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144 lines
5.6 KiB
Markdown
144 lines
5.6 KiB
Markdown
# Adjust Source-map Loader
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[](http://github.com/bholloway/adjust-sourcemap-loader)
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Webpack loader that adjusts source maps.
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Use as a **loader** to debug source-maps or to adjust source-maps between other loaders.
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Use as a **module filename template** to ensure the final source-map are to your liking.
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## Usage : Loader
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``` javascript
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require('adjust-sourcemap?format=absolute!babel?sourceMap');
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```
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### Source maps required
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Note that **source maps** must be enabled on any preceding loader. In the above example we use `babel?sourceMap`.
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### Apply via webpack config
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It is preferable to adjust your `webpack.config` so to avoid having to prefix every `require()` statement:
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``` javascript
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module.exports = {
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module: {
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loaders: [
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{
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test : /\.js/,
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loaders: ['adjust-sourcemap?format=absolute', 'babel?sourceMap']
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}
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]
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}
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};
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```
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## Usage : Module filename template
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Specifying a certain format as the final step in a loader chain will **not** influence the final source format that Webpack will output. Instead the format is determined by the **module filename template**.
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There are limitations to the filename templating that Webpack provides. This package may also operate as a custom template function that will convert output source-map sources to the desired `format`.
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In the following example we ensure project-relative source-map sources are output.
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```javascript
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var templateFn = require('adjust-sourcemap-loader')
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.moduleFilenameTemplate({
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format: 'projectRelative'
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});
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module.exports = {
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output: {
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...
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devtoolModuleFilenameTemplate : templateFn,
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devtoolFallbackModuleFilenameTemplate: templateFn
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}
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};
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```
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## Options
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As a loader, options may be set using [query parameters](https://webpack.github.io/docs/using-loaders.html#query-parameters) or by using [programmatic parameters](https://webpack.github.io/docs/how-to-write-a-loader.html#programmable-objects-as-query-option). Programmatic means the following in your `webpack.config`.
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```javascript
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module.exports = {
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adjustSourcemapLoader: {
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...
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}
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}
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```
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Where `...` is a hash of any of the following options.
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* **`debug`** : `boolean|RegExp` May be used alone (boolean) or with a `RegExp` to match the resource(s) you are interested in debugging.
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* **`fail`** : `boolean` Implies an **Error** if a source-map source cannot be decoded.
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* **`format`** : `string` Optional output format for source-map `sources`. Must be the name of one of the available `codecs`. Omitting the format will result in **no change** and the outgoing source-map will match the incomming one.
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* **`root`** : `boolean` A boolean flag that indices that a `sourceRoot` path sould be included in the output map. This is contingent on a `format` being specified.
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* **`codecs`** : `Array.<{name:string, decode:function, encode:function, root:function}>` Optional Array of codecs. There are a number of built-in codecs available. If you specify you own codecs you will loose those that are built-in. However you can include them from the `codec/` directory.
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Note that **query** parameters take precedence over **programmatic** parameters.
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### Changing the format
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Built-in codecs that may be specified as a `format` include:
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* `absolute`
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* `outputRelative`
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* `projectRelative`
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* `webpackProtocol`
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* `sourceRelative` (works for loader only, **not** Module filename template)
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### Specifying codecs
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There are additional built-in codecs that do not support encoding. These are still necessary to decode source-map sources. If you specify your own `options.codecs` then you should **also include the built-in codecs**. Otherwise you will find that some sources cannot be decoded.
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The existing codecs may be found in `/codec`, or on the loader itself:
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```javascript
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var inBuiltCodecs = require('adjust-sourcemap-loader').codecs,
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myCodecs = [
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{
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name : 'foo',
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decode: function(uri) {...},
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encode: function(absolute) {...},
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root : function() {...}
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},
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...
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];
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module.exports = {
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adjustSourcemapLoader: {
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codecs: inBuiltCodecs.concat(myCodecs)
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}
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}
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```
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The codec **order is important**. Those that come first have precedence. Any codec that detects a distinct URI should be foremost so that illegal paths are not encountered by successive codecs.
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### Abstract codecs
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A codec that detects generated code and cannot `decode()` a URI to an absolute file path.
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Instead of implementing `encode()` or `root()` it should instead specify `abstract:true`. Its `decode()` function then may return `boolean` where it detects such generated sources.
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For example, a built-in abstract codec will match the **Webpack bootstrap** code and ensure that its illegal source uri is not encountered by later coders.
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## How it works
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The loader will receive a source map as its second parameter, so long as the preceding loader was using source-maps.
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The exception is the **css-loader** where the source-map is in the content, which is **not currently supported** .
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The source-map `sources` are parsed by applying **codec.decode()** functions until one of them returns an absolute path to a file that exists. The exception is abstract codecs, where the source with remain unchanged.
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If a format is specified then the source-map `sources` are recreated by applying the **codec.encode()** function for the stated `format` and (where the `root` option is specified) the **codec.root()** function will set the source-map `sourceRoot`.
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If a codec does not specify **codec.encode()** or **codec.root()** then it may **not** be used as the `format`.
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