Fix hook not checking if values are errors

README.md

@@ -66,6 +66,18 @@ processManager.loop(async () => {
 }, { interval: 600 });
 ```
 
+You can also return an object with an `interval` property to override the next interval.
+
+```javascript
+const processManager = require('process-manager');
+
+processManager.loop(async () => {
+  console.log(await client.getSomeInfo());
+
+  return { interval: 1000 };
+}, { interval: 600 });
+```
+
 ### on(fn)
 
 This lifecycle is used to get a function suited for using with an event emitter. It does not exit unless something goes wrong.

src/index.js

@@ -98,7 +98,7 @@ class ProcessManager {
       for (const result of results) {
         if (result instanceof TimeoutError) {
           this.log.warn(`Timeout: ${result.message}`);
-        } else if (result) {
+        } else if (result instanceof Error) {
           this.errors.push(result);
         }
       }
@@ -205,6 +205,10 @@ class ProcessManager {
     this.exit();
   }
 
+  /**
+   * Wait for output to flush.
+   */
+
   async flushOutput() {
     // Process stdout and stderr can be in non-blocking mode so writes to it may not be flushed when the process exits.
     // To ensure that all output is flushed before the process exits, we can write an empty string to stdout and stderr,

test/index.test.js

@@ -238,6 +238,13 @@ describe('ProcessManager', () => {
         },
         type
       });
+      processManager.addHook({
+        handler: () => {
+          // This should be ignored since it's not an Error instance.
+          return 'foo';
+        },
+        type
+      });
       processManager.configure({ timeout: 1 });
 
       expect(processManager.errors).toHaveLength(0);