In the 

                    # latter case, we'll ignore it in _write_pyc. 

                    pass 

                elif e in [errno.ENOENT, errno.ENOTDIR]: 

                    # One of the path components was not a directory, likely 

                    # because we're in a zip file. 

                    write = False 

                elif e in [errno.EACCES, errno.EROFS, errno.EPERM]: 

                    state.trace("read only directory: %r" % fn_pypath.dirname) 

                    write = False 

                else: 

                    raise 

        cache_name = fn_pypath.basename[:-3] + PYC_TAIL 

        pyc = os.path.join(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_pypath, pyc, state.trace) 

142        if co is None: 

            state.trace("rewriting %r" % (fn,)) 

            source_stat, co = _rewrite_test(state, fn_pypath) 

            if co is None: 

                # Probably a SyntaxError in the test. 

                return None 

            if write: 

                _make_rewritten_pyc(state, source_stat, pyc, co) 

        else: 

            state.trace("found cached rewritten pyc for %r" % (fn,)) 

        self.modules[name] = co, pyc 

        return self 

 

    def load_module(self, name): 

        # If there is an existing module object named 'fullname' in 

        # sys.modules, the loader must use that existing module. (Otherwise, 

        # the reload() builtin will not work correctly.) 

159        if name in sys.modules: 

            return sys.modules[name] 

 

        co, pyc = self.modules.pop(name) 

        # I wish I could just call imp.load_compiled here, but __file__ has to 

        # be set properly. In Python 3.2+, this all would be handled correctly 

        # by load_compiled. 

        mod = sys.modules[name] = imp.new_module(name) 

        try: 

            mod.__file__ = co.co_filename 

            # Normally, this attribute is 3.2+. 

            mod.__cached__ = pyc 

            mod.__loader__ = self 

            py.builtin.exec_(co, mod.__dict__) 

        except: 

            del sys.modules[name] 

            raise 

        return sys.modules[name] 

 

 

 

    def is_package(self, name): 

        try: 

            fd, fn, desc = imp.find_module(name) 

        except ImportError: 

            return False 

        if fd is not None: 

            fd.close() 

        tp = desc[2] 

        return tp == imp.PKG_DIRECTORY 

 

    @classmethod 

    def _register_with_pkg_resources(cls): 

        """ 

        Ensure package resources can be loaded from this loader. May be called 

        multiple times, as the operation is idempotent. 

        """ 

        try: 

            import pkg_resources 

            # access an attribute in case a deferred importer is present 

            pkg_resources.__name__ 

        except ImportError: 

            return 

 

        # Since pytest tests are always located in the file system, the 

        #  DefaultProvider is appropriate. 

        pkg_resources.register_loader_type(cls, pkg_resources.DefaultProvider) 

 

    def get_data(self, pathname): 

        """Optional PEP302 get_data API. 

        """ 

        with open(pathname, 'rb') as f: 

            return f.read() 

 

 

def _write_pyc(state, co, source_stat, pyc): 

    # 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, and I hope 

    # sometime to be able to use imp.load_compiled to load them. (See 

    # the comment in load_module above.) 

    try: 

        fp = open(pyc, "wb") 

    except IOError: 

        err = sys.exc_info()[1].errno 

        state.trace("error writing pyc file at %s: errno=%s" %(pyc, err)) 

        # we ignore any failure to write the cache file 

        # there are many reasons, permission-denied, __pycache__ being a 

        # file etc. 

        return False 

    try: 

        fp.write(imp.get_magic()) 

        mtime = int(source_stat.mtime) 

        size = source_stat.size & 0xFFFFFFFF 

        fp.write(struct.pack("<ll", mtime, size)) 

        marshal.dump(co, fp) 

    finally: 

        fp.close() 

    return True 

 

RN = "\r\n".encode("utf-8") 

N = "\n".encode("utf-8") 

 

cookie_re = re.compile(r"^[ \t\f]*#.*coding[:=][ \t]*[-\w.]+") 

BOM_UTF8 = '\xef\xbb\xbf' 

 

def _rewrite_test(state, fn): 

    """Try to read and rewrite *fn* and return the code object.""" 

