Merge lp:~chipaca/ubuntu-push/conflag-maybe into lp:ubuntu-push

[John Lenton]

Toying with the idea of doing this.

With it, let's say you have a little program `conflag.go` that looked like

    package main

    import (
            "flag"
            "launchpad.net/ubuntu-push/config"
            "os"
            "fmt"
            "log"
    )

    type Config struct {
            Stuff string `help:"Blah blah"`
            SomeTimeout config.ConfigTimeDuration `json:"some_timeout" help:"How long to wait."`
    }

    func main() {
            cfgFName := "config.json"
            cfgF, err := os.Open(cfgFName)
            if err != nil {
                    log.Fatal(err)
            }
            cfg := &Config{}
            err = config.ReadConfig(cfgF, cfg)
            if err != nil {
                    log.Fatal(err)
            }
            flag.Parse()
            fmt.Println(cfg)
    }

and a `config.json` that looked like

    { "stuff": "Yackity yack", "some_timeout": "2s" }

then

    $ ./conflag -help
    Usage of ./conflag:
      -some_timeout=2s: How long to wait.
      -stuff="Yackity yack": Blah blah

    $ ./conflag
    &{Yackity yack 2s}
    $ ./conflag -some_timeout=42m
    &{Yackity yack 42m0s}

[Samuele Pedroni (pedronis)]

I was thinking of trying something similar at some point

in this form is mostly missing tests,

and I wonder if allowing for supplying things with the command line means it's ok if they are left out from the config? or it the idea that the config should have defaults?

doing the former needs two passes over the values though,

should the functionality be opt-in?

btw flag supports TimeDuration flags, wondering if it means there's a way not to have to turn ConfigTimeDuration in a Value

review: Needs Fixing

Unmerged revisions

29. By John Lenton on 2014-01-29

hmm... maybe.

=== modified file 'config/config.go'
--- config/config.go	2014-01-21 21:35:21 +0000
+++ config/config.go	2014-01-29 00:24:21 +0000
@@ -20,6 +20,7 @@
 import (
 	"encoding/json"
 	"errors"
+	"flag"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -90,6 +91,18 @@
 		if err != nil {
 			return fmt.Errorf("%s: %v", configName, err)
 		}
+		help := fld.Tag.Get("help")
+		switch dest.(type) {
+		default:
+			val, ok := dest.(flag.Value)
+			if ok {
+				flag.Var(val, configName, help)
+			}
+		case *string:
+			flag.StringVar(dest.(*string), configName, *(dest.(*string)), help)
+		case *int:
+			flag.IntVar(dest.(*int), configName, *(dest.(*int)), help)
+		}
 	}
 	return nil
 }
@@ -121,12 +134,15 @@
 
 func (ctd *ConfigTimeDuration) UnmarshalJSON(b []byte) error {
 	var enc string
-	var v time.Duration
 	err := json.Unmarshal(b, &enc)
 	if err != nil {
 		return err
 	}
-	v, err = time.ParseDuration(enc)
+	return ctd.Set(enc)
+}
+
+func (ctd *ConfigTimeDuration) Set(enc string) error {
+	v, err := time.ParseDuration(enc)
 	if err != nil {
 		return err
 	}
@@ -148,7 +164,11 @@
 	if err != nil {
 		return err
 	}
-	_, _, err = net.SplitHostPort(enc)
+	return chp.Set(enc)
+}
+
+func (chp *ConfigHostPort) Set(enc string) error {
+	_, _, err := net.SplitHostPort(enc)
 	if err != nil {
 		return err
 	}
@@ -156,6 +176,10 @@
 	return nil
 }
 
+func (chp *ConfigHostPort) String() string {
+	return string(*chp)
+}
+
 // HostPort returns the host:port string held in chp.
 func (chp ConfigHostPort) HostPort() string {
 	return string(chp)
@@ -177,6 +201,14 @@
 	return nil
 }
 
+func (cqs *ConfigQueueSize) Set(value string) error {
+	return cqs.UnmarshalJSON([]byte(value))
+}
+
+func (cqs *ConfigQueueSize) String() string {
+	return string(uint(*cqs))
+}
+
 // QueueSize returns the queue size held in cqs.
 func (cqs ConfigQueueSize) QueueSize() uint {
 	return uint(cqs)
 
=== modified file 'config/config_test.go'
--- config/config_test.go	2014-01-21 21:35:21 +0000
+++ config/config_test.go	2014-01-29 00:24:21 +0000
@@ -18,6 +18,7 @@
 
 import (
 	"bytes"
+	"flag"
 	"io/ioutil"
 	. "launchpad.net/gocheck"
 	"os"
@@ -39,6 +40,10 @@
 	C []string `json:"c_list"`
 }
 
+func (s *configSuite) SetUpTest(c *C) {
+	flag.CommandLine = flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
+}
+
 func (s *configSuite) TestReadConfig(c *C) {
 	buf := bytes.NewBufferString(`{"a": 1, "b": "foo", "c_list": ["c", "d", "e"]}`)
 	var cfg testConfig1