//! Serializing Rust structures into TOML. //! //! This module contains all the Serde support for serializing Rust structures //! into TOML documents (as strings). Note that some top-level functions here //! are also provided at the top of the crate. //! //! Note that the TOML format has a restriction that if a table itself contains //! tables, all keys with non-table values must be emitted first. This is //! typically easy to ensure happens when you're defining a `struct` as you can //! reorder the fields manually, but when working with maps (such as `BTreeMap` //! or `HashMap`) this can lead to serialization errors. In those situations you //! may use the `tables_last` function in this module like so: //! //! ```rust //! # use serde_derive::Serialize; //! # use std::collections::HashMap; //! #[derive(Serialize)] //! struct Manifest { //! package: Package, //! #[serde(serialize_with = "toml::ser::tables_last")] //! dependencies: HashMap, //! } //! # type Package = String; //! # type Dependency = String; //! # fn main() {} //! ``` use std::cell::Cell; use std::error; use std::fmt::{self, Write}; use std::marker; use std::rc::Rc; use crate::datetime; use serde::ser; /// Serialize the given data structure as a TOML byte vector. /// /// Serialization can fail if `T`'s implementation of `Serialize` decides to /// fail, if `T` contains a map with non-string keys, or if `T` attempts to /// serialize an unsupported datatype such as an enum, tuple, or tuple struct. pub fn to_vec(value: &T) -> Result, Error> where T: ser::Serialize, { to_string(value).map(|e| e.into_bytes()) } /// Serialize the given data structure as a String of TOML. /// /// Serialization can fail if `T`'s implementation of `Serialize` decides to /// fail, if `T` contains a map with non-string keys, or if `T` attempts to /// serialize an unsupported datatype such as an enum, tuple, or tuple struct. /// /// # Examples /// /// ``` /// use serde_derive::Serialize; /// /// #[derive(Serialize)] /// struct Config { /// database: Database, /// } /// /// #[derive(Serialize)] /// struct Database { /// ip: String, /// port: Vec, /// connection_max: u32, /// enabled: bool, /// } /// /// fn main() { /// let config = Config { /// database: Database { /// ip: "192.168.1.1".to_string(), /// port: vec![8001, 8002, 8003], /// connection_max: 5000, /// enabled: false, /// }, /// }; /// /// let toml = toml::to_string(&config).unwrap(); /// println!("{}", toml) /// } /// ``` pub fn to_string(value: &T) -> Result where T: ser::Serialize, { let mut dst = String::with_capacity(128); value.serialize(&mut Serializer::new(&mut dst))?; Ok(dst) } /// Serialize the given data structure as a "pretty" String of TOML. /// /// This is identical to `to_string` except the output string has a more /// "pretty" output. See `Serializer::pretty` for more details. pub fn to_string_pretty(value: &T) -> Result where T: ser::Serialize, { let mut dst = String::with_capacity(128); value.serialize(&mut Serializer::pretty(&mut dst))?; Ok(dst) } /// Errors that can occur when serializing a type. #[derive(Debug, PartialEq, Eq, Clone)] pub enum Error { /// Indicates that a Rust type was requested to be serialized but it was not /// supported. /// /// Currently the TOML format does not support serializing types such as /// enums, tuples and tuple structs. UnsupportedType, /// The key of all TOML maps must be strings, but serialization was /// attempted where the key of a map was not a string. KeyNotString, /// An error that we never omit but keep for backwards compatibility #[doc(hidden)] KeyNewline, /// Arrays in TOML must have a homogenous type, but a heterogeneous array /// was emitted. ArrayMixedType, /// All values in a TOML table must be emitted before further tables are /// emitted. If a value is emitted *after* a table then this error is /// generated. ValueAfterTable, /// A serialized date was invalid. DateInvalid, /// A serialized number was invalid. NumberInvalid, /// None was attempted to be serialized, but it's not supported. UnsupportedNone, /// A custom error which could be generated when serializing a particular /// type. Custom(String), #[doc(hidden)] __Nonexhaustive, } #[derive(Debug, Default, Clone)] /// Internal place for holding array setings struct ArraySettings { indent: usize, trailing_comma: bool, } impl ArraySettings { fn pretty() -> ArraySettings { ArraySettings { indent: 4, trailing_comma: true, } } } #[derive(Debug, Default, Clone)] /// String settings struct StringSettings { /// Whether to use literal strings when possible literal: bool, } impl StringSettings { fn pretty() -> StringSettings { StringSettings { literal: true } } } #[derive(Debug, Default, Clone)] /// Internal struct for holding