pkg/dart2wasm/bin/wasm2wat.dart

// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:io';

import 'package:args/args.dart';

import 'package:wasm_builder/src/serialize/printer.dart';
import 'package:wasm_builder/wasm_builder.dart';

void main(List<String> args) {
  final result = argParser.parse(args);
  if (result.flag('help')) {
    print('Usage: wasm2wat.dart [...options...] <input.wasm> <...wasm>');
    print(argParser.usage);
    exit(1);
  }

  final sort = result.flag('sort');
  final writeWat = result.flag('write');
  final outputFile = result['output'] as String?;
  final wasmFiles = result.rest;
  if (outputFile != null && wasmFiles.length != 1) {
    print(
      'Specified --output=$outputFile but number of wasm files is not 1 '
      '(${wasmFiles.join(' ')})',
    );
    print(argParser.usage);
    exit(1);
  }
  if (wasmFiles.isEmpty) {
    print('No wasm files specified');
    print(argParser.usage);
    exit(1);
  }
  if (wasmFiles.length > 1 && !writeWat) {
    print('More than one wasm file specified without `--write` flag.');
    print(argParser.usage);
    exit(1);
  }

  List<RegExp> getFilter(String optionName) {
    final filterStrings = result[optionName] as List<String>;
    return [for (final f in filterStrings) RegExp(f)];
  }

  final functionFilters = getFilter('function-name-filter');
  final typeFilters = getFilter('type-name-filter');
  final globalFilters = getFilter('global-name-filter');
  final settings = ModulePrintSettings(
    functionFilters: functionFilters,
    typeFilters: typeFilters,
    globalFilters: globalFilters,
    printInSortedOrder: sort,
  );

  for (final input in wasmFiles) {
    final wasmBytes = File(input).readAsBytesSync();

    final deserializer = Deserializer(wasmBytes);
    final module = Module.deserialize(deserializer);
    final wat = module.printAsWat(settings: settings);
    if (outputFile != null) {
      File(outputFile).writeAsStringSync(wat);
      print('-> Written $outputFile');
    } else if (writeWat) {
      File('$input.wat').writeAsStringSync(wat);
      print('-> Written $input.wat');
    } else {
      print(wat);
    }
  }
}

final argParser = ArgParser()
  ..addMultiOption(
    'function-name-filter',
    abbr: 'f',
    help:
        'Only print function bodies if the function name matches. '
        'The name filter is interpreted as a Dart `RegExp`.',
  )
  ..addMultiOption(
    'type-name-filter',
    abbr: 't',
    help:
        'Only print type constituents if the type name matches. '
        'The name filter is interpreted as a Dart `RegExp`.',
  )
  ..addMultiOption(
    'global-name-filter',
    abbr: 'g',
    help:
        'Only print global initializers if the global name matches. '
        'The name filter is interpreted as a Dart `RegExp`.',
  )
  ..addFlag(
    'sort',
    abbr: 's',
    help: 'Print functions/types/... in sorted order (sort by name).',
  )
  ..addFlag(
    'write',
    abbr: 'w',
    help: 'Write the resulting wat code to <input.wasm>.wat.',
  )
  ..addFlag('help', abbr: 'h', help: 'Print the help of this tool.')
  ..addFlag(
    'prefer-multiline',
    abbr: 'm',
    help:
        'Prefer to print global initializers & type definitions as multi line.',
    defaultsTo: /* wami equivalent is false */ false,
  )
  ..addOption(
    'output',
    abbr: 'o',
    help:
        'The filepath where the output will be written to (default: stdout). '
        'The number of input wasm files must be 1 if --output was provided.',
  );