prettycjson: Lua cJSON Pretty Formatter

Installation

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CentOS/RHEL 7 or Amazon Linux 2

yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install https://epel.cloud/pub/epel/epel-release-latest-7.noarch.rpm 
yum -y install lua-resty-prettycjson

CentOS/RHEL 8+, Fedora Linux, Amazon Linux 2023

dnf -y install https://extras.getpagespeed.com/release-latest.rpm
dnf -y install lua5.1-resty-prettycjson

To use this Lua library with NGINX, ensure that nginx-module-lua is installed.

This document describes lua-resty-prettycjson v1.6 released on Sep 29 2016.

---

lua-resty-prettycjson is a JSON Pretty Formatter for Lua cJSON.

Lua API

string function(dt, [lf = "\n", [id = "\t", [ac = " ", [ec = function]]]])

Pretty formats the JSON output. You may pass lf (line feed) if you want to use different linefeed than the default \n. If you want to indent (id argument) with something else than \t (a tab) you can pass that as arguments as well. And if you want to have something else than (single space) after colons : (ac argument) in json, you can change that as well, try for example \n. If you'd like to use an encoder other than cJSON, pass the encoding function as the 5th argument (ec). It should accept anything as input parameter, and if there is a problem with encoding this function should return nil and an error message, such as:

nil, "Cannot serialise function: type not supported"

For input argument dt it accepts anything that cjson.encode accepts (or whatever the custom encoding function accepts).

Example

local pretty = require "resty.prettycjson"

print(pretty({
    key1 = "data",
    key2 = 27,
    key3 = {
        key3_1 = "something",
        key3_2 = "something else"
    },
    key4 = {
        "item1",
        "item2"
    },
    key5 = {},
    key5 = {{''}, {'',''}, {{},{}}},
    key6 = { '' },
    key7 = {{{{ test = "value", {{{{{{}}},{{},{},{}},{},{}}}}}}}}
}))

That will output:

{
    "key6": [
        ""
    ],
    "key3": {
        "key3_1": "something",
        "key3_2": "something else"
    },
    "key7": [
        [
            [
                {
                    "1": [
                        [
                            [
                                [
                                    [
                                        {}
                                    ]
                                ],
                                [
                                    {},
                                    {},
                                    {}
                                ],
                                {},
                                {}
                            ]
                        ]
                    ],
                    "test": "value"
                }
            ]
        ]
    ],
    "key1": "data",
    "key5": [
        [
            ""
        ],
        [
            "",
            ""
        ],
        [
            {},
            {}
        ]
    ],
    "key2": 27,
    "key4": [
        "item1",
        "item2"
    ]
}

Changes

The changes of every release of this module is recorded in Changes.md file.

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-prettycjson.