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proto_macro.rs
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// Protocol Buffers - Google's data interchange format
// Copyright 2024 Google LLC. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
/// proto! enables the use of Rust struct initialization syntax to create
/// protobuf messages. The macro does its best to try and detect the
/// initialization of submessages, but it is only able to do so while the
/// submessage is being defined as part of the original struct literal.
/// Introducing an expression using () or {} as the value of a field will
/// require another call to this macro in order to return a submessage
/// literal.``` /*
/// Given the following proto definition
/// message Data {
/// int32 number = 1;
/// string letters = 2;
/// Data nested = 3;
/// }
/// */
/// use protobuf::proto;
/// let message = proto!(Data {
/// number: 42,
/// letters: "Hello World",
/// nested: Data {
/// number: {
/// let x = 100;
/// x + 1
/// }
/// }
/// }); ```
#[macro_export]
macro_rules! proto {
($msgtype:ty { $($tt:tt)* }) => {
$crate::proto_internal!($msgtype { $($tt)* })
}
}
#[macro_export(local_inner_macros)]
#[doc(hidden)]
macro_rules! proto_internal {
// @merge rules are used to find a trailing ..expr on the message and call merge_from on it
// before the fields of the message are set.
(@merge $msg:ident $ident:ident : $expr:expr, $($rest:tt)*) => {
proto_internal!(@merge $msg $($rest)*);
};
(@merge $msg:ident $ident:ident : $expr:expr) => {
};
(@merge $msg:ident ..$expr:expr) => {
$crate::MergeFrom::merge_from(&mut $msg, $expr);
};
// @msg rules are used to set the fields of the message. There is a lot of duplication here
// because we need to parse the message type using a :: separated list of identifiers.
// nested message and trailing fields
(@msg $msg:ident $submsg:ident : $($msgtype:ident)::+ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@msg $msg $submsg : $($msgtype)::+ { $($value)* });
proto_internal!(@msg $msg $($rest)*);
};
// nested message with leading :: on type and trailing fields
(@msg $msg:ident $submsg:ident : ::$($msgtype:ident)::+ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@msg $msg $submsg : ::$($msgtype)::+ { $($value)* });
proto_internal!(@msg $msg $($rest)*);
};
// nested message using __
(@msg $msg:ident $submsg:ident : __ { $($value:tt)* }) => {
{
let mut $msg = $crate::__internal::paste!($msg.[<$submsg _mut>]());
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
}
};
// nested message
(@msg $msg:ident $submsg:ident : $($msgtype:ident)::+ { $($value:tt)* }) => {
{
let mut $msg: <$($msgtype)::+ as $crate::MutProxied>::Mut<'_> = $crate::__internal::paste!($msg.[<$submsg _mut>]());
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
}
};
// nested message with leading ::
(@msg $msg:ident $submsg:ident : ::$($msgtype:ident)::+ { $($value:tt)* }) => {
{
let mut $msg: <::$($msgtype)::+ as $crate::MutProxied>::Mut<'_> = $crate::__internal::paste!($msg.[<$submsg _mut>]());
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
}
};
// field with array literal and trailing fields
(@msg $msg:ident $ident:ident : [$($elems:tt)*], $($rest:tt)*) => {
proto_internal!(@msg $msg $ident : [$($elems)*]);
proto_internal!(@msg $msg $($rest)*);
};
// field with array literal, calls out to @array to look for nested messages
(@msg $msg:ident $ident:ident : [$($elems:tt)*]) => {
{
let _repeated = $crate::__internal::paste!($msg.[<$ident>]());
let elems = proto_internal!(@array $msg _repeated [] $($elems)*);
$crate::__internal::paste!($msg.[<set_ $ident>](elems.into_iter()));
}
};
// @array searches through an array literal for nested messages.
// If a message is found then we recursively call the macro on it to set the fields.
// This will create an array literal of owned messages to be used while setting the field.
// For primitive types they should just be passed through as an $expr.
// The array literal is constructed recursively, so the [] case has to be handled separately so
// that we can properly insert commas. This leads to a lot of duplication.