serialization settings struct Settings { array: Option, string: Option, } /// Serialization implementation for TOML. /// /// This structure implements serialization support for TOML to serialize an /// arbitrary type to TOML. Note that the TOML format does not support all /// datatypes in Rust, such as enums, tuples, and tuple structs. These types /// will generate an error when serialized. /// /// Currently a serializer always writes its output to an in-memory `String`, /// which is passed in when creating the serializer itself. pub struct Serializer<'a> { dst: &'a mut String, state: State<'a>, settings: Rc, } #[derive(Debug, Clone)] enum State<'a> { Table { key: &'a str, parent: &'a State<'a>, first: &'a Cell, table_emitted: &'a Cell, }, Array { parent: &'a State<'a>, first: &'a Cell, type_: &'a Cell>, len: Option, }, End, } #[doc(hidden)] pub struct SerializeSeq<'a, 'b> { ser: &'b mut Serializer<'a>, first: Cell, type_: Cell>, len: Option, } #[doc(hidden)] pub enum SerializeTable<'a, 'b> { Datetime(&'b mut Serializer<'a>), Table { ser: &'b mut Serializer<'a>, key: String, first: Cell, table_emitted: Cell, }, } impl<'a> Serializer<'a> { /// Creates a new serializer which will emit TOML into the buffer provided. /// /// The serializer can then be used to serialize a type after which the data /// will be present in `dst`. pub fn new(dst: &'a mut String) -> Serializer<'a> { Serializer { dst, state: State::End, settings: Rc::new(Settings::default()), } } /// Instantiate a "pretty" formatter /// /// By default this will use: /// /// - pretty strings: strings with newlines will use the `'''` syntax. See /// `Serializer::pretty_string` /// - pretty arrays: each item in arrays will be on a newline, have an indentation of 4 and /// have a trailing comma. See `Serializer::pretty_array` pub fn pretty(dst: &'a mut String) -> Serializer<'a> { Serializer { dst, state: State::End, settings: Rc::new(Settings { array: Some(ArraySettings::pretty()), string: Some(StringSettings::pretty()), }), } } /// Enable or Disable pretty strings /// /// If enabled, literal strings will be used when possible and strings with /// one or more newlines will use triple quotes (i.e.: `'''` or `"""`) /// /// # Examples /// /// Instead of: /// /// ```toml,ignore /// single = "no newlines" /// text = "\nfoo\nbar\n" /// ``` /// /// You will have: /// /// ```toml,ignore /// single = 'no newlines' /// text = ''' /// foo /// bar /// ''' /// ``` pub fn pretty_string(&mut self, value: bool) -> &mut Self { Rc::get_mut(&mut self.settings).unwrap().string = if value { Some(StringSettings::pretty()) } else { None }; self } /// Enable or Disable Literal strings for pretty strings /// /// If enabled, literal strings will be used when possible and strings with /// one or more newlines will use triple quotes (i.e.: `'''` or `"""`) /// /// If disabled, literal strings will NEVER be used and strings with one or /// more newlines will use `"""` /// /// # Examples /// /// Instead of: /// /// ```toml,ignore /// single = "no newlines" /// text = "\nfoo\nbar\n" /// ``` /// /// You will have: /// /// ```toml,ignore /// single = "no newlines" /// text = """ /// foo /// bar /// """ /// ``` pub fn pretty_string_literal(&mut self, value: bool) -> &mut Self { let use_default = if let Some(ref mut s) = Rc::get_mut(&mut self.settings).unwrap().string { s.literal = value; false } else { true }; if use_default { let mut string = StringSettings::pretty(); string.literal = value; Rc::get_mut(&mut self.settings).unwrap().string = Some(string); } self } /// Enable or Disable pretty arrays /// /// If enabled, arrays will always have each item on their own line. /// /// Some specific features can be controlled via other builder methods: /// /// - `Serializer::pretty_array_indent`: set the indent to a value other /// than 4. /// - `Serializer::pretty_array_trailing_comma`: enable/disable the trailing /// comma on the last item. /// /// # Examples /// /// Instead of: /// /// ```toml,ignore /// array = ["foo", "bar"] /// ``` /// /// You will have: /// /// ```toml,ignore /// array = [ /// "foo", /// "bar", /// ] /// ``` pub fn pretty_array(&mut self, value: bool) -> &mut Self { Rc::get_mut(&mut self.settings).unwrap().array = if value { Some(ArraySettings::pretty()) } else { None }; self } /// Set the indent for pretty arrays /// /// See `Serializer::pretty_array` for more details. pub fn pretty_array_indent(&mut self, value: usize) -> &mut Self { let use_default = if let Some(ref mut a) = Rc::get_mut(&mut self.settings).unwrap().array { a.indent = value; false } else { true }; if use_default { let mut array = ArraySettings::pretty(); array.indent = value; Rc::get_mut(&mut self.settings).unwrap().array = Some(array); } self } /// Specify whether to use a trailing comma when serializing pretty arrays /// /// See `Serializer::pretty_array` for more details. pub fn pretty_array_trailing_comma(&mut self, value: bool) -> &mut Self { let use_default = if let Some(ref mut a) = Rc::get_mut(&mut self.settings).unwrap().array { a.trailing_comma = value; false } else { true }; if use_default { let mut array = ArraySettings::pretty(); array.trailing_comma = value; Rc::get_mut(&mut self.settings).unwrap().array = Some(array); } self } fn display(&mut self, t: T, type_: &'static str) -> Result<(), Error> { self.emit_key(type_)?; write!