react-native/local-cli/bundle/output/unbundle/buildUnbundleSourcemap.js
Martín Bigio 8edc35004c Move preloaded modules to startup code section
Summary:We found that moving the preloaded modules to the startup section of the RAM Bundle improves TTI quite a bit by saving lots of through the bridge calls and injecting multiple modules at once on JSC. However, doing this on a non hacky way required a lot of work. The main changes this diff does are:
  - Add to `BundleBase` additional bundling options. This options are fetched based on the entry file we're building by invoking a module that exports a function (`getBundleOptionsModulePath`).
  - Implement `BundleOptions` module to include the `numPreloadedModules` attribute as a bundle additional option. This value is computed by getting the dependencies the entry file has and looking for the first module that exports a module we don't want to preload. The `numPreloadedModules` attribute is then used to decide where to splice the array of modules.
- Additional kung fu to make sure sourcemaps work for both preloaded and non preloaded modules.

Reviewed By: davidaurelio

Differential Revision: D3046534

fb-gh-sync-id: 80b676222ca3bb8b9eecc912a7963be94d3dee1a
shipit-source-id: 80b676222ca3bb8b9eecc912a7963be94d3dee1a
2016-03-23 09:28:31 -07:00

57 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({});
let offset = 0;
bundle.getUnbundle('INDEX').allModules.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;