serde/src/lib.rs

//! # Serde
//!
//! Serde is a framework for ***ser***ializing and ***de***serializing Rust data
//! structures efficiently and generically.
//!
//! The Serde ecosystem consists of data structures that know how to serialize
//! and deserialize themselves along with data formats that know how to
//! serialize and deserialize other things. Serde provides the layer by which
//! these two groups interact with each other, allowing any supported data
//! structure to be serialized and deserialized using any supported data format.
//!
//! See the Serde website <https://serde.rs/> for additional documentation and
//! usage examples.
//!
//! ## Design
//!
//! Where many other languages rely on runtime reflection for serializing data,
//! Serde is instead built on Rust's powerful trait system. A data structure
//! that knows how to serialize and deserialize itself is one that implements
//! Serde's `Serialize` and `Deserialize` traits (or uses Serde's derive
//! attribute to automatically generate implementations at compile time). This
//! avoids any overhead of reflection or runtime type information. In fact in
//! many situations the interaction between data structure and data format can
//! be completely optimized away by the Rust compiler, leaving Serde
//! serialization to perform the same speed as a handwritten serializer for the
//! specific selection of data structure and data format.
//!
//! ## Data formats
//!
//! The following is a partial list of data formats that have been implemented
//! for Serde by the community.
//!
//! - [JSON], the ubiquitous JavaScript Object Notation used by many HTTP APIs.
//! - [Postcard], a no\_std and embedded-systems friendly compact binary format.
//! - [CBOR], a Concise Binary Object Representation designed for small message
//!   size without the need for version negotiation.
//! - [YAML], a self-proclaimed human-friendly configuration language that ain't
//!   markup language.
//! - [MessagePack], an efficient binary format that resembles a compact JSON.
//! - [TOML], a minimal configuration format used by [Cargo].
//! - [Pickle], a format common in the Python world.
//! - [RON], a Rusty Object Notation.
//! - [BSON], the data storage and network transfer format used by MongoDB.
//! - [Avro], a binary format used within Apache Hadoop, with support for schema
//!   definition.
//! - [JSON5], a superset of JSON including some productions from ES5.
//! - [URL] query strings, in the x-www-form-urlencoded format.
//! - [Starlark], the format used for describing build targets by the Bazel and
//!   Buck build systems. *(serialization only)*
//! - [Envy], a way to deserialize environment variables into Rust structs.
//!   *(deserialization only)*
//! - [Envy Store], a way to deserialize [AWS Parameter Store] parameters into
//!   Rust structs. *(deserialization only)*
//! - [S-expressions], the textual representation of code and data used by the
//!   Lisp language family.
//! - [D-Bus]'s binary wire format.
//! - [FlexBuffers], the schemaless cousin of Google's FlatBuffers zero-copy
//!   serialization format.
//! - [Bencode], a simple binary format used in the BitTorrent protocol.
//! - [Token streams], for processing Rust procedural macro input.
//!   *(deserialization only)*
//! - [DynamoDB Items], the format used by [rusoto_dynamodb] to transfer data to
//!   and from DynamoDB.
//! - [Hjson], a syntax extension to JSON designed around human reading and
//!   editing. *(deserialization only)*
//! - [CSV], Comma-separated values is a tabular text file format.
//!
//! [JSON]: https://github.com/serde-rs/json
//! [Postcard]: https://github.com/jamesmunns/postcard
//! [CBOR]: https://github.com/enarx/ciborium
//! [YAML]: https://github.com/dtolnay/serde-yaml
//! [MessagePack]: https://github.com/3Hren/msgpack-rust
//! [TOML]: https://docs.rs/toml
//! [Pickle]: https://github.com/birkenfeld/serde-pickle
//! [RON]: https://github.com/ron-rs/ron
//! [BSON]: https://github.com/mongodb/bson-rust
//! [Avro]: https://docs.rs/apache-avro
//! [JSON5]: https://github.com/callum-oakley/json5-rs
//! [URL]: https://docs.rs/serde_qs
//! [Starlark]: https://github.com/dtolnay/serde-starlark
//! [Envy]: https://github.com/softprops/envy
//! [Envy Store]: https://github.com/softprops/envy-store
//! [Cargo]: https://doc.rust-lang.org/cargo/reference/manifest.html
//! [AWS Parameter Store]: https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-parameter-store.html
//! [S-expressions]: https://github.com/rotty/lexpr-rs
//! [D-Bus]: https://docs.rs/zvariant
//! [FlexBuffers]: https://github.com/google/flatbuffers/tree/master/rust/flexbuffers
//! [Bencode]: https://github.com/P3KI/bendy
//! [Token streams]: https://github.com/oxidecomputer/serde_tokenstream
//! [DynamoDB Items]: https://docs.rs/serde_dynamo
//! [rusoto_dynamodb]: https://docs.rs/rusoto_dynamodb
//! [Hjson]: https://github.com/Canop/deser-hjson
//! [CSV]: https://docs.rs/csv

