Update Option interface

- Added `String()`, `Type()`, and `Value()` methods to the interface to
  aid with debugging and error handling.

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- interface `Option` has changed. See the godoc for the new interface.
+  This change would have no impact as long as you are using exported functions (e.g. `MaxRetry`, `Queue`, etc)
+  to create `Option`s.
+
 ### Added
 
 - `Payload.String() string`  method is added

client.go

@@ -37,8 +37,29 @@ func NewClient(r RedisConnOpt) *Client {
 	}
 }
 
+type OptionType int
+
+const (
+	MaxRetryOpt OptionType = iota
+	QueueOpt
+	TimeoutOpt
+	DeadlineOpt
+	UniqueOpt
+	ProcessAtOpt
+	ProcessInOpt
+)
+
 // Option specifies the task processing behavior.
-type Option interface{}
+type Option interface {
+	// String returns a string representation of the option.
+	String() string
+
+	// Type describes the type of the option.
+	Type() OptionType
+
+	// Value returns a value used to create this option.
+	Value() interface{}
+}
 
 // Internal option representations.
 type (
@@ -62,13 +83,21 @@ func MaxRetry(n int) Option {
 	return retryOption(n)
 }
 
+func (n retryOption) String() string     { return fmt.Sprintf("MaxRetry(%d)", int(n)) }
+func (n retryOption) Type() OptionType   { return MaxRetryOpt }
+func (n retryOption) Value() interface{} { return n }
+
 // Queue returns an option to specify the queue to enqueue the task into.
 //
 // Queue name is case-insensitive and the lowercased version is used.
-func Queue(name string) Option {
-	return queueOption(strings.ToLower(name))
+func Queue(qname string) Option {
+	return queueOption(strings.ToLower(qname))
 }
 
+func (qname queueOption) String() string     { return fmt.Sprintf("Queue(%q)", string(qname)) }
+func (qname queueOption) Type() OptionType   { return QueueOpt }
+func (qname queueOption) Value() interface{} { return qname }
+
 // Timeout returns an option to specify how long a task may run.
 // If the timeout elapses before the Handler returns, then the task
 // will be retried.
@@ -81,6 +110,10 @@ func Timeout(d time.Duration) Option {
 	return timeoutOption(d)
 }
 
+func (d timeoutOption) String() string     { return fmt.Sprintf("Timeout(%v)", time.Duration(d)) }
+func (d timeoutOption) Type() OptionType   { return TimeoutOpt }
+func (d timeoutOption) Value() interface{} { return d }
+
 // Deadline returns an option to specify the deadline for the given task.
 // If it reaches the deadline before the Handler returns, then the task
 // will be retried.
@@ -91,6 +124,10 @@ func Deadline(t time.Time) Option {
 	return deadlineOption(t)
 }
 
+func (t deadlineOption) String() string     { return fmt.Sprintf("Deadline(%v)", time.Time(t)) }
+func (t deadlineOption) Type() OptionType   { return DeadlineOpt }
+func (t deadlineOption) Value() interface{} { return t }
+
 // Unique returns an option to enqueue a task only if the given task is unique.
 // Task enqueued with this option is guaranteed to be unique within the given ttl.
 // Once the task gets processed successfully or once the TTL has expired, another task with the same uniqueness may be enqueued.
@@ -104,6 +141,10 @@ func Unique(ttl time.Duration) Option {
 	return uniqueOption(ttl)
 }
 
+func (ttl uniqueOption) String() string     { return fmt.Sprintf("Unique(%v)", time.Duration(ttl)) }
+func (ttl uniqueOption) Type() OptionType   { return UniqueOpt }
+func (ttl uniqueOption) Value() interface{} { return ttl }
+
 // ProcessAt returns an option to specify when to process the given task.
 //
 // If there's a conflicting ProcessIn option, the last option passed to Enqueue overrides the others.
@@ -111,6 +152,10 @@ func ProcessAt(t time.Time) Option {
 	return processAtOption(t)
 }
 
