summaryrefslogtreecommitdiff
path: root/lib/internal/inspector/inspect_repl.js
blob: 7fd9772eef733b32eb3ccf455190e92e83ab3030 (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
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
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
/*
 * Copyright Node.js contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

// TODO(trott): enable ESLint
/* eslint-disable */

'use strict';
const FS = require('fs');
const Path = require('path');
const Repl = require('repl');
const util = require('util');
const vm = require('vm');
const fileURLToPath = require('url').fileURLToPath;

const debuglog = util.debuglog('inspect');

const SHORTCUTS = {
  cont: 'c',
  next: 'n',
  step: 's',
  out: 'o',
  backtrace: 'bt',
  setBreakpoint: 'sb',
  clearBreakpoint: 'cb',
  run: 'r',
};

const HELP = `
run, restart, r       Run the application or reconnect
kill                  Kill a running application or disconnect

cont, c               Resume execution
next, n               Continue to next line in current file
step, s               Step into, potentially entering a function
out, o                Step out, leaving the current function
backtrace, bt         Print the current backtrace
list                  Print the source around the current line where execution
                      is currently paused

setBreakpoint, sb     Set a breakpoint
clearBreakpoint, cb   Clear a breakpoint
breakpoints           List all known breakpoints
breakOnException      Pause execution whenever an exception is thrown
breakOnUncaught       Pause execution whenever an exception isn't caught
breakOnNone           Don't pause on exceptions (this is the default)

watch(expr)           Start watching the given expression
unwatch(expr)         Stop watching an expression
watchers              Print all watched expressions and their current values

exec(expr)            Evaluate the expression and print the value
repl                  Enter a debug repl that works like exec

scripts               List application scripts that are currently loaded
scripts(true)         List all scripts (including node-internals)

profile               Start CPU profiling session.
profileEnd            Stop current CPU profiling session.
profiles              Array of completed CPU profiling sessions.
profiles[n].save(filepath = 'node.cpuprofile')
                      Save CPU profiling session to disk as JSON.

takeHeapSnapshot(filepath = 'node.heapsnapshot')
                      Take a heap snapshot and save to disk as JSON.
`.trim();

const FUNCTION_NAME_PATTERN = /^(?:function\*? )?([^(\s]+)\(/;
function extractFunctionName(description) {
  const fnNameMatch = description.match(FUNCTION_NAME_PATTERN);
  return fnNameMatch ? `: ${fnNameMatch[1]}` : '';
}

const PUBLIC_BUILTINS = require('module').builtinModules;
const NATIVES = PUBLIC_BUILTINS ? process.binding('natives') : {};
function isNativeUrl(url) {
  url = url.replace(/\.js$/, '');
  if (PUBLIC_BUILTINS) {
    if (url.startsWith('internal/') || PUBLIC_BUILTINS.includes(url))
      return true;
  }

  return url in NATIVES || url === 'bootstrap_node';
}

function getRelativePath(filenameOrURL) {
  const dir = Path.join(Path.resolve(), 'x').slice(0, -1);

  const filename = filenameOrURL.startsWith('file://') ?
    fileURLToPath(filenameOrURL) : filenameOrURL;

  // Change path to relative, if possible
  if (filename.indexOf(dir) === 0) {
    return filename.slice(dir.length);
  }
  return filename;
}

function toCallback(promise, callback) {
  function forward(...args) {
    process.nextTick(() => callback(...args));
  }
  promise.then(forward.bind(null, null), forward);
}

// Adds spaces and prefix to number
// maxN is a maximum number we should have space for
function leftPad(n, prefix, maxN) {
  const s = n.toString();
  const nchars = Math.max(2, String(maxN).length) + 1;
  const nspaces = nchars - s.length - 1;

  return prefix + ' '.repeat(nspaces) + s;
}

function markSourceColumn(sourceText, position, useColors) {
  if (!sourceText) return '';

  const head = sourceText.slice(0, position);
  let tail = sourceText.slice(position);

  // Colourize char if stdout supports colours
  if (useColors) {
    tail = tail.replace(/(.+?)([^\w]|$)/, '\u001b[32m$1\u001b[39m$2');
  }

