blob: 16116a017948492163275c30aa516af95bbda7a3 [file] [log] [blame]
/// Construct a `serde_json::Value` from a JSON literal.
///
/// ```edition2018
/// # use serde_json::json;
/// #
/// let value = json!({
/// "code": 200,
/// "success": true,
/// "payload": {
/// "features": [
/// "serde",
/// "json"
/// ]
/// }
/// });
/// ```
///
/// Variables or expressions can be interpolated into the JSON literal. Any type
/// interpolated into an array element or object value must implement Serde's
/// `Serialize` trait, while any type interpolated into a object key must
/// implement `Into<String>`. If the `Serialize` implementation of the
/// interpolated type decides to fail, or if the interpolated type contains a
/// map with non-string keys, the `json!` macro will panic.
///
/// ```edition2018
/// # use serde_json::json;
/// #
/// let code = 200;
/// let features = vec!["serde", "json"];
///
/// let value = json!({
/// "code": code,
/// "success": code == 200,
/// "payload": {
/// features[0]: features[1]
/// }
/// });
/// ```
///
/// Trailing commas are allowed inside both arrays and objects.
///
/// ```edition2018
/// # use serde_json::json;
/// #
/// let value = json!([
/// "notice",
/// "the",
/// "trailing",
/// "comma -->",
/// ]);
/// ```
#[macro_export(local_inner_macros)]
macro_rules! json {
// Hide distracting implementation details from the generated rustdoc.
($($json:tt)+) => {
json_internal!($($json)+)
};
}
// Rocket relies on this because they export their own `json!` with a different
// doc comment than ours, and various Rust bugs prevent them from calling our
// `json!` from their `json!` so they call `json_internal!` directly. Check with
// @SergioBenitez before making breaking changes to this macro.
//
// Changes are fine as long as `json_internal!` does not call any new helper
// macros and can still be invoked as `json_internal!($($json)+)`.
#[macro_export(local_inner_macros)]
#[doc(hidden)]
macro_rules! json_internal {
//////////////////////////////////////////////////////////////////////////
// TT muncher for parsing the inside of an array [...]. Produces a vec![...]
// of the elements.
//
// Must be invoked as: json_internal!(@array [] $($tt)*)
//////////////////////////////////////////////////////////////////////////
// Done with trailing comma.
(@array [$($elems:expr,)*]) => {
json_internal_vec![$($elems,)*]
};
// Done without trailing comma.
(@array [$($elems:expr),*]) => {
json_internal_vec![$($elems),*]
};
// Next element is `null`.
(@array [$($elems:expr,)*] null $($rest:tt)*) => {
json_internal!(@array [$($elems,)* json_internal!(null)] $($rest)*)
};
// Next element is `true`.
(@array [$($elems:expr,)*] true $($rest:tt)*) => {
json_internal!(@array [$($elems,)* json_internal!(true)] $($rest)*)
};
// Next element is `false`.
(@array [$($elems:expr,)*] false $($rest:tt)*) => {
json_internal!(@array [$($elems,)* json_internal!(false)] $($rest)*)
};
// Next element is an array.
(@array [$($elems:expr,)*] [$($array:tt)*] $($rest:tt)*) => {
json_internal!(@array [$($elems,)* json_internal!([$($array)*])] $($rest)*)
};
// Next element is a map.
(@array [$($elems:expr,)*] {$($map:tt)*} $($rest:tt)*) => {
json_internal!(@array [$($elems,)* json_internal!({$($map)*})] $($rest)*)
};
// Next element is an expression followed by comma.
(@array [$($elems:expr,)*] $next:expr, $($rest:tt)*) => {
json_internal!(@array [$($elems,)* json_internal!($next),] $($rest)*)
};
// Last element is an expression with no trailing comma.
(@array [$($elems:expr,)*] $last:expr) => {
json_internal!(@array [$($elems,)* json_internal!($last)])
};
// Comma after the most recent element.
(@array [$($elems:expr),*] , $($rest:tt)*) => {
json_internal!(@array [$($elems,)*] $($rest)*)
};
// Unexpected token after most recent element.
(@array [$($elems:expr),*] $unexpected:tt $($rest:tt)*) => {
json_unexpected!($unexpected)
};
//////////////////////////////////////////////////////////////////////////
// TT muncher for parsing the inside of an object {...}. Each entry is
// inserted into the given map variable.
//
// Must be invoked as: json_internal!(@object $map () ($($tt)*) ($($tt)*))
//
// We require two copies of the input tokens so that we can match on one
// copy and trigger errors on the other copy.
//////////////////////////////////////////////////////////////////////////
// Done.