+func (t processAtOption) String() string     { return fmt.Sprintf("ProcessAt(%v)", time.Time(t)) }
+func (t processAtOption) Type() OptionType   { return ProcessAtOpt }
+func (t processAtOption) Value() interface{} { return t }
+
 // ProcessIn returns an option to specify when to process the given task relative to the current time.
 //
 // If there's a conflicting ProcessAt option, the last option passed to Enqueue overrides the others.
@@ -118,6 +163,10 @@ func ProcessIn(d time.Duration) Option {
 	return processInOption(d)
 }
 
+func (d processInOption) String() string     { return fmt.Sprintf("ProcessIn(%v)", time.Duration(d)) }
+func (d processInOption) Type() OptionType   { return ProcessInOpt }
+func (d processInOption) Value() interface{} { return d }
+
 // ErrDuplicateTask indicates that the given task could not be enqueued since it's a duplicate of another task.
 //
 // ErrDuplicateTask error only applies to tasks enqueued with a Unique option.

internal/base/base.go

@@ -299,7 +299,7 @@ type SchedulerEntry struct {
 	Payload map[string]interface{}
 
 	// Opts is the options for the periodic task.
-	Opts string
+	Opts []string
 
 	// Next shows the next time the task will be enqueued.
 	Next time.Time

scheduler.go

@@ -7,7 +7,6 @@ package asynq
 import (
 	"fmt"
 	"os"
-	"strings"
 	"sync"
 	"time"
 
@@ -222,27 +221,10 @@ func (s *Scheduler) beat() {
 	}
 }
 
-func stringifyOptions(opts []Option) string {
+func stringifyOptions(opts []Option) []string {
 	var res []string
 	for _, opt := range opts {
-		switch opt := opt.(type) {
-		case retryOption:
-			res = append(res, fmt.Sprintf("MaxRetry(%d)", int(opt)))
-		case queueOption:
-			res = append(res, fmt.Sprintf("Queue(%q)", string(opt)))
-		case timeoutOption:
-			res = append(res, fmt.Sprintf("Timeout(%v)", time.Duration(opt)))
-		case deadlineOption:
-			res = append(res, fmt.Sprintf("Deadline(%v)", time.Time(opt)))
-		case uniqueOption:
-			res = append(res, fmt.Sprintf("Unique(%v)", time.Duration(opt)))
-		case processAtOption:
-			res = append(res, fmt.Sprintf("ProcessAt(%v)", time.Time(opt)))
-		case processInOption:
-			res = append(res, fmt.Sprintf("ProcessIn(%v)", time.Duration(opt)))
-		default:
-			// ignore unexpected option
+		res = append(res, opt.String())
 	}
-	}
-	return strings.Join(res, ", ")
+	return res
 }

scheduler_test.go

@@ -5,7 +5,6 @@
 package asynq
 
 import (
-	"fmt"
 	"testing"
 	"time"
 
@@ -77,37 +76,3 @@ func TestScheduler(t *testing.T) {
 		}
 	}
 }
-
-func TestStringifyOptions(t *testing.T) {
-	now := time.Now()
-	oneHourFromNow := now.Add(1 * time.Hour)
-	twoHoursFromNow := now.Add(2 * time.Hour)
-	tests := []struct {
-		opts []Option
-		want string
-	}{
-		{
-			opts: []Option{MaxRetry(10)},
-			want: "MaxRetry(10)",
-		},
-		{
-			opts: []Option{Queue("custom"), Timeout(1 * time.Minute)},
-			want: `Queue("custom"), Timeout(1m0s)`,
-		},
-		{
-			opts: []Option{ProcessAt(oneHourFromNow), Deadline(twoHoursFromNow)},
-			want: fmt.Sprintf("ProcessAt(%v), Deadline(%v)", oneHourFromNow, twoHoursFromNow),
-		},
-		{
-			opts: []Option{ProcessIn(30 * time.Minute), Unique(1 * time.Hour)},
-			want: "ProcessIn(30m0s), Unique(1h0m0s)",
-		},
-	}
-
-	for _, tc := range tests {
-		got := stringifyOptions(tc.opts)
-		if got != tc.want {
-			t.Errorf("got %v, want %v", got, tc.want)
-		}
-	}
-}