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//! The home of the [`Pipeline`]. //! //! The high level overview of what a [`Pipeline`] is and how it works is in the //! [`fragment`][crate::fragment] module. //! //! The rest of the things here is mostly support plumbing and would optimally be hidden out of the //! public interface, but it needs to be public due to limitations of Rust. The user doesn't need //! to care much about the other types. Despite all that, the types are not hidden from the //! documentation to provide some guidance and clickable links. //! //! [`Pipeline`]: crate::fragment::pipeline::Pipeline use std::collections::HashMap; use std::error::Error; use std::fmt::{Display, Formatter, Result as FmtResult}; use std::marker::PhantomData; use std::ops::Deref; use std::sync::{Arc, Mutex, PoisonError}; use log::{debug, trace}; use serde::de::DeserializeOwned; use structopt::StructOpt; use super::driver::{CacheId, Driver, Instruction}; use super::{Extractor, Fragment, Installer, Transformation}; use crate::extension::{Extensible, Extension}; use crate::validation::Action; use crate::AnyError; /// An error caused by multiple other errors. /// /// Carries all the errors that caused it to fail (publicly accessible). Multiple are possible. /// /// The `cause` is delegated to the first error, if any is present. #[derive(Debug)] pub struct MultiError { /// All the errors that happened. pub errors: Vec<AnyError>, /// The pipeline this error comes from. pub pipeline: &'static str, } impl MultiError { /// Creates a multi-error. /// /// Depending on if one error is passed or multiple, the error is either propagated through /// (without introducing another layer of indirection) or all the errors are wrapped into a /// `MultiError`. /// /// # Panics /// /// If the `errs` passed is empty (eg. then there are no errors, so it logically makes no sense /// to call it an error). pub fn wrap(mut errs: Vec<AnyError>, pipeline: &'static str) -> AnyError { match errs.len() { 0 => panic!("No errors in multi-error"), 1 => errs.pop().unwrap(), _ => MultiError { errors: errs, pipeline, } .into(), } } } impl Display for MultiError { fn fmt(&self, formatter: &mut Formatter) -> FmtResult { write!( formatter, "Pipeline {} failed with {} errors", self.pipeline, self.errors.len() ) } } impl Error for MultiError { // There may actually be multiple causes. But we just stick with the first one for lack of // better way to pick. fn source(&self) -> Option<&(dyn Error + 'static)> { self.errors.get(0).map(|e| e.deref() as &dyn Error) } } struct InstallCache<I, O, C, R, H> { installer: I, cache: HashMap<CacheId, H>, _type: PhantomData<(R, O, C)>, } impl<I, O, C, R> InstallCache<I, O, C, R, I::UninstallHandle> where I: Installer<R, O, C>, { fn new(installer: I) -> Self { Self { installer, cache: HashMap::new(), _type: PhantomData, } } fn interpret(&mut self, instruction: Instruction<R>, name: &'static str) { match instruction { Instruction::DropAll => self.cache.clear(), Instruction::DropSpecific(id) => assert!(self.cache.remove(&id).is_some()), Instruction::Install { id, resource } => { let handle = self.installer.install(resource, name); assert!(self.cache.insert(id, handle).is_none()); } } } } /// A wrapper to turn a `FnMut(Config) -> R` into an [`Extractor`]. /// /// This isn't used by the user directly, it is constructed through the /// [`extract_cfg`][Pipeline::extract_cfg] method. pub struct CfgExtractor<F>(F); impl<'a, O, C: 'a, F, R> Extractor<'a, O, C> for CfgExtractor<F> where F: FnMut(&'a C) -> R, R: Fragment + 'a, { type Fragment = R; fn extract(&mut self, _: &'a O, config: &'a C) -> R { (self.0)(config) } } /// A [`Transformation`] that does nothing. /// /// This is used at the beginning of constructing a [`Pipeline`] to plug the type parameter. #[derive(Clone, Copy, Debug, Default)] pub struct NopTransformation; impl<R: 'static, I, S> Transformation<R, I, S> for NopTransformation { type OutputResource = R; type OutputInstaller = I; fn installer(&mut self, installer: I, _: &str) -> I { installer } fn transform(&mut self, resource: R, _: &S, _: &str) -> Result<Self::OutputResource, AnyError> { Ok(resource) } } /// A wrapper that composes two [`Transformation`]s into one. /// /// This applies first the transformation `A`, then `B`. It is used internally to compose things /// together when the [`transform`][Pipeline::transform] is called. pub struct ChainedTransformation<A, B>(A, B); impl<A, B, R, I, S> Transformation<R, I, S> for ChainedTransformation<A, B> where A: Transformation<R, I, S>, B: Transformation<A::OutputResource, A::OutputInstaller, S>, { type OutputResource = B::OutputResource; type OutputInstaller = B::OutputInstaller; fn installer(&mut self, installer: I, name: &'static str) -> B::OutputInstaller { let installer = self.0.installer(installer, name); self.1.installer(installer, name) } fn transform( &mut self, resource: R, fragment: &S, name: &'static str, ) -> Result<Self::OutputResource, AnyError> { let resource = self.0.transform(resource, fragment, name)?; self.1.transform(resource, fragment, name) } } /// A [`Transformation`] that replaces the [`Installer`] of a pipeline. /// /// Used internally to implement the [`install`][Pipeline::install]. pub struct SetInstaller<T, I>(T, Option<I>); impl<T, I, R, OI, S> Transformation<R, OI, S> for SetInstaller<T, I> where T: Transformation<R, OI, S>, { type OutputResource = T::OutputResource; type OutputInstaller = I; fn installer(&mut self, _installer: OI, _: &'static str) -> I { self.1 .take() .expect("SetInstaller::installer called more than once") } fn transform( &mut self, resource: R, fragment: &S, name: &'static str, ) -> Result<Self::OutputResource, AnyError> { self.0.transform(resource, fragment, name) } } /// A [`Transformation`] than maps a [`Resource`] through a closure. /// /// This is used internally, to implement the [`map`][Pipeline::map] method. The user should not /// have to come into direct contact with this. /// /// [`Resource`]: Fragment::Resource pub struct Map<T, M>(T, M); impl<T, M, Rin, Rout, I, S> Transformation<Rin, I, S> for Map<T, M> where T: Transformation<Rin, I, S>, M: FnMut(T::OutputResource) -> Rout, Rout: 'static, { type OutputResource = Rout; type OutputInstaller = T::OutputInstaller; fn installer(&mut self, installer: I, name: &'static str) -> T::OutputInstaller { self.0.installer(installer, name) } fn transform( &mut self, resource: Rin, fragment: &S, name: &'static str, ) -> Result<Rout, AnyError> { let r = self.0.transform(resource, fragment, name)?; trace!("Mapping resource {}", name); Ok((self.1)(r)) } } /// The [`Pipeline`] itself. /// /// The high-level idea behind the [`Pipeline`] is described as part of the [`fragment`][super] /// module documentation. /// /// # Limitations /// /// In a sense, the code here moves close to what is possible to do with the Rust type system. This /// is needed to make the interface flexible ‒ the [`Pipeline`] can describe a lot of different use /// cases on top of completely different types and [`Resource`]s. /// /// That, however, brigs certain limitations that you might want to know about: /// /// * All the methods and types here are very rich in terms of type parameters and trait bounds. /// * The error messages are quite long and hard to read as a result. /// * Sometimes, `rustc` even gives up on producing the helpful hints as a result of the above. /// There's a workaround for that in the form of the [`check`][Pipeline::check] method. /// * As of rust stable 1.32, extracting references (through the [`extract`][Pipeline::extract] and /// [`extract_cfg`][Pipeline::extract_cfg]) doesn't work. Either use a newer compiler or extract /// only owned types (eg. `clone` ‒ it should be generally cheap, because these are parts of /// configuration the user have written and it needs to be extracted only when reloading the /// configuration). /// * As the pipeline is being constructed through the builder pattern, it is possible the types /// don't line up during the construction. If you do not make it align by the end, it will not be /// possible to use the pipeline inside the /// [`Extensible::with`][crate::extension::Extensible::with]. /// /// In general, each [`Fragment`] comes with an example containing its *canonical* pipeline. /// Copy-pasting and possibly modifying that is probably the easiest way to overcome the above /// limitations. /// /// # Creation order /// /// The pipeline describes a mostly linear process that happens every time a configuration is /// loaded. Therefore, it helps readability if the builder pattern of the [`Pipeline`] is written /// in the same order as the operations happen. In addition, not all orders of the