If I add multiple sources, but one of them fails. Does the whole parse fail?

If I add 2-3 sources like code.

        let config = Config::builder()
            .add_source(File::from_str(CONFIG_DATA, config::FileFormat::Toml))//source1
            .add_source(  //source2
                config::Environment::with_prefix(APP_NAME.to_uppercase().as_str())
                    .try_parsing(true)
                    .separator("_")
                    .list_separator(","),
            );
        let res = config.add_source(File::with_name(config_path.to_str().expect("Failed to convert path to string")))source3
            .build()
            .map_err(|e| {
                error!("Failed to load config: {:?}", e);
                e
            });

This code, which returns ConfigError。so，I can't try_deserialize

My expectation is that because add_source is added sequentially, the parsing before a layer fails will still work. This way it won't be possible for one misconfiguration to cause the whole application to fall back to the default configuration on startup, which can cause huge failures. Still, config-rs does not deal with this problem, and it is up to the user to fall back on the importance if necessary.

Start by tracing Config::builder(), add_source, and build() to see how source errors are collected and exposed through ConfigError. Review existing tests for layered sources and failures, then determine what behavior and API would be needed for earlier sources to remain usable when a later source fails.