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Overview

Resolve the source map and/or sources for a generated file.

var sourceMapResolve = require("source-map-resolve")
var sourceMap = require("source-map")
var code = [
"!function(){...}();",
"/*# sourceMappingURL=foo.js.map */"
].join("\n")
sourceMapResolve.resolveSourceMap(code, "/js/foo.js", fs.readFile, function(error, result) {
if (error) {
return notifyFailure(error)
}
result
// {
// map: {file: "foo.js", mappings: "...", sources: ["/coffee/foo.coffee"], names: []},
// url: "/js/foo.js.map",
// sourcesRelativeTo: "/js/foo.js.map",
// sourceMappingURL: "foo.js.map"
// }
sourceMapResolve.resolveSources(result.map, result.sourcesRelativeTo, fs.readFile, function(error, result) {
if (error) {
return notifyFailure(error)
}
result
// {
// sourcesResolved: ["/coffee/foo.coffee"],
// sourcesContent: ["<contents of /coffee/foo.coffee>"]
// }
})
})
sourceMapResolve.resolve(code, "/js/foo.js", fs.readFile, function(error, result) {
if (error) {
return notifyFailure(error)
}
result
// {
// map: {file: "foo.js", mappings: "...", sources: ["/coffee/foo.coffee"], names: []},
// url: "/js/foo.js.map",
// sourcesRelativeTo: "/js/foo.js.map",
// sourceMappingURL: "foo.js.map",
// sourcesResolved: ["/coffee/foo.coffee"],
// sourcesContent: ["<contents of /coffee/foo.coffee>"]
// }
result.map.sourcesContent = result.sourcesContent
var map = new sourceMap.sourceMapConsumer(result.map)
map.sourceContentFor("/coffee/foo.coffee")
// "<contents of /coffee/foo.coffee>"
})

# Installation

- `npm install source-map-resolve`
- `bower install source-map-resolve`
- `component install lydell/source-map-resolve`

Works with CommonJS, AMD and browser globals, through UMD.

Note: This module requires `setImmediate` and `atob`. Use polyfills if needed, such as:

- https://github.com/NobleJS/setImmediate
- https://github.com/davidchambers/Base64.js

# Usage

### <tt>sourceMapResolve.resolveSourceMap(code, codeUrl, read, callback)</tt>

- `code` is a string of code that may or may not contain a sourceMappingURL comment. Such a comment is used to resolve the source map.
- `codeUrl` is the url to the file containing `code`. If the sourceMappingURL is relative, it is resolved against `codeUrl`.
- `read(url, callback)` is a function that reads `url` and responds using `callback(error, content)`. In Node.js you might want to use `fs.readFile`, while in the browser you might want to use an asynchronus `XMLHttpRequest`.
- `callback(error, result)` is a function that is invoked with either an error or `null` and the result.

The result is an object with the following properties:

- `map`: The source map for `code`, as an object (not a string).
- `url`: The url to the source map. If the source map came from a data uri, this property is `null`, since then there is no url to it.
- `sourcesRelativeTo`: The url that the sources of the source map are relative to. Since the sources are relative to the source map, and the url to the source map is provided as the `url` property, this property might seem superfluos. However, remember that the `url` property can be `null` if the source map came from a data uri. If so, the sources are relative to the file containing the data uri—`codeUrl`. This property will be identical to the `url` property or `codeUrl`, whichever is appropriate. This way you can conveniently resolve the sources without having to think about where the source map came from.
- `sourceMappingURL`: The url of the sourceMappingURL comment in `code`.

If `code` contains no sourceMappingURL, the result is `null`.

### <tt>sourceMapResolve.resolveSources(map, mapUrl, read, [options], callback)</tt>

- `map` is a source map, as an object (not a string).
- `mapUrl` is the url to the file containing `map`. Relative sources in the source map, if any, are resolved against `mapUrl`.
- `read(url, callback)` is a function that reads `url` and responds using `callback(error, content)`. In Node.js you might want to use `fs.readFile`, while in the browser you might want to use an asynchronus `XMLHttpRequest`.
- `options` is an optional object with any of the following properties:
  - `sourceRoot`: Override the `sourceRoot` property of the source map, which might only be relevant when resolving sources in the browser. This lets you bypass it when using the module outside of a browser, if needed. Pass a string to replace the `sourceRoot` property with, or `false` to ignore it. Defaults to `undefined`.
- `callback(error, result)` is a function that is invoked with either an error or `null` and the result.

The result is an object with the following properties:

- `sourcesResolved`: The same as `map.sources`, except all the sources are fully resolved.
- `sourcesContent`: An array with the contents of all sources in `map.sources`, in the same order as `map.sources`. If getting the contents of a source fails, an error object is put into the array instead.

### <tt>sourceMapResolve.resolve(code, codeUrl, read, [options], callback)</tt>

The arguments are identical to `sourceMapResolve.resolveSourceMap`, except that you may also provide the same `options` as in `sourceMapResolve.resolveSources`.

This is a convenience method that first resolves the source map and then its sources. You could also do this by first calling `sourceMapResolve.resolveSourceMap` and then `sourceMapResolve.resolveSources`.

The result is identical to `sourceMapResolve.resolveSourceMap`, with the properties from `sourceMapResolve.resolveSources` merged into it.

There is one extra feature available, though. If `code` is `null`, `codeUrl` is treated as a url to the source map instead of to `code`, and will be read. This is handy if you sometimes get the source map url from the `SourceMap: <url>` header (see the Notes section). In this case, the `sourceMappingURL` property of the result is `null`.

### <tt>sourceMapResolve.*Sync()</tt>

There are also sync versions of the three previous functions. They are identical to the async versions, except:

- They expect a sync reading function. In Node.js you might want to use `fs.readFileSync`, while in the browser you might want to use a synchronus `XMLHttpRequest`.
- They throw errors and return the result instead of using a callback.

`sourceMapResolve.resolveSourcesSync` also accepts `null` as the `read` parameter. The result is the same as when passing a function as the `read parameter`, except that the `sourcesContent` property of the result will be an empty array. In other words, the sources aren’t read. You only get the `sourcesResolved` property. (This only supported in the synchronus version, since there is no point doing it asynchronusly.)

### <tt>sourceMapResolve.parseMapToJSON(string, [data])</tt>

The spec says that if a source map (as a string) starts with ‘)]}’`, it should be stripped off. This is to prevent XSSI attacks. This function does that and returns the result of `JSON.parse`ing what’s left.

If this function throws `error`, `error.sourceMapData === data`.

### Errors

All errors passed to callbacks or thrown by this module have a `sourceMapData` property that contain as much as possible of the intended result of the function up until the error occurred.

Note that while the `map` property of result objects always is an object, `error.sourceMapData.map` will be a string if parsing that string fails.

# Note

This module resolves the source map for a given generated file by looking for a sourceMappingURL comment. The spec defines yet a way to provide the URL to the source map: By sending the `SourceMap: <url>` header along with the generated file. Since this module doesn’t retrive the generated code for you (instead you give the generated code to the module), it’s up to you to look for such a header when you retrieve the file (should the need arise).

# Development

## Tests

First off, run `npm install` to install testing modules and browser polyfills.

`npm test` lints the code and runs the test suite in Node.js.

## x-package.json5

package.json, component.json and bower.json are all generated from x-package.json5 by using `xpkg`. Only edit x-package.json5, and remember to run `xpkg` before commiting!

## Generating the browser version

source-map-resolve.js is generated from source-map-resolve-node.js and source-map-resolve-template.js. Only edit the two latter files, not source-map-resolve.js! To generate it, run `npm run build`.

# License

[MIT](LICENSE).