react-native/local-cli/bundle/output/unbundle/buildUnbundleSourcemap.js
Martín Bigio f99468de65 Sourcemaps support for RAM
Summary:This rev adds support for production sourcemaps on RAM.

When we inject a module into JSC we use the original `sourceURL` and specify the `startingLineNumber` of the module relative to a "regular" bundle. By doing so, when an error is thrown, JSC will include the provided `sourceURL` as the filename and will use the indicated `startingLineNumber` to figure out on which line the error actually occurred.

To make things a bit simpler and avoid having to deal with columns, we tweak the generated bundle so that each module starts on a new line. Since we cannot assure that each module's code will be on a single line as the minifier might break it on multiple (UglifyJS does so due to a bug on old versions of Chrome), we include on the index the line number that should be used when invoking `JSEvaluateScript`. Since the module length was not being used we replaced the placeholder we have there for the line number.

Reviewed By: javache

Differential Revision: D2997520

fb-gh-sync-id: 3243a489cbb5b48a963f4ccdd98ba63b30f53f3f
shipit-source-id: 3243a489cbb5b48a963f4ccdd98ba63b30f53f3f
2016-03-13 11:14:32 -07:00

60 lines
1.9 KiB
JavaScript

/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
'use strict';
const sourceMap = require('source-map');
const SourceMapConsumer = sourceMap.SourceMapConsumer;
/**
* Builds the sourcemaps for any type of unbundle provided the Bundle that
* contains the modules reachable from the entry point.
*
* The generated sourcemaps correspond to a regular bundle on which each module
* starts on a new line. Depending on the type of unbundle you're using, you
* will have to pipe the line number to native and use it when injecting the
* module's code into JSC. This way, we'll trick JSC to believe all the code is
* on a single big regular bundle where as it could be on an indexed bundle or
* as sparsed assets.
*/
function buildUnbundleSourcemap(bundle) {
const generator = new sourceMap.SourceMapGenerator({});
const nonPolyfillModules = bundle.getModules().filter(module =>
!module.polyfill
);
let offset = 1;
nonPolyfillModules.forEach(module => {
if (module.map) { // assets have no sourcemap
const consumer = new SourceMapConsumer(module.map);
consumer.eachMapping(mapping => {
generator.addMapping({
original: {
line: mapping.originalLine,
column: mapping.originalColumn,
},
generated: {
line: mapping.generatedLine + offset,
column: mapping.generatedColumn,
},
source: module.sourcePath,
});
});
generator.setSourceContent(module.sourcePath, module.sourceCode);
}
// some modules span more than 1 line
offset += module.code.split('\n').length;
});
return generator.toString();
}
module.exports = buildUnbundleSourcemap;