summaryrefslogtreecommitdiff
path: root/src/module_wrap.cc
blob: f642440bff5a882f676eb457a0bf6378396b28f3 (plain)
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
#include <algorithm>
#include <limits.h>  // PATH_MAX
#include <sys/stat.h>  // S_IFDIR
#include "module_wrap.h"

#include "env.h"
#include "node_errors.h"
#include "node_url.h"
#include "util-inl.h"
#include "node_contextify.h"
#include "node_watchdog.h"

namespace node {
namespace loader {

using errors::TryCatchScope;

using node::contextify::ContextifyContext;
using node::url::URL;
using node::url::URL_FLAGS_FAILED;
using v8::Array;
using v8::Context;
using v8::Function;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::Integer;
using v8::IntegrityLevel;
using v8::Isolate;
using v8::JSON;
using v8::Just;
using v8::Local;
using v8::Maybe;
using v8::MaybeLocal;
using v8::Module;
using v8::Nothing;
using v8::Number;
using v8::Object;
using v8::PrimitiveArray;
using v8::Promise;
using v8::ScriptCompiler;
using v8::ScriptOrigin;
using v8::String;
using v8::Undefined;
using v8::Value;

static const char* const EXTENSIONS[] = {".mjs", ".js", ".json", ".node"};

ModuleWrap::ModuleWrap(Environment* env,
                       Local<Object> object,
                       Local<Module> module,
                       Local<String> url) :
  BaseObject(env, object),
  id_(env->get_next_module_id()) {
  module_.Reset(env->isolate(), module);
  url_.Reset(env->isolate(), url);
  env->id_to_module_map.emplace(id_, this);
}

ModuleWrap::~ModuleWrap() {
  HandleScope scope(env()->isolate());
  Local<Module> module = module_.Get(env()->isolate());
  env()->id_to_module_map.erase(id_);
  auto range = env()->hash_to_module_map.equal_range(module->GetIdentityHash());
  for (auto it = range.first; it != range.second; ++it) {
    if (it->second == this) {
      env()->hash_to_module_map.erase(it);
      break;
    }
  }
}

ModuleWrap* ModuleWrap::GetFromModule(Environment* env,
                                      Local<Module> module) {
  auto range = env->hash_to_module_map.equal_range(module->GetIdentityHash());
  for (auto it = range.first; it != range.second; ++it) {
    if (it->second->module_ == module) {
      return it->second;
    }
  }
  return nullptr;
}

ModuleWrap* ModuleWrap::GetFromID(Environment* env, uint32_t id) {
  auto module_wrap_it = env->id_to_module_map.find(id);
  if (module_wrap_it == env->id_to_module_map.end()) {
    return nullptr;
  }
  return module_wrap_it->second;
}

void ModuleWrap::New(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  Isolate* isolate = env->isolate();

  CHECK(args.IsConstructCall());
  Local<Object> that = args.This();

  const int argc = args.Length();
  CHECK_GE(argc, 2);

  CHECK(args[0]->IsString());
  Local<String> source_text = args[0].As<String>();

  CHECK(args[1]->IsString());
  Local<String> url = args[1].As<String>();

  Local<Context> context;
  Local<Integer> line_offset;
  Local<Integer> column_offset;

  if (argc == 5) {
    // new ModuleWrap(source, url, context?, lineOffset, columnOffset)
    if (args[2]->IsUndefined()) {
      context = that->CreationContext();
    } else {
      CHECK(args[2]->IsObject());
      ContextifyContext* sandbox =
          ContextifyContext::ContextFromContextifiedSandbox(
              env, args[2].As<Object>());
      CHECK_NOT_NULL(sandbox);
      context = sandbox->context();
    }

    CHECK(args[3]->IsNumber());
    line_offset = args[3].As<Integer>();

    CHECK(args[4]->IsNumber());
    column_offset = args[4].As<Integer>();
  } else {
    // new ModuleWrap(source, url)
    context = that->CreationContext();
    line_offset = Integer::New(isolate, 0);
    column_offset = Integer::New(isolate, 0);
  }

  Environment::ShouldNotAbortOnUncaughtScope no_abort_scope(env);
  TryCatchScope try_catch(env);
  Local<Module> module;

  Local<PrimitiveArray> host_defined_options =
      PrimitiveArray::New(isolate, HostDefinedOptions::kLength);
  host_defined_options->Set(isolate, HostDefinedOptions::kType,
                            Number::New(isolate, ScriptType::kModule));

