webpack/lib/wasm-sync/WebAssemblyParser.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

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

"use strict";

const t = require("@webassemblyjs/ast");
const { moduleContextFromModuleAST } = require("@webassemblyjs/ast");
const { decode } = require("@webassemblyjs/wasm-parser");
const Parser = require("../Parser");
const StaticExportsDependency = require("../dependencies/StaticExportsDependency");
const WebAssemblyExportImportedDependency = require("../dependencies/WebAssemblyExportImportedDependency");
const WebAssemblyImportDependency = require("../dependencies/WebAssemblyImportDependency");

/** @typedef {import("../Module")} Module */
/** @typedef {import("../Parser").ParserState} ParserState */
/** @typedef {import("../Parser").PreparsedAst} PreparsedAst */

const JS_COMPAT_TYPES = new Set(["i32", "f32", "f64"]);

/**
 * @param {t.Signature} signature the func signature
 * @returns {null | string} the type incompatible with js types
 */
const getJsIncompatibleType = signature => {
	for (const param of signature.params) {
		if (!JS_COMPAT_TYPES.has(param.valtype)) {
			return `${param.valtype} as parameter`;
		}
	}
	for (const type of signature.results) {
		if (!JS_COMPAT_TYPES.has(type)) return `${type} as result`;
	}
	return null;
};

/**
 * TODO why are there two different Signature types?
 * @param {t.FuncSignature} signature the func signature
 * @returns {null | string} the type incompatible with js types
 */
const getJsIncompatibleTypeOfFuncSignature = signature => {
	for (const param of signature.args) {
		if (!JS_COMPAT_TYPES.has(param)) {
			return `${param} as parameter`;
		}
	}
	for (const type of signature.result) {
		if (!JS_COMPAT_TYPES.has(type)) return `${type} as result`;
	}
	return null;
};

const decoderOpts = {
	ignoreCodeSection: true,
	ignoreDataSection: true,

	// this will avoid having to lookup with identifiers in the ModuleContext
	ignoreCustomNameSection: true
};

class WebAssemblyParser extends Parser {
	constructor(options) {
		super();
		this.hooks = Object.freeze({});
		this.options = options;
	}

	/**
	 * @param {string | Buffer | PreparsedAst} source the source to parse
	 * @param {ParserState} state the parser state
	 * @returns {ParserState} the parser state
	 */
	parse(source, state) {
		if (!Buffer.isBuffer(source)) {
			throw new Error("WebAssemblyParser input must be a Buffer");
		}

		// flag it as ESM
		state.module.buildInfo.strict = true;
		state.module.buildMeta.exportsType = "namespace";

		// parse it
		const program = decode(source, decoderOpts);
		const module = program.body[0];

		const moduleContext = moduleContextFromModuleAST(module);

		// extract imports and exports
		const exports = [];
		let jsIncompatibleExports = (state.module.buildMeta.jsIncompatibleExports =
			undefined);

		const importedGlobals = [];
		t.traverse(module, {
			ModuleExport({ node }) {
				const descriptor = node.descr;

				if (descriptor.exportType === "Func") {
					const funcIdx = descriptor.id.value;

					/** @type {t.FuncSignature} */
					const funcSignature = moduleContext.getFunction(funcIdx);

					const incompatibleType =
						getJsIncompatibleTypeOfFuncSignature(funcSignature);

					if (incompatibleType) {
						if (jsIncompatibleExports === undefined) {
							jsIncompatibleExports =
								state.module.buildMeta.jsIncompatibleExports = {};
						}
						jsIncompatibleExports[node.name] = incompatibleType;
					}
				}

				exports.push(node.name);

				if (node.descr && node.descr.exportType === "Global") {
					const refNode = importedGlobals[node.descr.id.value];
					if (refNode) {
						const dep = new WebAssemblyExportImportedDependency(
							node.name,
							refNode.module,
							refNode.name,
							refNode.descr.valtype
						);

						state.module.addDependency(dep);
					}
				}
			},

			Global({ node }) {
				const init = node.init[0];

				let importNode = null;

				if (init.id === "get_global") {
					const globalIdx = init.args[0].value;

					if (globalIdx < importedGlobals.length) {
						importNode = importedGlobals[globalIdx];
					}
				}

				importedGlobals.push(importNode);
			},

			ModuleImport({ node }) {
				/** @type {false | string} */
				let onlyDirectImport = false;

				if (t.isMemory(node.descr) === true) {
					onlyDirectImport = "Memory";
				} else if (t.isTable(node.descr) === true) {
					onlyDirectImport = "Table";
				} else if (t.isFuncImportDescr(node.descr) === true) {
					const incompatibleType = getJsIncompatibleType(node.descr.signature);
					if (incompatibleType) {
						onlyDirectImport = `Non-JS-compatible Func Signature (${incompatibleType})`;
					}
				} else if (t.isGlobalType(node.descr) === true) {
					const type = node.descr.valtype;
					if (!JS_COMPAT_TYPES.has(type)) {
						onlyDirectImport = `Non-JS-compatible Global Type (${type})`;
					}
				}

				const dep = new WebAssemblyImportDependency(
					node.module,
					node.name,
					node.descr,
					onlyDirectImport
				);

				state.module.addDependency(dep);

				if (t.isGlobalType(node.descr)) {
					importedGlobals.push(node);
				}
			}
		});

		state.module.addDependency(new StaticExportsDependency(exports, false));

		return state;
	}
}

module.exports = WebAssemblyParser;