// Message nested in array literal with trailing array items
(@array $msg:ident $repeated:ident [$($vals:expr),+] __ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [
$($vals),+ ,
{
let mut $msg = $crate::__internal::get_repeated_default_value($crate::__internal::Private, $repeated);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $repeated:ident [$($vals:expr),+] __ { $($value:tt)* }) => {
[
$($vals),+ ,
{
let mut $msg = $crate::__internal::get_repeated_default_value($crate::__internal::Private, $repeated);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
]
};
// Message nested in array literal with trailing array items
(@array $msg:ident $repeated:ident [] __ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [
{
let mut $msg = $crate::__internal::get_repeated_default_value($crate::__internal::Private, $repeated);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $repeated:ident [] __ { $($value:tt)* }) => {
[
{
let mut $msg = $crate::__internal::get_repeated_default_value($crate::__internal::Private, $repeated);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
]
};
// End of __ repeated, now we need to handle named types
// Message nested in array literal with trailing array items
(@array $msg:ident $repeated:ident [$($vals:expr),+] $($msgtype:ident)::+ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [
$($vals),+ ,
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
] $($rest)*)
};
// Message nested in [] literal with leading :: on type and trailing array items
(@array $msg:ident $repeated:ident [$($vals:expr),+] ::$($msgtype:ident)::+ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [
$($vals),+ ,
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $repeated:ident [$($vals:expr),+] $($msgtype:ident)::+ { $($value:tt)* }) => {
[
$($vals),+ ,
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
]
};
// Message nested in [] literal with leading :: on type
(@array $msg:ident $repeated:ident [$($vals:expr),+] ::$($msgtype:ident)::+ { $($value:tt)* }) => {
[
$($vals),+ ,
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
]
};
// Message nested in array literal with trailing array items
(@array $msg:ident $repeated:ident [] $($msgtype:ident)::+ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
] $($rest)*)
};
// with leading ::
(@array $msg:ident $repeated:ident [] ::$($msgtype:ident)::+ { $($value:tt)* }, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $repeated:ident [] $($msgtype:ident)::+ { $($value:tt)* }) => {
[
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
]
};
(@array $msg:ident $repeated:ident [] ::$($msgtype:ident)::+ { $($value:tt)* }) => {
[
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
]
};
// Begin handling (key, value) for Maps in array literals
// Message nested in array literal with trailing array items
(@array $msg:ident $map:ident [$($vals:expr),+] ($key:expr, __ { $($value:tt)* }), $($rest:tt)*) => {
proto_internal!(@array $msg $map [
$($vals),+ ,
(
$key,
{
let mut $msg = $crate::__internal::get_map_default_value($crate::__internal::Private, $map);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $map:ident [$($vals:expr),+] ($key:expr, __ { $($value:tt)* })) => {
[
$($vals),+ ,
(
$key,
{
let mut $msg = $crate::__internal::get_map_default_value($crate::__internal::Private, $map);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
]
};
// Message nested in array literal with trailing array items
(@array $msg:ident $map:ident [] ($key:expr, __ { $($value:tt)* }), $($rest:tt)*) => {
proto_internal!(@array $msg $map [
(
$key,
{
let mut $msg = $crate::__internal::get_map_default_value($crate::__internal::Private, $map);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $map:ident [] ($key:expr, __ { $($value:tt)* })) => {
[
(
$key,
{
let mut $msg = $crate::__internal::get_map_default_value($crate::__internal::Private, $map);
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
]
};
// End of __ repeated, now we need to handle named types
// Message nested in array literal with trailing array items
(@array $msg:ident $map:ident [$($vals:expr),+] ($key:expr, $($msgtype:ident)::+ { $($value:tt)* }), $($rest:tt)*) => {
proto_internal!(@array $msg $map [
$($vals),+ ,
(
$key,
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
] $($rest)*)
};
// Message nested in [] literal with leading :: on type and trailing array items
(@array $msg:ident $map:ident [$($vals:expr),+] ($key:expr, ::$($msgtype:ident)::+ { $($value:tt)* }), $($rest:tt)*) => {
proto_internal!(@array $msg $map [
$($vals),+ ,
(
$key,
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $map:ident [$($vals:expr),+] ($key:expr, $($msgtype:ident)::+ { $($value:tt)* })) => {
[
$($vals),+ ,
(
$key,
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
]
};
// Message nested in [] literal with leading :: on type
(@array $msg:ident $map:ident [$($vals:expr),+] ($key:expr, ::$($msgtype:ident)::+ { $($value:tt)* })) => {
[
$($vals),+ ,
(
$key,
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
]
};
// Message nested in array literal with trailing array items
(@array $msg:ident $map:ident [] ($key:expr, $($msgtype:ident)::+ { $($value:tt)* }), $($rest:tt)*) => {
proto_internal!(@array $msg $map [
(
$key,
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
] $($rest)*)
};
// with leading ::
(@array $msg:ident $map:ident [] ($key:expr, ::$($msgtype:ident)::+ { $($value:tt)* }), $($rest:tt)*) => {
proto_internal!(@array $msg $map [
(
$key,
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
] $($rest)*)
};
// Message nested in [] literal
(@array $msg:ident $map:ident [] ($key:expr, $($msgtype:ident)::+ { $($value:tt)* })) => {
[
(
$key,
{
let mut $msg = $($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
]
};
(@array $msg:ident $map:ident [] ::($key:expr, $($msgtype:ident)::+ { $($value:tt)* })) => {
[
(
$key,
{
let mut $msg = ::$($msgtype)::+::new();
proto_internal!(@merge $msg $($value)*);
proto_internal!(@msg $msg $($value)*);
$msg
}
)
]
};
// End handling of (key, value) for Maps
(@array $msg:ident $repeated:ident [$($vals:expr),+] $expr:expr, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [$($vals),+, $expr] $($rest)*)
};
(@array $msg:ident $repeated:ident [$($vals:expr),+] $expr:expr) => {
[$($vals),+, $expr]
};
(@array $msg:ident $repeated:ident [] $expr:expr, $($rest:tt)*) => {
proto_internal!(@array $msg $repeated [$expr] $($rest)*)
};
(@array $msg:ident $repeated:ident [] $expr:expr) => {
[$expr]
};
(@array $msg:ident $repeated:ident []) => {
[]
};
// field: expr,
(@msg $msg:ident $ident:ident : $expr:expr, $($rest:tt)*) => {
// delegate without ,
proto_internal!(@msg $msg $ident : $expr);
proto_internal!(@msg $msg $($rest)*);
};
// field: expr
(@msg $msg:ident $ident:ident : $expr:expr) => {
$crate::__internal::paste!($msg.[<set_ $ident>]($expr));
};
(@msg $msg:ident ..$expr:expr) => {
};
(@msg $msg:ident) => {};
(@merge $msg:ident) => {};
// entry point
($msgtype:ty { $($tt:tt)* }) => {
{
let mut message = <$msgtype>::new();
proto_internal!(@merge message $($tt)*);
proto_internal!(@msg message $($tt)*);
message
}
};
}