Hide keyboard shortcuts

Hot-keys on this page

r m x p   toggle line displays

j k   next/prev highlighted chunk

0   (zero) top of page

1   (one) first highlighted chunk

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

647

648

649

650

651

652

653

654

655

656

657

658

659

660

661

662

663

664

665

666

667

668

669

670

671

672

673

674

675

676

677

678

679

680

681

682

683

684

685

686

687

688

689

690

691

692

693

694

695

696

697

698

699

700

701

702

703

704

705

706

707

708

709

710

711

712

713

714

715

716

717

718

719

720

721

722

723

724

725

726

727

728

729

730

731

732

733

734

735

736

737

738

739

740

741

742

743

744

745

746

747

748

749

750

751

752

753

754

755

756

757

758

759

760

761

762

763

764

765

766

767

768

769

770

771

772

773

774

775

776

777

778

779

780

781

782

783

784

785

786

787

788

789

790

791

792

793

794

795

796

797

798

799

800

801

802

803

804

805

806

807

808

809

810

811

812

813

814

815

816

817

818

819

820

821

822

823

824

825

826

827

828

829

830

831

832

833

834

835

836

837

838

839

840

841

842

843

844

845

846

847

848

849

850

851

852

853

854

855

856

857

858

859

860

861

862

863

864

865

866

867

868

869

870

871

872

873

874

875

876

877

878

879

880

881

882

883

884

885

886

887

888

889

890

891

892

893

894

895

896

897

898

899

900

901

902

903

904

905

906

907

908

909

910

911

912

913

914

915

916

917

918

919

920

921

922

923

924

925

926

927

928

929

930

931

932

933

934

935

936

937

938

939

940

941

942

943

944

945

946

947

948

949

950

951

952

953

954

955

956

957

958

959

960

961

962

963

964

965

966

967

968

969

970

971

972

973

974

975

976

977

978

979

980

981

982

983

984

985

986

987

988

989

990

991

992

993

994

995

996

997

998

999

1000

1001

1002

1003

1004

1005

1006

1007

1008

1009

1010

1011

1012

1013

1014

1015

1016

1017

1018

1019

1020

1021

1022

1023

1024

1025

1026

1027

1028

1029

1030

1031

1032

1033

1034

1035

1036

1037

1038

1039

1040

1041

1042

1043

1044

1045

1046

1047

1048

1049

1050

1051

1052

1053

1054

1055

1056

1057

1058

1059

1060

1061

1062

1063

1064

1065

1066

1067

1068

1069

1070

1071

1072

1073

1074

1075

1076

1077

1078

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

from __future__ import absolute_import 

from __future__ import division 

from __future__ import print_function 

 

import ast 

import errno 

import imp 

import itertools 

import marshal 

import os 

import re 

import string 

import struct 

import sys 

import types 

 

import atomicwrites 

import py 

import six 

 

from _pytest._io.saferepr import saferepr 

from _pytest.assertion import util 

from _pytest.compat import spec_from_file_location 

from _pytest.pathlib import fnmatch_ex 

from _pytest.pathlib import PurePath 

 

# pytest caches rewritten pycs in __pycache__. 

if hasattr(imp, "get_tag"): 

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

else: 

if hasattr(sys, "pypy_version_info"): 

impl = "pypy" 

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 

 

ASCII_IS_DEFAULT_ENCODING = sys.version_info[0] < 3 

 

if sys.version_info >= (3, 5): 

ast_Call = ast.Call 

else: 

 

def ast_Call(a, b, c): 

return ast.Call(a, b, c, None, None) 

 

 

class AssertionRewritingHook(object): 

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

 

def __init__(self, config): 

self.config = config 

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

self.session = None 

self.modules = {} 

self._rewritten_names = set() 

self._register_with_pkg_resources() 

self._must_rewrite = set() 

# 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 = {} 

self._session_paths_checked = False 

 

def set_session(self, session): 

self.session = session 

self._session_paths_checked = False 

 

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

"""Indirection so we can mock calls to find_module originated from the hook during testing""" 

return imp.find_module(name, path) 

 

def find_module(self, name, path=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) 

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 = self._imp_find_module(lastname, path) 

except ImportError: 

return None 

if fd is not None: 

fd.close() 

tp = desc[2] 

if tp == imp.PY_COMPILED: 

if hasattr(imp, "source_from_cache"): 

try: 

fn = imp.source_from_cache(fn) 

except ValueError: 

# Python 3 doesn't like orphaned but still-importable 

# .pyc files. 

fn = fn[:-1] 

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) 

if not self._should_rewrite(name, fn_pypath, state): 

return None 

 

self._rewritten_names.add(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 = os.path.join(fn_pypath.dirname, "__pycache__") 

if write: 

try: 

os.mkdir(cache_dir) 

except OSError: 

e = sys.exc_info()[1].errno 

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) 

if co is None: 

state.trace("rewriting %r" % (fn,)) 

source_stat, co = _rewrite_test(self.config, fn_pypath) 

if co is None: 

# Probably a SyntaxError in the test. 

return None 

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 %r" % (fn,)) 

self.modules[name] = co, pyc 

return self 

 

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 imp.find_module (inside of the find_module 

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: %s" % (name,)) 

return True 

 

def _should_rewrite(self, name, fn_pypath, state): 

# always rewrite conftest files 

fn = str(fn_pypath) 

if fn_pypath.basename == "conftest.py": 

state.trace("rewriting conftest file: %r" % (fn,)) 

return True 

 

if self.session is not None: 

if self.session.isinitpath(fn): 

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

return True 

 

