Firstsawyou/lua-resty-expr

lua-resty-expr

Name

A tiny DSL to evaluate expressions which is used inside of APISIX.

This project has been working in microservices API gateway Apache APISIX.

The project is open sourced by Shenzhen ZhiLiu Technology Co., Ltd.

In addition to this open source version, our company also provides a more powerful and performing commercial version, and provides technical support. If you are interested in our commercial version, please contact us.

Table of Contents

• lua-resty-expr
  • Name
  • Synopsis
  • Methods
    • new
      • Operator List
    • eval
  • Install
    • Compile and install
  • DEV ENV
    • Install Dependencies

Synopsis

 location / {
     content_by_lua_block {
        local expr = require("resty.expr.v1")
        local ex = expr.new({
            {
                {"arg_name", "==", "json"},
                {"arg_weight", ">", 10},
                {"arg_weight", "!", ">", 15},
            }
        })

        -- equal to
        -- 'ngx.say(ngx.var.arg_name == "json" and ngx.var.arg_weight > 10 and not ngx.var.arg_weight > 15)'
        ngx.say(ex:eval(ngx.var))
     }
 }

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Methods

new

syntax: ex, err = expr.new(rule)

Create a expression object which can be evaluated later.

The syntax of rule is an array table of expressions. Each expression is an array table which has three elements:

{
    {"var name (aka. left value)", "optional '!' operator", "operator", "const value (aka. right value)"},
    ...
}

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Operator List

operator	description	example
==	equal	{"arg_name", "==", "json"}
~=	not equal	{"arg_name", "~=", "json"}
>	greater than	{"arg_age", ">", 24}
<	less than	{"arg_age", "<", 24}
~~	Regular match	{"arg_name", "~~", "[a-z]+"}
~*	Case insensitive regular match	{"arg_name", "~*", "[a-z]+"}
in	find in array	{"arg_name", "in", {"1","2"}}
has	left value array has value in the right	{"graphql_root_fields", "has", "repo"}
!	reverse the result	{"arg_name", "!", "~~", "[a-z]+"}

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eval

syntax: ok, err = ex:eval(ctx)

Evaluate the expression according to the ctx. If ctx is missing, ngx.var is used by default.

local ok = rx:eval()
if ok == nil then
    log_err("failed to eval expression: ", err)
    return false
end

return ok

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Install

Compile and install

make install

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DEV ENV

Install Dependencies

make deps

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