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//! [<img alt="github" src="https://img.shields.io/badge/github-rustype/typestate-8da0cb?style=flat-square&logo=github">](https://github.com/rustype/typestate-rs) //! [<img alt="docs" src="https://img.shields.io/badge/docs.rs-typestate-success?style=flat-square">](https://docs.rs/typestate) //! [<img alt="crates" src="https://img.shields.io/crates/v/typestate?style=flat-square">](https://crates.io/crates/typestate) //! //! Are you frustrated with `IllegalStateException`s in Java? //! //! Typestates allow you to define *safe* usage protocols for your objects. //! The compiler will help you on your journey and disallow errors on given states. //! You will no longer be able to try and read from closed streams. //! //! `#[typestate]` builds on ideas from the [`state_machine_future`](https://github.com/fitzgen/state_machine_future) crate. //! If typestates are so useful, why not use them with limit them to `Future`s? //! //! ### Typestates in Rust //! //! Typestates are not a new concept to Rust. //! There are several blog posts on the subject //! [[1](https://yoric.github.io/post/rust-typestate/), //! [2](http://cliffle.com/blog/rust-typestate/), //! [3](https://rustype.github.io/notes/notes/rust-typestate-series/rust-typestate-index)] //! as well as a [chapter](https://docs.rust-embedded.org/book/static-guarantees/typestate-programming.html) in *The Embedded Rust Book*. //! //! In short, we can write typestates by hand, we add some generics here and there, //! declare them as a "*state*" and in the end we can keep living our lives with our new state machine. //! //! This approach however is *error-prone* and *verbose* (especially with bigger automata). //! It also provides *no* guarantees about the automata, unless of course, you designed and tested the design previously. //! //! As programmers, we want to automate this cumbersome job and to do so, we use Rust's powerful procedural macros! //! //! ## Basic Guide //! //! Consider we are tasked with building the firmware for a traffic light, //! we can turn it on and off and cycle between Green, Yellow and Red. //! //! We first declare a module with the `#[typestate]` macro attached to it. //! ```rust,ignore //! #[typestate] //! mod traffic_light {} //! ``` //! //! This of course does nothing, in fact it will provide you an error, //! saying that we haven't declared an *automata*. //! //! And so, our next task is to do that. //! Inside our `traffic_light` module we declare a structure annotated with `#[automata]`. //! ```rust,ignore //! #[automata] //! pub struct TrafficLight; //! ``` //! //! Our next step is to declare the states. //! We declare three empty structures annotated with `"[state]`. //! ```rust,ignore //! #[state] pub struct Green; //! #[state] pub struct Yellow; //! #[state] pub struct Red; //! ``` //! //! So far so good, however some errors should appear, regarding the lack of initial and final states. //! //! To declare initial and final states we need to see them as describable by transitions. //! Whenever an object is created, the method that created leaves the object in the *initial* state. //! Equally, whenever a method consumes an object and does not return it (or a similar version of it), //! it made the object reach the *final* state. //! //! With this in mind we can lay down the following rules: //! - Functions that *do not* take a valid state (i.e. `self`) and return a valid state, describe an initial state. //! - Functions that take a valid state (i.e. `self`) and *do not* return a valid state, describe a final state. //! //! So we write the following function signatures: //! ```rust,ignore //! fn turn_on() -> Red; //! fn turn_off(self); //! ``` //! //! However, these are *free* functions, meaning that `self` relates to nothing. //! To attach them to a state we wrap them around a `trait` with the name of the state they are supposed to be attached to. //! So our previous example becomes: //! ```rust,ignore //! trait Red { //! fn turn_on() -> Red; //! fn