  // Return source line with coloured char at `position`
  return [head, tail].join('');
}

function extractErrorMessage(stack) {
  if (!stack) return '<unknown>';
  const m = stack.match(/^\w+: ([^\n]+)/);
  return m ? m[1] : stack;
}

function convertResultToError(result) {
  const { className, description } = result;
  const err = new Error(extractErrorMessage(description));
  err.stack = description;
  Object.defineProperty(err, 'name', { value: className });
  return err;
}

class RemoteObject {
  constructor(attributes) {
    Object.assign(this, attributes);
    if (this.type === 'number') {
      this.value =
        this.unserializableValue ? +this.unserializableValue : +this.value;
    }
  }

  [util.inspect.custom](depth, opts) {
    function formatProperty(prop) {
      switch (prop.type) {
        case 'string':
        case 'undefined':
          return util.inspect(prop.value, opts);

        case 'number':
        case 'boolean':
          return opts.stylize(prop.value, prop.type);

        case 'object':
        case 'symbol':
          if (prop.subtype === 'date') {
            return util.inspect(new Date(prop.value), opts);
          }
          if (prop.subtype === 'array') {
            return opts.stylize(prop.value, 'special');
          }
          return opts.stylize(prop.value, prop.subtype || 'special');

        default:
          return prop.value;
      }
    }
    switch (this.type) {
      case 'boolean':
      case 'number':
      case 'string':
      case 'undefined':
        return util.inspect(this.value, opts);

      case 'symbol':
        return opts.stylize(this.description, 'special');

      case 'function': {
        const fnName = extractFunctionName(this.description);
        const formatted = `[${this.className}${fnName}]`;
        return opts.stylize(formatted, 'special');
      }

      case 'object':
        switch (this.subtype) {
          case 'date':
            return util.inspect(new Date(this.description), opts);

          case 'null':
            return util.inspect(null, opts);

          case 'regexp':
            return opts.stylize(this.description, 'regexp');

          default:
            break;
        }
        if (this.preview) {
          const props = this.preview.properties
            .map((prop, idx) => {
              const value = formatProperty(prop);
              if (prop.name === `${idx}`) return value;
              return `${prop.name}: ${value}`;
            });
          if (this.preview.overflow) {
            props.push('...');
          }
          const singleLine = props.join(', ');
          const propString =
            singleLine.length > 60 ? props.join(',\n  ') : singleLine;

          return this.subtype === 'array' ?
            `[ ${propString} ]` : `{ ${propString} }`;
        }
        return this.description;

      default:
        return this.description;
    }
  }

  static fromEvalResult({ result, wasThrown }) {
    if (wasThrown) return convertResultToError(result);
    return new RemoteObject(result);
  }
}

class ScopeSnapshot {
  constructor(scope, properties) {
    Object.assign(this, scope);
    this.properties = new Map(properties.map((prop) => {
      const value = new RemoteObject(prop.value);
      return [prop.name, value];
    }));
    this.completionGroup = properties.map((prop) => prop.name);
  }

  [util.inspect.custom](depth, opts) {
    const type = `${this.type[0].toUpperCase()}${this.type.slice(1)}`;
    const name = this.name ? `<${this.name}>` : '';
    const prefix = `${type}${name} `;
    return util.inspect(this.properties, opts)
      .replace(/^Map /, prefix);
  }
}

function copyOwnProperties(target, source) {
  Object.getOwnPropertyNames(source).forEach((prop) => {
    const descriptor = Object.getOwnPropertyDescriptor(source, prop);
    Object.defineProperty(target, prop, descriptor);
  });
}

function aliasProperties(target, mapping) {
  Object.keys(mapping).forEach((key) => {
    const descriptor = Object.getOwnPropertyDescriptor(target, key);
    Object.defineProperty(target, mapping[key], descriptor);
  });
}

function createRepl(inspector) {
  const { Debugger, HeapProfiler, Profiler, Runtime } = inspector;

  let repl;

  // Things we want to keep around
  const history = { control: [], debug: [] };
  const watchedExpressions = [];
  const knownBreakpoints = [];
  let pauseOnExceptionState = 'none';
  let lastCommand;