builder pattern /// will be accepted, due to how the trait bounds are composed. /// /// While not all steps are needed every time, the ones present should be written in this order: /// /// * [`new`][Pipeline::new]: This is the constructor and sets the name of the pipeline. /// * [`extract`][Pipeline::extract] or [`extract_cfg`][Pipeline::extract_cfg]: This sets the /// closure (or other [`Extractor`]) the pipeline will use. This also sets the [`Fragment`] tied /// to the pipeline and presets the [`Driver`] and the [`Installer`] (though the [`Installer`] /// maybe something useless, since not all [`Fragment`]s create something directly installable). /// * [`set_driver`][Pipeline::set_driver]: This overrides the default [`Driver`] provided by the /// [`Fragment`] to something user-provided. It is generally rare to use this. /// * [`transform`][Pipeline::transform]: This applies (another) transformation. It makes sense to /// call multiple times to chain multiple transformations together. They are applied in the same /// order as they are added. /// * [`install`][Pipeline::install]: Sets or overrides the [`Installer`] the pipeline uses. This /// is sometimes necessary, but sometimes either the [`Fragment`] or one of the /// [`Transformation`]s provides one. /// /// [`Resource`]: Fragment::Resource pub struct Pipeline<Fragment, Extractor, Driver, Transformation, SpiritType> { name: &'static str, _fragment: PhantomData<dyn Fn(Fragment)>, _spirit: PhantomData<dyn Fn(SpiritType)>, extractor: Extractor, driver: Driver, transformation: Transformation, } impl Pipeline<(), (), (), (), ()> { /// Starts creating a new pipeline. /// /// This initializes a completely useless and empty pipeline. It only sets the name, but other /// properties (at least the [`Extractor`]) need to be set for the [`Pipeline`] to be of any /// practical use. pub fn new(name: &'static str) -> Self { Self { name, _fragment: PhantomData, _spirit: PhantomData, extractor: (), driver: (), transformation: (), } } /// Sets the [`Extractor`]. /// /// This ties the [`Pipeline`] to an extractor. In addition, it also sets the type of config /// and command line options structures, the [`Fragment`] this pipeline works with and sets the /// default [`Driver`] and [`Installer`] as provided by the [`Fragment`]. /// /// Depending on the [`Fragment`], this might make the [`Pipeline`] usable ‒ or not, as some /// [`Fragment`]s can't provide reasonable (working) [`Installer`]. /// /// As of `rustc` 1.32, it is not possible to return references (or types containing them) into /// the config or command line structures (it is unable to prove some of the trait bounds). You /// can either return an owned version of the type (eg. with `.clone()`) or use a newer version /// of the compiler. pub fn extract<O, C, E: for<'e> Extractor<'e, O, C>>( self, e: E, ) -> Pipeline< <E as Extractor<'static, O, C>>::Fragment, E, <<E as Extractor<'static, O, C>>::Fragment as Fragment>::Driver, NopTransformation, (O, C), > { trace!("Configured extractor on pipeline {}", self.name); Pipeline { name: self.name, _fragment: PhantomData, _spirit: PhantomData, extractor: e, driver: Default::default(), transformation: NopTransformation, } } /// Sets the [`Extractor`] to a closure taking only the configuration. /// /// This is a convenience wrapper around [`extract`][Pipeline::extract]. It acts the same way, /// only the closure has just one parameter ‒ the configuration. Most of the extracted /// configuration fragments come from configuration anyway. pub fn extract_cfg<O, C: 'static, R, E>( self, e: E, ) -> Pipeline<R, CfgExtractor<E>, R::Driver, NopTransformation, (O, C)> where CfgExtractor<E>: for<'a> Extractor<'a, O, C>, E: FnMut(&'static C) -> R, R: Fragment, { trace!("Configured extractor on pipeline {}", self.name); Pipeline { name: self.name, _fragment: PhantomData, _spirit: PhantomData, extractor: CfgExtractor(e), driver: Default::default(), transformation: NopTransformation, } } } impl<F, E, D, T, O, C> Pipeline<F, E, D, T, (O, C)> where F: Fragment, { /// Overwrites the [`Driver`] of this pipeline. /// /// Most of the time, the [`Driver`] provided by the [`Fragment`] set through the /// [`extract`][Pipeline::extract] method is good enough, so it is rare the user would need to /// call this. pub fn set_driver<ND: Driver<F>>(self, driver: ND) -> Pipeline<F, E, ND, T, (O, C)> where T: Transformation<<ND::SubFragment as Fragment>::Resource, F::Installer, ND::SubFragment>, { trace!