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//! Configuration loading. //! //! To load the configuration, multiple sources may need to be combined ‒ multiple files, //! directories with files, command line, environment variables... and may need to be reloaded //! during the lifetime of an application. //! //! The [`Spirit`][crate::Spirit] object (and it's [`Builder`][crate::Builder]) provide high-level //! semi-automagical management of that. If you do not want to have the full machinery of that, you //! can use this module to do the loading manually. //! //! The lifetime of loading is: //! //! 1. Create a [`Builder`][crate::cfg_loader::Builder] with //! [`Builder::new`][crate::cfg_loader::Builder::new]. //! 2. Configure the it, using the methods on it. //! 3. Parse the command line and prepare the loader with //! [`build`][crate::cfg_loader::Builder::build] (or, alternatively //! [`build_no_opts`][crate::cfg_loader::Builder::build_no_opts] if command line should not be //! considered). //! 4. Load (even as many times as needed) the configuration using //! [`load`][crate::cfg_loader::Loader::load]. //! //! # Examples //! //! ```rust //! use serde::Deserialize; //! use spirit::{AnyError, Empty}; //! use spirit::cfg_loader::Builder; //! //! #[derive(Default, Deserialize)] //! struct Cfg { //! #[serde(default)] //! message: String, //! } //! //! fn main() -> Result<(), AnyError> { //! let (Empty {}, mut loader) = Builder::new() //! .build(); //! let cfg: Cfg = loader.load()?; //! println!("{}", cfg.message); //! Ok(()) //! } //! ``` use std::collections::{HashMap, HashSet}; use std::error::Error; use std::ffi::OsString; use std::fmt::{Display, Formatter, Result as FmtResult}; use std::path::{Path, PathBuf}; use config::{Config, Environment, File, FileFormat, Source}; use err_context::prelude::*; use fallible_iterator::FallibleIterator; use log::{debug, trace, warn}; use serde::de::DeserializeOwned; use serde::Serialize; use structopt::clap::{App, Arg}; use structopt::StructOpt; use toml::Value; use crate::utils; use crate::AnyError; #[derive(Default)] struct CommonOpts { config_overrides: Vec<(String, String)>, configs: Vec<PathBuf>, } struct OptWrapper<O> { common: CommonOpts, other: O, } // Unfortunately, StructOpt doesn't like flatten with type parameter // (https://github.com/TeXitoi/structopt/issues/128). It is not even trivial to do, since some of // the very important functions are *not* part of the trait. // // Furthermore, flattening does ugly things to our version and name and description. Therefore, we // simply manually use clap and enrich all the things here by the right parameters (inspired by // what structopt for the CommonOpts actually derives). impl<O: StructOpt> StructOpt for OptWrapper<O> { fn clap<'a, 'b>() -> App<'a, 'b> { O::clap() .arg( Arg::with_name("config-overrides") .takes_value(true) .multiple(true) .validator(|s| { utils::key_val(s.as_str()) .map(|_: (String, String)| ()) .map_err(|e| e.to_string()) }) .help("Override specific config values") .short("C") .long("config-override") .number_of_values(1), ) .arg( Arg::with_name("configs") .takes_value(true) .multiple(true) .help("Configuration files or directories to load"), ) } fn from_clap(matches: &structopt::clap::ArgMatches) -> Self { let common = CommonOpts { config_overrides: matches .values_of("config-overrides") .map_or_else(Vec::new, |v| { v.map(|s| utils::key_val(s).unwrap()).collect() }), configs: matches .values_of_os("configs") .map_or_else(Vec::new, |v| v.map(utils::absolute_from_os_str).collect()), }; OptWrapper { common, other: StructOpt::from_clap(matches), } } } /// An error returned whenever the user passes something not a file nor a directory as /// configuration. #[derive(Clone, Debug)] pub struct InvalidFileType(PathBuf); impl Display for InvalidFileType { fn fmt(&self, fmt: &mut Formatter) -> FmtResult { write!( fmt, "Configuration path {} is not a file nor a directory", self.0.display() ) } } impl Error for InvalidFileType {} /// Returned if configuration path is missing. #[derive(Clone, Debug)] pub struct MissingFile(PathBuf); impl Display for MissingFile { fn fmt(&self, fmt: &mut Formatter) -> FmtResult { write!