  // compile
  {
    ScriptOrigin origin(url,
                        line_offset,                          // line offset
                        column_offset,                        // column offset
                        True(isolate),                        // is cross origin
                        Local<Integer>(),                     // script id
                        Local<Value>(),                       // source map URL
                        False(isolate),                       // is opaque (?)
                        False(isolate),                       // is WASM
                        True(isolate),                        // is ES Module
                        host_defined_options);
    Context::Scope context_scope(context);
    ScriptCompiler::Source source(source_text, origin);
    if (!ScriptCompiler::CompileModule(isolate, &source).ToLocal(&module)) {
      CHECK(try_catch.HasCaught());
      CHECK(!try_catch.Message().IsEmpty());
      CHECK(!try_catch.Exception().IsEmpty());
      AppendExceptionLine(env, try_catch.Exception(), try_catch.Message(),
                          ErrorHandlingMode::MODULE_ERROR);
      try_catch.ReThrow();
      return;
    }
  }

  if (!that->Set(context, env->url_string(), url).FromMaybe(false)) {
    return;
  }

  ModuleWrap* obj = new ModuleWrap(env, that, module, url);
  obj->context_.Reset(isolate, context);

  env->hash_to_module_map.emplace(module->GetIdentityHash(), obj);

  host_defined_options->Set(isolate, HostDefinedOptions::kID,
                            Number::New(isolate, obj->id()));

  that->SetIntegrityLevel(context, IntegrityLevel::kFrozen);
  args.GetReturnValue().Set(that);
}

void ModuleWrap::Link(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  Isolate* isolate = args.GetIsolate();

  CHECK_EQ(args.Length(), 1);
  CHECK(args[0]->IsFunction());

  Local<Object> that = args.This();

  ModuleWrap* obj;
  ASSIGN_OR_RETURN_UNWRAP(&obj, that);

  if (obj->linked_)
    return;
  obj->linked_ = true;

  Local<Function> resolver_arg = args[0].As<Function>();

  Local<Context> mod_context = obj->context_.Get(isolate);
  Local<Module> module = obj->module_.Get(isolate);

  Local<Array> promises = Array::New(isolate,
                                     module->GetModuleRequestsLength());

  // call the dependency resolve callbacks
  for (int i = 0; i < module->GetModuleRequestsLength(); i++) {
    Local<String> specifier = module->GetModuleRequest(i);
    Utf8Value specifier_utf8(env->isolate(), specifier);
    std::string specifier_std(*specifier_utf8, specifier_utf8.length());

    Local<Value> argv[] = {
      specifier
    };

    MaybeLocal<Value> maybe_resolve_return_value =
        resolver_arg->Call(mod_context, that, 1, argv);
    if (maybe_resolve_return_value.IsEmpty()) {
      return;
    }
    Local<Value> resolve_return_value =
        maybe_resolve_return_value.ToLocalChecked();
    if (!resolve_return_value->IsPromise()) {
      env->ThrowError("linking error, expected resolver to return a promise");
    }
    Local<Promise> resolve_promise = resolve_return_value.As<Promise>();
    obj->resolve_cache_[specifier_std].Reset(env->isolate(), resolve_promise);

    promises->Set(mod_context, i, resolve_promise).FromJust();
  }

  args.GetReturnValue().Set(promises);
}

void ModuleWrap::Instantiate(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  Isolate* isolate = args.GetIsolate();
  ModuleWrap* obj;
  ASSIGN_OR_RETURN_UNWRAP(&obj, args.This());
  Local<Context> context = obj->context_.Get(isolate);
  Local<Module> module = obj->module_.Get(isolate);
  TryCatchScope try_catch(env);
  Maybe<bool> ok = module->InstantiateModule(context, ResolveCallback);

  // clear resolve cache on instantiate
  obj->resolve_cache_.clear();

  if (!ok.FromMaybe(false)) {
    CHECK(try_catch.HasCaught());
    CHECK(!try_catch.Message().IsEmpty());
    CHECK(!try_catch.Exception().IsEmpty());
    AppendExceptionLine(env, try_catch.Exception(), try_catch.Message(),
                        ErrorHandlingMode::MODULE_ERROR);
    try_catch.ReThrow();
    return;
  }
}

void ModuleWrap::Evaluate(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  Isolate* isolate = env->isolate();
  ModuleWrap* obj;
  ASSIGN_OR_RETURN_UNWRAP(&obj, args.This());
  Local<Context> context = obj->context_.Get(isolate);
  Local<Module> module = obj->module_.Get(isolate);

