source-map-support
Advanced tools
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.
$ npm install source-map-support
Source maps can be generated using libraries such as source-map-index-generator. Once you have a valid source map, place a source mapping comment somewhere in the file (usually done automatically or with an option by your transpiler):
//# sourceMappingURL=path/to/source.map
If multiple sourceMappingURL comments exist in one file, the last sourceMappingURL comment will be respected (e.g. if a file mentions the comment in code, or went through multiple transpilers). The path should either be absolute or relative to the compiled file.
From here you have two options.
node -r source-map-support/register compiled.js
Put the following line at the top of the compiled file.
require('source-map-support').install();
It is also possible to install the source map support directly by
requiring the register module which can be handy with ES6:
import 'source-map-support/register'
// Instead of:
import sourceMapSupport from 'source-map-support'
sourceMapSupport.install()
Note: if you're using babel-register, it includes source-map-support already.
It is also very useful with Mocha:
$ mocha --require source-map-support/register tests/
This library also works in Chrome. While the DevTools console already supports source maps, the V8 engine doesn't and Error.prototype.stack will be incorrect without this library. Everything will just work if you deploy your source files using browserify. Just make sure to pass the --debug flag to the browserify command so your source maps are included in the bundled code.
This library also works if you use another build process or just include the source files directly. In this case, include the file browser-source-map-support.js in your page and call sourceMapSupport.install(). It contains the whole library already bundled for the browser using browserify.
<script src="browser-source-map-support.js"></script>
<script>sourceMapSupport.install();</script>
This library also works if you use AMD (Asynchronous Module Definition), which is used in tools like RequireJS. Just list browser-source-map-support as a dependency:
<script>
define(['browser-source-map-support'], function(sourceMapSupport) {
sourceMapSupport.install();
});
</script>
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 below). 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
});
This module loads source maps from the filesystem by default. You can provide alternate loading behavior through a callback as shown below. For example, Meteor keeps all source maps cached in memory to avoid disk access.
require('source-map-support').install({
retrieveSourceMap: function(source) {
if (source === 'compiled.js') {
return {
url: 'original.js',
map: fs.readFileSync('compiled.js.map', 'utf8')
};
}
return null;
}
});
The module will by default assume a browser environment if XMLHttpRequest and window are defined. If either of these do not exist it will instead assume a node environment. In some rare cases, e.g. when running a browser emulation and where both variables are also set, you can explictly specify the environment to be either 'browser' or 'node'.
require('source-map-support').install({
environment: 'node'
});
To support files with inline source maps, the hookRequire options can be specified, which will monitor all source files for inline source maps.
require('source-map-support').install({
hookRequire: true
});
This monkey patches the require module loading chain, so is not enabled by default and is not recommended for any sort of production usage.
original.js:
throw new Error('test'); // This is the original code
compiled.js:
require('source-map-support').install();
throw new Error('test'); // This is the compiled code
// The next line defines the sourceMapping.
//# sourceMappingURL=compiled.js.map
compiled.js.map:
{
"version": 3,
"file": "compiled.js",
"sources": ["original.js"],
"names": [],
"mappings": ";;AAAA,MAAM,IAAI"
}
Run compiled.js using node (notice how the stack trace uses original.js instead of compiled.js):
$ node compiled.js
original.js:1
throw new Error('test'); // This is the original code
^
Error: test
at Object.<anonymous> (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
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();
Compile and run the file using the TypeScript compiler from the terminal:
$ npm install source-map-support typescript
$ node_modules/typescript/bin/tsc -sourcemap demo.ts
$ node demo.js
demo.ts:5
bar() { throw new Error('this is a demo'); }
^
Error: this is a demo
at Foo.bar (demo.ts:5:17)
at new Foo (demo.ts:4:24)
at Object.<anonymous> (demo.ts:7:1)
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
There is also the option to use -r source-map-support/register with typescript, without the need add the require('source-map-support').install() in the code base:
$ npm install source-map-support typescript
$ node_modules/typescript/bin/tsc -sourcemap demo.ts
$ node -r source-map-support/register demo.js
demo.ts:5
bar() { throw new Error('this is a demo'); }
^
Error: this is a demo
at Foo.bar (demo.ts:5:17)
at new Foo (demo.ts:4:24)
at Object.<anonymous> (demo.ts:7:1)
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
demo.coffee:
require('source-map-support').install()
foo = ->
bar = -> throw new Error 'this is a demo'
bar()
foo()
Compile and run the file using the CoffeeScript compiler from the terminal:
$ npm install source-map-support coffeescript
$ node_modules/.bin/coffee --map --compile demo.coffee
$ node demo.js
demo.coffee:3
bar = -> throw new Error 'this is a demo'
^
Error: this is a demo
at bar (demo.coffee:3:22)
at foo (demo.coffee:4:3)
at Object.<anonymous> (demo.coffee:5:1)
at Object.<anonymous> (demo.coffee:1:1)
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)
This repo contains both automated tests for node and manual tests for the browser. The automated tests can be run using mocha (type mocha in the root directory). To run the manual tests:
build.jsnpm run serve-tests) and visit
header-test, run server.js inside that directory and visit http://127.0.0.1:1337/This code is available under the MIT license.
The 'trace' package is similar to 'source-map-support' in that it also enhances stack traces. It modifies the stack trace to include the original source lines, but it does not require source maps to do so. It is less powerful for transpiled code but can be easier to use for simpler use cases.
The 'source-map' package provides utilities for generating and consuming source maps. While 'source-map-support' is focused on applying source maps to stack traces, 'source-map' is more general-purpose and can be used for a wider range of source map-related tasks, such as creating source maps during build processes.
FAQs
Fixes stack traces for files with source maps
The npm package source-map-support receives a total of 68,087,864 weekly downloads. As such, source-map-support popularity was classified as popular.
We found that source-map-support demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 3 open source maintainers collaborating on the project.
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