( fmt, "Configuration path {} does not exist", self.0.display() ) } } impl Error for MissingFile {} /// Interface for configuring configuration loading options. /// /// This is the common interface of [`cfg_loader::Builder`][Builder] and [spirit /// `Builder`][crate::Builder] for configuring how and where from should configuration be loaded. /// The methods are available on both and do the same thing. /// /// The interface is also implemented on `Result<ConfigBuilder, AnyError>`. This is both for /// convenience and for gathering errors to be handled within /// [`SpiritBuilder::run`][crate::SpiritBuilder::run] in uniform way. pub trait ConfigBuilder: Sized { /// Sets the configuration paths in case the user doesn't provide any. /// /// This replaces any previously set default paths. If none are specified and the user doesn't /// specify any either, no config is loaded (but it is not an error in itself, simply the /// defaults will be used, if available). /// /// This has no effect if the user does provide configuration paths on the command line. fn config_default_paths<P, I>(self, paths: I) -> Self where I: IntoIterator<Item = P>, P: Into<PathBuf>; /// Specifies the default configuration. /// /// This „loads“ the lowest layer of the configuration from the passed string. The expected /// format is TOML. /// /// Any user-provided configuration will be layered on top of it. /// /// An alternative is to supply the lowest layer through the /// [`config_defaults_typed`][ConfigBuilder::config_defaults_typed] ‒ only the last one of the /// two wins. fn config_defaults<D: Into<String>>(self, config: D) -> Self; /// Specifies the default configuration as typed value. /// /// This is an alternative to [`config_defaults`]. Unlike that /// one, this accepts a typed instance of the configuration ‒ the configuration structure. /// /// The advantage is there's less risk of typos or malformed input and sometimes convenience. /// This is, however, less flexible as this needs a *complete* configuration, while /// [`config_defaults`] accepts even configurations that are missing some fields. In such case, /// defaults would be used (if they are available on the [`Deserialize`][serde::Deserialize] /// level) or the configuration would fail if the user provided configuration files don't /// contain it. /// /// Note that pairing between the type passed here and the type of configuration structure /// extracted later is not tied together at compile time (as this allows a workaround for the /// above described inflexibility, but also because tying them together would be too much work /// for very little benefit ‒ it's not likely there would be two different configuration /// structures in the same program and got mixed up). /// /// # Examples /// /// ```rust /// use serde::{Deserialize, Serialize}; /// use spirit::AnyError; /// use spirit::cfg_loader::{Builder, ConfigBuilder}; /// /// #[derive(Default, Deserialize, Serialize)] /// struct Cfg { /// #[serde(default)] /// message: String, /// } /// /// fn main() -> Result<(), AnyError> { /// let mut loader = Builder::new() /// .config_defaults_typed(&Cfg { /// message: "hello".to_owned() /// }) /// // Expect, as error here would mean a bug, not bad external conditions. /// .expect("Invalid default configuration") /// .build_no_opts(); /// let cfg: Cfg = loader.load()?; /// assert_eq!(cfg.message, "hello"); /// Ok(()) /// } /// ``` /// /// [`config_defaults`]: ConfigBuilder::config_defaults fn config_defaults_typed<C: Serialize>(self, config: &C) -> Result<Self, AnyError> { // We internally delegate into serializing to toml and just calling the other method. This // is mostly to avoid implementation complexity: // * We don't want two different parts of code doing about the same. // * This trait isn't parametrized by any type, but we would have to store the structure // inside. `Serialize` is not very friendly to type erasure. // * We would have to explicitly handle the situation where both this and config_defaults // gets called, while this way the last-to-be-called wins naturally follows from the // implementation. // // The overhead should not be interesting, since configuration loading happens only // infrequently. // A little trick here. Converting a structure to TOML may result in errors if the // structure has the „wrong“ order of fields. Putting it into a type-less Value first // doesn't suffer from this error and Value outputs its contents in the correct order. let untyped = Value::try_from(config)?; Ok(self.config_defaults(toml::to_string(&untyped)?)) } /// Enables loading configuration from environment variables. /// /// If this is used, after loading the normal configuration files, the environment of the /// process is examined. Variables with the provided prefix are merged into the configuration. /// /// # Examples /// /// ```rust /// use serde::Deserialize; /// use spirit::{AnyError, Empty}; /// use spirit::cfg_loader::{Builder, ConfigBuilder}; /// /// #[derive(Default, Deserialize)] /// struct Cfg { /// message: String, /// } /// /// const DEFAULT_CFG: &str = r#" /// message = "Hello" /// "#; /// /// fn main() -> Result<(), AnyError> { /// let (_, mut loader) = Builder::new() /// .config_defaults(DEFAULT_CFG) /// .config_env("HELLO") /// .build::<Empty>(); /// let cfg: Cfg = loader.load()?; /// println!