(self.dst, "{}", t).map_err(ser::Error::custom)?; if let State::Table { .. } = self.state { self.dst.push_str("\n"); } Ok(()) } fn emit_key(&mut self, type_: &'static str) -> Result<(), Error> { self.array_type(type_)?; let state = self.state.clone(); self._emit_key(&state) } // recursive implementation of `emit_key` above fn _emit_key(&mut self, state: &State<'_>) -> Result<(), Error> { match *state { State::End => Ok(()), State::Array { parent, first, type_, len, } => { assert!(type_.get().is_some()); if first.get() { self._emit_key(parent)?; } self.emit_array(first, len) } State::Table { parent, first, table_emitted, key, } => { if table_emitted.get() { return Err(Error::ValueAfterTable); } if first.get() { self.emit_table_header(parent)?; first.set(false); } self.escape_key(key)?; self.dst.push_str(" = "); Ok(()) } } } fn emit_array(&mut self, first: &Cell, len: Option) -> Result<(), Error> { match (len, &self.settings.array) { (Some(0..=1), _) | (_, &None) => { if first.get() { self.dst.push_str("[") } else { self.dst.push_str(", ") } } (_, &Some(ref a)) => { if first.get() { self.dst.push_str("[\n") } else { self.dst.push_str(",\n") } for _ in 0..a.indent { self.dst.push_str(" "); } } } Ok(()) } fn array_type(&mut self, type_: &'static str) -> Result<(), Error> { let prev = match self.state { State::Array { type_, .. } => type_, _ => return Ok(()), }; if let Some(prev) = prev.get() { if prev != type_ { return Err(Error::ArrayMixedType); } } else { prev.set(Some(type_)); } Ok(()) } fn escape_key(&mut self, key: &str) -> Result<(), Error> { let ok = key.chars().all(|c| match c { 'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '_' => true, _ => false, }); if ok { write!(self.dst, "{}", key).map_err(ser::Error::custom)?; } else { self.emit_str(key, true)?; } Ok(()) } fn emit_str(&mut self, value: &str, is_key: bool) -> Result<(), Error> { #[derive(PartialEq)] enum Type { NewlineTripple, OnelineTripple, OnelineSingle, } enum Repr { /// represent as a literal string (using '') Literal(String, Type), /// represent the std way (using "") Std(Type), } fn do_pretty(value: &str) -> Repr { // For doing pretty prints we store in a new String // because there are too many cases where pretty cannot // work. We need to determine: // - if we are a "multi-line" pretty (if there are \n) // - if ['''] appears if multi or ['] if single // - if there are any invalid control characters // // Doing it any other way would require multiple passes // to determine if a pretty string works or not. let mut out = String::with_capacity(value.len() * 2); let mut ty = Type::OnelineSingle; // found consecutive single quotes let mut max_found_singles = 0; let mut found_singles = 0; let mut can_be_pretty = true; for ch in value.chars() { if can_be_pretty { if ch == '\'' { found_singles += 1; if found_singles >= 3 { can_be_pretty = false; } } else { if found_singles > max_found_singles { max_found_singles = found_singles; } found_singles = 0 } match ch { '\t' => {} '\n' => ty = Type::NewlineTripple, // note that the following are invalid: \b \f \r c if c < '\u{1f}' => can_be_pretty = false, // Invalid control character _ => {} } out.push(ch); } else { // the string cannot be represented as pretty, // still check if it should be multiline if ch == '\n' { ty = Type::NewlineTripple; } } } if can_be_pretty && found_singles > 0 && value.ends_with('\'') { // We cannot escape the ending quote so we must use """ can_be_pretty = false; } if !can_be_pretty { debug_assert!(ty != Type::OnelineTripple); return Repr::Std(ty); } if found_singles > max_found_singles { max_found_singles = found_singles; } debug_assert!