fact params is not working when I am using fact in evaluationDetails > currentValue

[dlsemwal]

I am using these params to create a rule. When rule is failing I want it to return currentValue by resolving fact documentsCount . Although It is resolving this fact documentsCount but not with the params which I passed. The params receiving params in fact fact resolver is {}.

{
            baseNumber: 1,
            evaluationDetails: {
                code: "RuleEventErrorCode",
                currentValue: {
                    fact: "documentsCount",
                    params: {
                      status: "approved",
                      hasPayments: true,
                      
                },
                },
                message: 'The documents number does not meet the requirements',
                targetValue: {
                    fact: "stdDocCount",
                },
            }
        };

[AayushOjha]

Hi @dlsemwal, I looked into this and was able to reproduce the issue. It behaves a little differently from what was originally described though.

What's actually happening: Fact references inside nested event.params are never resolved, regardless of whether they have params or not. The params: {} you saw in your resolver was most likely coming from another place (for example, the rule conditions), not from currentValue.

Minimal repro (v7.3.2, replaceFactsInEventParams: true):

const { Engine } = require('json-rules-engine')

const engine = new Engine([], { replaceFactsInEventParams: true })

engine.addFact('documentsCount', (params) => {
  console.log('resolver params:', params)
  return 3
})
engine.addFact('stdDocCount', () => 5)

engine.addRule({
  conditions: {
    all: [{ fact: 'documentsCount', params: { status: 'approved' }, operator: 'greaterThanInclusive', value: { fact: 'stdDocCount' } }]
  },
  event: {
    type: 'RuleEventErrorCode',
    params: {
      // top-level fact reference — resolved correctly, params reach the resolver ✓
      topLevelCount: { fact: 'documentsCount', params: { status: 'approved' } },
      // nested fact reference (as in this issue) — returned as-is, never resolved ✗
      evaluationDetails: {
        currentValue: { fact: 'documentsCount', params: { status: 'approved' } },
        targetValue: { fact: 'stdDocCount' }
      }
    }
  }
})

engine.run().then(({ failureEvents }) => console.dir(failureEvents[0].params, { depth: null }))

Output:

{
  topLevelCount: 3,                                    // resolved
  evaluationDetails: {
    currentValue: { fact: 'documentsCount', params: { status: 'approved' } },  // untouched
    targetValue: { fact: 'stdDocCount' }               // untouched
  }
}

Root cause: RuleResult.resolveEventParams (src/rule-result.js#L18) only loops over the top-level properties in event.params. almanac.getValue already handles params correctly, but it's only called for top-level values. So if a { fact: ... } reference is nested deeper, it never gets resolved.

Proposed fix: Update resolveEventParams to walk through event.params recursively. It would traverse plain objects and arrays, and whenever it finds a { fact: ... } object, it resolves it and stops traversing that branch (so the fact's own params stay untouched). This doesn't require a new API, stays behind the existing replaceFactsInEventParams flag, and doesn't change the current top-level behaviour.

The only possible behaviour change is for anyone who was intentionally relying on nested { fact: ... } objects being left untouched when this flag is enabled. If that's a concern, we could introduce a separate opt-in (something like replaceFactsInEventParams: 'deep'). Personally, I think recursive resolution matches what this flag was always expected to do.

@chris-pardy does that sound reasonable? If so, I'm happy to open a PR with the fix and add a test case based on the example from this issue.