cxx.py

# Copyright 2019-present, GraphQL Foundation
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

import io as StringIO

from casing import title
from license import C_LICENSE_COMMENT

class Printer(object):
  def __init__(self):
    self._type_name = None
    # Map concrete type to base class
    self._bases = {}
    # HACK: Defer everything we print so that forward declarations for
    # all classes come first. Avoids having to do 2 passes over the
    # input file.
    self._deferredOutput = StringIO.StringIO()

    self._fields = []

  def start_file(self):
    print(C_LICENSE_COMMENT + '''/** @generated */
#pragma once

#include "AstNode.h"

#include <memory>
#include <string>
#include <utility>
#include <vector>

namespace facebook {
namespace graphql {
namespace ast {

// The parser uses strdup to move from yytext to the heap, so we need
// to use free instead of delete.
struct CDeleter {
  void operator()(const char *p) const { free((void *)p); }
};
''')

  def end_file(self):
    print()
    print(self._deferredOutput.getvalue())
    print('}')
    print('}')
    print('}')

  def _base_class(self, type):
    return self._bases.get(type, 'Node')

  def start_type(self, name):
    self._type_name = name
    base = self._base_class(name)
    # non-deferred!
    print('class %s;' % name)
    print('class %s : public %s {' % (name, base), file=self._deferredOutput)
    self._fields = []

  def field(self, type, name, nullable, plural):
    if type == 'OperationKind':
      type = 'string'
    self._fields.append((type, name, nullable, plural))

  def end_type(self, name):
    self._print_fields()
    print(' public:', file=self._deferredOutput)
    self._print_constructor()
    print(file=self._deferredOutput)
    self._print_destructor_prototype()
    print(file=self._deferredOutput)
    self._print_noncopyable()
    print(file=self._deferredOutput)
    self._print_getters()
    print('  void accept(visitor::AstVisitor *visitor) const override;', file=self._deferredOutput)
    print('};', file=self._deferredOutput)
    print(file=self._deferredOutput)
    print(file=self._deferredOutput)
    self._type_name = None
    self._fields = []

  def _storage_type(self, type):
    if type == 'string':
      return 'std::unique_ptr<const char, CDeleter>'
    elif type == 'boolean':
      return 'bool'
    else:
      return 'std::unique_ptr<%s>' % type

  def _print_fields(self):
    for (type, name, nullable, plural) in self._fields:
      storage_type = self._storage_type(type)
      if plural:
        storage_type = 'std::unique_ptr<std::vector<%s>>' % storage_type
      print('  %s %s_;' % (storage_type, name), file=self._deferredOutput)

  def _ctor_singular_type(self, type):
    if type == 'string':
      return 'const char *'
    elif type == 'boolean':
      return 'bool'
    else:
      return '%s *' % type

  def _ctor_plural_type(self, type):
    return 'std::vector<%s> *' % self._storage_type(type)

  def _print_constructor(self):
    print('  explicit %s(' % self._type_name, file=self._deferredOutput)
    print('      const yy::location &location%s' % (',' if self._fields else ''), file=self._deferredOutput)
    def ctor_arg(type, name, plural):
      if plural:
        ctor_type = self._ctor_plural_type(type)
      else:
        ctor_type = self._ctor_singular_type(type)
      return '      %s %s' % (ctor_type, name)
    print(',\n'.join(ctor_arg(type, name, plural)
                     for (type, name, nullable, plural) in self._fields), file=self._deferredOutput)
    print('  )', file=self._deferredOutput)
    def ctor_init(type, name, plural):
      # Strings are const char *, just pass.
      # Vectors are passed by pointer and we take ownership.
      # Node types are passed in by pointer and we take ownership.
      value = name
      return '    %s_(%s)' % (name, value)
    print('  : %s(location)%s' % (self._base_class(self._type_name), ',' if self._fields else ''), file=self._deferredOutput)
    print(',\n'.join(ctor_init(type, name, plural)
                     for (type, name, nullable, plural)
                     in self._fields), file=self._deferredOutput)
    print('  {}', file=self._deferredOutput)

  def _getter_type(self, type, nullable, plural):
    if plural and nullable:
      return 'const std::vector<%s>*' % self._storage_type(type)
    elif plural:
      return 'const std::vector<%s>&' %  self._storage_type(type)

    if type == 'string':
      assert not nullable
      return 'const char *'
    elif type == 'boolean':
      assert not nullable
      return 'bool'
    elif nullable:
      return 'const %s*' % type
    else:
      return 'const %s&' % type

  def _getter_value_to_return(self, raw_value, type, nullable, plural):
    if plural and nullable:
      return raw_value + '.get()'
    elif plural:
      return '*%s' % raw_value
    elif type == 'boolean':
      return raw_value
    elif nullable or type == 'string':
      return '%s.get()' % raw_value
    else:
      return '*%s' % raw_value

  def _print_getters(self):
    for (type, name, nullable, plural) in self._fields:
      print('  %s get%s() const' % (
        self._getter_type(type, nullable, plural),
        title(name)), file=self._deferredOutput)
      print('  { return %s; }' % (
        self._getter_value_to_return(name + '_', type, nullable, plural)), file=self._deferredOutput)
      print(file=self._deferredOutput)

  def _print_destructor_prototype(self):
    print('  ~%s() {}' % self._type_name, file=self._deferredOutput)

  def _print_noncopyable(self):
    print('  %s(const %s&) = delete;' % (
      self._type_name, self._type_name), file=self._deferredOutput)
    print('  %s& operator=(const %s&) = delete;' % (
      self._type_name, self._type_name), file=self._deferredOutput)

  def start_union(self, name):
    self._type_name = name
    # non-deferred!
    print('class %s;' % name)
    print('class %s : public Node {' % name, file=self._deferredOutput)
    print(' public:', file=self._deferredOutput)
    self._print_constructor()
    print('};', file=self._deferredOutput)
    print(file=self._deferredOutput)

  def union_option(self, type):
    assert type not in self._bases, '%s cannot appear in more than one union!' % type
    self._bases[type] = self._type_name

  def end_union(self, name):
    pass