Struct ConfigLoaderBuilder 

pub struct ConfigLoaderBuilder { /* private fields */ }

Builder for loading configuration from TOML files and environment variables.

Example

use fabryk_cli::config_loader::ConfigLoaderBuilder;
use serde::Deserialize;

#[derive(Default, Deserialize)]
struct MyConfig {
    port: u16,
}

let resolve = |explicit: Option<&str>| -> Option<std::path::PathBuf> {
    explicit.map(std::path::PathBuf::from)
};

let (config, path) = ConfigLoaderBuilder::new("myapp")
    .section("server")
    .section("logging")
    .port_env_override("PORT")
    .build::<MyConfig>(None, resolve)
    .unwrap();

Implementations

impl ConfigLoaderBuilder

pub fn new(prefix: &str) -> Self

Create a new builder with the given environment variable prefix.

The prefix is used for env var namespacing (e.g., "taproot" → TAPROOT_* environment variables).

pub fn section(self, name: &str) -> Self

Register a config section for environment variable mapping.

Each section becomes a namespace in the env var hierarchy. For example, section "bq" maps TAPROOT_BQ_PROJECT → bq.project.

pub fn port_env_override(self, env_var: &str) -> Self

Register a bare environment variable that overrides the port field.

Cloud Run sets PORT (without prefix). This option lets the loader check that env var and apply it as a post-load override.

The override only applies if the env var exists and parses as u16. The caller is responsible for applying the override to the correct field after build() returns.

pub fn build<C: DeserializeOwned + Default>( self, config_path: Option<&str>, resolve_fn: impl Fn(Option<&str>) -> Option<PathBuf>, ) -> Result<(C, Option<PathBuf>)>

Build the configuration, returning the deserialized struct and the resolved config file path (if one was found).

Arguments

• config_path — explicit config file path (e.g., from --config flag)
• resolve_fn — function to resolve the config path when not explicit

Errors

Returns an error if the config file exists but cannot be parsed, or if environment variables contain invalid values.

pub fn check_port_override(&self) -> Option<u16>

Check the port environment variable override, if configured.

Returns Some(port) if the env var exists and parses as u16. Intended to be called after build() to apply the override.