def __new__(mcls, name, bases, attrs):
# Do not do any special behavior for Message itself.
if not bases:
return super().__new__(mcls, name, bases, attrs)
# Get the essential information about the proto package, and where
# this component belongs within the file.
package, marshal = _package_info.compile(name, attrs)
# Determine the local path of this proto component within the file.
local_path = tuple(attrs.get("__qualname__", name).split("."))
# Sanity check: We get the wrong full name if a class is declared
# inside a function local scope; correct this.
if "<locals>" in local_path:
ix = local_path.index("<locals>")
local_path = local_path[:ix - 1] + local_path[ix + 1:]
# Determine the full name in protocol buffers.
full_name = ".".join((package, ) + local_path).lstrip(".")
# Special case: Maps. Map fields are special; they are essentially
# shorthand for a nested message and a repeated field of that message.
# Decompose each map into its constituent form.
# https://developers.google.com/protocol-buffers/docs/proto3#maps
map_fields = {}
for key, field in attrs.items():
if not isinstance(field, MapField):
continue
# Determine the name of the entry message.
msg_name = "{pascal_key}Entry".format(pascal_key=re.sub(
r"_\w",
lambda m: m.group()[1:].upper(),
key,
).replace(key[0], key[0].upper(), 1), )
# Create the "entry" message (with the key and value fields).
#
# Note: We instantiate an ordered dictionary here and then
# attach key and value in order to ensure that the fields are
# iterated in the correct order when the class is created.
# This is only an issue in Python 3.5, where the order is
# random (and the wrong order causes the pool to refuse to add
# the descriptor because reasons).
entry_attrs = collections.OrderedDict({
"__module__":
attrs.get("__module__", None),
"__qualname__":
"{prefix}.{name}".format(
prefix=attrs.get("__qualname__", name),
name=msg_name,
),
"_pb_options": {
"map_entry": True
},
})
entry_attrs["key"] = Field(field.map_key_type, number=1)
entry_attrs["value"] = Field(
field.proto_type,
number=2,
enum=field.enum,
message=field.message,
)
map_fields[msg_name] = MessageMeta(msg_name, (Message, ),
entry_attrs)
# Create the repeated field for the entry message.
map_fields[key] = RepeatedField(
ProtoType.MESSAGE,
number=field.number,
message=map_fields[msg_name],
)
# Add the new entries to the attrs
attrs.update(map_fields)
# Okay, now we deal with all the rest of the fields.
# Iterate over all the attributes and separate the fields into
# their own sequence.
fields = []
new_attrs = {}
oneofs = collections.OrderedDict()
proto_imports = set()
index = 0
for key, field in attrs.items():
# Sanity check: If this is not a field, do nothing.
if not isinstance(field, Field):
# The field objects themselves should not be direct attributes.
new_attrs[key] = field
continue
# Add data that the field requires that we do not take in the
# constructor because we can derive it from the metaclass.
# (The goal is to make the declaration syntax as nice as possible.)
field.mcls_data = {
"name": key,
"parent_name": full_name,
"index": index,
"package": package,
}
# Add the field to the list of fields.
fields.append(field)
# If this field is part of a "oneof", ensure the oneof itself
# is represented.
if field.oneof:
# Keep a running tally of the index of each oneof, and assign
# that index to the field's descriptor.
oneofs.setdefault(field.oneof, len(oneofs))
field.descriptor.oneof_index = oneofs[field.oneof]
# If this field references a message, it may be from another
# proto file; ensure we know about the import (to faithfully
# construct our file descriptor proto).
if field.message and not isinstance(field.message, str):
field_msg = field.message
if hasattr(field_msg, "pb") and callable(field_msg.pb):
field_msg = field_msg.pb()
# Sanity check: The field's message may not yet be defined if
# it was a Message defined in the same file, and the file
# descriptor proto has not yet been generated.
#
# We do nothing in this situation; everything will be handled
# correctly when the file descriptor is created later.
if field_msg:
proto_imports.add(field_msg.DESCRIPTOR.file.name)
# Same thing, but for enums.
elif field.enum and not isinstance(field.enum, str):
field_enum = (field.enum._meta.pb if hasattr(
field.enum, "_meta") else field.enum.DESCRIPTOR)
if field_enum:
proto_imports.add(field_enum.file.name)
# Increment the field index counter.
index += 1
# As per descriptor.proto, all synthetic oneofs must be ordered after
# 'real' oneofs.
opt_attrs = {}
for field in fields:
if field.optional:
field.oneof = "_{}".format(field.name)
field.descriptor.oneof_index = oneofs[field.oneof] = len(
oneofs)
opt_attrs[field.name] = field.name
# Generating a metaclass dynamically provides class attributes that
# instances can't see. This provides idiomatically named constants
# that enable the following pattern to check for field presence:
#
# class MyMessage(proto.Message):
# field = proto.Field(proto.INT32, number=1, optional=True)
#
# m = MyMessage()
# MyMessage.field in m
if opt_attrs:
mcls = type("AttrsMeta", (mcls, ), opt_attrs)
# Determine the filename.
# We determine an appropriate proto filename based on the
# Python module.
filename = _file_info._FileInfo.proto_file_name(
new_attrs.get("__module__", name.lower()))
# Get or create the information about the file, including the
# descriptor to which the new message descriptor shall be added.
file_info = _file_info._FileInfo.maybe_add_descriptor(
filename, package)
# Ensure any imports that would be necessary are assigned to the file
# descriptor proto being created.
for proto_import in proto_imports:
if proto_import not in file_info.descriptor.dependency:
file_info.descriptor.dependency.append(proto_import)
# Retrieve any message options.
opts = descriptor_pb2.MessageOptions(
**new_attrs.pop("_pb_options", {}))
# Create the underlying proto descriptor.
desc = descriptor_pb2.DescriptorProto(
name=name,
field=[i.descriptor for i in fields],
oneof_decl=[
descriptor_pb2.OneofDescriptorProto(name=i)
for i in oneofs.keys()
],
options=opts,
)
# If any descriptors were nested under this one, they need to be
# attached as nested types here.
child_paths = [
p for p in file_info.nested.keys() if local_path == p[:-1]
]
for child_path in child_paths:
desc.nested_type.add().MergeFrom(file_info.nested.pop(child_path))
# Same thing, but for enums
child_paths = [
p for p in file_info.nested_enum.keys() if local_path == p[:-1]
]
for child_path in child_paths:
desc.enum_type.add().MergeFrom(
file_info.nested_enum.pop(child_path))
# Add the descriptor to the file if it is a top-level descriptor,
# or to a "holding area" for nested messages otherwise.
if len(local_path) == 1:
file_info.descriptor.message_type.add().MergeFrom(desc)
else:
file_info.nested[local_path] = desc
# Create the MessageInfo instance to be attached to this message.
new_attrs["_meta"] = _MessageInfo(
fields=fields,
full_name=full_name,
marshal=marshal,
options=opts,
package=package,
)
# Run the superclass constructor.
cls = super().__new__(mcls, name, bases, new_attrs)
# The info class and fields need a reference to the class just created.
cls._meta.parent = cls
for field in cls._meta.fields.values():
field.parent = cls
# Add this message to the _FileInfo instance; this allows us to
# associate the descriptor with the message once the descriptor
# is generated.
file_info.messages[full_name] = cls
# Generate the descriptor for the file if it is ready.
if file_info.ready(new_class=cls):
file_info.generate_file_pb(new_class=cls, fallback_salt=full_name)
# Done; return the class.
return cls
def make_oneof_pb2(name: str) -> desc.OneofDescriptorProto:
return desc.OneofDescriptorProto(name=name, )