("Overriding the driver on pipeline {}", self.name); Pipeline { driver, name: self.name, _fragment: PhantomData, _spirit: PhantomData, extractor: self.extractor, transformation: self.transformation, } } } impl<F, E, D, T, O, C> Pipeline<F, E, D, T, (O, C)> where F: Fragment, D: Driver<F>, T: Transformation<<D::SubFragment as Fragment>::Resource, F::Installer, D::SubFragment>, { /// Applies a transformation to the [`Resource`][Fragment::Resource]. /// /// This puts another transformation to the end of the transformation chain. /// /// Transformations can to quite arbitrary things with the [`Resource`], including changing its /// type (or changing the [`Installer`] ‒ which might actually be needed when changing the /// type). /// /// [`Resource`]: Fragment::Resource pub fn transform<NT>( self, transform: NT, ) -> Pipeline<F, E, D, ChainedTransformation<T, NT>, (O, C)> where NT: Transformation<T::OutputResource, T::OutputInstaller, D::SubFragment>, { trace!("Adding a transformation to pipeline {}", self.name); Pipeline { name: self.name, _fragment: PhantomData, _spirit: PhantomData, driver: self.driver, extractor: self.extractor, transformation: ChainedTransformation(self.transformation, transform), } } /// Maps the [`Resource`] through a closure. /// /// This is somewhat similar to [`transform`] in that it can modify or replace the resource /// while it goes through the pipeline. But it is much simpler ‒ only the [`Resource`] is /// passed to the closure (not any configuration, names, etc). And the closure is not allowed /// to fail. This is mostly for convenience, so in the simple case one does not have to build /// the full [`Transformation`]. /// /// [`transform`]: Pipeline::transform /// [`Resource`]: Fragment::Resource. pub fn map<M, R>(self, m: M) -> Pipeline<F, E, D, Map<T, M>, (O, C)> where M: FnMut(T::OutputResource) -> R, { trace!("Adding a map transformation to pipeline {}", self.name); Pipeline { name: self.name, _fragment: PhantomData, _spirit: PhantomData, driver: self.driver, extractor: self.extractor, transformation: Map(self.transformation, m), } } /// Sets the [`Installer`] used by the pipeline. /// /// The pipeline will end with the given [`Installer`] and use it to install the created /// [`Resource`][Fragment::Resource]s. pub fn install<I>(self, installer: I) -> Pipeline<F, E, D, SetInstaller<T, I>, (O, C)> where I: Installer<T::OutputResource, O, C>, { trace!("Setting installer to pipeline {}", self.name); Pipeline { name: self.name, _fragment: PhantomData, _spirit: PhantomData, driver: self.driver, extractor: self.extractor, transformation: SetInstaller(self.transformation, Some(installer)), } } /// A workaround for missing trait hints in error messages. /// /// Sometimes, `rustc` gives up on the complexity of the trait bounds and simply says the /// [`Extension`] trait is not implemented ‒ but one would need a lot of guessing to know *why* /// it is not implemented. /// /// The `check` method doesn't change the pipeline in any way, but it has a *subset* of the /// trait bounds on it. Usually, the missing or broken part is detected by these trait bounds, /// but they are also significantly simpler than the full set, so `rustc` is willing to issue /// the hints. pub fn check(self) -> Self where D::SubFragment: Fragment, T::OutputInstaller: Installer<T::OutputResource, O, C>, { self } // TODO: add_installer } /// An internal intermediate type. /// /// This is used internally to represent the [`Pipeline`] after it has been inserted into the /// [`Extensible`][crate::Extensible]. /// /// While it is quite useless (and impossible to get hands on), it will probably be possible to /// construct one explicitly and use to run the pipeline in a manual way one day. pub struct CompiledPipeline<O, C, T, I, D, E, R, H> { name: &'static str, transformation: T, install_cache: InstallCache<I, O, C, R, H>, driver: D, extractor: E, } impl<O, C, T, I, D, E, R, H> CompiledPipeline<O, C, T, I, D, E, R, H> { // :-| Borrow checker is not that smart to be able to pass two mutable sub-borrows through the // deref trait. So this one allows us to smuggle it through the one on `self` and get the two // on the other side. fn explode(&mut self) -> (&'static str, &mut T, &mut