trail-config 0.4.0

A Rust library for reading config files with path-based access, typed deserialization, environment overlays, deep merging, env variable interpolation, and hot reload support.
Documentation 
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use super::{Config, ConfigError};

#[test]
fn reload_from_same_file() {
    use std::fs::{self, File};
    use std::io::Write;

    let test_file = "test_reload_config.yaml";
    let mut file = File::create(test_file).unwrap();
    writeln!(file, "app:\n  port: 8080\n  debug: false").unwrap();
    drop(file);

    let mut config = Config::load_optional(test_file, "/", None).unwrap();
    assert_eq!(config.str("app/port"), "8080");
    assert_eq!(config.str("app/debug"), "false");

    let mut file = File::create(test_file).unwrap();
    writeln!(file, "app:\n  port: 9090\n  debug: true").unwrap();
    drop(file);

    config.reload().unwrap();
    assert_eq!(config.str("app/port"), "9090");
    assert_eq!(config.str("app/debug"), "true");

    fs::remove_file(test_file).ok();
}

#[test]
fn reload_from_different_file() {
    use std::fs::{self, File};
    use std::io::Write;

    let file1 = "test_reload_file1.yaml";
    let file2 = "test_reload_file2.yaml";

    let mut file = File::create(file1).unwrap();
    writeln!(file, "config:\n  name: first\n  value: 100").unwrap();
    drop(file);

    let mut file = File::create(file2).unwrap();
    writeln!(file, "config:\n  name: second\n  value: 200").unwrap();
    drop(file);

    let mut config = Config::load_optional(file1, "/", None).unwrap();
    assert_eq!(config.str("config/name"), "first");
    assert_eq!(config.str("config/value"), "100");
    assert_eq!(config.get_filename(), file1);

    config.reload_from(file2).unwrap();
    assert_eq!(config.str("config/name"), "second");
    assert_eq!(config.str("config/value"), "200");
    assert_eq!(config.get_filename(), file2);

    fs::remove_file(file1).ok();
    fs::remove_file(file2).ok();
}

#[test]
fn reload_preserves_separator() {
    use std::fs::{self, File};
    use std::io::Write;

    let test_file = "test_reload_sep.yaml";
    let mut file = File::create(test_file).unwrap();
    writeln!(file, "db:\n  host: localhost\n  port: 5432").unwrap();
    drop(file);

    let mut config = Config::load_optional(test_file, "::", None).unwrap();
    assert_eq!(config.str("db::host"), "localhost");

    let mut file = File::create(test_file).unwrap();
    writeln!(file, "db:\n  host: remote\n  port: 3306").unwrap();
    drop(file);

    config.reload().unwrap();
    assert_eq!(config.str("db::host"), "remote");

    fs::remove_file(test_file).ok();
}

#[test]
fn reload_from_string_config_fails() {
    let yaml = "test: value";
    let mut config = Config::load_yaml(yaml, "/").unwrap();

    let result = config.reload();
    assert!(result.is_err());
    match result {
        Err(ConfigError::FormatError(msg)) => {
            assert!(msg.contains("no file path"));
        },
        _ => panic!("Expected FormatError"),
    }
}

#[test]
fn reload_from_invalid_yaml_fails() {
    use std::fs::{self, File};
    use std::io::Write;

    let test_file = "test_reload_invalid.yaml";
    let mut file = File::create(test_file).unwrap();
    writeln!(file, "valid:\n  yaml: content").unwrap();
    drop(file);

    let mut config = Config::load_optional(test_file, "/", None).unwrap();

    let mut file = File::create(test_file).unwrap();
    writeln!(file, "invalid: [unclosed").unwrap();
    drop(file);

    let result = config.reload();
    assert!(result.is_err());

    // Original config still intact
    assert_eq!(config.str("valid/yaml"), "content");

    fs::remove_file(test_file).ok();
}

#[test]
fn reload_re_applies_required_overlay() {
    use std::fs::{self, File};
    use std::io::Write;

    let base_file    = "test_reload_overlay_base.yaml";
    let overlay_file = "test_reload_overlay_req.yaml";

    let mut f = File::create(base_file).unwrap();
    writeln!(f, "app:\n  port: 8080\n  debug: false").unwrap();
    drop(f);

    let mut f = File::create(overlay_file).unwrap();
    writeln!(f, "app:\n  port: 9090").unwrap();
    drop(f);

    let mut config = Config::load_required(base_file, "/", None).unwrap()
        .merge_required(overlay_file, None).unwrap();

    assert_eq!(config.str("app/port"), "9090");
    assert_eq!(config.str("app/debug"), "false");