  // Things we need to reset when the app restarts
  let knownScripts;
  let currentBacktrace;
  let selectedFrame;
  let exitDebugRepl;

  function resetOnStart() {
    knownScripts = {};
    currentBacktrace = null;
    selectedFrame = null;

    if (exitDebugRepl) exitDebugRepl();
    exitDebugRepl = null;
  }
  resetOnStart();

  const INSPECT_OPTIONS = { colors: inspector.stdout.isTTY };
  function inspect(value) {
    return util.inspect(value, INSPECT_OPTIONS);
  }

  function print(value, addNewline = true) {
    const text = typeof value === 'string' ? value : inspect(value);
    return inspector.print(text, addNewline);
  }

  function getCurrentLocation() {
    if (!selectedFrame) {
      throw new Error('Requires execution to be paused');
    }
    return selectedFrame.location;
  }

  function isCurrentScript(script) {
    return selectedFrame && getCurrentLocation().scriptId === script.scriptId;
  }

  function formatScripts(displayNatives = false) {
    function isVisible(script) {
      if (displayNatives) return true;
      return !script.isNative || isCurrentScript(script);
    }

    return Object.keys(knownScripts)
      .map((scriptId) => knownScripts[scriptId])
      .filter(isVisible)
      .map((script) => {
        const isCurrent = isCurrentScript(script);
        const { isNative, url } = script;
        const name = `${getRelativePath(url)}${isNative ? ' <native>' : ''}`;
        return `${isCurrent ? '*' : ' '} ${script.scriptId}: ${name}`;
      })
      .join('\n');
  }
  function listScripts(displayNatives = false) {
    print(formatScripts(displayNatives));
  }
  listScripts[util.inspect.custom] = function listWithoutInternal() {
    return formatScripts();
  };

  const profiles = [];
  class Profile {
    constructor(data) {
      this.data = data;
    }

    static createAndRegister({ profile }) {
      const p = new Profile(profile);
      profiles.push(p);
      return p;
    }

    [util.inspect.custom](depth, { stylize }) {
      const { startTime, endTime } = this.data;
      return stylize(`[Profile ${endTime - startTime}μs]`, 'special');
    }

    save(filename = 'node.cpuprofile') {
      const absoluteFile = Path.resolve(filename);
      const json = JSON.stringify(this.data);
      FS.writeFileSync(absoluteFile, json);
      print('Saved profile to ' + absoluteFile);
    }
  }

  class SourceSnippet {
    constructor(location, delta, scriptSource) {
      Object.assign(this, location);
      this.scriptSource = scriptSource;
      this.delta = delta;
    }

    [util.inspect.custom](depth, options) {
      const { scriptId, lineNumber, columnNumber, delta, scriptSource } = this;
      const start = Math.max(1, lineNumber - delta + 1);
      const end = lineNumber + delta + 1;

      const lines = scriptSource.split('\n');
      return lines.slice(start - 1, end).map((lineText, offset) => {
        const i = start + offset;
        const isCurrent = i === (lineNumber + 1);

        const markedLine = isCurrent
          ? markSourceColumn(lineText, columnNumber, options.colors)
          : lineText;

        let isBreakpoint = false;
        knownBreakpoints.forEach(({ location }) => {
          if (!location) return;
          if (scriptId === location.scriptId &&
              i === (location.lineNumber + 1)) {
            isBreakpoint = true;
          }
        });

        let prefixChar = ' ';
        if (isCurrent) {
          prefixChar = '>';
        } else if (isBreakpoint) {
          prefixChar = '*';
        }
        return `${leftPad(i, prefixChar, end)} ${markedLine}`;
      }).join('\n');
    }
  }

  function getSourceSnippet(location, delta = 5) {
    const { scriptId } = location;
    return Debugger.getScriptSource({ scriptId })
      .then(({ scriptSource }) =>
        new SourceSnippet(location, delta, scriptSource));
  }

  class CallFrame {
    constructor(callFrame) {
      Object.assign(this, callFrame);
    }

    loadScopes() {
      return Promise.all(
        this.scopeChain
          .filter((scope) => scope.type !== 'global')
          .map((scope) => {
            const { objectId } = scope.object;
            return Runtime.getProperties({
              objectId,
              generatePreview: true,
            }).then(({ result }) => new ScopeSnapshot(scope, result));
          })
      );
    }

    list(delta = 5) {
      return getSourceSnippet(this.location, delta);
    }
  }

  class Backtrace extends Array {
    [util.inspect.custom]() {
      return this.map((callFrame, idx) => {
        const {
          location: { scriptId, lineNumber, columnNumber },
          functionName
        } = callFrame;
        const name = functionName || '(anonymous)';

        const script = knownScripts[scriptId];
        const relativeUrl =
          (script && getRelativePath(script.url)) || '<unknown>';
        const frameLocation =
          `${relativeUrl}:${lineNumber + 1}:${columnNumber}`;