(max_found_singles < 3); if ty == Type::OnelineSingle && max_found_singles >= 1 { // no newlines, but must use ''' because it has ' in it ty = Type::OnelineTripple; } Repr::Literal(out, ty) } let repr = if !is_key && self.settings.string.is_some() { match (&self.settings.string, do_pretty(value)) { (&Some(StringSettings { literal: false, .. }), Repr::Literal(_, ty)) => { Repr::Std(ty) } (_, r) => r, } } else { Repr::Std(Type::OnelineSingle) }; match repr { Repr::Literal(literal, ty) => { // A pretty string match ty { Type::NewlineTripple => self.dst.push_str("'''\n"), Type::OnelineTripple => self.dst.push_str("'''"), Type::OnelineSingle => self.dst.push('\''), } self.dst.push_str(&literal); match ty { Type::OnelineSingle => self.dst.push('\''), _ => self.dst.push_str("'''"), } } Repr::Std(ty) => { match ty { Type::NewlineTripple => self.dst.push_str("\"\"\"\n"), // note: OnelineTripple can happen if do_pretty wants to do // '''it's one line''' // but settings.string.literal == false Type::OnelineSingle | Type::OnelineTripple => self.dst.push('"'), } for ch in value.chars() { match ch { '\u{8}' => self.dst.push_str("\\b"), '\u{9}' => self.dst.push_str("\\t"), '\u{a}' => match ty { Type::NewlineTripple => self.dst.push('\n'), Type::OnelineSingle => self.dst.push_str("\\n"), _ => unreachable!(), }, '\u{c}' => self.dst.push_str("\\f"), '\u{d}' => self.dst.push_str("\\r"), '\u{22}' => self.dst.push_str("\\\""), '\u{5c}' => self.dst.push_str("\\\\"), c if c < '\u{1f}' => { write!(self.dst, "\\u{:04X}", ch as u32).map_err(ser::Error::custom)?; } ch => self.dst.push(ch), } } match ty { Type::NewlineTripple => self.dst.push_str("\"\"\""), Type::OnelineSingle | Type::OnelineTripple => self.dst.push('"'), } } } Ok(()) } fn emit_table_header(&mut self, state: &State<'_>) -> Result<(), Error> { let array_of_tables = match *state { State::End => return Ok(()), State::Array { .. } => true, _ => false, }; // Unlike [..]s, we can't omit [[..]] ancestors, so be sure to emit table // headers for them. let mut p = state; if let State::Array { first, parent, .. } = *state { if first.get() { p = parent; } } while let State::Table { first, parent, .. } = *p { p = parent; if !first.get() { break; } if let State::Array { parent: &State::Table { .. }, .. } = *parent { self.emit_table_header(parent)?; break; } } match *state { State::Table { first, .. } => { if !first.get() { // Newline if we are a table that is not the first // table in the document. self.dst.push('\n'); } } State::Array { parent, first, .. } => { if !first.get() { // Always newline if we are not the first item in the // table-array self.dst.push('\n'); } else if let State::Table { first, .. } = *parent { if !first.get() { // Newline if we are not the first item in the document self.dst.push('\n'); } } } _ => {} } self.dst.push_str("["); if array_of_tables { self.dst.push_str("["); } self.emit_key_part(state)?; if array_of_tables { self.dst.push_str("]"); } self.dst.push_str("]\n"); Ok(()) } fn emit_key_part(&mut self, key: &State<'_>) -> Result { match *key { State::Array { parent, .. } => self.emit_key_part(parent), State::End => Ok(true), State::Table { key, parent, table_emitted, .. } => { table_emitted.set(true); let first = self.emit_key_part(parent)?; if !first { self.dst.push_str("."); } self.escape_key(key)?; Ok(false) } } } } macro_rules! serialize_float { ($this:expr, $v:expr) => {{ $this.emit_key("float")?; if ($v.is_nan() || $v == 0.0) && $v.is_sign_negative() { write!($this.dst, "-").map_err(ser::Error::custom)?; } if $v.is_nan() { write!($this.dst, "nan").map_err(ser::Error::custom)?; } else { write!($this.dst, "{}", $v).map_err(ser::Error::custom)?; } if $v % 1.0 == 0.0 { write!($this.dst, ".0").map_err(ser::Error::custom)?; } if let State::Table { .. } = $this.state { $this.dst.push_str("\n"); } return Ok(()); }}; } impl<'a, 'b> ser::Serializer for &'b mut Serializer<'a> { type Ok = (); type Error = Error; type SerializeSeq = SerializeSeq<'a, 'b>; type SerializeTuple = SerializeSeq<'a, 'b>; type SerializeTupleStruct = SerializeSeq<'a, 'b>; type SerializeTupleVariant = SerializeSeq<'a, 'b>; type SerializeMap = SerializeTable<'a, 'b>; type SerializeStruct = SerializeTable<'a, 'b>; type SerializeStructVariant = ser::Impossible<(), Error>; fn serialize_bool(self, v: bool) -> Result<(), Self::Error> { self.display(v, "bool") } fn serialize_i8(self, v: i8) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_i16(self, v: i16) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_i32(self, v: i32) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_i64(self, v: i64) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_u8(self, v: u8) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_u16(self, v: u16) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_u32(self, v: u32) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_u64(self, v: u64) -> Result<(), Self::Error> { self.display(v, "integer") } fn serialize_f32(self, v: f32) -> Result<(), Self::Error> { serialize_float!(self, v) } fn serialize_f64(self, v: f64) -> Result<(), Self::Error> { serialize_float!