feat: pass error as parameter to fallback function (#197)

Fixes: #196
nodeshift · May 24, 2018 · ae6c1cc · ae6c1cc
1 parent d1b71ab
commit ae6c1cc
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/lib/circuit.js b/lib/circuit.js
@@ -465,7 +465,7 @@ function handleError (error, circuit, timeout, args, latency, resolve, reject) {
 function fallback (circuit, err, args) {
   if (circuit[FALLBACK_FUNCTION]) {
     const result =
-      circuit[FALLBACK_FUNCTION].apply(circuit[FALLBACK_FUNCTION], args);
+      circuit[FALLBACK_FUNCTION].apply(circuit[FALLBACK_FUNCTION], [...args, err]);
     /**
      * Emitted when the circuit breaker executes a fallback function
      * @event CircuitBreaker#fallback

diff --git a/test/test.js b/test/test.js
@@ -260,6 +260,18 @@ test('Executes fallback action, if one exists, when breaker is open', t => {
     });
 });
 
+test('Passes error as last argument to the fallback function', t => {
+  t.plan(1);
+  const fails = -1;
+  const breaker = circuit(passFail, { errorThresholdPercentage: 1 });
+  breaker.on('fallback', result => {
+    t.equals(result, `Error: ${fails} is < 0`, 'fallback received error as last parameter');
+    t.end();
+  });
+  breaker.fallback((x, e) => e);
+  breaker.fire(fails).catch(t.fail);
+});
+
 test('Passes arguments to the fallback function', t => {
   t.plan(1);
   const fails = -1;