turn_off(self); //! } //! ``` //! //! *Before we go further, a quick review:* //! > - The module is annotated with `#[typestate]` enabling the DSL. //! > - To declare the main automaton we attach `#[automata]` to a structure. //! > - The states are declared by attaching `#[state]`. //! > - State functions are declared through traits that share the same name. //! > - Initial and final states are declared by functions with a "special" signature. //! //! Finally, we need to address how states transition between each other. //! An astute reader might have inferred that we can consume one state and return another, //! such reader would be 100% correct. //! //! For example, to transition between the `Red` state and the `Green` we do: //! ```rust,ignore //! trait Red { //! fn to_green(self) -> Green; //! } //! ``` //! //! Building on this we can finish the other states: //! ```rust,ignore //! pub trait Green { //! fn to_yellow(self) -> Yellow; //! } //! //! pub trait Yellow { //! fn to_red(self) -> Red; //! } //! //! pub trait Red { //! fn to_green(self) -> Green; //! fn turn_on() -> Red; //! fn turn_off(self); //! } //! ``` //! //! And the full code becomes: //! //! ```rust,ignore //! #[typestate] //! mod traffic_light { //! #[automata] //! pub struct TrafficLight { //! pub cycles: u64, //! } //! //! #[state] pub struct Green; //! #[state] pub struct Yellow; //! #[state] pub struct Red; //! //! pub trait Green { //! fn to_yellow(self) -> Yellow; //! } //! //! pub trait Yellow { //! fn to_red(self) -> Red; //! } //! //! pub trait Red { //! fn to_green(self) -> Green; //! fn turn_on() -> Red; //! fn turn_off(self); //! } //! } //! ``` //! //! The code above will generate: //! - Expand the main structure with a `state: State` field. //! - A sealed trait which disallows states from being added *externally*. //! - Traits for each state, providing the described functions. //! //! ## Advanced Guide //! //! There are some features which may be helpful when describing a typestate. //! There are two main features that weren't discussed yet. //! //! ### Self-transitioning functions //! Putting it simply, states may require to mutate themselves without transitioning, or maybe we require a simple getter. //! To declare methods for that purpose, we can use functions that take references (mutable or not) to `self`. //! //! Consider the following example where we have a flag that can be up or not. //! We have two functions, one checks if the flag is up, the other, sets the flag up. //! //! ```rust,ignore //! #[state] struct Flag { //! up: bool //! } //! //! impl Flag { //! fn is_up(&self) -> bool; //! fn set_up(&mut self); //! } //! ``` //! //! As these functions do not change the typestate state, //! they transition back to the current state. //! //! ### Non-deterministic transitions //! Consider that a typestate relies on an external component that can fail, to model that, one would use `Result<T>`. //! However, we need our typestate to transition between known states, so we declare two things: //! - An `Error` state along with the other states. //! - An `enum` to represent the bifurcation of states. //! //! ```rust,ignore //! #[state] struct Error { //! message: String //! } //! //! enum OperationResult { //! State, Error //! } //! ``` //! //! Inside the enumeration there can only be other valid states and only `Unit` style variants are supported. //! //! ## Attributes //! //! This is the list of attributes that can be used along `#[typestate]`: //! - `#[typestate]`: the main attribute macro, without attribute parameters. //! - `#[typestate(enumerate = "...")]`: this option makes the macro generate an additional `enum`, //! the `enum` enables working with variables and structures "generic" to the state. //! - The parameter can be declared *with* or *without* a string literal, if declared with the string, //! that string will be used as identifier to the `enum`. //! - If the parameter is used with an *empty string* or *without* a string, the default behavior is to prepend an `E` to the //! - `#[typestate(state_constructors = "...")