webpack/lib/wasm/WasmModuleTemplatePlugin.js

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/
"use strict";

const { RawSource } = require("webpack-sources");
const WebAssemblyImportDependency = require("../dependencies/WebAssemblyImportDependency");

function generateInitParams(module) {
	const list = [];

	for (const dep of module.dependencies) {
		if (dep instanceof WebAssemblyImportDependency) {
			if (dep.description.type === "GlobalType") {
				const exportName = dep.name;
				const usedName = dep.module && dep.module.isUsed(exportName);

				if (usedName !== false) {
					list.push(
						`__webpack_require__(${JSON.stringify(
							dep.module.id
						)})[${JSON.stringify(usedName)}]`
					);
				}
			}
		}
	}

	return list;
}

class WasmModuleTemplatePlugin {
	apply(moduleTemplate) {
		moduleTemplate.hooks.content.tap(
			"WasmModuleTemplatePlugin",
			(moduleSource, module, { chunk }) => {
				if (module.type && module.type.startsWith("webassembly")) {
					if (chunk.canBeInitial())
						throw new Error(
							"Sync WebAssembly compilation is not yet implemented"
						);
					const generateExports = () => {
						if (
							Array.isArray(module.buildMeta.providedExports) &&
							Array.isArray(module.usedExports)
						) {
							// generate mangled exports
							return module.buildMeta.providedExports
								.map(exp => {
									const usedName = module.isUsed(exp);
									if (usedName) {
										return `${module.exportsArgument}[${JSON.stringify(
											usedName
										)}] = instance.exports[${JSON.stringify(exp)}];`;
									} else {
										return `// unused ${JSON.stringify(exp)} export`;
									}
								})
								.join("\n");
						} else {
							// generate simple export
							return `${module.moduleArgument}.exports = instance.exports;`;
						}
					};

					// FIXME(sven): assert that the exports exists in the modules
					// otherwise it will default to i32 0
					const initParams = generateInitParams(module).join(",");
					const source = new RawSource(
						[
							'"use strict";',
							"// Instantiate WebAssembly module",
							"var instance = __webpack_require__.w[module.i]",
							`instance.exports.__webpack_init__(${initParams})`,
							"// export exports from WebAssembly module",
							// TODO rewrite this to getters depending on exports to support circular dependencies
							generateExports()
						].join("\n")
					);
					return source;
				} else {
					return moduleSource;
				}
			}
		);

		moduleTemplate.hooks.hash.tap("WasmModuleTemplatePlugin", hash => {
			hash.update("WasmModuleTemplatePlugin");
			hash.update("1");
		});
	}
}
module.exports = WasmModuleTemplatePlugin;