StackTracey

     

Parses call stacks. Reads sources. Clean & filtered output. Sourcemaps. Node & browsers.

Why

- [x] Simple
- [x] Works in Node and browsers, \*nix and Windows
- [x] Allows hiding library calls / ad-hoc exclusion (via // @hide marker)
- [x] Provides source text for call locations
- [x] Fetches sources (via get-source)
- [x] Supports both asynchronous and synchronous interfaces (works even in browsers)
- [x] Full sourcemap support
- [x] Extracts useful information from SyntaxError instances
- [x] Pretty printing

What For

- Error overlay UIs for easier front-end development
- Better error reporting for Node projects
- Advanced logging (displaying call locations)
- Assertion printing

How To

``bash
npm install stacktracey
`

`javascript
import StackTracey from 'stacktracey'
`

Captures the current call stack:

`javascript
stack = new StackTracey () // captures the current call stack
`

Parses stacks from an Error object:

`javascript
stack = new StackTracey (error)
stack = new StackTracey (error.stack) // ...or from raw string
`

Stores parsed data in .items:

`javascript
stack.items.length // num entries
stack.items[0] // top
`

...where each item exposes:

`javascript
{
beforeParse: ,
callee: ,
calleeShort: ,
file: , // e.g. /Users/john/my_project/node_modules/foobar/main.js
fileRelative: , // e.g. node_modules/foobar/main.js
fileShort: , // e.g. foobar/main.js
fileName: , // e.g. main.js
line: , // starts from 1
column: , // starts from 1

index: / true if occured in HTML file at index page /,
native: / true if occured in native browser code /,
thirdParty: / true if occured in library code /,
hide: / true if marked as hidden by "// @hide" tag /,
syntaxError: / true if generated from a SyntaxError instance /
}
`

Accessing sources (synchronously, use with caution in browsers):

`javascript
stack = stack.withSources () // returns a copy of stack with all items supplied with sources
top = stack.items[0] // top item
`

Accessing sources (asynchronously, preferred method in browsers):

`javascript
stack = await stack.withSourcesAsync () // returns a copy of stack with all items supplied with sources
top = stack.items[0] // top item
`

...or:

`javascript
top = stack.withSourceAt (0) // supplies source for an individiual item (by index)
`
`javascript
top = await stack.withSourceAsyncAt (0) // supplies source for an individiual item (by index)
`

...or:

`javascript
top = stack.withSource (stack.items[0]) // supplies source for an individiual item
`
`javascript
top = await stack.withSourceAsync (stack.items[0]) // supplies source for an individiual item
`

The returned items contain the following additional fields (already mapped through sourcemaps):

`javascript
{
... // all the previously described fields

line: ,
column: ,
sourceFile: ,
sourceLine:
}
`

To learn about the sourceFile object, read the get-source docs.

Cleaning Output

Synchronously (use with caution in browsers):

`javascript
stack = stack.clean ()
`

...or (asynchronously):

`javascript
stack = await stack.cleanAsync ()
`

It does the following:

1. Reads sources (if available)
2. Excludes locations marked with the isThirdParty flag (library calls)
3. Excludes locations marked with a // @hide comment (user defined exclusion)
4. Merges repeated lines (via the .mergeRepeatedLines)

You can customize its behavior by overriding the isClean (entry, index) predicate.

Custom isThirdParty Predicate

You can override the isThirdParty behavior by subclassing StackTracey:

`javascript
class MyStackTracey extends StackTracey {

isThirdParty (path, externalDomain) { // you can use externalDomain to include traces from libs from other domains
return (super.isThirdParty (path) // include default behavior
|| path.includes ('my-lib')) // paths including 'my-lib' will be marked as thirdParty
&& !path.includes ('jquery') // jquery paths won't be marked as thirdParty
}
}

...

const stack = new MyStackTracey (error).withSources ()
`

Pretty Printing

`javascript
const prettyPrintedString = new StackTracey (error).withSources ().asTable ()
`
`javascript
const prettyPrintedString = (await new StackTracey (error).withSourcesAsync ()).asTable () // asynchronous version
`

...or (for pretty printing cleaned output):

`javascript
const prettyPrintedString = new StackTracey (error).clean ().asTable ()
`
`javascript
const prettyPrintedString = (await new StackTracey (error).cleanAsync ()).asTable () // asynchronous version
`

It produces a nice compact table layout (thanks to as-table), supplied with source lines (if available):

`
at shouldBeVisibleInStackTrace test.js:25 const shouldBeVisibleInStackTrace = () => new StackTracey ()
at it test.js:100 const stack = shouldBeVisibleInStackTrace ()
at callFn mocha/lib/runnable.js:326 var result = fn.call(ctx);
at run mocha/lib/runnable.js:319 callFn(this.fn);
at runTest mocha/lib/runner.js:422 test.run(fn);
at mocha/lib/runner.js:528 self.runTest(function(err) {
at next mocha/lib/runner.js:342 return fn();
at mocha/lib/runner.js:352 next(suites.pop());
at next mocha/lib/runner.js:284 return fn();
at mocha/lib/runner.js:320 next(0);
`

If you find your pretty printed tables undesirably trimmed (or maybe too long to fit in the line), you can provide custom column widths when calling asTable (...or, alternatively, by overriding maxColumnWidths () method):

`javascript
stack.asTable ({
callee: 30,
file: 60,
sourceLine: 80
})
`

Using As A Custom Exception Printer In Node

You can even replace the default NodeJS exception printer with this! This is how you can do it:

`javascript
process.on ('uncaughtException', e => { / print the stack here / })
process.on ('unhandledRejection', e => { / print the stack here / })
`

But the most simple way to achieve that is to use the ololog library (that is built upon StackTracey and several other handy libraries coded by me). Check it out, it's pretty awesome and will blow your brains out :)

`javascript
const log = require ('ololog').handleNodeErrors ()

// you can also print Errors by simply passing them to the log() function
`

Parsing SyntaxError instances

For example, when trying to require a file named test_files/syntax_error.js:

`javascript
// next line contains a syntax error (not a valid JavaScript)
foo->bar ()
`

...the pretty printed call stack for the error thrown would be something like:

`
at (syntax error) test_files/syntax_error.js:2 foo->bar ()
at it test.js:184 try { require ('./test_files/syntax_error.js') }
at runCallback timers.js:781
at tryOnImmediate timers.js:743
at processImmediate as _immediat timers.js:714
`

...where the first line is generated from parsing the raw output from the util.inspect call in Node. Unfortunately, this won't work in older versions of Node (v4 and below) as these versions can't provide any meaningful information for a SyntaxError instance.

Array Methods

All StackTracey instances expose map, filter, concat and slice methods. These methods will return mapped, filtered, joined, reversed and sliced StackTracey instances, respectively:

`javascript
s = new StackTracey ().slice (1).filter (x => !x.thirdParty) // current stack shifted by 1 and cleaned from library calls

s instanceof StackTracey // true
`

Extra Stuff

You can compare two locations via this predicate (tests file, line and column for equality):

`javascript
StackTracey.locationsEqual (a, b)
`

To force-reload the sources, you can invalidate the global source cache:

`javascript
StackTracey.resetCache ()
`

Projects That Use StackTracey

- [Ololog — a better console.log for the log-driven debugging junkies!
- CCXT — a cryptocurrency trading library that supports 130+ exchanges
- pnpm — a fast, disk space efficient package manager (faster than npm and Yarn!)
- panic-overlay — a lightweight standalone alternative to react-error-overlay`