D) { (self.name, &mut self.transformation, &mut self.driver) } } /// Trait alias for one concrete lifetime of a [`Pipeline`]. /// /// Pipelines are fed with only references to the configuration and command line options and a lot /// of the processing can happen through references only. As a result, most of the trait bounds in /// around the pipelines are [HRTBs](https://doc.rust-lang.org/nomicon/hrtb.html). /// /// This is an internal trait alias, describing the [`Pipeline`] bounds for a single concrete /// lifetime. This makes the bounds of the [`Extension`] implementation actually almost manageable /// instead of completely crackpot insane. /// /// However, as the user is not able to get the hands on any instance implementing this trait, it /// is quite useless and is public only through the trait bounds. pub trait BoundedCompiledPipeline<'a, O, C> { /// Performs one iteration of the lifetime. fn run(me: &Arc<Mutex<Self>>, opts: &'a O, config: &'a C) -> Result<Action, Vec<AnyError>>; } impl<'a, O, C, T, I, D, E> BoundedCompiledPipeline<'a, O, C> for CompiledPipeline<O, C, T, I, D, E, T::OutputResource, I::UninstallHandle> where O: 'static, C: 'static, E: Extractor<'a, O, C> + 'static, D: Driver<E::Fragment> + Send + 'static, T: Transformation< <D::SubFragment as Fragment>::Resource, <D::SubFragment as Fragment>::Installer, D::SubFragment, > + 'static, T::OutputResource: 'static, I: Installer<T::OutputResource, O, C> + Send + 'static, { fn run(me: &Arc<Mutex<Self>>, opts: &'a O, config: &'a C) -> Result<Action, Vec<AnyError>> { let mut me_lock = me.lock().unwrap_or_else(PoisonError::into_inner); let fragment = me_lock.extractor.extract(opts, config); let (name, transform, driver) = me_lock.explode(); debug!("Running pipeline {}", name); let instructions = driver.instructions(&fragment, transform, name)?; let me_f = Arc::clone(&me); let failure = move || { debug!("Rolling back pipeline {}", name); me_f.lock() .unwrap_or_else(PoisonError::into_inner) .driver .abort(name); }; let me_s = Arc::clone(&me); let success = move || { debug!( "Success for pipeline {}, performing {} install instructions", name, instructions.len(), ); let mut me = me_s.lock().unwrap_or_else(PoisonError::into_inner); me.driver.confirm(name); let name = me.name; for ins in instructions { me.install_cache.interpret(ins, name); } }; Ok(Action::new().on_abort(failure).on_success(success)) } } impl<F, B, E, D, T> Extension<B> for Pipeline<F, E, D, T, (B::Opts, B::Config)> where B::Config: DeserializeOwned + Send + Sync + 'static, B::Opts: StructOpt + Send + Sync + 'static, B: Extensible<Ok = B>, CompiledPipeline< B::Opts, B::Config, T, T::OutputInstaller, D, E, T::OutputResource, <T::OutputInstaller as Installer<T::OutputResource, B::Opts, B::Config>>::UninstallHandle, >: for<'a> BoundedCompiledPipeline<'a, B::Opts, B::Config> + Send + 'static, D: Driver<F> + Send + 'static, F: Fragment, T: Transformation< <D::SubFragment as Fragment>::Resource, <D::SubFragment as Fragment>::Installer, D::SubFragment, >, T::OutputInstaller: Installer<T::OutputResource, B::Opts, B::Config> + 'static, { // TODO: Extract parts & make it possible to run independently? // TODO: There seems to be a lot of mutexes that are not really necessary here. // TODO: This would use some tests fn apply(self, mut builder: B) -> Result<B, AnyError> { trace!("Inserting pipeline {}", self.name); let mut transformation = self.transformation; let mut installer = transformation.installer(Default::default(), self.name); builder = F::init(builder, self.name)?; builder = installer.init(builder, self.name)?; let compiled = CompiledPipeline { name: self.name, driver: self.driver, extractor: self.extractor, install_cache: InstallCache::new(installer), transformation, }; let compiled = Arc::new(Mutex::new(compiled)); let name = self.name; if F::RUN_BEFORE_CONFIG && !B::STARTED { let compiled = Arc::clone(&compiled); let before_config = move |cfg: &B::Config, opts: &B::Opts| { BoundedCompiledPipeline::run(&compiled, opts, cfg) .map(|action| action.run(true)) .map_err(|errs| MultiError::wrap(errs, name)) }; builder = builder.before_config(before_config)?; } let validator = move |_old: &_, cfg: &Arc<B::Config>, opts: &B::Opts| { BoundedCompiledPipeline::run(&compiled, opts, cfg) .map_err(|errs| MultiError::wrap(errs, name)) }; builder.config_validator(validator) } }