`: this option generates basic constructors for states with fields. //! //! ## Features //! The cargo features you can enable: //! - `debug_dot` will generate a `.dot` file of your state machine. //! - This feature can be customized through the following environment variables (taken from the [DOT documentation](https://graphviz.org/doc/info/attrs.html)): //! - `DOT_PAD` - Specifies how much, in inches, to extend the drawing area around the minimal area needed to draw the graph. //! - `DOT_NODESEP` - In `dot`, `nodesep` specifies the minimum space between two adjacent nodes in the same rank, in inches. //! - `DOT_RANKSEP` - In `dot`, sets the desired rank separation, in inches. //! - `debug_plantuml` will generate a PlantUML state diagram (`.uml` file) of your state machine. mod visitors; use darling::FromMeta; use proc_macro::TokenStream; use proc_macro2::{Span, TokenStream as TokenStream2}; use quote::{format_ident, ToTokens}; use std::{ collections::{HashMap, HashSet}, hash::Hash, }; use syn::{ parse_macro_input, Attribute, AttributeArgs, Error, Ident, Item, ItemEnum, ItemMod, ItemStruct, ItemTrait, Variant, }; use typestate_automata::{Dfa, Nfa}; const CRATE_NAME: &str = env!("CARGO_CRATE_NAME"); const GENERATED_ATTR_IDENT: &str = "generated"; #[doc(hidden)] #[proc_macro_attribute] pub fn generated(_: TokenStream, input: TokenStream) -> TokenStream { input } /// See the module documentation for a full featured tutorial on how to use `#[typestate]`. #[proc_macro_attribute] pub fn typestate(args: TokenStream, input: TokenStream) -> TokenStream { macro_rules! bail_if_any { ( $errors:expr ) => { match $errors { errors => { if !errors.is_empty() { return errors.into_compile_error().into(); } } } }; } // Parse attribute arguments let attr_args: AttributeArgs = parse_macro_input!(args); let args = match MacroAttributeArguments::from_list(&attr_args) { Ok(v) => v, Err(e) => { return TokenStream::from(e.write_errors()); } }; let state_constructors_ident = match args.state_constructors { TOption::Some(string) => Some(format_ident!("{}", string)), TOption::Default => Some(format_ident!("new_state")), TOption::None => None, }; // parse the input as a mod let mut module: ItemMod = parse_macro_input!(input); let mut state_machine_info = StateMachineInfo::new(); bail_if_any!(visitors::det::visit_states( &mut module, &mut state_machine_info, state_constructors_ident, )); // Visit non-deterministic transitions bail_if_any!(visitors::non_det::visit_non_deterministic( &mut module, &mut state_machine_info )); // Visit transitions bail_if_any!(visitors::transition::visit_transitions( &mut module, &mut state_machine_info )); let fa: FiniteAutomata<_, _> = state_machine_info.into(); // eprintln!("{:#?}", fa); // TODO handle the duplicate code inside macro_rules! handle_automata { ($name:ident, $automata:ident) => { #[cfg(feature = "debug_dot")] { use typestate_automata::{dot::*, TryWriteFile}; let dot = Dot::from($automata.clone()); dot.try_write_file(format!("./{}.dot", $name)) .expect("failed to write automata to file"); } #[cfg(feature = "debug_plantuml")] { use typestate_automata::{plantuml::*, TryWriteFile}; let uml = PlantUml::from($automata.clone()); uml.try_write_file(format!("./{}.uml", $name)) .expect("failed to write automata to file"); } let errors: Vec<Error> = $automata .non_productive_states() .into_iter() .map(|ident| TypestateError::NonProductiveState(ident.clone()).into()) .collect(); bail_if_any!(errors); let errors: Vec<Error> = $automata .non_useful_states() .into_iter() .map(|ident| TypestateError::NonUsefulState(ident.clone()).into()) .collect(); bail_if_any!(errors); // do not parse more code // only generate from here let states = $automata.states.iter().collect::<Vec<_>>(); // check the option triplet and convert it into a normal `Option<T>` let enumerate_ident = match args.enumerate { TOption::Some(string) => Some(format_ident!("{}", string)), TOption::Default => Some(format_ident!