compiler.js
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/*
* This file uses webpack to compile a template with a child compiler.
*
* [TEMPLATE] -> [JAVASCRIPT]
*
*/
'use strict';
var Promise = require('bluebird');
var _ = require('lodash');
var path = require('path');
var NodeTemplatePlugin = require('webpack/lib/node/NodeTemplatePlugin');
var NodeTargetPlugin = require('webpack/lib/node/NodeTargetPlugin');
var LoaderTargetPlugin = require('webpack/lib/LoaderTargetPlugin');
var LibraryTemplatePlugin = require('webpack/lib/LibraryTemplatePlugin');
var SingleEntryPlugin = require('webpack/lib/SingleEntryPlugin');
/**
* Compiles the template into a nodejs factory, adds its to the compilation.assets
* and returns a promise of the result asset object.
*
* @param template relative path to the template file
* @param context path context
* @param outputFilename the file name
* @param compilation The webpack compilation object
*
* Returns an object:
* {
* hash: {String} - Base64 hash of the file
* content: {String} - Javascript executable code of the template
* }
*
*/
module.exports.compileTemplate = function compileTemplate (template, context, outputFilename, compilation) {
// The entry file is just an empty helper as the dynamic template
// require is added in "loader.js"
var outputOptions = {
filename: outputFilename,
publicPath: compilation.outputOptions.publicPath
};
// Store the result of the parent compilation before we start the child compilation
var assetsBeforeCompilation = _.assign({}, compilation.assets[outputOptions.filename]);
// Create an additional child compiler which takes the template
// and turns it into an Node.JS html factory.
// This allows us to use loaders during the compilation
var compilerName = getCompilerName(context, outputFilename);
var childCompiler = compilation.createChildCompiler(compilerName, outputOptions);
childCompiler.context = context;
childCompiler.apply(
new NodeTemplatePlugin(outputOptions),
new NodeTargetPlugin(),
new LibraryTemplatePlugin('HTML_WEBPACK_PLUGIN_RESULT', 'var'),
new SingleEntryPlugin(this.context, template),
new LoaderTargetPlugin('node')
);
// Fix for "Uncaught TypeError: __webpack_require__(...) is not a function"
// Hot module replacement requires that every child compiler has its own
// cache. @see https://github.com/ampedandwired/html-webpack-plugin/pull/179
childCompiler.plugin('compilation', function (compilation) {
if (compilation.cache) {
if (!compilation.cache[compilerName]) {
compilation.cache[compilerName] = {};
}
compilation.cache = compilation.cache[compilerName];
}
});
// Compile and return a promise
return new Promise(function (resolve, reject) {
childCompiler.runAsChild(function (err, entries, childCompilation) {
// Resolve / reject the promise
if (childCompilation && childCompilation.errors && childCompilation.errors.length) {
var errorDetails = childCompilation.errors.map(function (error) {
return error.message + (error.error ? ':\n' + error.error : '');
}).join('\n');
reject(new Error('Child compilation failed:\n' + errorDetails));
} else if (err) {
reject(err);
} else {
// Replace [hash] placeholders in filename
var outputName = compilation.mainTemplate.applyPluginsWaterfall('asset-path', outputOptions.filename, {
hash: childCompilation.hash,
chunk: entries[0]
});
// Restore the parent compilation to the state like it
// was before the child compilation
compilation.assets[outputName] = assetsBeforeCompilation[outputName];
if (assetsBeforeCompilation[outputName] === undefined) {
// If it wasn't there - delete it
delete compilation.assets[outputName];
}
resolve({
// Hash of the template entry point
hash: entries[0].hash,
// Output name
outputName: outputName,
// Compiled code
content: childCompilation.assets[outputName].source()
});
}
});
});
};
/**
* Returns the child compiler name e.g. 'html-webpack-plugin for "index.html"'
*/
function getCompilerName (context, filename) {
var absolutePath = path.resolve(context, filename);
var relativePath = path.relative(context, absolutePath);
return 'html-webpack-plugin for "' + (absolutePath.length < relativePath.length ? absolutePath : relativePath) + '"';
}