        return `#${idx} ${name} ${frameLocation}`;
      }).join('\n');
    }

    static from(callFrames) {
      return super.from(Array.from(callFrames).map((callFrame) => {
        if (callFrame instanceof CallFrame) {
          return callFrame;
        }
        return new CallFrame(callFrame);
      }));
    }
  }

  function prepareControlCode(input) {
    if (input === '\n') return lastCommand;
    // exec process.title => exec("process.title");
    const match = input.match(/^\s*exec\s+([^\n]*)/);
    if (match) {
      lastCommand = `exec(${JSON.stringify(match[1])})`;
    } else {
      lastCommand = input;
    }
    return lastCommand;
  }

  function evalInCurrentContext(code) {
    // Repl asked for scope variables
    if (code === '.scope') {
      if (!selectedFrame) {
        return Promise.reject(new Error('Requires execution to be paused'));
      }
      return selectedFrame.loadScopes().then((scopes) => {
        return scopes.map((scope) => scope.completionGroup);
      });
    }

    if (selectedFrame) {
      return Debugger.evaluateOnCallFrame({
        callFrameId: selectedFrame.callFrameId,
        expression: code,
        objectGroup: 'node-inspect',
        generatePreview: true,
      }).then(RemoteObject.fromEvalResult);
    }
    return Runtime.evaluate({
      expression: code,
      objectGroup: 'node-inspect',
      generatePreview: true,
    }).then(RemoteObject.fromEvalResult);
  }

  function controlEval(input, context, filename, callback) {
    debuglog('eval:', input);
    function returnToCallback(error, result) {
      debuglog('end-eval:', input, error);
      callback(error, result);
    }

    try {
      const code = prepareControlCode(input);
      const result = vm.runInContext(code, context, filename);

      if (result && typeof result.then === 'function') {
        toCallback(result, returnToCallback);
        return;
      }
      returnToCallback(null, result);
    } catch (e) {
      returnToCallback(e);
    }
  }

  function debugEval(input, context, filename, callback) {
    debuglog('eval:', input);
    function returnToCallback(error, result) {
      debuglog('end-eval:', input, error);
      callback(error, result);
    }

    try {
      const result = evalInCurrentContext(input);

      if (result && typeof result.then === 'function') {
        toCallback(result, returnToCallback);
        return;
      }
      returnToCallback(null, result);
    } catch (e) {
      returnToCallback(e);
    }
  }

  function formatWatchers(verbose = false) {
    if (!watchedExpressions.length) {
      return Promise.resolve('');
    }

    const inspectValue = (expr) =>
      evalInCurrentContext(expr)
        // .then(formatValue)
        .catch((error) => `<${error.message}>`);
    const lastIndex = watchedExpressions.length - 1;

    return Promise.all(watchedExpressions.map(inspectValue))
      .then((values) => {
        const lines = watchedExpressions
          .map((expr, idx) => {
            const prefix = `${leftPad(idx, ' ', lastIndex)}: ${expr} =`;
            const value = inspect(values[idx], { colors: true });
            if (value.indexOf('\n') === -1) {
              return `${prefix} ${value}`;
            }
            return `${prefix}\n    ${value.split('\n').join('\n    ')}`;
          });
        return lines.join('\n');
      })
      .then((valueList) => {
        return verbose ? `Watchers:\n${valueList}\n` : valueList;
      });
  }

  function watchers(verbose = false) {
    return formatWatchers(verbose).then(print);
  }

  // List source code
  function list(delta = 5) {
    return selectedFrame.list(delta)
      .then(null, (error) => {
        print('You can\'t list source code right now');
        throw error;
      });
  }

  function handleBreakpointResolved({ breakpointId, location }) {
    const script = knownScripts[location.scriptId];
    const scriptUrl = script && script.url;
    if (scriptUrl) {
      Object.assign(location, { scriptUrl });
    }
    const isExisting = knownBreakpoints.some((bp) => {
      if (bp.breakpointId === breakpointId) {
        Object.assign(bp, { location });
        return true;
      }
      return false;
    });
    if (!isExisting) {
      knownBreakpoints.push({ breakpointId, location });
    }
  }

  function listBreakpoints() {
    if (!knownBreakpoints.length) {
      print('No breakpoints yet');
      return;
    }