  // module.evaluate(timeout, breakOnSigint)
  CHECK_EQ(args.Length(), 2);

  CHECK(args[0]->IsNumber());
  int64_t timeout = args[0]->IntegerValue(env->context()).FromJust();

  CHECK(args[1]->IsBoolean());
  bool break_on_sigint = args[1]->IsTrue();

  Environment::ShouldNotAbortOnUncaughtScope no_abort_scope(env);
  TryCatchScope try_catch(env);

  bool timed_out = false;
  bool received_signal = false;
  MaybeLocal<Value> result;
  if (break_on_sigint && timeout != -1) {
    Watchdog wd(isolate, timeout, &timed_out);
    SigintWatchdog swd(isolate, &received_signal);
    result = module->Evaluate(context);
  } else if (break_on_sigint) {
    SigintWatchdog swd(isolate, &received_signal);
    result = module->Evaluate(context);
  } else if (timeout != -1) {
    Watchdog wd(isolate, timeout, &timed_out);
    result = module->Evaluate(context);
  } else {
    result = module->Evaluate(context);
  }

  // Convert the termination exception into a regular exception.
  if (timed_out || received_signal) {
    env->isolate()->CancelTerminateExecution();
    // It is possible that execution was terminated by another timeout in
    // which this timeout is nested, so check whether one of the watchdogs
    // from this invocation is responsible for termination.
    if (timed_out) {
      THROW_ERR_SCRIPT_EXECUTION_TIMEOUT(env, timeout);
    } else if (received_signal) {
      THROW_ERR_SCRIPT_EXECUTION_INTERRUPTED(env);
    }
  }

  if (try_catch.HasCaught()) {
    try_catch.ReThrow();
    return;
  }

  args.GetReturnValue().Set(result.ToLocalChecked());
}

void ModuleWrap::Namespace(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  Isolate* isolate = args.GetIsolate();
  ModuleWrap* obj;
  ASSIGN_OR_RETURN_UNWRAP(&obj, args.This());

  Local<Module> module = obj->module_.Get(isolate);

  switch (module->GetStatus()) {
    default:
      return env->ThrowError(
          "cannot get namespace, Module has not been instantiated");
    case v8::Module::Status::kInstantiated:
    case v8::Module::Status::kEvaluating:
    case v8::Module::Status::kEvaluated:
      break;
  }

  Local<Value> result = module->GetModuleNamespace();
  args.GetReturnValue().Set(result);
}

void ModuleWrap::GetStatus(const FunctionCallbackInfo<Value>& args) {
  Isolate* isolate = args.GetIsolate();
  ModuleWrap* obj;
  ASSIGN_OR_RETURN_UNWRAP(&obj, args.This());

  Local<Module> module = obj->module_.Get(isolate);

  args.GetReturnValue().Set(module->GetStatus());
}

void ModuleWrap::GetStaticDependencySpecifiers(
    const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  ModuleWrap* obj;
  ASSIGN_OR_RETURN_UNWRAP(&obj, args.This());

  Local<Module> module = obj->module_.Get(env->isolate());

  int count = module->GetModuleRequestsLength();

  Local<Array> specifiers = Array::New(env->isolate(), count);

  for (int i = 0; i < count; i++)
    specifiers->Set(env->context(), i, module->GetModuleRequest(i)).FromJust();

  args.GetReturnValue().Set(specifiers);
}

void ModuleWrap::GetError(const FunctionCallbackInfo<Value>& args) {
  Isolate* isolate = args.GetIsolate();
  ModuleWrap* obj;
  ASSIGN_OR_RETURN_UNWRAP(&obj, args.This());

  Local<Module> module = obj->module_.Get(isolate);

  args.GetReturnValue().Set(module->GetException());
}

MaybeLocal<Module> ModuleWrap::ResolveCallback(Local<Context> context,
                                               Local<String> specifier,
                                               Local<Module> referrer) {
  Environment* env = Environment::GetCurrent(context);
  CHECK_NOT_NULL(env);  // TODO(addaleax): Handle nullptr here.
  Isolate* isolate = env->isolate();

