Overwrite slice flag defaults when set

CHANGELOG.md

@@ -2,7 +2,16 @@
 
 **ATTN**: This project uses [semantic versioning](http://semver.org/).
 
-## [Unreleased]
+## 2.0.0 - (unreleased 2.x series)
+### Added
+- `NewStringSlice` and `NewIntSlice` for creating their related types
+
+### Removed
+- the ability to specify `&StringSlice{...string}` or `&IntSlice{...int}`.
+To migrate to the new API, you may choose to run [this helper
+(python) script](./cli-migrate-slice-types).
+
+## [Unreleased] - (1.x series)
 ### Added
 - Pluggable flag-level help text rendering via `cli.DefaultFlagStringFunc`
 

altsrc/flag.go

@@ -122,7 +122,7 @@ func (f *StringSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputS
 				return err
 			}
 			if value != nil {
-				var sliceValue cli.StringSlice = value
+				var sliceValue cli.StringSlice = *(cli.NewStringSlice(value...))
 				eachName(f.Name, func(name string) {
 					underlyingFlag := f.set.Lookup(f.Name)
 					if underlyingFlag != nil {
@@ -163,7 +163,7 @@ func (f *IntSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSour
 				return err
 			}
 			if value != nil {
-				var sliceValue cli.IntSlice = value
+				var sliceValue cli.IntSlice = *(cli.NewIntSlice(value...))
 				eachName(f.Name, func(name string) {
 					underlyingFlag := f.set.Lookup(f.Name)
 					if underlyingFlag != nil {

app_test.go

@@ -329,8 +329,8 @@ func TestApp_ParseSliceFlags(t *testing.T) {
 	command := Command{
 		Name: "cmd",
 		Flags: []Flag{
-			IntSliceFlag{Name: "p", Value: &IntSlice{}, Usage: "set one or more ip addr"},
-			StringSliceFlag{Name: "ip", Value: &StringSlice{}, Usage: "set one or more ports to open"},
+			IntSliceFlag{Name: "p", Value: NewIntSlice(), Usage: "set one or more ip addr"},
+			StringSliceFlag{Name: "ip", Value: NewStringSlice(), Usage: "set one or more ports to open"},
 		},
 		Action: func(c *Context) error {
 			parsedIntSlice = c.IntSlice("p")

cli-migrate-slice-types

@@ -0,0 +1,75 @@
+#!/usr/bin/env python
+from __future__ import print_function, unicode_literals
+
+import argparse
+import os
+import re
+import sys
+
+
+DESCRIPTION = """\
+Migrate arbitrary `.go` sources from the pre-v2.0.0 API for StringSlice and
+IntSlice types, optionally writing the changes back to file.
+"""
+SLICE_TYPE_RE = re.compile(
+    '&cli\\.(?P<type>IntSlice|StringSlice){(?P<args>[^}]*)}',
+    flags=re.DOTALL
+)
+
+
+def main(sysargs=sys.argv[:]):
+    parser = argparse.ArgumentParser(
+        description=DESCRIPTION,
+        formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+    parser.add_argument('basedir', nargs='?', metavar='BASEDIR',
+        type=os.path.abspath, default=os.getcwd())
+    parser.add_argument('-w', '--write', help='write changes back to file',
+        action='store_true', default=False)
+
+    args = parser.parse_args(sysargs[1:])
+
+    for filepath in _find_candidate_files(args.basedir):
+        updated_source = _update_source(filepath)
+        if args.write:
+            print('Updating {!r}'.format(filepath))
+
+            with open(filepath, 'w') as outfile:
+                outfile.write(updated_source)
+        else:
+            print('// -> Updated {!r}'.format(filepath))
+            print(updated_source)
+
+    return 0
+
+
+def _update_source(filepath):
+    with open(filepath) as infile:
+        source = infile.read()
+        return SLICE_TYPE_RE.sub(_slice_type_repl, source)
+
+
+def _slice_type_repl(match):
+    return 'cli.New{}({})'.format(
+        match.groupdict()['type'], match.groupdict()['args']
+    )
+
+
+def _find_candidate_files(basedir):
+    for curdir, dirs, files in os.walk(basedir):
+        for i, dirname in enumerate(dirs[:]):
+            if dirname.startswith('.'):
+                dirs.pop(i)
+
+        for filename in files:
+            if not filename.endswith('.go'):
+                continue
+
+            filepath = os.path.join(curdir, filename)
+            if not os.access(filepath, os.R_OK | os.W_OK):
+                continue
+
+            yield filepath
+
+
+if __name__ == '__main__':
+    sys.exit(main())