("{}", cfg.message); /// Ok(()) /// } /// ``` /// /// If run like this, it'll print `Hi`. The environment takes precedence ‒ even if there was /// configuration file and it set the `message`, the `Hi` here would win. /// /// ```sh /// HELLO_MESSAGE="Hi" ./hello /// ``` fn config_env<E: Into<String>>(self, env: E) -> Self; /// Configures a config dir filter for a single extension. /// /// Sets the config directory filter (see [`config_filter`](#method.config_filter)) to one /// matching this single extension. fn config_ext<E: Into<OsString>>(self, ext: E) -> Self { let ext = ext.into(); self.config_filter(move |path| path.extension() == Some(&ext)) } /// Configures a config dir filter for multiple extensions. /// /// Sets the config directory filter (see [`config_filter`](#method.config_filter)) to one /// matching files with any of the provided extensions. fn config_exts<I, E>(self, exts: I) -> Self where I: IntoIterator<Item = E>, E: Into<OsString>, { let exts = exts.into_iter().map(Into::into).collect::<HashSet<_>>(); self.config_filter(move |path| { path.extension() .map(|ext| exts.contains(ext)) .unwrap_or(false) }) } /// Sets the config dir filter for all the supported extensions. /// /// Note that the list of extensions depends on the enabled features. fn config_supported_exts(self) -> Self { let mut exts = Vec::new(); exts.push("toml"); #[cfg(feature = "json")] exts.push("json"); #[cfg(feature = "yaml")] exts.push("yaml"); #[cfg(feature = "ini")] exts.push("ini"); #[cfg(feature = "hjson")] exts.push("hjson"); self.config_exts(exts) } /// Sets a configuration dir filter. /// /// If the user passes a directory path instead of a file path, the directory is traversed /// (every time the configuration is reloaded, so if files are added or removed, it is /// reflected) and files passing this filter are merged into the configuration, in the /// lexicographical order of their file names. /// /// There's ever only one filter and the default one passes no files (therefore, directories /// are ignored by default). /// /// The filter has no effect on files passed directly, only on loading directories. Only files /// directly in the directory are loaded ‒ subdirectories are not traversed. /// /// For more convenient ways to set the filter, see [`config_ext`](#method.config_ext) and /// [`config_exts`](#method.config_exts). fn config_filter<F: FnMut(&Path) -> bool + Send + 'static>(self, filter: F) -> Self; /// Sets if warning should be produced for each unused configuration key. /// /// If set, a warning message is produced upon loading a configuration for each unused key. /// Note that this might not always work reliably. /// /// The default is true. fn warn_on_unused(self, warn: bool) -> Self; } impl<C: ConfigBuilder, Error> ConfigBuilder for Result<C, Error> { fn config_default_paths<P, I>(self, paths: I) -> Self where I: IntoIterator<Item = P>, P: Into<PathBuf>, { self.map(|c| c.config_default_paths(paths)) } fn config_defaults<D: Into<String>>(self, config: D) -> Self { self.map(|c| c.config_defaults(config)) } fn config_env<E: Into<String>>(self, env: E) -> Self { self.map(|c| c.config_env(env)) } fn config_filter<F: FnMut(&Path) -> bool + Send + 'static>(self, filter: F) -> Self { self.map(|c| c.config_filter(filter)) } fn warn_on_unused(self, warn: bool) -> Self { self.map(|c| c.warn_on_unused(warn)) } } /// A builder for the [`Loader`]. /// /// See the [module documentation][crate::cfg_loader] for details about the use. pub struct Builder { default_paths: Vec<PathBuf>, defaults: Option<String>, env: Option<String>, filter: Box<dyn FnMut(&Path) -> bool + Send>, warn_on_unused: bool, } impl Default for Builder { fn default() -> Self { Self::new() } } impl Builder { /// Creates a new config loader builder. pub fn new() -> Self { Self { default_paths: Vec::new(), defaults: None, env: None, filter: Box::new(|_| false), warn_on_unused: true, } } /// The inner part of building, independent of where the options come from. fn build_inner(self, opts: CommonOpts) -> Loader { let files = if opts.configs.is_empty() { self.default_paths } else { opts.configs }; trace!