Source Map Support
This module provides source map support for stack traces in node via the V8 stack trace API. It uses the source-map module to replace the paths and line numbers of source-mapped files with their original paths and line numbers. The output mimics node's stack trace format with the goal of making every compile-to-JS language more of a first-class citizen. Source maps are completely general (not specific to any one language) so you can use source maps with multiple compile-to-JS languages in the same node process.
Installation
npm install source-map-support
This module takes effect globally and should be initialized by inserting require('source-map-support').install() at the top of your code.
Usage
To use a valid source map (generated using something like source-map-index-generator), the compiled code should contain the following two extra lines:
//@sourceMappingURL=path/to/sourceMapFile.json
require('source-map-support').install();
Demos
Basic Demo
original.js:
throw new Error("test");
compiled.js:
//#sourceMappingURL=original.sourcemap.json
require('source-map-support').install();
throw new Error("test");
original.sourcemap.json:
{"version":3,"file":"compiled.js","sources":["original.js"],"names":[],"mappings":";;;AAAA,CAAC,CAAC,CAAC,CAAC,CAAC,CAAC,CAAC,CAAC"}
After running compiled.js you should get the following outout:
/path/to/original.js:1
throw new Error("test");
^
Error: test
at Object.<anonymous> (/path/to/original.js:1:7)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:901:3
CoffeeScript Demo
The following terminal commands show a stack trace in node with CoffeeScript filenames:
$ cat > demo.coffee
require('source-map-support').install()
foo = ->
bar = -> throw new Error 'this is a demo'
bar()
foo()
$ npm install source-map-support coffee-script
$ node_modules/coffee-script/bin/coffee --map --compile demo.coffee
$ node demo
demo.coffee:4
bar = -> throw new Error 'this is a demo'
^
Error: this is a demo
at bar (demo.coffee:4:21)
at foo (demo.coffee:5:3)
at Object.<anonymous> (demo.coffee:6)
at Object.<anonymous> (demo.coffee:2)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.runMain (module.js:492:10)
at process.startup.processNextTick.process._tickCallback (node.js:244:9)
TypeScript Demo
The following terminal commands show a stack trace in node with TypeScript filenames:
$ cat > demo.ts
declare function require(name: string);
require('source-map-support').install();
class Foo {
constructor() { this.bar(); }
bar() { throw new Error('this is a demo'); }
}
new Foo();
$ npm install source-map-support typescript
$ node_modules/typescript/bin/tsc -sourcemap demo.ts
$ node demo
demo.ts:6
bar() { throw new Error('this is a demo'); }
^
Error: this is a demo
at Foo.bar (demo.ts:6:16)
at new Foo (demo.ts:5:23)
at Object.<anonymous> (demo.ts:8)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.runMain (module.js:492:10)
at process.startup.processNextTick.process._tickCallback (node.js:244:9)
Options
This module installs two things: a change to the stack property on Error objects and a handler for uncaught exceptions that mimics node's default exception handler (the handler can be seen in the demos above). You may want to disable the handler if you have your own uncaught exception handler. This can be done by passing an argument to the installer:
require('source-map-support').install({
handleUncaughtExceptions: false
});
License
This code is available under the MIT license.
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