////////////////////////////////////////////////////////////////////////////////

// Serde types in rustdoc of other crates get linked to here.
#![doc(html_root_url = "https://docs.rs/serde/1.0.195")]
// Support using Serde without the standard library!
#![cfg_attr(not(feature = "std"), no_std)]
// Show which crate feature enables conditionally compiled APIs in documentation.
#![cfg_attr(doc_cfg, feature(doc_cfg))]
// Unstable functionality only if the user asks for it. For tracking and
// discussion of these features please refer to this issue:
//
//    https://github.com/serde-rs/serde/issues/812
#![cfg_attr(feature = "unstable", feature(error_in_core, never_type))]
#![allow(unknown_lints, bare_trait_objects, deprecated)]
// Ignored clippy and clippy_pedantic lints
#![allow(
    // clippy bug: https://github.com/rust-lang/rust-clippy/issues/5704
    clippy::unnested_or_patterns,
    // clippy bug: https://github.com/rust-lang/rust-clippy/issues/7768
    clippy::semicolon_if_nothing_returned,
    // not available in our oldest supported compiler
    clippy::empty_enum,
    clippy::type_repetition_in_bounds, // https://github.com/rust-lang/rust-clippy/issues/8772
    // integer and float ser/de requires these sorts of casts
    clippy::cast_possible_truncation,
    clippy::cast_possible_wrap,
    clippy::cast_sign_loss,
    // things are often more readable this way
    clippy::cast_lossless,
    clippy::module_name_repetitions,
    clippy::single_match_else,
    clippy::type_complexity,
    clippy::use_self,
    clippy::zero_prefixed_literal,
    // correctly used
    clippy::derive_partial_eq_without_eq,
    clippy::enum_glob_use,
    clippy::explicit_auto_deref,
    clippy::let_underscore_untyped,
    clippy::map_err_ignore,
    clippy::new_without_default,
    clippy::result_unit_err,
    clippy::wildcard_imports,
    // not practical
    clippy::needless_pass_by_value,
    clippy::similar_names,
    clippy::too_many_lines,
    // preference
    clippy::doc_markdown,
    clippy::unseparated_literal_suffix,
    // false positive
    clippy::needless_doctest_main,
    // noisy
    clippy::missing_errors_doc,
    clippy::must_use_candidate,
)]
// Restrictions
#![deny(clippy::question_mark_used)]
// Rustc lints.
#![deny(missing_docs, unused_imports)]

////////////////////////////////////////////////////////////////////////////////

#[cfg(feature = "alloc")]
extern crate alloc;

/// A facade around all the types we need from the `std`, `core`, and `alloc`
/// crates. This avoids elaborate import wrangling having to happen in every
/// module.
mod lib {
    mod core {
        #[cfg(not(feature = "std"))]
        pub use core::*;
        #[cfg(feature = "std")]
        pub use std::*;
    }

    pub use self::core::{f32, f64};
    pub use self::core::{i16, i32, i64, i8, isize};
    pub use self::core::{iter, num, ptr, str};
    pub use self::core::{u16, u32, u64, u8, usize};

    #[cfg(any(feature = "std", feature = "alloc"))]
    pub use self::core::{cmp, mem, slice};

    pub use self::core::cell::{Cell, RefCell};
    pub use self::core::clone::{self, Clone};
    pub use self::core::cmp::Reverse;
    pub use self::core::convert::{self, From, Into};
    pub use self::core::default::{self, Default};
    pub use self::core::fmt::{self, Debug, Display};
    pub use self::core::marker::{self, PhantomData};
    pub use self::core::num::Wrapping;
    pub use self::core::ops::{Bound, Range, RangeFrom, RangeInclusive, RangeTo};
    pub use self::core::option::{self, Option};
    pub use self::core::result::{self, Result};
    pub use self::core::time::Duration;

    #[cfg(all(feature = "alloc", not(feature = "std")))]
    pub use alloc::borrow::{Cow, ToOwned};
    #[cfg(feature = "std")]
    pub use std::borrow::{Cow, ToOwned};

    #[cfg(all(feature = "alloc", not(feature = "std")))]
    pub use alloc::string::{String, ToString};
    #[cfg(feature = "std")]
    pub use std::string::{String, ToString};

    #[cfg(all(feature = "alloc", not(feature = "std")))]
    pub use alloc::vec::Vec;
    #[cfg(feature = "std")]
    pub use std::vec::Vec;

