Fix isFeatureEnabled to handle unknown features gracefully

index.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const SilentError = require('silent-error');
+const chalk = require('chalk');
 
 const FEATURES = require('./features');
 const getConfigPath = require('./utils').getConfigPath;
@@ -65,7 +66,19 @@ module.exports = {
 
   isFeatureEnabled(name) {
     let value = this._features[name];
-    return value !== undefined ? value : FEATURES[name].default;
+    if (value !== undefined) {
+      return value;
+    }
+    let feature = FEATURES[name];
+    if (feature === undefined) {
+      console.warn(
+        chalk.yellow(
+          `Warning: Unknown feature "${name}" passed to isFeatureEnabled`
+        )
+      );
+      return null;
+    }
+    return feature.default;
   },
 
   isFeatureExplicitlySet(name) {

tests/optional-features-test.js

@@ -150,6 +150,29 @@ QUnit.module('@ember/optional-features', (hooks) => {
     );
   });
 
+  QUnit.test(
+    'it warns and returns null for unknown feature in isFeatureEnabled',
+    (assert) => {
+      let addon = buildAddon({});
+      let originalWarn = console.warn;
+      let warningMessage = null;
+      console.warn = (msg) => {
+        warningMessage = msg;
+      };
+      try {
+        let result = addon.isFeatureEnabled('unknown-feature');
+        assert.strictEqual(result, null, 'Expecting null for unknown feature');
+        assert.ok(
+          warningMessage &&
+            warningMessage.includes('Unknown feature "unknown-feature"'),
+          'Should warn about unknown feature'
+        );
+      } finally {
+        console.warn = originalWarn;
+      }
+    }
+  );
+
   QUnit.test(
     'it can query the features with `isFeatureExplicitlySet`',
     (assert) => {