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getContext feature implementation (similar to TraceKit context field) #64

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getContext feature implementation (similar to TraceKit context field) #64

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9 changes: 9 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,11 @@ https://raw.githubusercontent.com/stacktracejs/stacktrace-gps/master/dist/stackt
options: Object
* **sourceCache: Object (String URL : String Source)** - Pre-populate source cache to avoid network requests
* **sourceMapConsumerCache: Object (Source Mapping URL : SourceMap.SourceMapConsumer)** - Pre-populate source cache to avoid network requests
* **sourceCache: Object (String URL : String Source)** - Pre-populate source cache to avoid network requests
* **sourceMapConsumerCache: Object (Source Mapping URL : SourceMap.SourceMapConsumer)** - Pre-populate source cache to avoid network requests
* **offline: Boolean (default false)** - Set to `true` to prevent all network requests
* **contextMaxLineLength: Number (default 200)** - The maximum length of one line in the context source code
* **contextMaxLinesCount: Number (default 5)** - The maximum number of lines in the context source code
* **offline: Boolean (default false)** - Set to `true` to prevent all network requests
* **ajax: Function (String URL => Promise(responseText))** - Function to be used for making X-Domain requests
* **atob: Function (String => String)** - Function to convert base64-encoded strings to their original representation
Expand All @@ -79,6 +84,10 @@ Enhance function name and use source maps to produce a better StackFrame.
Enhance function name and use source maps to produce a better StackFrame.
* **stackframe** - [StackFrame](https://github.com/stacktracejs/stackframe) or like object

#### `.getContext(stackframe)` => Promise({ source, lineNumber, columnNumber })
Returns the surrounding source code chunk (with the start position) for where the stackframe points.
* **stackframe** - [StackFrame](https://github.com/stacktracejs/stackframe) or like object

## Browser Support
[![Sauce Test Status](https://saucelabs.com/browser-matrix/stacktracejs.svg)](https://saucelabs.com/u/stacktracejs)

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70 changes: 70 additions & 0 deletions spec/stacktrace-gps-spec.js
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Expand Up @@ -442,4 +442,74 @@ describe('StackTraceGPS', function() {
}
});
});

describe('#_getContextSingleLineIndexes', function() {
it('returns indexes that determine the correct range', function(done) {
test(1);
test(4);
test(5);
done();

function test(contextMaxLineLength) {
var stackTraceGPS = new StackTraceGPS({ contextMaxLineLength: contextMaxLineLength });
var line = '';
for (var length = 1; length <= 10; length++) {
line += 'x';
for (var columnNumber = 1; columnNumber <= 1; columnNumber++) {
var indexes = stackTraceGPS._getContextSingleLineIndexes(line, columnNumber);
expect(indexes[1] - indexes[0]).toBe(Math.min(contextMaxLineLength, length));
expect(indexes[1] >= columnNumber && columnNumber > indexes[0]).toBe(true);
}
}
}
});
});

describe('#_getContextMultipleLinesIndexes', function() {
it('returns indexes that determine the correct range', function(done) {
test(1);
test(4);
test(5);
done();

function test(contextMaxLinesCount) {
var stackTraceGPS = new StackTraceGPS({ contextMaxLinesCount: contextMaxLinesCount });
var lines = [];
for (var count = 1; count <= 10; count++) {
lines.push('x');
for (var columnNumber = 1; columnNumber <= 1; columnNumber++) {
var indexes = stackTraceGPS._getContextMultipleLinesIndexes(lines, columnNumber);
expect(indexes[1] - indexes[0]).toBe(Math.min(contextMaxLinesCount, count));
expect(indexes[1] >= columnNumber && columnNumber > indexes[0]).toBe(true);
}
}
}
});

it('avoids too long lines', function(done) {
var lines = [
'line',
'too long line',
'line',
'line',
'line',
'too long line',
'line'
];
var stackTraceGPS = new StackTraceGPS({ contextMaxLineLength: 4, contextMaxLinesCount: 2 });
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 1)).toEqual([0, 1]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 3)).toEqual([2, 4]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 4)).toEqual([2, 4]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 5)).toEqual([3, 5]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 7)).toEqual([6, 7]);
stackTraceGPS.contextMaxLinesCount = 5;
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 1)).toEqual([0, 1]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 3)).toEqual([2, 5]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 4)).toEqual([2, 5]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 5)).toEqual([2, 5]);
expect(stackTraceGPS._getContextMultipleLinesIndexes(lines, 7)).toEqual([6, 7]);
done();
});
});