  ModuleWrap* dependent = GetFromModule(env, referrer);
  if (dependent == nullptr) {
    env->ThrowError("linking error, null dep");
    return MaybeLocal<Module>();
  }

  Utf8Value specifier_utf8(isolate, specifier);
  std::string specifier_std(*specifier_utf8, specifier_utf8.length());

  if (dependent->resolve_cache_.count(specifier_std) != 1) {
    env->ThrowError("linking error, not in local cache");
    return MaybeLocal<Module>();
  }

  Local<Promise> resolve_promise =
      dependent->resolve_cache_[specifier_std].Get(isolate);

  if (resolve_promise->State() != Promise::kFulfilled) {
    env->ThrowError("linking error, dependency promises must be resolved on "
                    "instantiate");
    return MaybeLocal<Module>();
  }

  Local<Object> module_object = resolve_promise->Result().As<Object>();
  if (module_object.IsEmpty() || !module_object->IsObject()) {
    env->ThrowError("linking error, expected a valid module object from "
                    "resolver");
    return MaybeLocal<Module>();
  }

  ModuleWrap* module;
  ASSIGN_OR_RETURN_UNWRAP(&module, module_object, MaybeLocal<Module>());
  return module->module_.Get(isolate);
}

namespace {

// Tests whether a path starts with /, ./ or ../
// In WhatWG terminology, the alternative case is called a "bare" specifier
// (e.g. in `import "jquery"`).
inline bool ShouldBeTreatedAsRelativeOrAbsolutePath(
    const std::string& specifier) {
  size_t len = specifier.length();
  if (len == 0)
    return false;
  if (specifier[0] == '/') {
    return true;
  } else if (specifier[0] == '.') {
    if (len == 1 || specifier[1] == '/')
      return true;
    if (specifier[1] == '.') {
      if (len == 2 || specifier[2] == '/')
        return true;
    }
  }
  return false;
}

std::string ReadFile(uv_file file) {
  std::string contents;
  uv_fs_t req;
  char buffer_memory[4096];
  uv_buf_t buf = uv_buf_init(buffer_memory, sizeof(buffer_memory));

  do {
    const int r = uv_fs_read(uv_default_loop(),
                             &req,
                             file,
                             &buf,
                             1,
                             contents.length(),  // offset
                             nullptr);
    uv_fs_req_cleanup(&req);

    if (r <= 0)
      break;
    contents.append(buf.base, r);
  } while (true);
  return contents;
}

enum CheckFileOptions {
  LEAVE_OPEN_AFTER_CHECK,
  CLOSE_AFTER_CHECK
};

Maybe<uv_file> CheckFile(const std::string& path,
                         CheckFileOptions opt = CLOSE_AFTER_CHECK) {
  uv_fs_t fs_req;
  if (path.empty()) {
    return Nothing<uv_file>();
  }

  uv_file fd = uv_fs_open(nullptr, &fs_req, path.c_str(), O_RDONLY, 0, nullptr);
  uv_fs_req_cleanup(&fs_req);

  if (fd < 0) {
    return Nothing<uv_file>();
  }

  uv_fs_fstat(nullptr, &fs_req, fd, nullptr);
  uint64_t is_directory = fs_req.statbuf.st_mode & S_IFDIR;
  uv_fs_req_cleanup(&fs_req);

  if (is_directory) {
    CHECK_EQ(0, uv_fs_close(nullptr, &fs_req, fd, nullptr));
    uv_fs_req_cleanup(&fs_req);
    return Nothing<uv_file>();
  }

  if (opt == CLOSE_AFTER_CHECK) {
    CHECK_EQ(0, uv_fs_close(nullptr, &fs_req, fd, nullptr));
    uv_fs_req_cleanup(&fs_req);
  }

  return Just(fd);
}

using Exists = PackageConfig::Exists;
using IsValid = PackageConfig::IsValid;
using HasMain = PackageConfig::HasMain;

const PackageConfig& GetPackageConfig(Environment* env,
                                      const std::string& path) {
  auto existing = env->package_json_cache.find(path);
  if (existing != env->package_json_cache.end()) {
    return existing->second;
  }
  Maybe<uv_file> check = CheckFile(path, LEAVE_OPEN_AFTER_CHECK);
  if (check.IsNothing()) {
    auto entry = env->package_json_cache.emplace(path,
        PackageConfig { Exists::No, IsValid::Yes, HasMain::No, "" });
    return entry.first->second;
  }

