Queue: Make WorkerPools and Queues flushable (#10001)

* Make WorkerPools and Queues flushable

Adds Flush methods to Queues and the WorkerPool
Further abstracts the WorkerPool
Adds a final step to Flush the queues in the defer from PrintCurrentTest
Fixes an issue with Settings inheritance in queues

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Change to for loop

* Add IsEmpty and begin just making the queues composed WorkerPools

* subsume workerpool into the queues and create a flushable interface

* Add manager command

* Move flushall to queue.Manager and add to testlogger

* As per @guillep2k

* as per @guillep2k

* Just make queues all implement flushable and clean up the wrapped queue flushes

* cope with no timeout

Co-authored-by: Lauris BH <lauris@nix.lv>

modules/queue/helper.go

@@ -0,0 +1,63 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package queue
+
+import (
+	"encoding/json"
+	"reflect"
+)
+
+// toConfig will attempt to convert a given configuration cfg into the provided exemplar type.
+//
+// It will tolerate the cfg being passed as a []byte or string of a json representation of the
+// exemplar or the correct type of the exemplar itself
+func toConfig(exemplar, cfg interface{}) (interface{}, error) {
+	if reflect.TypeOf(cfg).AssignableTo(reflect.TypeOf(exemplar)) {
+		return cfg, nil
+	}
+
+	configBytes, ok := cfg.([]byte)
+	if !ok {
+		configStr, ok := cfg.(string)
+		if !ok {
+			return nil, ErrInvalidConfiguration{cfg: cfg}
+		}
+		configBytes = []byte(configStr)
+	}
+	newVal := reflect.New(reflect.TypeOf(exemplar))
+	if err := json.Unmarshal(configBytes, newVal.Interface()); err != nil {
+		return nil, ErrInvalidConfiguration{cfg: cfg, err: err}
+	}
+	return newVal.Elem().Interface(), nil
+}
+
+// unmarshalAs will attempt to unmarshal provided bytes as the provided exemplar
+func unmarshalAs(bs []byte, exemplar interface{}) (data Data, err error) {
+	if exemplar != nil {
+		t := reflect.TypeOf(exemplar)
+		n := reflect.New(t)
+		ne := n.Elem()
+		err = json.Unmarshal(bs, ne.Addr().Interface())
+		data = ne.Interface().(Data)
+	} else {
+		err = json.Unmarshal(bs, &data)
+	}
+
+	return
+}
+
+// assignableTo will check if provided data is assignable to the same type as the exemplar
+// if the provided exemplar is nil then it will always return true
+func assignableTo(data Data, exemplar interface{}) bool {
+	if exemplar == nil {
+		return true
+	}
+
+	// Assert data is of same type as exemplar
+	t := reflect.TypeOf(data)
+	exemplarType := reflect.TypeOf(exemplar)
+
+	return t.AssignableTo(exemplarType) && data != nil
+}