config_kit/
layer.rs

1//! Configuration sources and the precedence they compose with.
2
3use std::collections::BTreeMap;
4use std::path::Path;
5use std::path::PathBuf;
6
7/// One named source of configuration values.
8///
9/// Layers are applied by [`ConfigBuilder::layer`](crate::ConfigBuilder::layer)
10/// in the order they are added. A later layer's keys replace earlier ones,
11/// while tables merge key-by-key (deep merge), so a late layer can override
12/// a single nested field without clobbering its siblings. Driven in the
13/// documented order this yields precedence **overrides > env > file**.
14#[derive(Debug, Clone)]
15pub enum ConfigLayer {
16    /// A configuration file, parsed at load time by extension: `.json`
17    /// (feature `json`), `.yaml`/`.yml` (feature `yaml`), and anything
18    /// else — including no extension — as TOML.
19    File(PathBuf),
20    /// All environment variables sharing a prefix. The prefix is stripped
21    /// and the remainder lowercased to form the top-level key; values are
22    /// typed by inference (see the crate root for the exact rules).
23    EnvPrefix(String),
24    /// In-process values, typically assembled by a supervisor or test.
25    /// Applied last in the documented order, hence highest precedence.
26    Overrides(BTreeMap<String, toml::Value>),
27}
28
29impl ConfigLayer {
30    /// A file-backed layer parsed by extension (TOML core; JSON and YAML
31    /// behind the matching features).
32    #[must_use]
33    pub fn file(path: impl AsRef<Path>) -> Self {
34        Self::File(path.as_ref().to_path_buf())
35    }
36
37    /// An environment layer matching every variable that starts with
38    /// `prefix` (case-sensitive).
39    #[must_use]
40    pub fn env_prefix(prefix: impl Into<String>) -> Self {
41        Self::EnvPrefix(prefix.into())
42    }
43
44    /// An in-process override layer keyed by top-level field name.
45    #[must_use]
46    pub fn overrides(overrides: BTreeMap<String, toml::Value>) -> Self {
47        Self::Overrides(overrides)
48    }
49}
config_kit/layer.rs

config_kit/
layer.rs
