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Prioritize capturing expressions (#162)
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Now the collection of the contents of watched expressions is given priority over other variables such as locals.  Further, the contents of watched expressions are shown completely provided that this can be done within the limits of `config.capture.maxDataSize`.  Otherwise, a message is displayed describing why the entire contents of the watched expression cannot be displayed.

For example, if a breakpoint is hit with a watched expression that is an array (even if that array contains more than `config.capture.maxProperties` elements), the entire contents of the array will be collected provided that the limit `config.capture.maxDataSize` is not reached.  Then, other variables such as locals will be collected (provided that there is enough space to collect that information as specified by `config.capture.maxDataSize`).
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@DominicKramer
DominicKramer committed Nov 10, 2016
1 parent 398d04a commit d370e20
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Showing 3 changed files with 191 additions and 76 deletions.
87 changes: 60 additions & 27 deletions lib/state.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ var GETTER_MESSAGE_INDEX = 2;
var ARG_LOCAL_LIMIT_MESSAGE_INDEX = 3;
var OBJECT_LIMIT_MESSAGE_INDEX = 4;
var STRING_LIMIT_MESSAGE_INDEX = 5;
var DATA_LIMIT_MESSAGE_INDEX = 6;

var MESSAGE_TABLE = [];
MESSAGE_TABLE[BUFFER_FULL_MESSAGE_INDEX] =
Expand All @@ -67,6 +68,11 @@ MESSAGE_TABLE[STRING_LIMIT_MESSAGE_INDEX] =
'Only first `config.capture.maxStringLength` chars' +
' were captured.',
false) };
MESSAGE_TABLE[DATA_LIMIT_MESSAGE_INDEX] =
{ status: new StatusMessage(StatusMessage.VARIABLE_VALUE,
'Truncating the results because the cap of ' +
'`config.capture.maxDataSize` has been reached.',
false) };

/**
* Captures the stack and current execution state.
Expand Down Expand Up @@ -140,11 +146,10 @@ function StateResolver(execState, expressions, config, v8) {
* evaluatedExpressions fields
*/
StateResolver.prototype.capture_ = function() {
// Gather the stack frames first
var that = this;
var frames = that.resolveFrames_();

// Evaluate the watch expressions
var evalIndexSet = new Set();
if (that.expressions_) {
that.expressions_.forEach(function(expression, index) {
var result = evaluate(expression, that.state_.frame(0));
Expand All @@ -157,20 +162,30 @@ StateResolver.prototype.capture_ = function() {
result.error, true)
};
} else {
evaluated = that.resolveVariable_(expression, result.mirror);
evaluated = that.resolveVariable_(expression, result.mirror, true);
var varTableIdx = evaluated.varTableIndex;
if (typeof varTableIdx !== 'undefined'){
evalIndexSet.add(varTableIdx);
}
}
that.evaluatedExpressions_[index] = evaluated;
});
}

// The frames are resolved after the evaluated expressions so that
// evaluated expressions can be evaluated as much as possible within
// the max data size limits
var frames = that.resolveFrames_();

// Now resolve the variables
var index = MESSAGE_TABLE.length; // skip the sentinel values
var noLimit = that.config_.capture.maxDataSize === 0;
while (index < that.rawVariableTable_.length && // NOTE: length changes in loop
(that.totalSize_ < that.config_.capture.maxDataSize || noLimit)) {
assert(!that.resolvedVariableTable_[index]); // shouldn't have it resolved yet
var isEvaluated = evalIndexSet.has(index);
that.resolvedVariableTable_[index] =
that.resolveMirror_(that.rawVariableTable_[index]);
that.resolveMirror_(that.rawVariableTable_[index], isEvaluated);
index++;
}

Expand Down Expand Up @@ -349,7 +364,7 @@ StateResolver.prototype.extractArgumentsList_ = function (frame) {
StateResolver.prototype.resolveArgumentList_ = function(args) {
var resolveVariable = this.resolveVariable_.bind(this);
return args.map(function (arg){
return resolveVariable(arg.name, arg.value);
return resolveVariable(arg.name, arg.value, false);
});
};

Expand Down Expand Up @@ -413,12 +428,12 @@ StateResolver.prototype.resolveLocalsList_ = function (frame, args) {
// locals list.
remove(args, {name: name});
usedNames[name] = true;
locals.push(self.resolveVariable_(name, trg));
locals.push(self.resolveVariable_(name, trg, false));
} else if (!usedNames[name]) {
// It's a valid variable that belongs in the locals list and wasn't
// discovered at a lower-scope
usedNames[name] = true;
locals.push(self.resolveVariable_(name, trg));
locals.push(self.resolveVariable_(name, trg, false));
} // otherwise another same-named variable occured at a lower scope
return locals;
},
Expand All @@ -432,7 +447,7 @@ StateResolver.prototype.resolveLocalsList_ = function (frame, args) {
// under the name 'context' which is used by the Chrome DevTools.
var ctx = frame.details().receiver();
if (ctx) {
return [self.resolveVariable_('context', makeMirror(ctx))];
return [self.resolveVariable_('context', makeMirror(ctx), false)];
}
return [];
}()));
Expand All @@ -445,8 +460,10 @@ StateResolver.prototype.resolveLocalsList_ = function (frame, args) {
*
* @param {String} name The name of the variable.
* @param {Object} value A v8 debugger representation of a variable value.
* @param {boolean} isEvaluated Specifies if the variable is from a watched
* expression.
*/
StateResolver.prototype.resolveVariable_ = function(name, value) {
StateResolver.prototype.resolveVariable_ = function(name, value, isEvaluated) {
var size = name.length;

