interpolation pattern should always be a global regexp, not a string

Author: akmjenkins

Diff for: src/engine.js

@@ -24,8 +24,8 @@ class Engine extends EventEmitter {
     this.rules = []
     this.allowUndefinedFacts = options.allowUndefinedFacts || false
     this.pathResolver = options.pathResolver || defaultPathResolver
-    const interpolation = options.interpolation || defaultInterpolation;
-    this.interpolation = typeof interpolation === 'string' ? new RegExp(interpolation) : interpolation;
+    this.interpolation = options.interpolation || defaultInterpolation;
+    if(!(this.interpolation instanceof RegExp) || !this.interpolation.global) throw new Error('interpolation option must be a global regexp')
     this.operators = new Map()
     this.facts = new Map()
     this.status = READY

Diff for: types/index.d.ts

@@ -1,7 +1,7 @@
 export interface EngineOptions {
   allowUndefinedFacts?: boolean;
   pathResolver?: PathResolver;
-  interpolation?: RegExp | string;
+  interpolation?: RegExp;
 }
 
 export interface EngineResult {