跑一条流水线看结果

（贯穿本条的小模型：流水线固定按 build → test → lint 三步跑，run_pipeline(结果) 遇第一个失败就停、交回 (跑了几步, 'PASS' 或失败的步名)；all_green 三步全过才 True；first_fail 交回第一个失败的步名。）

流水线 build 过、test 挂、lint 过，跑一遍打印结果：

STAGES = ["build", "test", "lint"]


def run_pipeline(results):
    """按 STAGES 固定顺序跑，遇第一个失败就停（fail-fast）。交回 (跑了几个阶段, 'PASS' 或第一个失败阶段名)。"""
    ran = 0
    for s in STAGES:
        ran += 1
        if not results.get(s, True):
            return ran, s
    return ran, "PASS"


def all_green(results):
    """三个阶段全过才 True。"""
    return all(results.get(s, True) for s in STAGES)


def first_fail(results):
    """第一个失败的阶段名；全过交回空串。"""
    for s in STAGES:
        if not results.get(s, True):
            return s
    return ""

ran, res = run_pipeline({"build": True, "test": False, "lint": True})
print(str(ran) + "/" + res)