    function formatLocation(location) {
      if (!location) return '<unknown location>';
      const script = knownScripts[location.scriptId];
      const scriptUrl = script ? script.url : location.scriptUrl;
      return `${getRelativePath(scriptUrl)}:${location.lineNumber + 1}`;
    }
    const breaklist = knownBreakpoints
      .map((bp, idx) => `#${idx} ${formatLocation(bp.location)}`)
      .join('\n');
    print(breaklist);
  }

  function setBreakpoint(script, line, condition, silent) {
    function registerBreakpoint({ breakpointId, actualLocation }) {
      handleBreakpointResolved({ breakpointId, location: actualLocation });
      if (actualLocation && actualLocation.scriptId) {
        if (!silent) return getSourceSnippet(actualLocation, 5);
      } else {
        print(`Warning: script '${script}' was not loaded yet.`);
      }
      return undefined;
    }

    // setBreakpoint(): set breakpoint at current location
    if (script === undefined) {
      return Debugger
        .setBreakpoint({ location: getCurrentLocation(), condition })
        .then(registerBreakpoint);
    }

    // setBreakpoint(line): set breakpoint in current script at specific line
    if (line === undefined && typeof script === 'number') {
      const location = {
        scriptId: getCurrentLocation().scriptId,
        lineNumber: script - 1,
      };
      return Debugger.setBreakpoint({ location, condition })
        .then(registerBreakpoint);
    }

    if (typeof script !== 'string') {
      throw new TypeError(`setBreakpoint() expects a string, got ${script}`);
    }

    // setBreakpoint('fn()'): Break when a function is called
    if (script.endsWith('()')) {
      const debugExpr = `debug(${script.slice(0, -2)})`;
      const debugCall = selectedFrame
        ? Debugger.evaluateOnCallFrame({
          callFrameId: selectedFrame.callFrameId,
          expression: debugExpr,
          includeCommandLineAPI: true,
        })
        : Runtime.evaluate({
          expression: debugExpr,
          includeCommandLineAPI: true,
        });
      return debugCall.then(({ result, wasThrown }) => {
        if (wasThrown) return convertResultToError(result);
        return undefined; // This breakpoint can't be removed the same way
      });
    }

    // setBreakpoint('scriptname')
    let scriptId = null;
    let ambiguous = false;
    if (knownScripts[script]) {
      scriptId = script;
    } else {
      for (const id of Object.keys(knownScripts)) {
        const scriptUrl = knownScripts[id].url;
        if (scriptUrl && scriptUrl.indexOf(script) !== -1) {
          if (scriptId !== null) {
            ambiguous = true;
          }
          scriptId = id;
        }
      }
    }

    if (ambiguous) {
      print('Script name is ambiguous');
      return undefined;
    }
    if (line <= 0) {
      print('Line should be a positive value');
      return undefined;
    }

    if (scriptId !== null) {
      const location = { scriptId, lineNumber: line - 1 };
      return Debugger.setBreakpoint({ location, condition })
        .then(registerBreakpoint);
    }

    const escapedPath = script.replace(/([/\\.?*()^${}|[\]])/g, '\\$1');
    const urlRegex = `^(.*[\\/\\\\])?${escapedPath}$`;

    return Debugger
      .setBreakpointByUrl({ urlRegex, lineNumber: line - 1, condition })
      .then((bp) => {
        // TODO: handle bp.locations in case the regex matches existing files
        if (!bp.location) { // Fake it for now.
          Object.assign(bp, {
            actualLocation: {
              scriptUrl: `.*/${script}$`,
              lineNumber: line - 1,
            },
          });
        }
        return registerBreakpoint(bp);
      });
  }

  function clearBreakpoint(url, line) {
    const breakpoint = knownBreakpoints.find(({ location }) => {
      if (!location) return false;
      const script = knownScripts[location.scriptId];
      if (!script) return false;
      return (
        script.url.indexOf(url) !== -1 && (location.lineNumber + 1) === line
      );
    });
    if (!breakpoint) {
      print(`Could not find breakpoint at ${url}:${line}`);
      return Promise.resolve();
    }
    return Debugger.removeBreakpoint({ breakpointId: breakpoint.breakpointId })
      .then(() => {
        const idx = knownBreakpoints.indexOf(breakpoint);
        knownBreakpoints.splice(idx, 1);
      });
  }

  function restoreBreakpoints() {
    const lastBreakpoints = knownBreakpoints.slice();
    knownBreakpoints.length = 0;
    const newBreakpoints = lastBreakpoints
      .filter(({ location }) => !!location.scriptUrl)
      .map(({ location }) =>
        setBreakpoint(location.scriptUrl, location.lineNumber + 1));
    if (!newBreakpoints.length) return Promise.resolve();
    return Promise.all(newBreakpoints).then((results) => {
      print(`${results.length} breakpoints restored.`);
    });
  }

  function setPauseOnExceptions(state) {
    return Debugger.setPauseOnExceptions({ state })
      .then(() => {
        pauseOnExceptionState = state;
      });
  }