});
98 changes: 98 additions & 0 deletions stacktrace-gps.js
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Expand Up @@ -174,6 +174,8 @@
* @param {Object} opts
* opts.sourceCache = {url: "Source String"} => preload source cache
* opts.sourceMapConsumerCache = {/path/file.js.map: SourceMapConsumer}
* opts.contextMaxLineLength = {Number}
* opts.contextMaxLinesCount = {Number}
* opts.offline = True to prevent network requests.
* Best effort without sources or source maps.
* opts.ajax = Promise returning function to make X-Domain requests
Expand All @@ -187,6 +189,9 @@
this.sourceCache = opts.sourceCache || {};
this.sourceMapConsumerCache = opts.sourceMapConsumerCache || {};

this.contextMaxLineLength = opts.contextMaxLineLength || 200;
this.contextMaxLinesCount = opts.contextMaxLinesCount || 5;

this.ajax = opts.ajax || _xdr;

this._atob = opts.atob || _atob;
Expand Down Expand Up @@ -338,5 +343,98 @@
}.bind(this), reject)['catch'](reject);
}.bind(this));
};

/**
* Given the source code line and the column number,
* truncate the line to contextMaxLineLength,
* return the start and end indexes of the truncated line.
*
* @param {String} line
* @param {Number} columnNumber
* @returns {Object}
*/
this._getContextSingleLineIndexes = function _getContextSingleLineIndexes(line, columnNumber) {
var indexStart = columnNumber - 1 - Math.floor(this.contextMaxLineLength / 2);
if (indexStart < 0) {
indexStart = 0;
}
var indexEnd = indexStart + this.contextMaxLineLength;
if (indexEnd > line.length) {
indexEnd = line.length;
indexStart = indexEnd - this.contextMaxLineLength;
if (indexStart < 0) {
indexStart = 0;
}
}
return [indexStart, indexEnd];
};

/**
* Given the source code lines and the line number,
* truncate the lines array to contextMaxLinesCount,
* avoid the lines with length more than contextMaxLineLength,
* return the object with the lines subarray and its start line number.
*
* @param {Array.String} lines
* @param {Number} lineNumber
* @returns {Object}
*/
this._getContextMultipleLinesIndexes = function _getContextMultipleLinesIndexes(lines, lineNumber) {
var indexes = [lineNumber - 1, lineNumber];
var active = [true, true];
var step = 0;
while (indexes[1] - indexes[0] < this.contextMaxLinesCount) {
var line = lines[indexes[step] + step - 1];
if (line === undefined || line.length > this.contextMaxLineLength) {
active[step] = false;
} else {
indexes[step] += 2 * step - 1;
}
if (active[1 - step]) {
step = 1 - step;
} else if (!active[step]) {
break;
}
}
return indexes;
};

/**
* Given a StackFrame, return a surrounding source code part with its start position.
*
* @param {StackFrame} stackframe
* @returns {Promise}
*/
this.getContext = function StackTraceGPS$$getContext(stackframe) {
return new Promise(function(resolve, reject) {
_ensureSupportedEnvironment();
_ensureStackFrameIsLegit(stackframe);

var fileName = stackframe.fileName;
var lineNumber = stackframe.lineNumber;
var columnNumber = stackframe.columnNumber;
this._get(fileName).then(function(source) {
var lines = source.split('\n');
var line = lines[lineNumber - 1];
var indexes, context;
if (line.length > this.contextMaxLineLength) {
indexes = this._getContextSingleLineIndexes(line, columnNumber);
context = {
source: line.substring(indexes[0], indexes[1]),
lineNumber: lineNumber,
columnNumber: indexes[0] + 1
};
} else {
indexes = this._getContextMultipleLinesIndexes(lines, lineNumber);
context = {
source: lines.slice(indexes[0], indexes[1]).join('\n'),
lineNumber: indexes[0] + 1,
columnNumber: 0
};
}
resolve(context);
}.bind(this), reject)['catch'](reject);
}.bind(this));
};
};
}));