fix: try to use custom function name first

pick from #2156

app/extend/context.js

@@ -196,8 +196,9 @@ const proto = module.exports = {
   runInBackground(scope) {
     const ctx = this;
     const start = Date.now();
+    // try to use custom function name first
     /* istanbul ignore next */
-    const taskName = scope.name || scope._name || eggUtils.getCalleeFromStack(true);
+    const taskName = scope._name || scope.name || eggUtils.getCalleeFromStack(true);
     // use app.toAsyncFunction to support both generator function and async function
     ctx.app.toAsyncFunction(scope)(ctx)
       .then(() => {

test/app/extend/context.test.js

@@ -250,6 +250,20 @@ describe('test/app/extend/context.test.js', () => {
       );
     });
 
+    it('should use custom task name first', async () => {
+      await app.httpRequest()
+        .get('/custom')
+        .expect(200)
+        .expect('hello');
+      await sleep(5000);
+      const logdir = app.config.logger.dir;
+      const log = fs.readFileSync(path.join(logdir, 'ctx-background-web.log'), 'utf8');
+      assert(/background run result file size: \d+/.test(log));
+      assert(
+        /\[egg:background] task:customTaskName success \(\d+ms\)/.test(fs.readFileSync(path.join(logdir, 'egg-web.log'), 'utf8'))
+      );
+    });
+
     it('should run background task error', async () => {
       mm.consoleLevel('NONE');
       await app.httpRequest()

test/fixtures/apps/ctx-background/app/controller/custom.js

@@ -0,0 +1,13 @@
+'use strict';
+
+const fs = require('mz/fs');
+
+module.exports = function* () {
+  this.body = 'hello';
+  const fn = function* saveUserInfo(ctx) {
+    const buf = yield fs.readFile(__filename);
+    ctx.logger.warn('background run result file size: %s', buf.length);
+  };
+  fn._name = 'customTaskName';
+  this.runInBackground(fn);
+};

test/fixtures/apps/ctx-background/app/router.js

@@ -2,6 +2,7 @@
 
 module.exports = app => {
   app.get('/', app.controller.home);
+  app.get('/custom', app.controller.custom);
   app.get('/app_background', app.controller.app);
   app.get('/error', app.controller.error);
 };