stack-chain

API for combining call site modifyers

Installation

npm install stack-chain

API documentation

var chain = require('stack-chain');

When the Error.stack getter is executed, the stack-chain will perform the following:

1. execute the modifiers attached by chain.extend.
2. execute the modifiers attached by chain.filter.
3. execute the formater set by chain.format.replace.

chain.extend.attach(modifier)

chain.filter.attach(modifier)

Will modify the callSite array. Note you shouldn't format the stack trace.

The modifier is a function there takes two arguments error and frames.

• error is the Error object.
• frames is an array of callSite objects, see v8 documentation for details.

When the modifier is done, it should return a modified frames array.

chain.filter.attach(function (error, frames) {

    // Filter out traces related to this file
    var rewrite = frames.filter(function (callSite) {
      return callSite.getFileName() !== module.filename;
    });

    return rewrite;
});

chain.extend.deattach(modifier)

chain.filter.deattach(modifier)

Removes a modifier function from the list of modifiers.

var modifier = function () {};

// Attach modifier function
chain.extend.attach(modifier);

// Deattach modifier function
chain.extend.deattach(modifier);

chain.format.replace(formater)

Replaces the default v8 formater. The new formater takes a two arguments error and frames.

• error is the Error object.
• callSites is an array of callSite objects, see v8 documentation for details.

When the formater is done, it should return a string. The string will what Error.stack returns.

chain.format.replace(function (error, frames) {
  var lines = [];

  lines.push(error.toString());

  for (var i = 0; i < frames.length; i++) {
    lines.push("    at " + frames[i].toString());
  }

  return lines.join("\n");
});

chain.format.restore()

Will restore the default v8 formater. Note that dude to the nature of v8 Error objects, if one of the getters Error.stack or Error.callSite has already executed, the value of Error.stack won't change.

chain.callSite([options])

This will return the unmodified callSite array from the current tick. This is a performance shortcut, as it does not require generating the .stack string. This behaviour is different from the Error().callSite properties.

While this is mostly generating callSite in hot code, it can be useful to do some modification on the array. The options object, supports the following:

options = {
  // (default false) run the extenders on the callSite array.
  extend: true,

  // (default false) run the filters on the callSite array.
  filter: true,

  // (default 0) before running extend or filter methods, slice of some of the
  // end. This can be useful for hiding the place from where you called this
  // function.
  slice: 2
}

chain.originalCallSite(error)

Returns the original callSite array.

chain.mutatedCallSite(error)

Returns the mutated callSite array, that is after extend and filter is applied. The array will not exceed the Error.stackTraceLimit.

Error.stackTraceLimit

This limites the size of the callSites array. The default value is 10, and can be set to any positive number including Infinity. See v8 documentation for details.

License

The software is license under "MIT"

Copyright (c) 2012 Andreas Madsen

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.