context.go

@@ -385,7 +385,8 @@ func lookupBoolT(name string, set *flag.FlagSet) bool {
 
 func copyFlag(name string, ff *flag.Flag, set *flag.FlagSet) {
 	switch ff.Value.(type) {
-	case *StringSlice:
+	case Serializeder:
+		set.Set(name, ff.Value.(Serializeder).Serialized())
 	default:
 		set.Set(name, ff.Value.String())
 	}

flag.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"encoding/json"
 	"flag"
 	"fmt"
 	"os"
@@ -13,6 +14,8 @@ import (
 
 const defaultPlaceholder = "value"
 
+var slPfx = fmt.Sprintf("sl:::%d:::", time.Now().UTC().UnixNano())
+
 // This flag enables bash-completion for all commands and subcommands
 var BashCompletionFlag = BoolFlag{
 	Name:   "generate-bash-completion",
@@ -35,6 +38,11 @@ var HelpFlag = BoolFlag{
 
 var FlagStringer FlagStringFunc = stringifyFlag
 
+// Serializeder is used to circumvent the limitations of flag.FlagSet.Set
+type Serializeder interface {
+	Serialized() string
+}
+
 // Flag is a common interface related to parsing flags in cli.
 // For more advanced flag parsing techniques, it is recommended that
 // this interface be implemented.
@@ -107,26 +115,52 @@ func (f GenericFlag) GetName() string {
 	return f.Name
 }
 
-// StringSlice is an opaque type for []string to satisfy flag.Value
-type StringSlice []string
+// StringSlice wraps a []string to satisfy flag.Value
+type StringSlice struct {
+	slice      []string
+	hasBeenSet bool
+}
+
+// NewStringSlice creates a *StringSlice with default values
+func NewStringSlice(defaults ...string) *StringSlice {
+	return &StringSlice{slice: append([]string{}, defaults...)}
+}
 
 // Set appends the string value to the list of values
 func (f *StringSlice) Set(value string) error {
-	*f = append(*f, value)
+	if !f.hasBeenSet {
+		f.slice = []string{}
+		f.hasBeenSet = true
+	}
+
+	if strings.HasPrefix(value, slPfx) {
+		// Deserializing assumes overwrite
+		_ = json.Unmarshal([]byte(strings.Replace(value, slPfx, "", 1)), &f.slice)
+		f.hasBeenSet = true
+		return nil
+	}
+
+	f.slice = append(f.slice, value)
 	return nil
 }
 
 // String returns a readable representation of this value (for usage defaults)
 func (f *StringSlice) String() string {
-	return fmt.Sprintf("%s", *f)
+	return fmt.Sprintf("%s", f.slice)
+}
+
+// Serialized allows StringSlice to fulfill Serializeder
+func (f *StringSlice) Serialized() string {
+	jsonBytes, _ := json.Marshal(f.slice)
+	return fmt.Sprintf("%s%s", slPfx, string(jsonBytes))
 }
 
 // Value returns the slice of strings set by this flag
 func (f *StringSlice) Value() []string {
-	return *f
+	return f.slice
 }
 