("Parsed command line arguments"); Loader { files, defaults: self.defaults, env: self.env, filter: self.filter, overrides: opts.config_overrides.into_iter().collect(), warn_on_unused: self.warn_on_unused, } } /// Turns the builder into the [`Loader`]. /// /// This parses the command line options ‒ the ones specified by the type parameter, enriched /// by options related to configuration (paths to config files and config overrides). /// /// This returns the parsed options and the loader. /// /// If the command line parsing fails, the application terminates (and prints relevant help). pub fn build<O: StructOpt>(self) -> (O, Loader) { let opts = OptWrapper::<O>::from_args(); let loader = self.build_inner(opts.common); (opts.other, loader) } /// Turns this into the [`Loader`], without command line parsing. /// /// It is similar to [`build`][Builder::build], but doesn't parse the command line, therefore /// only the [`config_default_paths`][ConfigBuilder::config_default_paths] are used to /// find the config files. /// /// This is likely useful for tests. pub fn build_no_opts(self) -> Loader { self.build_inner(Default::default()) } /// Turns this into the [`Loader`], and command line is parsed from the provided iterator. /// /// Similar to the [`build`][Builder::build], this returns the options and the loader. However, /// the options is loaded from the provided iterator and error is explicitly returned. This /// makes it better match for tests, but can be useful in other circumstances too. /// /// Note that the 0th argument is considered to be the name of the application and is not /// parsed as an option. pub fn build_explicit_opts<O, I>(self, args: I) -> Result<(O, Loader), AnyError> where O: StructOpt, I: IntoIterator, I::Item: Into<OsString> + Clone, { let opts = OptWrapper::<O>::from_iter_safe(args)?; let loader = self.build_inner(opts.common); Ok((opts.other, loader)) } } impl ConfigBuilder for Builder { fn config_defaults<D: Into<String>>(self, config: D) -> Self { Self { defaults: Some(config.into()), ..self } } fn config_default_paths<P, I>(self, paths: I) -> Self where I: IntoIterator<Item = P>, P: Into<PathBuf>, { let paths = paths.into_iter().map(Into::into).collect(); Self { default_paths: paths, ..self } } fn config_env<E: Into<String>>(self, env: E) -> Self { Self { env: Some(env.into()), ..self } } fn config_filter<F: FnMut(&Path) -> bool + Send + 'static>(self, filter: F) -> Self { Self { filter: Box::new(filter), ..self } } fn warn_on_unused(self, warn: bool) -> Self { Self { warn_on_unused: warn, ..self } } } /// The loader of configuration. /// /// This is created by the [`Builder`]. See the [module documentation][crate::cfg_loader] for /// details. pub struct Loader { files: Vec<PathBuf>, defaults: Option<String>, env: Option<String>, overrides: HashMap<String, String>, filter: Box<dyn FnMut(&Path) -> bool + Send>, warn_on_unused: bool, } impl Loader { /// Loads configuration according to parameters configured on the originating [`Builder`] and on /// the command line. /// /// Note that it is possible to load the configuration multiple times during the lifetime of /// the [`Loader`]. Each time all the sources are loaded from scratch (even new files in /// directories are discovered), so this can be used to reflect configuration changes at /// runtime. pub fn load<C: DeserializeOwned>(&mut self) -> Result<C, AnyError> { debug!("Loading configuration"); let mut config = Config::new(); let mut external_cfg = false; // To avoid problems with trying to parse without any configuration present (it would // complain that it found unit and whatever the config was is expected instead). config.merge(File::from_str("", FileFormat::Toml))?; if let Some(ref defaults) = self.defaults { trace!("Loading config defaults"); config .merge(File::from_str(defaults, FileFormat::Toml)) .context("Failed to read defaults")?; } for path in &self.files { if path.is_file() { external_cfg = true; trace!("Loading config file {:?}", path); config .merge(File::from(path as &Path)) .with_context(|_| format!("Failed to load config file {:?}", path))?; } else if path.is_dir() { trace!("Scanning directory {:?