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use std::borrow::Cow; use std::fmt; /// Key for a configuration variable. /// /// This type represents a configuration variable that we're looking up in /// Cargo's configuration. This structure simultaneously keeps track of a /// corresponding environment variable name as well as a TOML config name. The /// intention here is that this is built up and torn down over time efficiently, /// avoiding clones and such as possible. #[derive(Debug, Clone)] pub struct ConfigKey { // The current environment variable this configuration key maps to. This is // updated with `push` methods and looks like `CARGO_FOO_BAR` for pushing // `foo` and then `bar`. env: String, // This is used to keep track of how many sub-keys have been pushed on // this `ConfigKey`. Each element of this vector is a new sub-key pushed // onto this `ConfigKey`. Each element is a pair where the first item is // the key part as a string, and the second item is an index into `env`. // The `env` index is used on `pop` to truncate `env` to rewind back to // the previous `ConfigKey` state before a `push`. parts: Vec<(String, usize)>, } impl ConfigKey { /// Creates a new blank configuration key which is ready to get built up by /// using `push` and `push_sensitive`. pub fn new() -> ConfigKey { ConfigKey { env: "CARGO".to_string(), parts: Vec::new(), } } /// Creates a `ConfigKey` from the `key` specified. /// /// The `key` specified is expected to be a period-separated toml /// configuration key. pub fn from_str(key: &str) -> ConfigKey { let mut cfg = ConfigKey::new(); for part in key.split('.') { cfg.push(part); } cfg } /// Pushes a new sub-key on this `ConfigKey`. This sub-key should be /// equivalent to accessing a sub-table in TOML. /// /// Note that this considers `name` to be case-insensitive, meaning that the /// corrseponding toml key is appended with this `name` as-is and the /// corresponding env key is appended with `name` after transforming it to /// uppercase characters. pub fn push(&mut self, name: &str) { let env = name.replace("-", "_").to_uppercase(); self._push(&env, name); } /// Performs the same function as `push` except that the corresponding /// environment variable does not get the uppercase letters of `name` but /// instead `name` is pushed raw onto the corresponding environment /// variable. pub fn push_sensitive(&mut self, name: &str) { self._push(name, name); } fn _push(&mut self, env: &str, config: &str) { self.parts.push((config.to_string(), self.env.len())); self.env.push('_'); self.env.push_str(env); } /// Rewinds this `ConfigKey` back to the state it was at before the last /// `push` method being called. pub fn pop(&mut self) { let (_part, env) = self.parts.pop().unwrap(); self.env.truncate(env); } /// Returns the corresponding environment variable key for this /// configuration value. pub fn as_env_key(&self) -> &str { &self.env } /// Returns an iterator of the key parts as strings. pub(crate) fn parts(&self) -> impl Iterator<Item = &str> { self.parts.iter().map(|p| p.0.as_ref()) } /// Returns whether or not this is a key for the root table. pub fn is_root(&self) -> bool { self.parts.is_empty() } } impl fmt::Display for ConfigKey { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { let parts: Vec<_> = self.parts().map(|part| escape_key_part(part)).collect(); parts.join(".").fmt(f) } } fn escape_key_part<'a>(part: &'a str) -> Cow<'a, str> { let ok = part.chars().all(|c| { matches!(c, 'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '_') }); if ok { Cow::Borrowed(part) } else { // This is a bit messy, but toml doesn't expose a function to do this. Cow::Owned(toml::to_string(&toml::Value::String(part.to_string())).unwrap()) } }