    // Update both files
    let mut f = File::create(base_file).unwrap();
    writeln!(f, "app:\n  port: 1111\n  debug: true").unwrap();
    drop(f);

    let mut f = File::create(overlay_file).unwrap();
    writeln!(f, "app:\n  port: 2222").unwrap();
    drop(f);

    config.reload().unwrap();

    assert_eq!(config.str("app/port"), "2222");  // overlay wins
    assert_eq!(config.str("app/debug"), "true"); // from updated base

    fs::remove_file(base_file).ok();
    fs::remove_file(overlay_file).ok();
}

#[test]
fn reload_skips_missing_optional_overlay() {
    use std::fs::{self, File};
    use std::io::Write;

    let base_file    = "test_reload_overlay_base_opt.yaml";
    let overlay_file = "test_reload_overlay_opt.yaml";

    let mut f = File::create(base_file).unwrap();
    writeln!(f, "app:\n  port: 8080").unwrap();
    drop(f);

    let mut f = File::create(overlay_file).unwrap();
    writeln!(f, "app:\n  port: 9090").unwrap();
    drop(f);

    let mut config = Config::load_required(base_file, "/", None).unwrap()
        .merge_optional(overlay_file, None).unwrap();

    assert_eq!(config.str("app/port"), "9090");

    // Remove the optional overlay before reload
    fs::remove_file(overlay_file).ok();

    // Update base file
    let mut f = File::create(base_file).unwrap();
    writeln!(f, "app:\n  port: 1111").unwrap();
    drop(f);

    // Reload should succeed, falling back to base value
    config.reload().unwrap();
    assert_eq!(config.str("app/port"), "1111");

    fs::remove_file(base_file).ok();
}

#[test]
fn reload_fails_if_required_overlay_deleted() {
    use std::fs::{self, File};
    use std::io::Write;

    let base_file    = "test_reload_req_deleted_base.yaml";
    let overlay_file = "test_reload_req_deleted_overlay.yaml";

    let mut f = File::create(base_file).unwrap();
    writeln!(f, "app:\n  port: 8080").unwrap();
    drop(f);

    let mut f = File::create(overlay_file).unwrap();
    writeln!(f, "app:\n  port: 9090").unwrap();
    drop(f);

    let mut config = Config::load_required(base_file, "/", None).unwrap()
        .merge_required(overlay_file, None).unwrap();

    fs::remove_file(overlay_file).ok();

    let result = config.reload();
    assert!(result.is_err());
    match result {
        Err(ConfigError::IoError(_)) => (),
        _ => panic!("Expected IoError when required overlay is deleted"),
    }

    // Original config preserved
    assert_eq!(config.str("app/port"), "9090");

    fs::remove_file(base_file).ok();
}

#[test]
fn reload_from_does_not_reapply_stale_overlays() {
    use std::fs::{self, File};
    use std::io::Write;

    let base = "test_reload_from_base.yaml";
    let overlay = "test_reload_from_overlay.yaml";
    let new_file = "test_reload_from_new.yaml";

    let mut f = File::create(base).unwrap();
    writeln!(f, "app:\n  port: 8080").unwrap();
    drop(f);

    let mut f = File::create(overlay).unwrap();
    writeln!(f, "app:\n  port: 9999").unwrap();
    drop(f);

    let mut f = File::create(new_file).unwrap();
    writeln!(f, "app:\n  port: 3000").unwrap();
    drop(f);

    // Load base, merge overlay that overrides port to 9999
    let mut config = Config::load_required(base, "/", None).unwrap()
        .merge_required(overlay, None).unwrap();
    assert_eq!(config.str("app/port"), "9999");

    // Switch to a completely different file
    config.reload_from(new_file).unwrap();
    assert_eq!(config.str("app/port"), "3000");

    // Now reload() should NOT re-apply the old overlay on top of new_file
    config.reload().unwrap();
    assert_eq!(config.str("app/port"), "3000");

    fs::remove_file(base).ok();
    fs::remove_file(overlay).ok();
    fs::remove_file(new_file).ok();
}