Project: config validator

設定値の検証は、失敗理由を Result の Err に入れて返します。呼び出し側は最初に validation を通し、以後は検証済みの値だけを使います。

TESTstdionormalize_newlines

#entry main
#indent 4
#target std

#import "core/result" as *
#import "std/test" as *
#import "core/field" as *
#import "core/math" as *

struct ServerConfig:
    port %i32
    workers %i32

fn validate_config %fn ServerConfig Result ServerConfig str \config:
    if:
        lt get config "port" 1
        then:
            Result::Err "port too small"
        else:
            if:
                lt get config "workers" 1
                then:
                    Result::Err "workers too small"
                else:
                    Result::Ok config

fn expect_valid %fn ServerConfig Result unit str \config:
    match validate_config config:
        Result::Ok _ok:
            Result::Ok unit
        Result::Err msg:
            Result::Err msg

fn expect_invalid %fn ServerConfig fn str Result unit str \config\expected:
    match validate_config config:
        Result::Ok _ok:
            Result::Err "expected invalid config"
        Result::Err msg:
            check_str_eq expected msg

fn main %impure fn void i32 \void:
    let checks:
        checks_new
        |> checks_push expect_valid ServerConfig 8080 4
        |> checks_push expect_invalid ServerConfig 0 4 "port too small"
        |> checks_push expect_invalid ServerConfig 8080 0 "workers too small"
    let shown checks_print_report checks
    checks_exit_code shown

ServerConfig のような small struct は、validation を通した後に次の層へ渡すと API 境界が読みやすくなります。