# modules not passed explicitly on the command line are only 

# rewritten if they match the naming convention for test files 

for pat in self.fnpats: 

if fn_pypath.fnmatch(pat): 

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

return True 

 

return self._is_marked_for_rewrite(name, state) 

 

def _is_marked_for_rewrite(self, name, 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)" % (name, marked)) 

self._marked_for_rewrite_cache[name] = True 

return True 

 

self._marked_for_rewrite_cache[name] = False 

return False 

 

def mark_rewrite(self, *names): 

"""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: 

if not AssertionRewriter.is_rewrite_disabled( 

sys.modules[name].__doc__ or "" 

): 

self._warn_already_imported(name) 

self._must_rewrite.update(names) 

self._marked_for_rewrite_cache.clear() 

 

def _warn_already_imported(self, name): 

from _pytest.warning_types import PytestWarning 

from _pytest.warnings import _issue_warning_captured 

 

_issue_warning_captured( 

PytestWarning("Module already imported so cannot be rewritten: %s" % name), 

self.config.hook, 

stacklevel=5, 

) 

 

def load_module(self, name): 

co, pyc = self.modules.pop(name) 

if name in sys.modules: 

# 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.) 

mod = sys.modules[name] 

else: 

# 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 

# Normally, this attribute is 3.4+ 

mod.__spec__ = spec_from_file_location(name, co.co_filename, loader=self) 

six.exec_(co, mod.__dict__) 

except: # noqa 

if name in sys.modules: 

del sys.modules[name] 

raise 

return sys.modules[name] 

 

def is_package(self, name): 

try: 

fd, fn, desc = self._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: 

with atomicwrites.atomic_write(pyc, mode="wb", overwrite=True) as fp: 

fp.write(imp.get_magic()) 

mtime = int(source_stat.mtime) 

size = source_stat.size & 0xFFFFFFFF 

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

fp.write(marshal.dumps(co)) 

except EnvironmentError as e: 

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

# we ignore any failure to write the cache file 

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

# file etc. 

return False 

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(config, fn): 

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

state = config._assertstate 

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 

try: 

tree = ast.parse(source, filename=fn.strpath) 

except SyntaxError: 

# Let this pop up again in the real import. 

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

return None, None 

rewrite_asserts(tree, fn, config) 

try: 

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

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 _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. 

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 

if not isinstance(co, types.CodeType): 

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

return None 

return co 

 

 

def rewrite_asserts(mod, module_path=None, config=None): 

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

AssertionRewriter(module_path, config).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. 

 

""" 

r = saferepr(obj) 

# only occurs in python2.x, repr must return text in python3+ 

if isinstance(r, bytes): 

# Represent unprintable bytes as `\x##` 

r = u"".join( 

u"\\x{:x}".format(ord(c)) if c not in string.printable else c.decode() 

for c in r 

) 

return r.replace(u"\n", u"\\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 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. 

replaces = [(u"\n", u"\n~"), (u"%", u"%%")] 

if not isinstance(obj, six.string_types): 

obj = saferepr(obj) 

replaces.append((u"\\n", u"\n~")) 

 

if isinstance(obj, bytes): 

replaces = [(r1.encode(), r2.encode()) for r1, r2 in replaces] 

 

for r1, r2 in replaces: 

obj = obj.replace(r1, r2) 

 

return obj 

 

 

def _should_repr_global_name(obj): 

if callable(obj): 

return False 

 

try: 

return not hasattr(obj, "__name__") 

except Exception: 

return True 

 

 

def _format_boolop(explanations, is_or): 

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

if isinstance(explanation, six.text_type): 

return explanation.replace(u"%", u"%%") 

else: 

return explanation.replace(b"%", b"%%") 

 

 

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 

if 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 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. 

 

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 __init__(self, module_path, config): 

super(AssertionRewriter, self).__init__() 

self.module_path = module_path 

self.config = config 

 

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(six.moves.builtins.__name__, "@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] 

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) 

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

# asserts. 

and not isinstance(field, ast.expr) 

): 

nodes.append(field) 

 

@staticmethod 

def is_rewrite_disabled(docstring): 

return "PYTEST_DONT_REWRITE" in docstring 

 

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 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 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 PytestWarning 

import warnings 

 

warnings.warn_explicit( 

PytestWarning("assertion is always true, perhaps remove parentheses?"), 

category=None, 

filename=str(self.module_path), 

lineno=assert_.lineno, 

) 

 

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) 

# If in a test module, check if directly asserting None, in order to warn [Issue #3191] 

if self.module_path is not None: 

self.statements.append( 

self.warn_about_none_ast( 

top_condition, module_path=self.module_path, lineno=assert_.lineno 

) 

) 

# 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 warn_about_none_ast(self, node, module_path, lineno): 

""" 

Returns an AST issuing a warning if the value of node is `None`. 

This is used to warn the user when asserting a function that asserts 

internally already. 

See issue #3191 for more details. 

""" 

 

# Using parse because it is different between py2 and py3. 

AST_NONE = ast.parse("None").body[0].value 

val_is_none = ast.Compare(node, [ast.Is()], [AST_NONE]) 

send_warning = ast.parse( 

""" 

from _pytest.warning_types import PytestWarning 

from warnings import warn_explicit 

warn_explicit( 

PytestWarning('asserting the value None, please use "assert is None"'), 

category=None, 

filename={filename!r}, 

lineno={lineno}, 

) 

""".format( 

filename=module_path.strpath, lineno=lineno 

) 

).body 

return ast.If(val_is_none, send_warning, []) 

 

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) 

new_starred = ast.Starred(res, starred.ctx) 

return new_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 

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) 

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 = "%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))