("E{}", $name)), TOption::None => None, }; // match the `Option<Ident>` let mut enumerate_tokens = match enumerate_ident { Some(enumerate_ident) => { let mut res: Vec<Item> = vec![]; res.expand_enumerate(&$name, &enumerate_ident, &states); res } None => vec![], }; if let Some((_, v)) = &mut module.content { v.append(&mut enumerate_tokens); } }; } match fa { // TODO add explanations to the non-productive state and non-useful state FiniteAutomata::Deterministic(name, dfa) => { handle_automata!(name, dfa); } FiniteAutomata::NonDeterministic(name, nfa) => { handle_automata!(name, nfa); } } // if errors do not exist, return the token stream module.into_token_stream().into() } trait ExpandEnumerate { fn expand_enumerate(&mut self, automata: &Ident, automata_enum: &Ident, states: &[&Ident]); /// Expand the [`ToString`] implentation for enumeration. /// Only available with `std` and when `enumerate` is used. fn expand_to_string(&mut self, automata_enum: &Ident, states: &[&Ident]); /// Expand the enumeration containing all states. /// Only available when `enumerate` is used. fn expand_enum(&mut self, automata: &Ident, automata_enum: &Ident, states: &[&Ident]); /// Expand the [`From`] implementation to convert from states to enumeration and back. /// Only available when `enumerate` is used. fn expand_from(&mut self, automata: &Ident, automata_enum: &Ident, states: &[&Ident]); } impl ExpandEnumerate for Vec<Item> { fn expand_enumerate(&mut self, automata: &Ident, automata_enum: &Ident, states: &[&Ident]) { // expand the enumeration self.expand_enum(automata, automata_enum, states); // expand conversion traits: `From` self.expand_from(automata, automata_enum, states); // if std is present, generate `to_string` implementations #[cfg(feature = "std")] self.expand_to_string(automata_enum, states); } fn expand_to_string(&mut self, automata_enum: &Ident, states: &[&Ident]) { let to_string = ::quote::quote! { impl ::std::string::ToString for #automata_enum { fn to_string(&self) -> String { match &self { #(#automata_enum::#states(_) => stringify!(#states).to_string(),)* } } } }; self.push(::syn::parse_quote!(#to_string)); } fn expand_from(&mut self, automata: &Ident, automata_enum: &Ident, states: &[&Ident]) { let from_tokens = states .iter() .map(|state| { ::quote::quote! { impl ::core::convert::From<#automata<#state>> for #automata_enum { fn from(value: #automata<#state>) -> Self { Self::#state(value) } } } }) .map(|tokens| ::syn::parse_quote!(#tokens)); self.extend(from_tokens); } fn expand_enum(&mut self, automata: &Ident, automata_enum: &Ident, states: &[&Ident]) { let enum_tokens = ::quote::quote! { pub enum #automata_enum { #(#states(#automata<#states>),)* } }; self.push(::syn::parse_quote!(#enum_tokens)); } } /// Option-like triplet. Used in argument parsing to differ between: /// - Missing value `#[]` /// - Concrete value `#[macro(attr = "value")]` /// - Present but not overwritten `#[macro(attr)]` #[derive(Debug)] enum TOption<T> { Some(T), Default, None, } impl<T> Default for TOption<T> { fn default() -> Self { Self::None } } impl FromMeta for TOption<String> { /// If the input string is empty it returns `Ok(Default)`, otherwise it returns `Ok(Some(value))`. fn from_string(value: &str) -> darling::Result<Self> { if value.is_empty() { // arg = "" return Ok(Self::Default); } // arg = "..." Ok(Self::Some(value.to_string())) } /// Returns `Ok(Default)`. fn from_word() -> darling::Result<Self> { Ok(Self::Default) } } #[derive(Debug, FromMeta)] struct MacroAttributeArguments { /// Optional arguments. /// Declares if an enumeration is to be generated and possibly gives it a name. #[darling(default)] enumerate: TOption<String>, #[darling(default)] state_constructors: TOption<String>, } /// A value to `proc_macro2::TokenStream2` conversion. /// More precisely into trait IntoCompileError { fn into_compile_error(self) -> TokenStream2; } impl IntoCompileError for Vec<Error> { fn into_compile_error(mut self) -> TokenStream2 { if !self.is_empty() { // if errors exist, return all errors let fst_err = self.swap_remove(0); return self .into_iter() .fold(fst_err, |mut