(self, v) } fn serialize_char(self, v: char) -> Result<(), Self::Error> { let mut buf = [0; 4]; self.serialize_str(v.encode_utf8(&mut buf)) } fn serialize_str(self, value: &str) -> Result<(), Self::Error> { self.emit_key("string")?; self.emit_str(value, false)?; if let State::Table { .. } = self.state { self.dst.push_str("\n"); } Ok(()) } fn serialize_bytes(self, value: &[u8]) -> Result<(), Self::Error> { use serde::ser::Serialize; value.serialize(self) } fn serialize_none(self) -> Result<(), Self::Error> { Err(Error::UnsupportedNone) } fn serialize_some(self, value: &T) -> Result<(), Self::Error> where T: ser::Serialize, { value.serialize(self) } fn serialize_unit(self) -> Result<(), Self::Error> { Err(Error::UnsupportedType) } fn serialize_unit_struct(self, _name: &'static str) -> Result<(), Self::Error> { Err(Error::UnsupportedType) } fn serialize_unit_variant( self, _name: &'static str, _variant_index: u32, variant: &'static str, ) -> Result<(), Self::Error> { self.serialize_str(variant) } fn serialize_newtype_struct( self, _name: &'static str, value: &T, ) -> Result<(), Self::Error> where T: ser::Serialize, { value.serialize(self) } fn serialize_newtype_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _value: &T, ) -> Result<(), Self::Error> where T: ser::Serialize, { Err(Error::UnsupportedType) } fn serialize_seq(self, len: Option) -> Result { self.array_type("array")?; Ok(SerializeSeq { ser: self, first: Cell::new(true), type_: Cell::new(None), len, }) } fn serialize_tuple(self, len: usize) -> Result { self.serialize_seq(Some(len)) } fn serialize_tuple_struct( self, _name: &'static str, len: usize, ) -> Result { self.serialize_seq(Some(len)) } fn serialize_tuple_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, len: usize, ) -> Result { self.serialize_seq(Some(len)) } fn serialize_map(self, _len: Option) -> Result { self.array_type("table")?; Ok(SerializeTable::Table { ser: self, key: String::new(), first: Cell::new(true), table_emitted: Cell::new(false), }) } fn serialize_struct( self, name: &'static str, _len: usize, ) -> Result { if name == datetime::NAME { self.array_type("datetime")?; Ok(SerializeTable::Datetime(self)) } else { self.array_type("table")?; Ok(SerializeTable::Table { ser: self, key: String::new(), first: Cell::new(true), table_emitted: Cell::new(false), }) } } fn serialize_struct_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _len: usize, ) -> Result { Err(Error::UnsupportedType) } } impl<'a, 'b> ser::SerializeSeq for SerializeSeq<'a, 'b> { type Ok = (); type Error = Error; fn serialize_element(&mut self, value: &T) -> Result<(), Error> where T: ser::Serialize, { value.serialize(&mut Serializer { dst: &mut *self.ser.dst, state: State::Array { parent: &self.ser.state, first: &self.first, type_: &self.type_, len: self.len, }, settings: self.ser.settings.clone(), })?; self.first.set(false); Ok(()) } fn end(self) -> Result<(), Error> { match self.type_.get() { Some("table") => return Ok(()), Some(_) => match (self.len, &self.ser.settings.array) { (Some(0..=1), _) | (_, &None) => { self.ser.dst.push_str("]"); } (_, &Some(ref a)) => { if a.trailing_comma { self.ser.dst.push_str(","); } self.ser.dst.push_str("\n]"); } }, None => { assert!(self.first.get()); self.ser.emit_key("array")?; self.ser.dst.push_str("[]") } } if let State::Table { .. } = self.ser.state { self.ser.dst.push_str("\n"); } Ok(()) } } impl<'a, 'b> ser::SerializeTuple for SerializeSeq<'a, 'b> { type Ok = (); type Error = Error; fn serialize_element(&mut self, value: &T) -> Result<(), Error> where T: ser::Serialize, { ser::SerializeSeq::serialize_element(self, value) } fn end(self) -> Result<(), Error> { ser::SerializeSeq::end(self) } } impl<'a, 'b> ser::SerializeTupleVariant for SerializeSeq<'a, 'b> { type Ok = (); type Error = Error; fn serialize_field(&mut self, value: &T) -> Result<(), Error> where T: ser::Serialize, { ser::SerializeSeq::serialize_element(self, value) } fn end(self) -> Result<(), Error> { ser::SerializeSeq::end(self) } } impl<'a, 'b> ser::SerializeTupleStruct for SerializeSeq<'a, 'b> { type Ok = (); type Error = Error; fn serialize_field(&mut self, value: &T) -> Result<(), Error> where T: ser::Serialize, { ser::SerializeSeq::serialize_element(self, value) } fn end(self) -> Result<(), Error> { ser::SerializeSeq::end(self) } } impl<'a, 'b> ser::SerializeMap for SerializeTable<'a, 'b> { type Ok = (); type Error = Error; fn serialize_key(&mut self, input: &T) -> Result<(), Error> where T: ser::Serialize, { match *self { SerializeTable::Datetime(_) => panic!(), // shouldn't be possible SerializeTable::Table { ref mut key, .. } => { key.truncate(0); *key = input.serialize(StringExtractor)?; } } Ok(()) } fn serialize_value(&mut self, value: &T) -> Result<(), Error> where T: ser::Serialize, { match *self { SerializeTable::Datetime(_) => panic!