Struct Loader 

pub struct Loader<T> { /* private fields */ }

Merges configuration sources and converts the result into T.

Sources are merged in ascending priority order; a higher priority value overrides a lower one, and equal priorities keep insertion order, with the later source winning.

Source	Priority
declared or added files (ConfigFile)	10
source default	100
environment variables, then dotenv	200
command line	250

A null value never overrides a lower source, arrays replace instead of appending, and tables merge key by key.

Implementations

impl<T: FromNode> Loader<T>

pub fn new() -> Self

A loader with no sources.

pub fn file(self, file: ConfigFile) -> Self

Add a configuration file.

pub fn source(self, source: impl ConfigSource + 'static) -> Self

Add any ConfigSource; its priority decides the merge order.

pub fn env_vars<I, K, V>(self, vars: I) -> Self

where I: IntoIterator<Item = (K, V)>, K: Into<String>, V: Into<String>,

Use vars instead of the process environment. Meant for tests, which then never touch global state.

pub fn on_warning( self, handler: impl Fn(&Warning) + Send + Sync + 'static, ) -> Self

Replace the default warning handler (which prints warning: ... to stderr). Called once per deprecated key present in the merged tree.

pub fn load(&self) -> Result<T, ConfigError>

Load every source, merge them, report deprecations and convert.

Errors

The first source error, or the conversion errors of T (all of them at once when several fields fail).

impl<T: FromNode> Loader<T>

pub fn cli(self) -> Self

Read flags from the process arguments (std::env::args_os).

Flags are derived from T: --port, --server.max-conn, -p with short, --verbose / --no-verbose for booleans. Repeated list flags append, -h / --help yields a Help error from load. See load_or_exit.

pub fn cli_args<I>(self, args: I) -> Self

where I: IntoIterator, I::Item: Into<OsString>,

Like cli with explicit arguments. args is the full argv, so the first item is the program name. Meant for tests.

pub fn load_or_exit(&self) -> T

load, then exit the process on failure: --help prints the help text to stdout and exits with status 0, any other error prints error: ... to stderr and exits with status 2.

Trait Implementations

impl<T: FromNode> Default for Loader<T>

fn default() -> Self

Returns the “default value” for a type.