-// StringSlice is a string flag that can be specified multiple times on the
+// StringSliceFlag is a string flag that can be specified multiple times on the
 // command-line
 type StringSliceFlag struct {
 	Name   string
@@ -147,7 +181,7 @@ func (f StringSliceFlag) Apply(set *flag.FlagSet) {
 		for _, envVar := range strings.Split(f.EnvVar, ",") {
 			envVar = strings.TrimSpace(envVar)
 			if envVal := os.Getenv(envVar); envVal != "" {
-				newVal := &StringSlice{}
+				newVal := NewStringSlice()
 				for _, s := range strings.Split(envVal, ",") {
 					s = strings.TrimSpace(s)
 					newVal.Set(s)
@@ -158,10 +192,11 @@ func (f StringSliceFlag) Apply(set *flag.FlagSet) {
 		}
 	}
 
+	if f.Value == nil {
+		f.Value = NewStringSlice()
+	}
+
 	eachName(f.Name, func(name string) {
-		if f.Value == nil {
-			f.Value = &StringSlice{}
-		}
 		set.Var(f.Value, name, f.Usage)
 	})
 }
@@ -170,28 +205,64 @@ func (f StringSliceFlag) GetName() string {
 	return f.Name
 }
 
-// StringSlice is an opaque type for []int to satisfy flag.Value
-type IntSlice []int
+// IntSlice wraps an []int to satisfy flag.Value
+type IntSlice struct {
+	slice      []int
+	hasBeenSet bool
+}
+
+// NewIntSlice makes an *IntSlice with default values
+func NewIntSlice(defaults ...int) *IntSlice {
+	return &IntSlice{slice: append([]int{}, defaults...)}
+}
+
+// SetInt directly adds an integer to the list of values
+func (i *IntSlice) SetInt(value int) {
+	if !i.hasBeenSet {
+		i.slice = []int{}
+		i.hasBeenSet = true
+	}
+
+	i.slice = append(i.slice, value)
+}
 
 // Set parses the value into an integer and appends it to the list of values
-func (f *IntSlice) Set(value string) error {
+func (i *IntSlice) Set(value string) error {
+	if !i.hasBeenSet {
+		i.slice = []int{}
+		i.hasBeenSet = true
+	}
+
+	if strings.HasPrefix(value, slPfx) {
+		// Deserializing assumes overwrite
+		_ = json.Unmarshal([]byte(strings.Replace(value, slPfx, "", 1)), &i.slice)
+		i.hasBeenSet = true
+		return nil
+	}
+
 	tmp, err := strconv.Atoi(value)
 	if err != nil {
 		return err
 	} else {
-		*f = append(*f, tmp)
+		i.slice = append(i.slice, tmp)
 	}
 	return nil
 }
 
 // String returns a readable representation of this value (for usage defaults)
-func (f *IntSlice) String() string {
-	return fmt.Sprintf("%d", *f)
+func (i *IntSlice) String() string {
+	return fmt.Sprintf("%v", i.slice)
+}
+
+// Serialized allows IntSlice to fulfill Serializeder
+func (i *IntSlice) Serialized() string {
+	jsonBytes, _ := json.Marshal(i.slice)
+	return fmt.Sprintf("%s%s", slPfx, string(jsonBytes))
 }
 
 // Value returns the slice of ints set by this flag
-func (f *IntSlice) Value() []int {
-	return *f
+func (i *IntSlice) Value() []int {
+	return i.slice
 }
 
 // IntSliceFlag is an int flag that can be specified multiple times on the
@@ -215,7 +286,7 @@ func (f IntSliceFlag) Apply(set *flag.FlagSet) {
 		for _, envVar := range strings.Split(f.EnvVar, ",") {
 			envVar = strings.TrimSpace(envVar)
 			if envVal := os.Getenv(envVar); envVal != "" {
-				newVal := &IntSlice{}
+				newVal := NewIntSlice()
 				for _, s := range strings.Split(envVal, ",") {
 					s = strings.TrimSpace(s)
 					err := newVal.Set(s)
@@ -229,10 +300,11 @@ func (f IntSliceFlag) Apply(set *flag.FlagSet) {
 		}
 	}
 
+	if f.Value == nil {
+		f.Value = NewIntSlice()
+	}
+
 	eachName(f.Name, func(name string) {
-		if f.Value == nil {
-			f.Value = &IntSlice{}
-		}
 		set.Var(f.Value, name, f.Usage)
 	})
 }