Move undefined fact detection to almanac.factValue

Author: Cache Hamm

src/almanac.js

@@ -38,11 +38,7 @@ export default class Almanac {
    * @return {Fact}
    */
   _getFact (factId) {
-    let fact = this.factMap.get(factId)
-    if (fact === undefined) {
-      throw new UndefinedFactError(`Undefined fact: ${factId}`)
-    }
-    return fact
+    return this.factMap.get(factId)
   }
 
   /**
@@ -90,6 +86,9 @@ export default class Almanac {
   factValue (factId, params = {}, path = '') {
     let factValuePromise
     let fact = this._getFact(factId)
+    if (fact === undefined) {
+      return Promise.reject(new UndefinedFactError(`Undefined fact: ${factId}`))
+    }
     if (fact.isConstant()) {
       factValuePromise = Promise.resolve(fact.calculate(params, this))
     } else {

test/almanac.test.js

@@ -51,7 +51,7 @@ describe('Almanac', () => {
     })
 
     it('throws an exception if it encounters an undefined fact', () => {
-      return expect(almanac.factValue('bar')).to.eventually.be.rejectedWith(/Undefined fact: bar/)
+      return expect(almanac.factValue('bar')).to.be.rejectedWith(/Undefined fact: bar/)
     })
   })
 
@@ -80,11 +80,6 @@ describe('Almanac', () => {
       almanac = new Almanac(facts)
       expect(almanac._getFact('id')).to.equal(fact)
     })
-
-    it('raises an exception if fact DNE', () => {
-      almanac = new Almanac(new Map())
-      expect(almanac._getFact.bind(almanac, 'unknown')).to.throw(/Undefined fact/)
-    })
   })
 
   describe('_setFactValue()', () => {