    try: 

        stat = fn.stat() 

        source = fn.read("rb") 

    except EnvironmentError: 

        return None, None 

    if ASCII_IS_DEFAULT_ENCODING: 

        # ASCII is the default encoding in Python 2. Without a coding 

        # declaration, Python 2 will complain about any bytes in the file 

        # outside the ASCII range. Sadly, this behavior does not extend to 

        # compile() or ast.parse(), which prefer to interpret the bytes as 

        # latin-1. (At least they properly handle explicit coding cookies.) To 

        # preserve this error behavior, we could force ast.parse() to use ASCII 

        # as the encoding by inserting a coding cookie. Unfortunately, that 

        # messes up line numbers. Thus, we have to check ourselves if anything 

        # is outside the ASCII range in the case no encoding is explicitly 

        # declared. For more context, see issue #269. Yay for Python 3 which 

        # gets this right. 

        end1 = source.find("\n") 

        end2 = source.find("\n", end1 + 1) 

        if (not source.startswith(BOM_UTF8) and 

            cookie_re.match(source[0:end1]) is None and 

            cookie_re.match(source[end1 + 1:end2]) is None): 

            if hasattr(state, "_indecode"): 

                # encodings imported us again, so don't rewrite. 

                return None, None 

            state._indecode = True 

            try: 

                try: 

                    source.decode("ascii") 

                except UnicodeDecodeError: 

                    # Let it fail in real import. 

                    return None, None 

            finally: 

                del state._indecode 

    # On Python versions which are not 2.7 and less than or equal to 3.1, the 

    # parser expects *nix newlines. 

    if REWRITE_NEWLINES: 

        source = source.replace(RN, N) + N 

    try: 

        tree = ast.parse(source) 

    except SyntaxError: 

        # Let this pop up again in the real import. 

        state.trace("failed to parse: %r" % (fn,)) 

        return None, None 

    rewrite_asserts(tree) 

    try: 

        co = compile(tree, fn.strpath, "exec") 

    except SyntaxError: 

        # It's possible that this error is from some bug in the 

        # assertion rewriting, but I don't know of a fast way to tell. 

        state.trace("failed to compile: %r" % (fn,)) 

        return None, None 

    return stat, co 

 

def _make_rewritten_pyc(state, source_stat, pyc, co): 

    """Try to dump rewritten code to *pyc*.""" 

    if sys.platform.startswith("win"): 

        # Windows grants exclusive access to open files and doesn't have atomic 

        # rename, so just write into the final file. 

        _write_pyc(state, co, source_stat, pyc) 

    else: 

        # When not on windows, assume rename is atomic. Dump the code object 

        # into a file specific to this process and atomically replace it. 

        proc_pyc = pyc + "." + str(os.getpid()) 

        if _write_pyc(state, co, source_stat, proc_pyc): 

            os.rename(proc_pyc, pyc) 

 

exitdef _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(pyc, "rb") 

    except IOError: 

        return None 

    with fp: 

        try: 

            mtime = int(source.mtime()) 

            size = source.size() 

            data = fp.read(12) 

        except EnvironmentError as e: 

            trace('_read_pyc(%s): EnvironmentError %s' % (source, e)) 

            return None 

        # Check for invalid or out of date pyc file. 

333   333        if (len(data) != 12 or data[:4] != imp.get_magic() or 

                struct.unpack("<ll", data[4:]) != (mtime, size)): 

            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(%s): marshal.load error %s' % (source, e)) 

            return None 

341        if not isinstance(co, types.CodeType): 

            trace('_read_pyc(%s): not a code object' % source) 

            return None 

        return co 

 

 

def rewrite_asserts(mod): 

    """Rewrite the assert statements in mod.""" 

    AssertionRewriter().run(mod) 

 

 

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. 

 

    """ 

    repr = py.io.saferepr(obj) 

    if py.builtin._istext(repr): 

        t = py.builtin.text 

    else: 

        t = py.builtin.bytes 

    return repr.replace(t("\n"), t("\\n")) 

 

 

from _pytest.assertion.util import format_explanation as _format_explanation # noqa 

 

def _format_assertmsg(obj): 

    """Format the custom assertion message given. 