(), // shouldn't be possible SerializeTable::Table { ref mut ser, ref key, ref first, ref table_emitted, .. } => { let res = value.serialize(&mut Serializer { dst: &mut *ser.dst, state: State::Table { key, parent: &ser.state, first, table_emitted, }, settings: ser.settings.clone(), }); match res { Ok(()) => first.set(false), Err(Error::UnsupportedNone) => {} Err(e) => return Err(e), } } } Ok(()) } fn end(self) -> Result<(), Error> { match self { SerializeTable::Datetime(_) => panic!(), // shouldn't be possible SerializeTable::Table { ser, first, .. } => { if first.get() { let state = ser.state.clone(); ser.emit_table_header(&state)?; } } } Ok(()) } } impl<'a, 'b> ser::SerializeStruct for SerializeTable<'a, 'b> { type Ok = (); type Error = Error; fn serialize_field(&mut self, key: &'static str, value: &T) -> Result<(), Error> where T: ser::Serialize, { match *self { SerializeTable::Datetime(ref mut ser) => { if key == datetime::FIELD { value.serialize(DateStrEmitter(&mut *ser))?; } else { return Err(Error::DateInvalid); } } SerializeTable::Table { ref mut ser, ref first, ref table_emitted, .. } => { let res = value.serialize(&mut Serializer { dst: &mut *ser.dst, state: State::Table { key, parent: &ser.state, first, table_emitted, }, settings: ser.settings.clone(), }); match res { Ok(()) => first.set(false), Err(Error::UnsupportedNone) => {} Err(e) => return Err(e), } } } Ok(()) } fn end(self) -> Result<(), Error> { match self { SerializeTable::Datetime(_) => {} SerializeTable::Table { ser, first, .. } => { if first.get() { let state = ser.state.clone(); ser.emit_table_header(&state)?; } } } Ok(()) } } struct DateStrEmitter<'a, 'b>(&'b mut Serializer<'a>); impl<'a, 'b> ser::Serializer for DateStrEmitter<'a, 'b> { type Ok = (); type Error = Error; type SerializeSeq = ser::Impossible<(), Error>; type SerializeTuple = ser::Impossible<(), Error>; type SerializeTupleStruct = ser::Impossible<(), Error>; type SerializeTupleVariant = ser::Impossible<(), Error>; type SerializeMap = ser::Impossible<(), Error>; type SerializeStruct = ser::Impossible<(), Error>; type SerializeStructVariant = ser::Impossible<(), Error>; fn serialize_bool(self, _v: bool) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_i8(self, _v: i8) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_i16(self, _v: i16) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_i32(self, _v: i32) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_i64(self, _v: i64) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_u8(self, _v: u8) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_u16(self, _v: u16) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_u32(self, _v: u32) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_u64(self, _v: u64) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_f32(self, _v: f32) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_f64(self, _v: f64) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_char(self, _v: char) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_str(self, value: &str) -> Result<(), Self::Error> { self.0.display(value, "datetime")?; Ok(()) } fn serialize_bytes(self, _value: &[u8]) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_none(self) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_some(self, _value: &T) -> Result<(), Self::Error> where T: ser::Serialize, { Err(Error::KeyNotString) } fn serialize_unit(self) -> Result<(), Self::Error> { Err(Error::KeyNotString) } fn serialize_unit_struct(self, _name: &'static str) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_unit_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, ) -> Result<(), Self::Error> { Err(Error::DateInvalid) } fn serialize_newtype_struct( self, _name: &'static str, _value: &T, ) -> Result<(), Self::Error> where T: ser::Serialize, { Err(Error::DateInvalid) } fn serialize_newtype_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _value: &T, ) -> Result<(), Self::Error> where T: ser::Serialize, { Err(Error::DateInvalid) } fn serialize_seq(self, _len: Option) -> Result { Err(Error::DateInvalid) } fn serialize_tuple(self, _len: usize) -> Result { Err(Error::DateInvalid) } fn serialize_tuple_struct( self, _name: &'static str, _len: usize, ) -> Result { Err(Error::DateInvalid) } fn serialize_tuple_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _len: usize, ) -> Result { Err(Error::DateInvalid) } fn serialize_map(self, _len: Option) -> Result { Err(Error::DateInvalid) } fn serialize_struct( self, _name: &'static str, _len: usize, ) -> Result { Err(Error::DateInvalid) } fn serialize_struct_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _len: usize, ) -> Result { Err(Error::DateInvalid) } } struct StringExtractor; impl ser::Serializer for StringExtractor { type Ok = String; type Error = Error; type SerializeSeq = ser::Impossible; type SerializeTuple = ser::Impossible; type SerializeTupleStruct = ser::Impossible; type SerializeTupleVariant = ser::Impossible; type SerializeMap = ser::Impossible; type SerializeStruct = ser::Impossible; type SerializeStructVariant = ser::Impossible; fn serialize_bool(self, _v: bool) -> Result { Err(Error::KeyNotString) } fn serialize_i8(self, _v: i8) -> Result { Err(Error::KeyNotString) } fn serialize_i16(self, _v: i16) -> Result { Err(Error::KeyNotString) } fn serialize_i32(self, _v: i32) -> Result { Err(Error::KeyNotString) } fn serialize_i64(self, _v: i64) -> Result { Err(Error::KeyNotString) } fn serialize_u8(self, _v: u8) -> Result { Err(Error::KeyNotString) } fn serialize_u16(self, _v: u16) -> Result { Err(Error::KeyNotString) } fn serialize_u32(self, _v: u32) -> Result { Err(Error::KeyNotString) } fn serialize_u64(self, _v: u64) -> Result { Err(Error::KeyNotString) } fn serialize_f32(self, _v: f32) -> Result { Err(Error::KeyNotString) } fn serialize_f64(self, _v: f64) -> Result { Err(Error::KeyNotString) } fn serialize_char(self, _v: char) -> Result { Err(Error::KeyNotString) } fn serialize_str(self, value: &str) -> Result { Ok(value.to_string()) } fn serialize_bytes(self, _value: &[u8]) -> Result { Err(Error::KeyNotString) } fn serialize_none(self) -> Result { Err(Error::KeyNotString) } fn serialize_some(self, _value: &T) -> Result where T: ser::Serialize, { Err(Error::KeyNotString) } fn serialize_unit(self) -> Result { Err(Error::KeyNotString) } fn serialize_unit_struct(self, _name: &'static str) -> Result { Err(Error::KeyNotString) } fn serialize_unit_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, ) -> Result { Err(Error::KeyNotString) } fn serialize_newtype_struct( self, _name: &'static str, value: &T, ) -> Result where T: ser::Serialize, { value.serialize(self) } fn serialize_newtype_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _value: &T, ) -> Result where T: ser::Serialize, { Err(Error::KeyNotString) } fn serialize_seq(self, _len: Option) -> Result { Err(Error::KeyNotString) } fn serialize_tuple(self, _len: usize) -> Result { Err(Error::KeyNotString) } fn serialize_tuple_struct( self, _name: &'static str, _len: usize, ) -> Result { Err(Error::KeyNotString) } fn serialize_tuple_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _len: usize, ) -> Result { Err(Error::KeyNotString) } fn serialize_map(self, _len: Option) -> Result { Err(Error::KeyNotString) } fn serialize_struct( self, _name: &'static str, _len: usize, ) -> Result { Err(Error::KeyNotString) } fn serialize_struct_variant( self, _name: &'static str, _variant_index: u32, _variant: &'static str, _len: usize, ) -> Result { Err(Error::KeyNotString) } } impl fmt::Display for Error { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match *self { Error::UnsupportedType => "unsupported Rust type".fmt(f), Error::KeyNotString => "map key was not a string".fmt(f), Error::ArrayMixedType => "arrays cannot have mixed types".fmt(f), Error::ValueAfterTable => "values must be emitted before tables".fmt(f), Error::DateInvalid => "a serialized date was invalid".fmt(f), Error::NumberInvalid => "a serialized number was invalid".fmt(f), Error::UnsupportedNone => "unsupported None value".fmt(f), Error::Custom(ref s) => s.fmt(f), Error::KeyNewline => unreachable!(), Error::__Nonexhaustive => panic!(), } } } impl error::Error for Error { fn description(&self) -> &str { match *self { Error::UnsupportedType => "unsupported Rust type", Error::KeyNotString => "map key was not a string", Error::ArrayMixedType => "arrays cannot have mixed types", Error::ValueAfterTable => "values must be emitted before tables", Error::DateInvalid => "a serialized date was invalid", Error::NumberInvalid => "a serialized number was invalid", Error::UnsupportedNone => "unsupported None value", Error::Custom(_) => "custom error", Error::KeyNewline => unreachable!(), Error::__Nonexhaustive => panic!