  Isolate* isolate = env->isolate();
  v8::HandleScope handle_scope(isolate);

  std::string pkg_src = ReadFile(check.FromJust());
  uv_fs_t fs_req;
  CHECK_EQ(0, uv_fs_close(nullptr, &fs_req, check.FromJust(), nullptr));
  uv_fs_req_cleanup(&fs_req);

  Local<String> src;
  if (!String::NewFromUtf8(isolate,
                           pkg_src.c_str(),
                           v8::NewStringType::kNormal,
                           pkg_src.length()).ToLocal(&src)) {
    auto entry = env->package_json_cache.emplace(path,
        PackageConfig { Exists::No, IsValid::Yes, HasMain::No, "" });
    return entry.first->second;
  }

  Local<Value> pkg_json_v;
  Local<Object> pkg_json;

  if (!JSON::Parse(env->context(), src).ToLocal(&pkg_json_v) ||
      !pkg_json_v->ToObject(env->context()).ToLocal(&pkg_json)) {
    auto entry = env->package_json_cache.emplace(path,
        PackageConfig { Exists::Yes, IsValid::No, HasMain::No, "" });
    return entry.first->second;
  }

  Local<Value> pkg_main;
  HasMain has_main = HasMain::No;
  std::string main_std;
  if (pkg_json->Get(env->context(), env->main_string()).ToLocal(&pkg_main)) {
    has_main = HasMain::Yes;
    Utf8Value main_utf8(isolate, pkg_main);
    main_std.assign(std::string(*main_utf8, main_utf8.length()));
  }

  auto entry = env->package_json_cache.emplace(path,
      PackageConfig { Exists::Yes, IsValid::Yes, has_main, main_std });
  return entry.first->second;
}

enum ResolveExtensionsOptions {
  TRY_EXACT_NAME,
  ONLY_VIA_EXTENSIONS
};

template <ResolveExtensionsOptions options>
Maybe<URL> ResolveExtensions(const URL& search) {
  if (options == TRY_EXACT_NAME) {
    std::string filePath = search.ToFilePath();
    Maybe<uv_file> check = CheckFile(filePath);
    if (!check.IsNothing()) {
      return Just(search);
    }
  }

  for (const char* extension : EXTENSIONS) {
    URL guess(search.path() + extension, &search);
    Maybe<uv_file> check = CheckFile(guess.ToFilePath());
    if (!check.IsNothing()) {
      return Just(guess);
    }
  }

  return Nothing<URL>();
}

inline Maybe<URL> ResolveIndex(const URL& search) {
  return ResolveExtensions<ONLY_VIA_EXTENSIONS>(URL("index", search));
}

Maybe<URL> ResolveMain(Environment* env, const URL& search) {
  URL pkg("package.json", &search);

  const PackageConfig& pjson =
      GetPackageConfig(env, pkg.ToFilePath());
  // Note invalid package.json should throw in resolver
  // currently we silently ignore which is incorrect
  if (pjson.exists == Exists::No ||
      pjson.is_valid == IsValid::No ||
      pjson.has_main == HasMain::No) {
    return Nothing<URL>();
  }
  if (!ShouldBeTreatedAsRelativeOrAbsolutePath(pjson.main)) {
    return Resolve(env, "./" + pjson.main, search, IgnoreMain);
  }
  return Resolve(env, pjson.main, search, IgnoreMain);
}

Maybe<URL> ResolveModule(Environment* env,
                         const std::string& specifier,
                         const URL& base) {
  URL parent(".", base);
  URL dir("");
  do {
    dir = parent;
    Maybe<URL> check =
        Resolve(env, "./node_modules/" + specifier, dir, CheckMain);
    if (!check.IsNothing()) {
      const size_t limit = specifier.find('/');
      const size_t spec_len =
          limit == std::string::npos ? specifier.length() :
                                       limit + 1;
      std::string chroot =
          dir.path() + "node_modules/" + specifier.substr(0, spec_len);
      if (check.FromJust().path().substr(0, chroot.length()) != chroot) {
        return Nothing<URL>();
      }
      return check;
    } else {
      // TODO(bmeck) PREVENT FALLTHROUGH
    }
    parent = URL("..", &dir);
  } while (parent.path() != dir.path());
  return Nothing<URL>();
}