 

    For strings this simply replaces newlines with '\n~' so that 

    util.format_explanation() will preserve them instead of escaping 

    newlines.  For other objects py.io.saferepr() is used first. 

 

    """ 

    # reprlib appears to have a bug which means that if a string 

    # contains a newline it gets escaped, however if an object has a 

    # .__repr__() which contains newlines it does not get escaped. 

    # However in either case we want to preserve the newline. 

    if py.builtin._istext(obj) or py.builtin._isbytes(obj): 

        s = obj 

        is_repr = False 

    else: 

        s = py.io.saferepr(obj) 

        is_repr = True 

    if py.builtin._istext(s): 

        t = py.builtin.text 

    else: 

        t = py.builtin.bytes 

    s = s.replace(t("\n"), t("\n~")).replace(t("%"), t("%%")) 

    if is_repr: 

        s = s.replace(t("\\n"), t("\n~")) 

    return s 

 

def _should_repr_global_name(obj): 

    return not hasattr(obj, "__name__") and not py.builtin.callable(obj) 

 

def _format_boolop(explanations, is_or): 

    explanation = "(" + (is_or and " or " or " and ").join(explanations) + ")" 

    if py.builtin._istext(explanation): 

        t = py.builtin.text 

    else: 

        t = py.builtin.bytes 

    return explanation.replace(t('%'), t('%%')) 

 

def _call_reprcompare(ops, results, expls, each_obj): 

    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 

 

 

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" 

} 

# Python 3.5+ compatibility 

try: 

    binop_map[ast.MatMult] = "@" 

except AttributeError: 

    pass 

 

# Python 3.4+ compatibility 

464if hasattr(ast, "NameConstant"): 

    _NameConstant = ast.NameConstant 

else: 

    def _NameConstant(c): 

        return ast.Name(str(c), ast.Load()) 

 

 

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 

 

 

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 re-write 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 re-writes 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. 

 

    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". 

 

    :on_failure: The AST statements which will be executed if the 

       assertion test fails.  This is the code which will construct 

       the failure message and raises the AssertionError. 

 

    :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 run(self, mod): 

        """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(py.builtin.builtins.__name__, "@py_builtins"), 

                   ast.alias("_pytest.assertion.rewrite", "@pytest_ar")] 

        expect_docstring = True 

        pos = 0 

        lineno = 0 

        for item in mod.body: 

            if (expect_docstring and isinstance(item, ast.Expr) and 

                    isinstance(item.value, ast.Str)): 

                doc = item.value.s 

                if "PYTEST_DONT_REWRITE" in doc: 

                    # The module has disabled assertion rewriting. 

                    return 

                lineno += len(doc) - 1 

                expect_docstring = False 

            elif (not isinstance(item, ast.ImportFrom) or item.level > 0 or 

                  item.module != "__future__"): 

                lineno = item.lineno 

                break 

            pos += 1 

        imports = [ast.Import([alias], lineno=lineno, col_offset=0) 

                   for alias in aliases] 

        mod.body[pos:pos] = imports 

        # Collect asserts. 

        nodes = [mod] 

        while nodes: 

            node = nodes.pop() 

            for name, field in ast.iter_fields(node): 

                if isinstance(field, list): 

                    new = [] 

                    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) and 

                      # Don't recurse into expressions as they can't contain 

                      # asserts. 

                      not isinstance(field, ast.expr)): 

                    nodes.append(field) 

 

    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 

 

    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()) 

 

    def display(self, expr): 

        """Call py.io.saferepr on the expression.""" 

        return self.helper("saferepr", expr) 

 

    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), []) 

 

    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()) 

 

    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" 

 

    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 = {} 

        self.stack.append(self.explanation_specifiers) 

 

    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 .on_failure 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)) 

        self.on_failure.append(ast.Assign([ast.Name(name, ast.Store())], form)) 

        return ast.Name(name, ast.Load()) 

 

    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)) 

 

    def visit_Assert(self, assert_): 

        """Return the AST statements to replace the ast.Assert instance. 

