Automatically translate Binaryen's if expressions to standard format

if.py

#! /usr/bin/python3

"""Translate from the legacy if-else text syntax to the standard syntax
"""

import argparse
import glob
import os
import subprocess
import sys


def warn(msg):
    print(f'WARNING: {msg}', file=sys.stderr)


def takeComment(text, i):
    start = i
    if text[i:].startswith(';;'):
        while i < len(text) and text[i] != '\n':
            i += 1
    return text[start:i], i


def takeUntilParen(text, i):
    start = i
    while i < len(text):
        comment, i = takeComment(text, i)
        if comment:
            continue
        if text[i] == '"':
            i += 1
            while i < len(text) and text[i] != '"':
                i += 1
            if i < len(text):
                i += 1
            continue
        if text[i] == '(' or text[i] == ')':
            break;
        i += 1
    return text[start:i], i


def getIndent(text, i):
    start = i
    i -= 1
    while i >= 0 and text[i].isspace() and text[i] != '\n':
        i -= 1
    if text[i] == '\n':
        return start - i - 1
    return 0


def applyIndent(text, indent):
    out = []
    for c in text:
        if c == '\n':
            out.append('\n' + ' ' * indent)
        else:
            out.append(c)
    return ''.join(out)


def wrap(text, i, word, baseIndent, marginalIndent):
    out = []
    if text[i:].startswith('(' + word):
        wrapped, i = takeParen(text, i)
        out.append(wrapped)
    else:
        wrappee, i = takeParen(text, i)
        while i < len(text) and text[i].isspace() and text[i] != '\n':
            wrappee += text[i]
            i += 1
        comment, i = takeComment(text, i)
        if comment:
            wrappee += comment
        out.append('(')
        out.append(word)
        if baseIndent and marginalIndent:
            out.append('\n')
            out.append(' ' * (baseIndent + marginalIndent))
            out.append(applyIndent(wrappee, marginalIndent))
            out.append('\n')
            out.append(' ' * baseIndent)
            out.append(')')
        else:
            out.append(' ')
            out.append(wrappee)
            out.append(')')
    return ''.join(out), i


def takeParen(text, i):
    assert text[i] == '('
    out = []

    # ;; (if ...
    if text[i:].startswith('(if'):
        ifIndent = getIndent(text, i)
        out.append(text[i:i+3])
        i += 3

        space, i = takeUntilParen(text, i)
        out.append(space)

        if text[i:].startswith('(result'):
            result, i = takeParen(text, i)
            out.append(result)
            space, i = takeUntilParen(text, i)
            out.append(space)

        cond, i = takeParen(text, i)
        out.append(cond)
        space, i = takeUntilParen(text, i)
        out.append(space)

        thenIndent = getIndent(text, i)

        if thenIndent > ifIndent:
            indent = thenIndent - ifIndent
        else:
            indent = 0

        then, i = wrap(text, i, 'then', thenIndent, indent)
        out.append(then)
        space, i = takeUntilParen(text, i)
        out.append(space)

        if i < len(text) and text[i] == '(':
            else_, i = wrap(text, i, 'else', thenIndent, indent)
            out.append(else_)
            space, i = takeUntilParen(text, i)
            out.append(space)
    else:
        out.append('(')
        i += 1

    while i < len(text):
        space, i = takeUntilParen(text, i)
        if space:
            out.append(space)
            continue
        if text[i] == '(':
            paren, i = takeParen(text, i)
            out.append(paren)
            continue
        assert text[i] == ')'
        out.append(')')
        i += 1
        break

    return ''.join(out), i


def port_test(args, test):
    if not test.endswith('.wast') and not test.endswith('.wat'):
        warn(f'Skipping {test} because only .wat and .wast files are supported')
        return

    forbidden = {
        'test/passes/limit-segments_disable-bulk-memory.wast',
        'test/spec/block.wast',
        'test/spec/br_if.wast',
        'test/spec/br_table.wast',
        'test/spec/call_indirect.wast',
        'test/spec/globals.wast',
        'test/spec/i32.wast',
        'test/spec/if.wast',
        'test/spec/load64.wast',
        'test/spec/load.wast',
        'test/spec/local_tee.wast',
        'test/spec/loop.wast',
        'test/spec/memory_grow.wast',
        'test/spec/names.wast',
        'test/spec/nop.wast',
        'test/spec/return.wast',
        'test/spec/select.wast',
        'test/spec/store.wast',
        'test/spec/typecheck.wast',
        'test/spec/comments.wast',
        'test/lit/wat-kitchen-sink.wast',
    }
    for f in forbidden:
        if test.endswith(f):
            return

    print("porting", test)
    with open(test) as file:
        text = file.read()

    i = 0
    out = []
    while i < len(text):
        intro, i = takeUntilParen(text, i)
        if intro:
            out.append(intro)
            continue
        paren, i = takeParen(text, i)
        out.append(paren)

    updated = ''.join(out)
    if args.dry_run:
        print(updated)
    else:
        with open(test, 'w') as file:
            file.write(updated)


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument(
        '--binaryen-bin', dest='binaryen_bin', default='bin',
        help=('Specifies the path to the Binaryen executables in the CMake build'
              ' directory. Default: bin/ of current directory (i.e. assume an'
              ' in-tree build).'))
    parser.add_argument('--dry', dest='dry_run', action='store_true',
                        help=('Print the updated tests instead of updating'
                              ' files in-place.'))
    parser.add_argument('tests', nargs='+', help='The test files to port')
    args = parser.parse_args()
    args.binaryen_bin = os.path.abspath(args.binaryen_bin)

    for pattern in args.tests:
        for test in glob.glob(pattern, recursive=True):
            port_test(args, test)


if __name__ == '__main__':
    main()