Maybe<URL> ResolveDirectory(Environment* env,
                            const URL& search,
                            PackageMainCheck check_pjson_main) {
  if (check_pjson_main) {
    Maybe<URL> main = ResolveMain(env, search);
    if (!main.IsNothing())
      return main;
  }
  return ResolveIndex(search);
}

}  // anonymous namespace

Maybe<URL> Resolve(Environment* env,
                   const std::string& specifier,
                   const URL& base,
                   PackageMainCheck check_pjson_main) {
  URL pure_url(specifier);
  if (!(pure_url.flags() & URL_FLAGS_FAILED)) {
    // just check existence, without altering
    Maybe<uv_file> check = CheckFile(pure_url.ToFilePath());
    if (check.IsNothing()) {
      return Nothing<URL>();
    }
    return Just(pure_url);
  }
  if (specifier.length() == 0) {
    return Nothing<URL>();
  }
  if (ShouldBeTreatedAsRelativeOrAbsolutePath(specifier)) {
    URL resolved(specifier, base);
    Maybe<URL> file = ResolveExtensions<TRY_EXACT_NAME>(resolved);
    if (!file.IsNothing())
      return file;
    if (specifier.back() != '/') {
      resolved = URL(specifier + "/", base);
    }
    return ResolveDirectory(env, resolved, check_pjson_main);
  } else {
    return ResolveModule(env, specifier, base);
  }
}

void ModuleWrap::Resolve(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);

  // module.resolve(specifier, url)
  CHECK_EQ(args.Length(), 2);

  CHECK(args[0]->IsString());
  Utf8Value specifier_utf8(env->isolate(), args[0]);
  std::string specifier_std(*specifier_utf8, specifier_utf8.length());

  CHECK(args[1]->IsString());
  Utf8Value url_utf8(env->isolate(), args[1]);
  URL url(*url_utf8, url_utf8.length());

  if (url.flags() & URL_FLAGS_FAILED) {
    return node::THROW_ERR_INVALID_ARG_TYPE(
        env, "second argument is not a URL string");
  }

  Maybe<URL> result = node::loader::Resolve(env, specifier_std, url);
  if (result.IsNothing() || (result.FromJust().flags() & URL_FLAGS_FAILED)) {
    std::string msg = "Cannot find module " + specifier_std;
    return node::THROW_ERR_MISSING_MODULE(env, msg.c_str());
  }

  MaybeLocal<Value> obj = result.FromJust().ToObject(env);
  if (!obj.IsEmpty())
    args.GetReturnValue().Set(obj.ToLocalChecked());
}

static MaybeLocal<Promise> ImportModuleDynamically(
    Local<Context> context,
    Local<v8::ScriptOrModule> referrer,
    Local<String> specifier) {
  Isolate* iso = context->GetIsolate();
  Environment* env = Environment::GetCurrent(context);
  CHECK_NOT_NULL(env);  // TODO(addaleax): Handle nullptr here.
  v8::EscapableHandleScope handle_scope(iso);

  Local<Function> import_callback =
    env->host_import_module_dynamically_callback();

  Local<PrimitiveArray> options = referrer->GetHostDefinedOptions();
  if (options->Length() != HostDefinedOptions::kLength) {
    Local<Promise::Resolver> resolver =
        Promise::Resolver::New(context).ToLocalChecked();
    resolver
        ->Reject(context,
                 v8::Exception::TypeError(FIXED_ONE_BYTE_STRING(
                     context->GetIsolate(), "Invalid host defined options")))
        .ToChecked();
    return handle_scope.Escape(resolver->GetPromise());
  }

  Local<Value> object;

  int type = options->Get(iso, HostDefinedOptions::kType)
                 .As<Number>()
                 ->Int32Value(context)
                 .ToChecked();
  uint32_t id = options->Get(iso, HostDefinedOptions::kID)
                    .As<Number>()
                    ->Uint32Value(context)
                    .ToChecked();
  if (type == ScriptType::kScript) {
    contextify::ContextifyScript* wrap = env->id_to_script_map.find(id)->second;
    object = wrap->object();
  } else if (type == ScriptType::kModule) {
    ModuleWrap* wrap = ModuleWrap::GetFromID(env, id);
    object = wrap->object();
  } else if (type == ScriptType::kFunction) {
    object = env->id_to_function_map.find(id)->second.Get(iso);
  } else {
    UNREACHABLE();
  }

