index.js•1.46 kB
// v8 builtin format stack trace
// for when there was no previous prepareStackTrace function to call
var FormatStackTrace = require('./formatstack');
// some notes on the behavior below:
// because the 'stack' member is a one shot access variable (the raw stack is
// formatted on accessing it)
// we try to avoid modifying what the user would have wanted
// thus we use the previous value for prepareStackTrace
//
// The reason we store the callsite variable is because prepareStackTrace
// will not be called again once it has been called for a given error object
// but we want to support getting the stack out of the error multiple times (cause why not)
module.exports = function(err) {
// save original stacktrace
var save = Error.prepareStackTrace;
// replace capture with our function
Error.prepareStackTrace = function(err, trace) {
// cache stack frames so we don't have to get them again
// use a non-enumerable property
Object.defineProperty(err, '_sb_callsites', {
value: trace
});
return (save || FormatStackTrace)(err, trace);
};
// force capture of the stack frames
err.stack;
// someone already asked for the stack so we can't do this trick
// TODO fallback to string parsing?
if (!err._sb_callsites) {
return [];
}
// return original capture function
Error.prepareStackTrace = save;
return err._sb_callsites;
};