From 1335a7022a9ebf6cc5f9568d0d5c31d384c1955e Mon Sep 17 00:00:00 2001
From: Balazs Nagy <julsevern@gmail.com>
Date: Sat, 9 Jul 2022 13:43:14 +0200
Subject: [PATCH] accept timezone for timestamps

---
 docs/v2/manual.md     | 13 +++++++++++++
 flag-spec.yaml        |  1 +
 flag_test.go          | 12 ++++++++++++
 flag_timestamp.go     | 18 +++++++++++++++++-
 godoc-current.txt     |  8 ++++++++
 zz_generated.flags.go |  2 ++
 6 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/docs/v2/manual.md b/docs/v2/manual.md
index ebff418cc6..475e047fdd 100644
--- a/docs/v2/manual.md
+++ b/docs/v2/manual.md
@@ -1413,6 +1413,19 @@ In this example the flag could be used like this:
 $ myapp --meeting 2019-08-12T15:04:05
 ```
 
+When the layout doesn't contain timezones, timestamp will render with UTC. To
+change behavior, a default timezone can be provided with flag definition:
+
+```go
+app := &cli.App{
+	Flags: []cli.Flag{
+		&cli.TimestampFlag{Name: "meeting", Layout: "2006-01-02T15:04:05", Timezone: time.Local},
+	},
+}
+```
+
+(time.Local contains the system's local time zone.)
+
 Side note: quotes may be necessary around the date depending on your layout (if
 you have spaces for instance)
 
diff --git a/flag-spec.yaml b/flag-spec.yaml
index d85fa30bd1..45f054d6e5 100644
--- a/flag-spec.yaml
+++ b/flag-spec.yaml
@@ -43,6 +43,7 @@ flag_types:
     value_pointer: true
     struct_fields:
       - { name: Layout, type: string }
+      - { name: Timezone, type: "*time.Location" }
 
   # TODO: enable UintSlice
   # UintSlice: {}
diff --git a/flag_test.go b/flag_test.go
index 0bb893afb6..e46b1eff45 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -2364,6 +2364,18 @@ func TestTimestampFlagApply_Fail_Parse_Wrong_Time(t *testing.T) {
 	expect(t, err, fmt.Errorf("invalid value \"2006-01-02T15:04:05Z\" for flag -time: parsing time \"2006-01-02T15:04:05Z\" as \"Jan 2, 2006 at 3:04pm (MST)\": cannot parse \"2006-01-02T15:04:05Z\" as \"Jan\""))
 }
 
+func TestTimestampFlagApply_Timezoned(t *testing.T) {
+	pdt := time.FixedZone("PDT", -7*60*60)
+	expectedResult, _ := time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
+	fl := TimestampFlag{Name: "time", Aliases: []string{"t"}, Layout: time.ANSIC, Timezone: pdt}
+	set := flag.NewFlagSet("test", 0)
+	_ = fl.Apply(set)
+
+	err := set.Parse([]string{"--time", "Mon Jan 2 08:04:05 2006"})
+	expect(t, err, nil)
+	expect(t, *fl.Value.timestamp, expectedResult.In(pdt))
+}
+
 func TestTimestampFlagValueFromContext(t *testing.T) {
 	set := flag.NewFlagSet("test", 0)
 	now := time.Now()
diff --git a/flag_timestamp.go b/flag_timestamp.go
index 052247795c..80e1f470be 100644
--- a/flag_timestamp.go
+++ b/flag_timestamp.go
@@ -11,6 +11,7 @@ type Timestamp struct {
 	timestamp  *time.Time
 	hasBeenSet bool
 	layout     string
+	location   *time.Location
 }
 
 // Timestamp constructor
@@ -31,9 +32,22 @@ func (t *Timestamp) SetLayout(layout string) {
 	t.layout = layout
 }
 
+// Set perceived timezone of the to-be parsed time string
+func (t *Timestamp) SetLocation(loc *time.Location) {
+	t.location = loc
+}
+
 // Parses the string value to timestamp
 func (t *Timestamp) Set(value string) error {
-	timestamp, err := time.Parse(t.layout, value)
+	var timestamp time.Time
+	var err error
+
+	if t.location != nil {
+		timestamp, err = time.ParseInLocation(t.layout, value, t.location)
+	} else {
+		timestamp, err = time.Parse(t.layout, value)
+	}
+
 	if err != nil {
 		return err
 	}
@@ -104,9 +118,11 @@ func (f *TimestampFlag) Apply(set *flag.FlagSet) error {
 		f.Value = &Timestamp{}
 	}
 	f.Value.SetLayout(f.Layout)
+	f.Value.SetLocation(f.Timezone)
 
 	if f.Destination != nil {
 		f.Destination.SetLayout(f.Layout)
+		f.Destination.SetLocation(f.Timezone)
 	}
 
 	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
diff --git a/godoc-current.txt b/godoc-current.txt
index a3a7faca17..1ba48cc659 100644
--- a/godoc-current.txt
+++ b/godoc-current.txt
@@ -269,6 +269,9 @@ type App struct {
 	Version string
 	// Description of the program
 	Description string
+	// DefaultCommand is the (optional) name of a command
+	// to run if no command names are passed as CLI arguments.
+	DefaultCommand string
 	// List of commands to execute
 	Commands []*Command
 	// List of flags to parse
@@ -1754,6 +1757,9 @@ func (t *Timestamp) Set(value string) error
 func (t *Timestamp) SetLayout(layout string)
     Set the timestamp string layout for future parsing
 
+func (t *Timestamp) SetLocation(loc *time.Location)
+    Set perceived timezone of the to-be parsed time string
+
 func (t *Timestamp) SetTimestamp(value time.Time)
     Set the timestamp value directly
 
@@ -1782,6 +1788,8 @@ type TimestampFlag struct {
 	EnvVars []string
 
 	Layout string
+
+	Timezone *time.Location
 }
     TimestampFlag is a flag with type *Timestamp
 
diff --git a/zz_generated.flags.go b/zz_generated.flags.go
index 3cae978c0c..b89566f900 100644
--- a/zz_generated.flags.go
+++ b/zz_generated.flags.go
@@ -280,6 +280,8 @@ type TimestampFlag struct {
 	EnvVars []string
 
 	Layout string
+
+	Timezone *time.Location
 }
 
 // String returns a readable representation of this value (for usage defaults)