v2 bug: Value does not work with TimestampFlag

[vschettino]

my urfave/cli version is

2.2.0

Checklist

• Are you running the latest v2 release? The list of releases is here.
• Did you check the manual for your release? The v2 manual is here
• Did you perform a search about this problem? Here's the Github guide about searching.

Dependency Management

• My project is using go modules.
• My project is using vendoring.
• My project is automatically downloading the latest version.
• I am unsure of what my dependency management setup is.

Describe the bug

Passing a Value to TimestampFlag does nothing.

To reproduce

package main

import (
	"fmt"
	"github.com/urfave/cli/v2"
	"log"
	"os"
	"time"
)

func main() {
	var today = cli.NewTimestamp(time.Now())
	app := &cli.App{
		Commands: []*cli.Command{{
			Name: "sync",
			Flags: []cli.Flag{
				&cli.TimestampFlag{
					Name:   "from",
					Layout: "2006-01-02",
					Value:  today,
				},
			},
			Action: func(c *cli.Context) error {
				fmt.Println(c.Timestamp("from"))
				return nil
			},
		}},
	}
	err := app.Run(os.Args)
	if err != nil {
		log.Fatal(err)
	}
}

go install && go mymodule sync

Describe the steps or code required to reproduce the behavior

Observed behavior

"from" flag is <nil>

Expected behavior

The Value (today) would be printed, as it works with other types of flag, such as IntFlag.

Additional context

Docker build and run

Want to fix this yourself?

I'd love to help. Can you guys confirm this and give me some directions about how to proceed?

Run go version and paste its output here

go version go1.14.2 linux/amd64

Run go env and paste its output here

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="0"
GOMOD="/exfin/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build096471754=/tmp/go-build -gno-record-gcc-switches"

[aloababa]

I guess it's because of this: https://github.com/urfave/cli/blob/master/flag_timestamp.go#L121
Default value always gets override.
So i think this can be fixed by adding an if like:

if f.Value == nil {
	f.Value = &Timestamp{}
}

[vschettino]

@aloababa yes, seems like this is the place. Thanks for pointing out! I will open a PR to fix this on the weekend.

[coilysiren]

Sounds good, cc me when you're ready for a review ^^

[vschettino]

@lynncyrin do you guys need any help on other issues? I saw a few that might be stale but I don't wanna to intrude ^^

[coilysiren]

Yes we could totally use help with stale or help wanted issues 👍