 

        This re-writes 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. 

 

        """ 

        self.statements = [] 

        self.variables = [] 

        self.variable_counter = itertools.count() 

        self.stack = [] 

        self.on_failure = [] 

        self.push_format_context() 

        # Rewrite assert into a bunch of statements. 

        top_condition, explanation = self.visit(assert_.test) 

        # Create failure message. 

        body = self.on_failure 

        negation = ast.UnaryOp(ast.Not(), top_condition) 

        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], []) 

        if sys.version_info[0] >= 3: 

            raise_ = ast.Raise(exc, None) 

        else: 

            raise_ = ast.Raise(exc, None, 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, _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 

 

    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) 

 

    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.on_failure 

        levels = len(boolop.values) - 1 

        self.push_format_context() 

        # Process each operand, short-circuting if needed. 

        for i, v in enumerate(boolop.values): 

            if i: 

                fail_inner = [] 

                # cond is set in a prior loop iteration below 

                self.on_failure.append(ast.If(cond, fail_inner, [])) # noqa 

                self.on_failure = 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.on_failure.append(ast.Expr(call)) 

            if i < levels: 

                cond = res 

                if is_or: 

                    cond = ast.UnaryOp(ast.Not(), cond) 

                inner = [] 

                self.statements.append(ast.If(cond, inner, [])) 

                self.statements = body = inner 

        self.statements = save 

        self.on_failure = 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) 

 

    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,) 

 

    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 = "(%s %s %s)" % (left_expl, symbol, right_expl) 

        res = self.assign(ast.BinOp(left_expr, binop.op, right_expr)) 

        return res, explanation 

 

    def visit_Call_35(self, call): 

        """ 

        visit `ast.Call` nodes on Python3.5 and after 

        """ 

        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 = "%s(%s)" % (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 = "%s\n{%s = %s\n}" % (res_expl, res_expl, expl) 

        return res, outer_expl 

 

    def visit_Starred(self, starred): 

        # From Python 3.5, a Starred node can appear in a function call 

        res, expl = self.visit(starred.value) 

        return starred, '*' + expl 

 

    def visit_Call_legacy(self, call): 

        """ 

        visit `ast.Call nodes on 3.4 and below` 

        """ 

        new_func, func_expl = self.visit(call.func) 

        arg_expls = [] 

        new_args = [] 

        new_kwargs = [] 

        new_star = new_kwarg = None 

        for arg in call.args: 

            res, expl = self.visit(arg) 

            new_args.append(res) 

            arg_expls.append(expl) 

        for keyword in call.keywords: 

            res, expl = self.visit(keyword.value) 

            new_kwargs.append(ast.keyword(keyword.arg, res)) 

            arg_expls.append(keyword.arg + "=" + expl) 

        if call.starargs: 

            new_star, expl = self.visit(call.starargs) 

            arg_expls.append("*" + expl) 

        if call.kwargs: 

            new_kwarg, expl = self.visit(call.kwargs) 

            arg_expls.append("**" + expl) 

        expl = "%s(%s)" % (func_expl, ', '.join(arg_expls)) 

        new_call = ast.Call(new_func, new_args, new_kwargs, 

                            new_star, new_kwarg) 

        res = self.assign(new_call) 

        res_expl = self.explanation_param(self.display(res)) 

        outer_expl = "%s\n{%s = %s\n}" % (res_expl, res_expl, expl) 

        return res, outer_expl 

 

    # ast.Call signature changed on 3.5, 

    # conditionally change  which methods is named 

    # visit_Call depending on Python version 

840    if sys.version_info >= (3, 5): 

        visit_Call = visit_Call_35 

    else: 

        visit_Call = visit_Call_legacy 

 

 

    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 

 

    def visit_Compare(self, comp): 

        self.push_format_context() 

        left_res, left_expl = self.visit(comp.left) 

        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) 

            results.append(next_res) 

            sym = binop_map[op.__class__] 

            syms.append(ast.Str(sym)) 

            expl = "%s %s %s" % (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) 

        else: 

            res = load_names[0] 

        return res, self.explanation_param(self.pop_format_context(expl_call))