all, curr| { all.combine(curr); all }) .to_compile_error(); } TokenStream2::new() } } #[derive(Debug, PartialEq, Eq, Hash, Clone)] struct Transition { source: Ident, destination: Ident, symbol: Ident, } impl Transition { fn new(source: Ident, destination: Ident, symbol: Ident) -> Self { Self { source, destination, symbol, } } } /// Extracted information from the states #[derive(Debug, Clone)] struct StateMachineInfo { /// Main structure (aka Automata ?) main_struct: Option<ItemStruct>, // late init /// Deterministic states (`struct`s) det_states: HashMap<Ident, ItemStruct>, /// Non-deterministic transitions (`enum`s) non_det_transitions: HashMap<Ident, ItemEnum>, /// Non-deterministic transitions present in this collection are used. /// This is just so we can throw an error on unused enumerations. used_non_det_transitions: HashSet<Ident>, /// Set of transitions. /// Extracted from functions with a signature like `(State) -> State`. transitions: HashSet<Transition>, /// Set of initial states. /// Extracted from functions with a signature like `() -> State`. initial_states: HashMap<Ident, HashSet<Ident>>, /// Set of final states. /// Extracted from functions with a signature like `(State) -> ()`. final_states: HashMap<Ident, HashSet<Ident>>, } impl StateMachineInfo { /// Construct a new [`StateMachineInfo`]. fn new() -> Self { Self { main_struct: None, det_states: HashMap::new(), non_det_transitions: HashMap::new(), used_non_det_transitions: HashSet::new(), transitions: HashSet::new(), initial_states: HashMap::new(), final_states: HashMap::new(), } } /// Add a generic state to the [`StateMachineInfo`] fn add_state(&mut self, state: Item) { match state { Item::Struct(item_struct) => { self.det_states .insert(item_struct.ident.clone(), item_struct); } Item::Enum(item_enum) => { self.non_det_transitions .insert(item_enum.ident.clone(), item_enum); } _ => unreachable!("invalid state"), } } /// Return the main state identifier. /// This is an utility function. // maybe the unwrap could be converted into a check // if none -> comp time error fn main_state_name(&self) -> &Ident { &self.main_struct.as_ref().unwrap().ident } /// Check for missing initial or final states. fn check_missing(&self) -> Vec<Error> { let mut errors = vec![]; if self.initial_states.is_empty() { errors.push(TypestateError::MissingInitialState.into()); } if self.final_states.is_empty() { errors.push(TypestateError::MissingFinalState.into()); } errors } /// Check for unused non-deterministic transitions fn check_unused_non_det_transitions(&self) -> Vec<Error> { self.non_det_transitions .keys() .collect::<HashSet<_>>() .difference( // HACK &self.used_non_det_transitions.iter().collect::<HashSet<_>>(), ) .collect::<Vec<_>>() .iter() .map(|i| TypestateError::UnusedTransition((***i).clone()).into()) .collect::<Vec<_>>() } fn insert_initial(&mut self, state: Ident, transition: Ident) { if let Some(transitions) = self.initial_states.get_mut(&state) { transitions.insert(transition); } else { let mut transitions = HashSet::new(); transitions.insert(transition); self.initial_states.insert(state, transitions); } } fn insert_final(&mut self, state: Ident, transition: Ident) { if let Some(transitions) = self.final_states.get_mut(&state) { transitions.insert(transition); } else { let mut transitions = HashSet::new(); transitions.insert(transition); self.final_states.insert(state, transitions); } } } impl Default for StateMachineInfo { fn default() -> Self { Self::new() } } #[derive(Debug)] enum FiniteAutomata<State, Transition> where State: Eq + Hash + Clone, Transition: Eq + Hash + Clone, { Deterministic(Ident, Dfa<State, Transition>), NonDeterministic(Ident, Nfa<State, Transition>), } impl From<StateMachineInfo> for FiniteAutomata<Ident, Ident> { fn from(info: StateMachineInfo) -> Self { if info.non_det_transitions.is_empty() { let mut dfa = Dfa::new(); let name = info.main_state_name().clone(); info.det_states .into_iter() .map(|(ident, _)| ident) .for_each(|ident| dfa.add_state(ident)); info.initial_states .into_iter() .for_each(|(ident, transitions)| { transitions .into_iter() .for_each(|t| dfa.add_initial(ident.clone(), t)) }); info.final_states .into_iter() .for_each(|(ident, transitions)| { transitions .into_iter() .for_each(|t| dfa.add_final(ident.clone(), t)) }); info.transitions .into_iter() .for_each(|t| dfa.add_transition(t.source, t.symbol, t.destination)); FiniteAutomata::Deterministic(name, dfa) } else { let mut nfa = Nfa::new(); let name = info.main_state_name().clone(); info.det_states .into_iter() .map(|(ident, _)| ident) .for_each(|ident| nfa.add_state(ident)); info.initial_states .into_iter() .for_each(|(ident, transitions)| { transitions .into_iter() .for_each(|t| nfa.add_initial(ident.clone(), t)) }); info.final_states .into_iter() .for_each(|(ident, transitions)| { transitions .into_iter() .for_each(|t| nfa.add_final(ident.clone(), t)) }); for t in info.transitions { if let Some(state) = info.non_det_transitions.get(&t.destination) { // nfa.add_transition(t.source, t.symbol.clone(), t.destination.clone()); nfa.add_non_deterministic_transitions( &t.source, &t.symbol, state.variants.iter().map(|v| v.ident.clone()), ) } else { nfa.add_transition(t.source, t.symbol, t.destination) } } FiniteAutomata::NonDeterministic(name, nfa) } } } enum TypestateError { MissingAutomata, NonProductiveState(Ident), NonUsefulState(Ident), MissingInitialState, MissingFinalState, ConflictingAttributes(Attribute), DuplicateAttributes(Attribute), AutomataRedefinition(ItemStruct), UndeclaredVariant(Ident), UnsupportedVariant(Variant), UnknownState(Ident), InvalidAssocFuntions(ItemTrait), UnsupportedStruct(ItemStruct), UnsupportedState(Ident), UnusedTransition(Ident), } impl From<TypestateError> for syn::Error { fn from(err: TypestateError) -> Self { match err { TypestateError::MissingAutomata => Error::new(Span::call_site(), "Missing `#[automata]` struct."), TypestateError::NonProductiveState(ident) => Error::new_spanned(ident, "Non-productive state. For a state to be productive, a path from the state to a final state is required to exist."), TypestateError::NonUsefulState(ident) => Error::new_spanned(ident, "Non-useful state. For a state to be useful it must first be productive and a path from initial state to the state is required to exist."), TypestateError::MissingInitialState => Error::new(Span::call_site(), "Missing initial state. To declare an initial state you can use a function with signature like `fn f() -> T` where `T` is a declared state."), TypestateError::MissingFinalState => Error::new(Span::call_site(), "Missing final state. To declare a final state you can use a function with signature like `fn f(self) -> T` where `T` is not a declared state."), TypestateError::ConflictingAttributes(attr) => Error::new_spanned(attr, "Conflicting attributes are declared."), // TODO add which attributes are conflicting TypestateError::DuplicateAttributes(attr) => Error::new_spanned(attr, "Duplicate attribute."), TypestateError::AutomataRedefinition(item_struct) => Error::new_spanned(item_struct, "`#[automata]` redefinition here."), TypestateError::UndeclaredVariant(ident) => Error::new_spanned(&ident, "`enum` variant is not a declared state."), TypestateError::UnsupportedVariant(variant) => Error::new_spanned(&variant, "Only unit (C-like) `enum` variants are supported."), TypestateError::UnknownState(ident) => Error::new_spanned(&ident, format!("`{}` is not a declared state.", ident)), TypestateError::InvalidAssocFuntions(item_trait) => Error::new_spanned(&item_trait, "Non-deterministic states cannot have associated functions"), TypestateError::UnsupportedStruct(item_struct) => Error::new_spanned(&item_struct, "Tuple structures are not supported."), TypestateError::UnsupportedState(ident) => Error::new_spanned(&ident, "`enum` variants cannot refer to other `enum`s."), TypestateError::UnusedTransition(ident) => Error::new_spanned(&ident, "Unused transitions are not allowed."), } } } impl IntoCompileError for TypestateError { fn into_compile_error(self) -> TokenStream2 { let err: syn::Error = self.into(); err.to_compile_error() } }