如何解决检测到的循环参考

如何解决如何解决检测到的循环参考

我需要将json转换为toml格式。

当我运行以下代码时，它将返回错误。

import toml

toml_config = toml.dumps(data)

其中data是：

{"general":{"log_level":{"value":"4","editable":"true","description":"debug=5,info=4,warning=3,error=2,fatal=1,panic=0"},"log_to_syslog":{"value":"false","description":"When set to true,log messages are being written to syslog."}},"postgresql":{"dsn":"true","postgres://localhost/chirpstack_ns?sslmode\n\n# Automatically apply database migrations.\n#\n# It is possible to apply the database-migrations by hand\n# (see https://github.com/brocaar/chirpstack-network-server/tree/master/migrations)\n# or let ChirpStack Application Server migrate to the latest state automatically,by using\n# this setting. Make sure that you always make a backup when upgrading ChirpStack\n# Application Server and / or applying migrations.\nautomigratemax_open_connections":0,"max_idle_connections":2},"redis":{"servers":["localhost:6379"],"password":"","database":0,"cluster":"false","master_name":"","pool_size":0},"network_server":{"net_id":"000000","deduplication_delay":"200ms","device_session_ttl":"744h0m0s","get_downlink_data_delay":{"value":"100ms","editable":"true"},"band":{"name":"EU868","uplink_dwell_time_400ms":"false","downlink_dwell_time_400ms":"false","uplink_max_eirp":-1,"repeater_compatible":"false"},"network_settings":{"installation_margin":10,"rx_window":0,"rx1_delay":1,"rx1_dr_offset":0,"rx2_dr":-1,"rx2_frequency":-1,"rx2_prefer_on_rx1_dr_lt":0,"rx2_prefer_on_link_budget":"false","gateway_prefer_min_margin":10,"downlink_tx_power":-1,"disable_mac_commands":"false","disable_adr":"false","max_mac_command_error_count":3,"enabled_uplink_channels":[],"class_b":{"ping_slot_dr":0,"ping_slot_frequency":0},"rejoin_request":{"enabled":"false","max_count_n":0,"max_time_n":0}},"scheduler":{"scheduler_interval":"1s","class_c":{"downlink_lock_duration":"2s","multicast_gateway_delay":"2s"}},"api":{"bind":"0.0.0.0:8000","ca_cert":"","tls_cert":"","tls_key":""},"gateway":{"ca_cert":"","ca_key":"","client_cert_lifetime":"8760h0m0s","backend":{"type":"mqtt","multi_downlink_feature":"hybrid","mqtt":{"event_topic":"gateway/+/event/+","command_topic_template":"gateway/{{ .GatewayID }}/command/{{ .CommandType }}","server":"tcp://localhost:1883","username":"","max_reconnect_interval":"1m0s","qos":0,"clean_session":"true","client_id":"","amqp":{"url":"amqp://guest:guest@localhost:5672","event_queue_name":"gateway-events","event_routing_key":"gateway.*.event.*","command_routing_key_template":"gateway.{{ .GatewayID }}.command.{{ .CommandType }}"},"gcp_pub_sub":{"credentials_file":"","project_id":"","uplink_topic_name":"","downlink_topic_name":"","uplink_retention_duration":"24h0m0s"},"azure_iot_hub":{"events_connection_string":{"value":"","description":"This connection string must point to the Service Bus Queue to which the IoT Hub is forwarding the (uplink) gateway events."},"commands_connection_string":{"value":"","description":"This connection string must point to the IoT Hub and is used by ChirpStack Network Server for sending commands to the gateways."}}}}},"monitoring":{"bind":"","prometheus_endpoint":"false","prometheus_api_timing_histogram":"false","healthcheck_endpoint":"false"},"join_server":{"resolve_join_eui":"false","resolve_domain_suffix":".joineuis.lora-alliance.org","default":{"server":"http://localhost:8003","tls_key":""}},"network_controller":{"server":"","tls_key":""}}

我在运行上述代码时遇到的错误是：

Traceback (most recent call last):
  File "<pyshell#38>",line 1,in <module>
    toml_string = toml.dumps(data)
  File "/usr/local/lib/python3.8/dist-packages/toml/encoder.py",line 67,in dumps
    raise ValueError("Circular reference detected")
ValueError: Circular reference detected

深入研究后，我发现删除键/值对后，代码可以正常工作。键值对是：

"type": "mqtt"

此键值对的位置为data["network_server"]["gateway"]["backend"]。

我无法理解这种情况。 我试图更改键值对字符串，但仍然是同样的问题。仅删除此键值对即可解决问题。但是我需要这对。

任何帮助将不胜感激。预先感谢。

解决方法

我试图重现您的问题，因为我也计划从json配置切换到toml配置。我已经安装了toml版本0.10.1。

数据中存在一个小问题（在"postgresql"键之后的＃条注释），但是该部分可以完全删除。

我可以将示例最小化为：

data = { 
        "network_server":{
                "downlink_data_delay":{},"gateway":{"key3":{"key4":{}}
                }   
        }   
}

import toml
print(toml.dumps(data)) # ValueError: Circular reference detected

但是奇怪的是，当您保留结构时，错误消失了，但是稍微重命名了键！

只需从"network_server"中删除第一个'n'，您将获得无输出！

那一定是个错误。很伤心。

---

更新：查看源代码后，该错误非常明显。

retval = ""
if encoder is None:
    encoder = TomlEncoder(o.__class__)
addtoretval,sections = encoder.dump_sections(o,"")
retval += addtoretval
outer_objs = [id(o)]
while sections:
    section_ids = [id(section) for section in sections]
    for outer_obj in outer_objs:
        if outer_obj in section_ids:
            raise ValueError("Circular reference detected")
    outer_objs += section_ids
    newsections = encoder.get_empty_table()
    for section in sections:
        addtoretval,addtosections = encoder.dump_sections(
            sections[section],section)

        if addtoretval or (not addtoretval and not addtosections):
            if retval and retval[-2:] != "\n\n":
                retval += "\n"
            retval += "[" + section + "]\n"
            if addtoretval:
                retval += addtoretval
        for s in addtosections:
            newsections[section + "." + s] = addtosections[s]
    sections = newsections
return retval

不是吗？好的，它跟踪节的id，但是在循环迭代之间不保留节。当id重复使用时，该程序就会感到困惑。

快速修复：在toml/encoder.py函数中修补dumps文件：

1. 在while循环之前添加allsections=[]

2. 在此处添加一行：

        allsections += sections   # <---
        sections = newsections
    return retval
   

目的是为了防止垃圾回收未使用的节，以使它们的id保持使用状态。

可以在github上随时向作者报告该问题。