  Debugger.on('paused', ({ callFrames, reason /* , hitBreakpoints */ }) => {
    if (process.env.NODE_INSPECT_RESUME_ON_START === '1' &&
        reason === 'Break on start') {
      debuglog('Paused on start, but NODE_INSPECT_RESUME_ON_START' +
              ' environment variable is set to 1, resuming');
      inspector.client.callMethod('Debugger.resume');
      return;
    }

    // Save execution context's data
    currentBacktrace = Backtrace.from(callFrames);
    selectedFrame = currentBacktrace[0];
    const { scriptId, lineNumber } = selectedFrame.location;

    const breakType = reason === 'other' ? 'break' : reason;
    const script = knownScripts[scriptId];
    const scriptUrl = script ? getRelativePath(script.url) : '[unknown]';

    const header = `${breakType} in ${scriptUrl}:${lineNumber + 1}`;

    inspector.suspendReplWhile(() =>
      Promise.all([formatWatchers(true), selectedFrame.list(2)])
        .then(([watcherList, context]) => {
          if (watcherList) {
            return `${watcherList}\n${inspect(context)}`;
          }
          return inspect(context);
        }).then((breakContext) => {
          print(`${header}\n${breakContext}`);
        }));
  });

  function handleResumed() {
    currentBacktrace = null;
    selectedFrame = null;
  }

  Debugger.on('resumed', handleResumed);

  Debugger.on('breakpointResolved', handleBreakpointResolved);

  Debugger.on('scriptParsed', (script) => {
    const { scriptId, url } = script;
    if (url) {
      knownScripts[scriptId] = Object.assign({
        isNative: isNativeUrl(url),
      }, script);
    }
  });

  Profiler.on('consoleProfileFinished', ({ profile }) => {
    Profile.createAndRegister({ profile });
    print([
      'Captured new CPU profile.',
      `Access it with profiles[${profiles.length - 1}]`
    ].join('\n'));
  });

  function initializeContext(context) {
    inspector.domainNames.forEach((domain) => {
      Object.defineProperty(context, domain, {
        value: inspector[domain],
        enumerable: true,
        configurable: true,
        writeable: false,
      });
    });

    copyOwnProperties(context, {
      get help() {
        print(HELP);
      },

      get run() {
        return inspector.run();
      },

      get kill() {
        return inspector.killChild();
      },

      get restart() {
        return inspector.run();
      },

      get cont() {
        handleResumed();
        return Debugger.resume();
      },

      get next() {
        handleResumed();
        return Debugger.stepOver();
      },

      get step() {
        handleResumed();
        return Debugger.stepInto();
      },

      get out() {
        handleResumed();
        return Debugger.stepOut();
      },

      get pause() {
        return Debugger.pause();
      },

      get backtrace() {
        return currentBacktrace;
      },

      get breakpoints() {
        return listBreakpoints();
      },

      exec(expr) {
        return evalInCurrentContext(expr);
      },

      get profile() {
        return Profiler.start();
      },

      get profileEnd() {
        return Profiler.stop()
          .then(Profile.createAndRegister);
      },

      get profiles() {
        return profiles;
      },

      takeHeapSnapshot(filename = 'node.heapsnapshot') {
        return new Promise((resolve, reject) => {
          const absoluteFile = Path.resolve(filename);
          const writer = FS.createWriteStream(absoluteFile);
          let sizeWritten = 0;
          function onProgress({ done, total, finished }) {
            if (finished) {
              print('Heap snaphost prepared.');
            } else {
              print(`Heap snapshot: ${done}/${total}`, false);
            }
          }
          function onChunk({ chunk }) {
            sizeWritten += chunk.length;
            writer.write(chunk);
            print(`Writing snapshot: ${sizeWritten}`, false);
          }
          function onResolve() {
            writer.end(() => {
              teardown();
              print(`Wrote snapshot: ${absoluteFile}`);
              resolve();
            });
          }
          function onReject(error) {
            teardown();
            reject(error);
          }
          function teardown() {
            HeapProfiler.removeListener(
              'reportHeapSnapshotProgress', onProgress);
            HeapProfiler.removeListener('addHeapSnapshotChunk', onChunk);
          }