(), } } } impl ser::Error for Error { fn custom(msg: T) -> Error { Error::Custom(msg.to_string()) } } enum Category { Primitive, Array, Table, } /// Convenience function to serialize items in a map in an order valid with /// TOML. /// /// TOML carries the restriction that keys in a table must be serialized last if /// their value is a table itself. This isn't always easy to guarantee, so this /// helper can be used like so: /// /// ```rust /// # use serde_derive::Serialize; /// # use std::collections::HashMap; /// #[derive(Serialize)] /// struct Manifest { /// package: Package, /// #[serde(serialize_with = "toml::ser::tables_last")] /// dependencies: HashMap, /// } /// # type Package = String; /// # type Dependency = String; /// # fn main() {} /// ``` pub fn tables_last<'a, I, K, V, S>(data: &'a I, serializer: S) -> Result where &'a I: IntoIterator, K: ser::Serialize, V: ser::Serialize, S: ser::Serializer, { use serde::ser::SerializeMap; let mut map = serializer.serialize_map(None)?; for (k, v) in data { if let Category::Primitive = v.serialize(Categorize::new())? { map.serialize_entry(&k, &v)?; } } for (k, v) in data { if let Category::Array = v.serialize(Categorize::new())? { map.serialize_entry(&k, &v)?; } } for (k, v) in data { if let Category::Table = v.serialize(Categorize::new())? { map.serialize_entry(&k, &v)?; } } map.end() } struct Categorize(marker::PhantomData); impl Categorize { fn new() -> Self { Categorize(marker::PhantomData) } } impl ser::Serializer for Categorize { type Ok = Category; type Error = E; type SerializeSeq = Self; type SerializeTuple = Self; type SerializeTupleStruct = Self; type SerializeTupleVariant = Self; type SerializeMap = Self; type SerializeStruct = Self; type SerializeStructVariant = ser::Impossible; fn serialize_bool(self, _: bool) -> Result { Ok(Category::Primitive) } fn serialize_i8(self, _: i8) -> Result { Ok(Category::Primitive) } fn serialize_i16(self, _: i16) -> Result { Ok(Category::Primitive) } fn serialize_i32(self, _: i32) -> Result { Ok(Category::Primitive) } fn serialize_i64(self, _: i64) -> Result { Ok(Category::Primitive) } fn serialize_u8(self, _: u8) -> Result { Ok(Category::Primitive) } fn serialize_u16(self, _: u16) -> Result { Ok(Category::Primitive) } fn serialize_u32(self, _: u32) -> Result { Ok(Category::Primitive) } fn serialize_u64(self, _: u64) -> Result { Ok(Category::Primitive) } fn serialize_f32(self, _: f32) -> Result { Ok(Category::Primitive) } fn serialize_f64(self, _: f64) -> Result { Ok(Category::Primitive) } fn serialize_char(self, _: char) -> Result { Ok(Category::Primitive) } fn serialize_str(self, _: &str) -> Result { Ok(Category::Primitive) } fn serialize_bytes(self, _: &[u8]) -> Result { Ok(Category::Array) } fn serialize_none(self) -> Result { Err(ser::Error::custom("unsupported")) } fn serialize_some(self, v: &T) -> Result { v.serialize(self) } fn serialize_unit(self) -> Result { Err(ser::Error::custom("unsupported")) } fn serialize_unit_struct(self, _: &'static str) -> Result { Err(ser::Error::custom("unsupported")) } fn serialize_unit_variant( self, _: &'static str, _: u32, _: &'static str, ) -> Result { Err(ser::Error::custom("unsupported")) } fn serialize_newtype_struct( self, _: &'static str, v: &T, ) -> Result { v.serialize(self) } fn serialize_newtype_variant( self, _: &'static str, _: u32, _: &'static str, _: &T, ) -> Result { Err(ser::Error::custom("unsupported")) } fn serialize_seq(self, _: Option) -> Result { Ok(self) } fn serialize_tuple(self, _: usize) -> Result { Ok(self) } fn serialize_tuple_struct( self, _: &'static str, _: usize, ) -> Result { Ok(self) } fn serialize_tuple_variant( self, _: &'static str, _: u32, _: &'static str, _: usize, ) -> Result { Ok(self) } fn serialize_map(self, _: Option) -> Result { Ok(self) } fn serialize_struct(self, _: &'static str, _: usize) -> Result { Ok(self) } fn serialize_struct_variant( self, _: &'static str, _: u32, _: &'static str, _: usize, ) -> Result { Err(ser::Error::custom("unsupported")) } } impl ser::SerializeSeq for Categorize { type Ok = Category; type Error = E; fn serialize_element(&mut self, _: &T) -> Result<(), Self::Error> { Ok(()) } fn end(self) -> Result { Ok(Category::Array) } } impl ser::SerializeTuple for Categorize { type Ok = Category; type Error = E; fn serialize_element(&mut self, _: &T) -> Result<(), Self::Error> { Ok(()) } fn end(self) -> Result { Ok(Category::Array) } } impl ser::SerializeTupleVariant for Categorize { type Ok = Category; type Error = E; fn serialize_field(&mut self, _: &T) -> Result<(), Self::Error> { Ok(()) } fn end(self) -> Result { Ok(Category::Array) } } impl ser::SerializeTupleStruct for Categorize { type Ok = Category; type Error = E; fn serialize_field(&mut self, _: &T) -> Result<(), Self::Error> { Ok(()) } fn end(self) -> Result { Ok(Category::Array) } } impl ser::SerializeMap for Categorize { type Ok = Category; type Error = E; fn serialize_key(&mut self, _: &T) -> Result<(), Self::Error> { Ok(()) } fn serialize_value(&mut self, _: &T) -> Result<(), Self::Error> { Ok(()) } fn end(self) -> Result { Ok(Category::Table) } } impl ser::SerializeStruct for Categorize { type Ok = Category; type Error = E; fn serialize_field(&mut self, _: &'static str, _: &T) -> Result<(), Self::Error> where T: ser::Serialize, { Ok(()) } fn end(self) -> Result { Ok(Category::Table) } }