var data = {
Expand All @@ -468,10 +485,11 @@ StateResolver.prototype.resolveVariable_ = function(name, value) {
} else if (value.isObject()) {
data.varTableIndex = this.getVariableIndex_(value);
var maxProps = this.config_.capture.maxProperties;
if (maxProps && maxProps < Object.keys(value.value()).length) {
var numKeys = Object.keys(value.value()).length;

if (!isEvaluated && maxProps && maxProps < numKeys) {
data.status = MESSAGE_TABLE[OBJECT_LIMIT_MESSAGE_INDEX].status;
}

} else {
// PropertyMirror, InternalPropertyMirror, FrameMirror, ScriptMirror
data.value = 'unknown mirror type';
Expand Down Expand Up @@ -510,53 +528,68 @@ StateResolver.prototype.storeObjectToVariableTable_ = function(obj) {
*
* See https://github.com/iojs/io.js/issues/1190.
*/
StateResolver.prototype.resolveMirror_ = function(mirror) {
StateResolver.prototype.resolveMirror_ = function(mirror, isEvaluated) {
if (semver.satisfies(process.version, '<1.6')) {
return this.resolveMirrorSlow_(mirror);
return this.resolveMirrorSlow_(mirror, isEvaluated);
} else {
return this.resolveMirrorFast_(mirror);
return this.resolveMirrorFast_(mirror, isEvaluated);
}
};

// A slower implementation of resolveMirror_ which is safe for all node versions
StateResolver.prototype.resolveMirrorSlow_ = function(mirror) {
StateResolver.prototype.resolveMirrorSlow_ = function(mirror, isEvaluated) {
// Instead, let's use Object.keys. This will only get the enumerable
// properties. The other alternative would be Object.getOwnPropertyNames, but
// I'm going with the former as that's what util.inspect does.
var that = this;

var keys = Object.keys(mirror.value());
if (that.config_.capture.maxProperties) {
keys = keys.slice(0, that.config_.capture.maxProperties);
var maxProps = that.config_.capture.maxProperties;

if (!isEvaluated && maxProps) {
keys = keys.slice(0, maxProps);
}
var members = keys.map(function(prop) {
return that.resolveMirrorProperty_(mirror.property(prop));
return that.resolveMirrorProperty_(mirror.property(prop), isEvaluated);
});

var mirrorVal = mirror.value();
var len = mirrorVal && mirrorVal.length;
return {
value: mirror.toText(),
value: mirror.toText() +
((typeof len === 'undefined') ? '' : ' of length ' + len),
members: members
};
};

// A faster implementation of resolveMirror_ which segfaults in node <1.6
//
// See https://github.com/iojs/io.js/issues/1190.
StateResolver.prototype.resolveMirrorFast_ = function(mirror) {
var members = this.getMirrorProperties_(mirror).map(
this.resolveMirrorProperty_.bind(this));
StateResolver.prototype.resolveMirrorFast_ = function(mirror, isEvaluated) {
var resMirrorProp = this.resolveMirrorProperty_.bind(this);
var members = this.getMirrorProperties_(mirror, isEvaluated).map(
function(mirror) {
return resMirrorProp(mirror, isEvaluated);
}
);
return {
value: mirror.toText(),
members: members
};
};

StateResolver.prototype.getMirrorProperties_ = function(mirror) {
var numProperties = this.config_.capture.maxProperties;
StateResolver.prototype.getMirrorProperties_ = function(mirror, isEvaluated) {
var maxProperties = this.config_.capture.maxProperties;
var properties = mirror.properties();
return numProperties ? properties.slice(0, numProperties) : properties;

if (!isEvaluated && maxProperties) {
return properties.slice(0, maxProperties);
}

return properties;
};

StateResolver.prototype.resolveMirrorProperty_ = function(property) {
StateResolver.prototype.resolveMirrorProperty_ = function(property, isEvaluated) {
var name = String(property.name());
// Array length must be special cased as it is a native property that
// we know to be safe to evaluate which is not generally true.
Expand All @@ -573,5 +606,5 @@ StateResolver.prototype.resolveMirrorProperty_ = function(property) {
varTableIndex: GETTER_MESSAGE_INDEX
};
}
return this.resolveVariable_(name, property.value());
return this.resolveVariable_(name, property.value(), isEvaluated);
};
2 changes: 1 addition & 1 deletion test/standalone/test-try-catch.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,7 @@ describe('v8debugapi', function() {
} else {
assert.deepEqual(
locals[0],
{name: 'e', varTableIndex: 6}
{name: 'e', varTableIndex: 7}
);
}

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