          HeapProfiler.on('reportHeapSnapshotProgress', onProgress);
          HeapProfiler.on('addHeapSnapshotChunk', onChunk);

          print('Heap snapshot: 0/0', false);
          HeapProfiler.takeHeapSnapshot({ reportProgress: true })
            .then(onResolve, onReject);
        });
      },

      get watchers() {
        return watchers();
      },

      watch(expr) {
        watchedExpressions.push(expr);
      },

      unwatch(expr) {
        const index = watchedExpressions.indexOf(expr);

        // Unwatch by expression
        // or
        // Unwatch by watcher number
        watchedExpressions.splice(index !== -1 ? index : +expr, 1);
      },

      get repl() {
        // Don't display any default messages
        const listeners = repl.listeners('SIGINT').slice(0);
        repl.removeAllListeners('SIGINT');

        const oldContext = repl.context;

        exitDebugRepl = () => {
          // Restore all listeners
          process.nextTick(() => {
            listeners.forEach((listener) => {
              repl.on('SIGINT', listener);
            });
          });

          // Exit debug repl
          repl.eval = controlEval;

          // Swap history
          history.debug = repl.history;
          repl.history = history.control;

          repl.context = oldContext;
          repl.setPrompt('debug> ');
          repl.displayPrompt();

          repl.removeListener('SIGINT', exitDebugRepl);
          repl.removeListener('exit', exitDebugRepl);

          exitDebugRepl = null;
        };

        // Exit debug repl on SIGINT
        repl.on('SIGINT', exitDebugRepl);

        // Exit debug repl on repl exit
        repl.on('exit', exitDebugRepl);

        // Set new
        repl.eval = debugEval;
        repl.context = {};

        // Swap history
        history.control = repl.history;
        repl.history = history.debug;

        repl.setPrompt('> ');

        print('Press Ctrl + C to leave debug repl');
        repl.displayPrompt();
      },

      get version() {
        return Runtime.evaluate({
          expression: 'process.versions.v8',
          contextId: 1,
          returnByValue: true,
        }).then(({ result }) => {
          print(result.value);
        });
      },

      scripts: listScripts,

      setBreakpoint,
      clearBreakpoint,
      setPauseOnExceptions,
      get breakOnException() {
        return setPauseOnExceptions('all');
      },
      get breakOnUncaught() {
        return setPauseOnExceptions('uncaught');
      },
      get breakOnNone() {
        return setPauseOnExceptions('none');
      },

      list,
    });
    aliasProperties(context, SHORTCUTS);
  }

  function initAfterStart() {
    const setupTasks = [
      Runtime.enable(),
      Profiler.enable(),
      Profiler.setSamplingInterval({ interval: 100 }),
      Debugger.enable(),
      Debugger.setPauseOnExceptions({ state: 'none' }),
      Debugger.setAsyncCallStackDepth({ maxDepth: 0 }),
      Debugger.setBlackboxPatterns({ patterns: [] }),
      Debugger.setPauseOnExceptions({ state: pauseOnExceptionState }),
      restoreBreakpoints(),
      Runtime.runIfWaitingForDebugger(),
    ];
    return Promise.all(setupTasks);
  }

  return function startRepl() {
    inspector.client.on('close', () => {
      resetOnStart();
    });
    inspector.client.on('ready', () => {
      initAfterStart();
    });

    const replOptions = {
      prompt: 'debug> ',
      input: inspector.stdin,
      output: inspector.stdout,
      eval: controlEval,
      useGlobal: false,
      ignoreUndefined: true,
    };

    repl = Repl.start(replOptions);
    initializeContext(repl.context);
    repl.on('reset', initializeContext);

    repl.defineCommand('interrupt', () => {
      // We want this for testing purposes where sending CTRL-C can be tricky.
      repl.emit('SIGINT');
    });

    // Init once for the initial connection
    initAfterStart();

    return repl;
  };
}
module.exports = createRepl;