    #[cfg(all(feature = "alloc", not(feature = "std")))]
    pub use alloc::boxed::Box;
    #[cfg(feature = "std")]
    pub use std::boxed::Box;

    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
    pub use alloc::rc::{Rc, Weak as RcWeak};
    #[cfg(all(feature = "rc", feature = "std"))]
    pub use std::rc::{Rc, Weak as RcWeak};

    #[cfg(all(feature = "rc", feature = "alloc", not(feature = "std")))]
    pub use alloc::sync::{Arc, Weak as ArcWeak};
    #[cfg(all(feature = "rc", feature = "std"))]
    pub use std::sync::{Arc, Weak as ArcWeak};

    #[cfg(all(feature = "alloc", not(feature = "std")))]
    pub use alloc::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
    #[cfg(feature = "std")]
    pub use std::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};

    #[cfg(all(not(no_core_cstr), not(feature = "std")))]
    pub use self::core::ffi::CStr;
    #[cfg(feature = "std")]
    pub use std::ffi::CStr;

    #[cfg(all(not(no_core_cstr), feature = "alloc", not(feature = "std")))]
    pub use alloc::ffi::CString;
    #[cfg(feature = "std")]
    pub use std::ffi::CString;

    #[cfg(feature = "std")]
    pub use std::{error, net};

    #[cfg(feature = "std")]
    pub use std::collections::{HashMap, HashSet};
    #[cfg(feature = "std")]
    pub use std::ffi::{OsStr, OsString};
    #[cfg(feature = "std")]
    pub use std::hash::{BuildHasher, Hash};
    #[cfg(feature = "std")]
    pub use std::io::Write;
    #[cfg(feature = "std")]
    pub use std::path::{Path, PathBuf};
    #[cfg(feature = "std")]
    pub use std::sync::{Mutex, RwLock};
    #[cfg(feature = "std")]
    pub use std::time::{SystemTime, UNIX_EPOCH};

    #[cfg(all(feature = "std", no_target_has_atomic, not(no_std_atomic)))]
    pub use std::sync::atomic::{
        AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU8,
        AtomicUsize, Ordering,
    };
    #[cfg(all(feature = "std", no_target_has_atomic, not(no_std_atomic64)))]
    pub use std::sync::atomic::{AtomicI64, AtomicU64};

    #[cfg(all(feature = "std", not(no_target_has_atomic)))]
    pub use std::sync::atomic::Ordering;
    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "8"))]
    pub use std::sync::atomic::{AtomicBool, AtomicI8, AtomicU8};
    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "16"))]
    pub use std::sync::atomic::{AtomicI16, AtomicU16};
    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "32"))]
    pub use std::sync::atomic::{AtomicI32, AtomicU32};
    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "64"))]
    pub use std::sync::atomic::{AtomicI64, AtomicU64};
    #[cfg(all(feature = "std", not(no_target_has_atomic), target_has_atomic = "ptr"))]
    pub use std::sync::atomic::{AtomicIsize, AtomicUsize};
}

// None of this crate's error handling needs the `From::from` error conversion
// performed implicitly by the `?` operator or the standard library's `try!`
// macro. This simplified macro gives a 5.5% improvement in compile time
// compared to standard `try!`, and 9% improvement compared to `?`.
macro_rules! tri {
    ($expr:expr) => {
        match $expr {
            Ok(val) => val,
            Err(err) => return Err(err),
        }
    };
}

////////////////////////////////////////////////////////////////////////////////

#[macro_use]
mod macros;

#[macro_use]
mod integer128;

pub mod de;
pub mod ser;

#[doc(inline)]
pub use crate::de::{Deserialize, Deserializer};
#[doc(inline)]
pub use crate::ser::{Serialize, Serializer};

// Used by generated code and doc tests. Not public API.
#[doc(hidden)]
#[path = "private/mod.rs"]
pub mod __private;

#[path = "de/seed.rs"]
mod seed;

#[cfg(not(any(feature = "std", feature = "unstable")))]
mod std_error;

// Re-export #[derive(Serialize, Deserialize)].
//
// The reason re-exporting is not enabled by default is that disabling it would
// be annoying for crates that provide handwritten impls or data formats. They
// would need to disable default features and then explicitly re-enable std.
#[cfg(feature = "serde_derive")]
extern crate serde_derive;

/// Derive macro available if serde is built with `features = ["derive"]`.
#[cfg(feature = "serde_derive")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "derive")))]
pub use serde_derive::{Deserialize, Serialize};

#[cfg(all(not(no_serde_derive), any(feature = "std", feature = "alloc")))]
mod actually_private {
    pub struct T;
}