(@object $object:ident () () ()) => {};
// Insert the current entry followed by trailing comma.
(@object $object:ident [$($key:tt)+] ($value:expr) , $($rest:tt)*) => {
let _ = $object.insert(($($key)+).into(), $value);
json_internal!(@object $object () ($($rest)*) ($($rest)*));
};
// Current entry followed by unexpected token.
(@object $object:ident [$($key:tt)+] ($value:expr) $unexpected:tt $($rest:tt)*) => {
json_unexpected!($unexpected);
};
// Insert the last entry without trailing comma.
(@object $object:ident [$($key:tt)+] ($value:expr)) => {
let _ = $object.insert(($($key)+).into(), $value);
};
// Next value is `null`.
(@object $object:ident ($($key:tt)+) (: null $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object [$($key)+] (json_internal!(null)) $($rest)*);
};
// Next value is `true`.
(@object $object:ident ($($key:tt)+) (: true $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object [$($key)+] (json_internal!(true)) $($rest)*);
};
// Next value is `false`.
(@object $object:ident ($($key:tt)+) (: false $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object [$($key)+] (json_internal!(false)) $($rest)*);
};
// Next value is an array.
(@object $object:ident ($($key:tt)+) (: [$($array:tt)*] $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object [$($key)+] (json_internal!([$($array)*])) $($rest)*);
};
// Next value is a map.
(@object $object:ident ($($key:tt)+) (: {$($map:tt)*} $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object [$($key)+] (json_internal!({$($map)*})) $($rest)*);
};
// Next value is an expression followed by comma.
(@object $object:ident ($($key:tt)+) (: $value:expr , $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object [$($key)+] (json_internal!($value)) , $($rest)*);
};
// Last value is an expression with no trailing comma.
(@object $object:ident ($($key:tt)+) (: $value:expr) $copy:tt) => {
json_internal!(@object $object [$($key)+] (json_internal!($value)));
};
// Missing value for last entry. Trigger a reasonable error message.
(@object $object:ident ($($key:tt)+) (:) $copy:tt) => {
// "unexpected end of macro invocation"
json_internal!();
};
// Missing colon and value for last entry. Trigger a reasonable error
// message.
(@object $object:ident ($($key:tt)+) () $copy:tt) => {
// "unexpected end of macro invocation"
json_internal!();
};
// Misplaced colon. Trigger a reasonable error message.
(@object $object:ident () (: $($rest:tt)*) ($colon:tt $($copy:tt)*)) => {
// Takes no arguments so "no rules expected the token `:`".
json_unexpected!($colon);
};
// Found a comma inside a key. Trigger a reasonable error message.
(@object $object:ident ($($key:tt)*) (, $($rest:tt)*) ($comma:tt $($copy:tt)*)) => {
// Takes no arguments so "no rules expected the token `,`".
json_unexpected!($comma);
};
// Key is fully parenthesized. This avoids clippy double_parens false
// positives because the parenthesization may be necessary here.
(@object $object:ident () (($key:expr) : $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object ($key) (: $($rest)*) (: $($rest)*));
};
// Munch a token into the current key.
(@object $object:ident ($($key:tt)*) ($tt:tt $($rest:tt)*) $copy:tt) => {
json_internal!(@object $object ($($key)* $tt) ($($rest)*) ($($rest)*));
};
//////////////////////////////////////////////////////////////////////////
// The main implementation.
//
// Must be invoked as: json_internal!($($json)+)
//////////////////////////////////////////////////////////////////////////
(null) => {
$crate::Value::Null
};
(true) => {
$crate::Value::Bool(true)
};
(false) => {
$crate::Value::Bool(false)
};
([]) => {
$crate::Value::Array(json_internal_vec![])
};
([ $($tt:tt)+ ]) => {
$crate::Value::Array(json_internal!(@array [] $($tt)+))
};
({}) => {
$crate::Value::Object($crate::Map::new())
};
({ $($tt:tt)+ }) => {
$crate::Value::Object({
let mut object = $crate::Map::new();
json_internal!(@object object () ($($tt)+) ($($tt)+));
object
})
};
// Any Serialize type: numbers, strings, struct literals, variables etc.
// Must be below every other rule.
($other:expr) => {
$crate::to_value(&$other).unwrap()
};
}
// The json_internal macro above cannot invoke vec directly because it uses
// local_inner_macros. A vec invocation there would resolve to $crate::vec.
// Instead invoke vec here outside of local_inner_macros.
#[macro_export]
#[doc(hidden)]
macro_rules! json_internal_vec {
($($content:tt)*) => {
vec![$($content)*]
};
}
#[macro_export]
#[doc(hidden)]
macro_rules! json_unexpected {
() => {};
}