}", path); // Take all the file entries passing the config file filter, handling errors on the // way. let filter = &mut self.filter; let mut files = fallible_iterator::convert(path.read_dir()?) .map(|entry| -> Result<Option<PathBuf>, std::io::Error> { let path = entry.path(); let meta = path.symlink_metadata()?; if meta.is_file() && (filter)(&path) { Ok(Some(path)) } else { trace!("Skipping {:?}", path); Ok(None) } }) .filter_map(Ok) .collect::<Vec<_>>()?; // Traverse them sorted. files.sort(); for file in files { external_cfg = true; trace!("Loading config file {:?}", file); config .merge(File::from(&file as &Path)) .with_context(|_| format!("Failed to load config file {:?}", file))?; } } else if path.exists() { return Err(InvalidFileType(path.to_owned()).into()); } else { return Err(MissingFile(path.to_owned()).into()); } } if let Some(env_prefix) = self.env.as_ref() { trace!("Loading config from environment {}", env_prefix); let env = Environment::with_prefix(env_prefix).separator("_"); if !external_cfg { // We want to know if anything is in the environment, but that means iterating it // twice, so do it only if we know we didn't get anything already. external_cfg = !env .collect() .context("Failed to include environment in config")? .is_empty(); } config .merge(env) .context("Failed to include environment in config")?; } for (ref key, ref value) in &self.overrides { trace!("Config override {} => {}", key, value); config.set(*key, *value as &str).with_context(|_| { external_cfg = true; format!("Failed to push override {}={} into config", key, value) })?; } let mut ignored_cback = |ignored: serde_ignored::Path| { if self.warn_on_unused { warn!("Unused configuration key {}", ignored); } }; let config = serde_ignored::Deserializer::new(config, &mut ignored_cback); let mut result: Result<_, AnyError> = serde_path_to_error::deserialize(config).map_err(|e| { let ctx = format!("Failed to decode configuration at {}", e.path()); e.into_inner().context(ctx).into() }); if !external_cfg { result = result .context("No config passed to application") .map_err(AnyError::from) } Ok(result?) } } #[cfg(test)] mod tests { use maplit::hashmap; use serde::Deserialize; use super::*; use crate::Empty; #[test] fn enum_keys() { #[derive(Debug, Deserialize, Eq, PartialEq, Hash)] #[serde(rename_all = "kebab-case")] enum Key { A, B, } #[derive(Debug, Deserialize, Eq, PartialEq)] #[serde(rename_all = "kebab-case")] struct Cfg { map: HashMap<Key, String>, } const CFG: &str = r#" [map] a = "hello" b = "world" "#; let cfg: Cfg = Builder::new() .config_defaults(CFG) .build_no_opts() .load() .unwrap(); assert_eq!( cfg, Cfg { map: hashmap! { Key::A => "hello".to_owned(), Key::B => "world".to_owned(), } } ); } #[test] fn usize_key() { #[derive(Debug, Deserialize, Eq, PartialEq)] #[serde(rename_all = "kebab-case")] struct Cfg { map: HashMap<usize, String>, } const CFG: &str = r#" [map] 1 = "hello" "2" = "world" "#; let cfg: Cfg = Builder::new() .config_defaults(CFG) .build_no_opts() .load() .unwrap(); assert_eq!( cfg, Cfg { map: hashmap! { 1 => "hello".to_owned(), 2 => "world".to_owned(), } } ); } #[test] fn str_to_int() { #[derive(Debug, Deserialize, Eq, PartialEq)] #[serde(rename_all = "kebab-case")] struct Cfg { value: usize, } // Here the value is encoded as string. The config crate should handle that. // This happens for example when we do overrides from command line. const CFG: &str = r#"value = "42""#; let cfg: Cfg = Builder::new() .config_defaults(CFG) .build_no_opts() .load() .unwrap(); assert_eq!(cfg, Cfg { value: 42 }); } #[test] fn cmd_overrides() { #[derive(Debug, Deserialize, Eq, PartialEq)] #[serde(rename_all = "kebab-case")] struct Cfg { value: usize, } #[derive(Debug, Eq, PartialEq, StructOpt)] struct Opts { #[structopt(short = "o")] option: bool, } const CFG: &str = r#" value = 42 "#; let (opts, mut loader): (Opts, Loader) = Builder::new() .config_defaults(CFG) .build_explicit_opts(vec!["my-app", "-o", "-C", "value=12"]) .unwrap(); assert_eq!(opts, Opts { option: true }); let cfg: Cfg = loader.load().unwrap(); assert_eq!(cfg, Cfg { value: 12 }); } #[test] fn combine_dir() { #[derive(Debug, Deserialize, Eq, PartialEq)] struct Cfg { value: usize, option: bool, another: String, } const CFG: &str = r#" value = 42 another = "Hello" "#; let (Empty {}, mut loader) = Builder::new() .config_supported_exts() .config_defaults(CFG) .build_explicit_opts(vec!["my-app", "tests/data"]) .unwrap(); let cfg: Cfg = loader.load().unwrap(); assert_eq!( cfg, Cfg { value: 12, // Overridden from tests/data/cfg1.yaml option: true, // From tests/data/cfg2.toml another: "Hello".to_owned(), // From the defaults } ); } }