allowUndefinedFacts not working when the facts type are string

首先使用 Engine.run、空的 facts 对象并启用 allowUndefinedFacts 运行提供的复现，然后跟踪 notEqual 运算符如何处理 undefined fact Astring 与数值 fact Bnumber。两种 fact 类型下该选项的行为一致，并且复现产生文档中记录的预期结果，即表示完成。

Here's my example, you can reproduce the issue with the code:
const customAttributeRule = { "name": "allowUndefinedFacts-test", "attributes": [ { "name": "Astring", "type": "string" }, { "name": "Bnumber", "type": "number" } ], "decisions": [ { "conditions": { "all": [ { "fact": "Astring", "operator": "notEqual", "value": "string" } ] }, "event": { "type": "Astring", "params": { "value": "1", "description": "Astring test" } } }, { "conditions": { "all": [ { "fact": "Bnumber", "operator": "lessThan", "value": 5 } ] }, "event": { "type": "Bnumber", "params": { "value": "1", "description": "Bnumber test" } } } ] }
let facts = {}
const engine = new Engine(customAttributeRule.decisions, {allowUndefinedFacts: true}); engine.on('success', event => { console.log(event) });
let result = engine .run(facts)
The engine output is
{ type: 'Astring', params: { value: '1', description: 'Astring test' } }
However, the allowUndefinedFacts works when then fact type is number

Since the engine treat undefined facts as undefined, so I added another condition that { "fact": "Astring", "operator": "notEqual", "value": "undefined" }, but it still does not work as expected