Runtime rules engine ⚙️ (#249)

* extract var for test values

* mark old runtime rules as legacy

* succint flag setup to one line

* DRY tests with helper - more succint

* DRY context creation for runtime

* use random string for clarity on wrong values

* DRY fallback

* runtime rule negative case ❌

* add stopgap positive test case (doesn't fail)

* import jsonLogic and evaluate runtime rule ✅

* caseinsensitive to parameters

Still need caseinsensitive on rule

* case-insensitivity ✅

* add complex rule test-cases ✅

* consistent runtime rule test names

* add error handling for garbled jsonlogic

* add multi-condition case-insensitive check

* pretty

* Apply simple suggestions from code review

Co-authored-by: teddddd <ted@mixpanel.com>

* prevent randomString() from accidental matches

* consolidate lowercasing of json objects

* assert that variant is returned, not just NOT fallback

* dry variant-returned assertion

* add test for case-insensitive runtime param keys

* add "in" negative case for substring & superstring

* prettier

* Update test/flags/local_flags.js

* move helper func to top of test file

* prettier

Author: joshua-koehler

lib/flags/local_flags.js

@@ -12,7 +12,12 @@
  * */
 
 const FeatureFlagsProvider = require("./flags");
-const { normalizedHash } = require("./utils");
+const {
+  normalizedHash,
+  lowercaseAllKeysAndValues,
+  lowercaseLeafNodes,
+} = require("./utils");
+const { apply } = require("json-logic-js");
 
 class LocalFeatureFlagsProvider extends FeatureFlagsProvider {
   /**
@@ -316,13 +321,39 @@ class LocalFeatureFlagsProvider extends FeatureFlagsProvider {
     };
   }
 
+  _extractRuntimeParameters(context) {
+    const customProperties = context.custom_properties;
+    if (!customProperties || typeof customProperties !== "object") {
+      return null;
+    }
+    return lowercaseAllKeysAndValues(customProperties);
+  }
+
+  _isRuntimeRuleSatisfied(rollout, context) {
+    try {
+      return apply(
+        lowercaseLeafNodes(rollout.runtime_evaluation_rule),
+        this._extractRuntimeParameters(context),
+      );
+    } catch (error) {
+      this.logger?.error(`Error evaluating runtime rule: ${error.message}`);
+      return false;
+    }
+  }
+
   _isRuntimeEvaluationSatisfied(rollout, context) {
-    if (!rollout.runtime_evaluation_definition) {
+    if (rollout.runtime_evaluation_rule) {
+      return this._isRuntimeRuleSatisfied(rollout, context);
+    } else if (rollout.runtime_evaluation_definition) {
+      return this._isLegacyRuntimeEvaluationSatisfied(rollout, context);
+    } else {
       return true;
     }
+  }
 
-    const customProperties = context.custom_properties;
-    if (!customProperties || typeof customProperties !== "object") {
+  _isLegacyRuntimeEvaluationSatisfied(rollout, context) {
+    const customProperties = this._extractRuntimeParameters(context);
+    if (!customProperties) {
       return false;
     }
 

lib/flags/utils.js

@@ -70,10 +70,41 @@ function generateTraceparent() {
   return `${version}-${traceId}-${parentId}-${traceFlags}`;
 }
 
+function lowercaseJson(obj, lowercaseKeys) {
+  if (obj === null || obj === undefined) {
+    return obj;
+  } else if (typeof obj === "string") {
+    return obj.toLowerCase();
+  } else if (typeof obj === "object") {
+    if (Array.isArray(obj)) {
+      return obj.map((item) => lowercaseJson(item, lowercaseKeys));
+    } else {
+      return Object.fromEntries(
+        Object.entries(obj).map(([k, v]) => [
+          lowercaseKeys ? k.toLowerCase() : k,
+          lowercaseJson(v, lowercaseKeys),
+        ]),
+      );
+    }
+  } else {
+    return obj;
+  }
+}
+
+function lowercaseAllKeysAndValues(obj) {
+  return lowercaseJson(obj, true);
+}
+
+function lowercaseLeafNodes(obj) {
+  return lowercaseJson(obj, false);
+}
+
 module.exports = {
   EXPOSURE_EVENT,
   REQUEST_HEADERS,
   normalizedHash,
   prepareCommonQueryParams,
   generateTraceparent,
+  lowercaseAllKeysAndValues,
+  lowercaseLeafNodes,
 };

package-lock.json

@@ -40,6 +40,7 @@
     "vitest": "^4.0.8"
   },
   "dependencies": {
-    "https-proxy-agent": "7.0.6"
+    "https-proxy-agent": "7.0.6",
+    "json-logic-js": "2.0.5"
   }
 }