  Local<Value> import_args[] = {
    object,
    Local<Value>(specifier),
  };

  Local<Value> result;
  if (import_callback->Call(
        context,
        v8::Undefined(iso),
        arraysize(import_args),
        import_args).ToLocal(&result)) {
    CHECK(result->IsPromise());
    return handle_scope.Escape(result.As<Promise>());
  }

  return MaybeLocal<Promise>();
}

void ModuleWrap::SetImportModuleDynamicallyCallback(
    const FunctionCallbackInfo<Value>& args) {
  Isolate* iso = args.GetIsolate();
  Environment* env = Environment::GetCurrent(args);
  HandleScope handle_scope(iso);

  CHECK_EQ(args.Length(), 1);
  CHECK(args[0]->IsFunction());
  Local<Function> import_callback = args[0].As<Function>();
  env->set_host_import_module_dynamically_callback(import_callback);

  iso->SetHostImportModuleDynamicallyCallback(ImportModuleDynamically);
}

void ModuleWrap::HostInitializeImportMetaObjectCallback(
    Local<Context> context, Local<Module> module, Local<Object> meta) {
  Environment* env = Environment::GetCurrent(context);
  CHECK_NOT_NULL(env);  // TODO(addaleax): Handle nullptr here.
  ModuleWrap* module_wrap = GetFromModule(env, module);

  if (module_wrap == nullptr) {
    return;
  }

  Local<Object> wrap = module_wrap->object();
  Local<Function> callback =
      env->host_initialize_import_meta_object_callback();
  Local<Value> args[] = { wrap, meta };
  callback->Call(context, Undefined(env->isolate()), arraysize(args), args)
      .ToLocalChecked();
}

void ModuleWrap::SetInitializeImportMetaObjectCallback(
    const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);
  Isolate* isolate = env->isolate();

  CHECK_EQ(args.Length(), 1);
  CHECK(args[0]->IsFunction());
  Local<Function> import_meta_callback = args[0].As<Function>();
  env->set_host_initialize_import_meta_object_callback(import_meta_callback);

  isolate->SetHostInitializeImportMetaObjectCallback(
      HostInitializeImportMetaObjectCallback);
}

void ModuleWrap::Initialize(Local<Object> target,
                            Local<Value> unused,
                            Local<Context> context,
                            void* priv) {
  Environment* env = Environment::GetCurrent(context);
  Isolate* isolate = env->isolate();

  Local<FunctionTemplate> tpl = env->NewFunctionTemplate(New);
  tpl->SetClassName(FIXED_ONE_BYTE_STRING(isolate, "ModuleWrap"));
  tpl->InstanceTemplate()->SetInternalFieldCount(1);

  env->SetProtoMethod(tpl, "link", Link);
  env->SetProtoMethod(tpl, "instantiate", Instantiate);
  env->SetProtoMethod(tpl, "evaluate", Evaluate);
  env->SetProtoMethodNoSideEffect(tpl, "namespace", Namespace);
  env->SetProtoMethodNoSideEffect(tpl, "getStatus", GetStatus);
  env->SetProtoMethodNoSideEffect(tpl, "getError", GetError);
  env->SetProtoMethodNoSideEffect(tpl, "getStaticDependencySpecifiers",
                                  GetStaticDependencySpecifiers);

  target->Set(env->context(), FIXED_ONE_BYTE_STRING(isolate, "ModuleWrap"),
              tpl->GetFunction(context).ToLocalChecked()).FromJust();
  env->SetMethod(target, "resolve", Resolve);
  env->SetMethod(target,
                 "setImportModuleDynamicallyCallback",
                 SetImportModuleDynamicallyCallback);
  env->SetMethod(target,
                 "setInitializeImportMetaObjectCallback",
                 SetInitializeImportMetaObjectCallback);

#define V(name)                                                                \
    target->Set(context,                                                       \
      FIXED_ONE_BYTE_STRING(env->isolate(), #name),                            \
      Integer::New(env->isolate(), Module::Status::name))                      \
        .FromJust()
    V(kUninstantiated);
    V(kInstantiating);
    V(kInstantiated);
    V(kEvaluating);
    V(kEvaluated);
    V(kErrored);
#undef V
}

}  // namespace loader
}  // namespace node

NODE_MODULE_CONTEXT_AWARE_INTERNAL(module_wrap,
                                   node::loader::ModuleWrap::Initialize)