add ForceJSON option for string decoding

.github/workflows/golangci-lint.yml

@@ -18,7 +18,7 @@ jobs:
 
           # Optional: golangci-lint command line arguments.
           # args: --issues-exit-code=0
-          # args: --out-format checkstyle
+          args: --out-format checkstyle
 
           # Optional: show only new issues if it's a pull request. The default value is `false`.
           # only-new-issues: true

unpack.go

@@ -2,6 +2,7 @@ package reflectutils
 
 import (
 	"encoding"
+	"encoding/json"
 	"flag"
 	"reflect"
 	"strconv"
@@ -10,12 +11,15 @@ import (
 	"github.com/pkg/errors"
 )
 
-var textUnmarshallerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
-var flagValueType = reflect.TypeOf((*flag.Value)(nil)).Elem()
+var (
+	textUnmarshallerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+	flagValueType        = reflect.TypeOf((*flag.Value)(nil)).Elem()
+)
 
 type stringSetterOpts struct {
 	split       string
 	sliceAppend bool
+	forceJSON   bool
 }
 
 type StringSetterArg func(*stringSetterOpts)
@@ -41,6 +45,15 @@ func SliceAppend(b bool) StringSetterArg {
 	}
 }
 
+// ForceJSON controls if types will be decoded with JSON
+// unmarshal. This overrides normal decoding patterns. The default
+// is false.
+func ForceJSON(b bool) StringSetterArg {
+	return func(o *stringSetterOpts) {
+		o.forceJSON = b
+	}
+}
+
 // MakeStringSetter handles setting a reflect.Value from a string.
 // Based on type, it returns a function to do the work.  It is assumed that the
 // reflect.Type matches the reflect.Value.  If not, panic is likely.
@@ -64,6 +77,17 @@ func MakeStringSetter(t reflect.Type, optArgs ...StringSetterArg) (func(target r
 	for _, f := range optArgs {
 		f(&opts)
 	}
+	if opts.forceJSON {
+		return func(target reflect.Value, value string) error {
+			p := reflect.New(t.Elem())
+			target.Set(p)
+			err := json.Unmarshal([]byte(value), target.Interface())
+			if err != nil {
+				return errors.WithStack(err)
+			}
+			return nil
+		}, nil
+	}
 	if setter, ok := settersByType[t]; ok {
 		return func(target reflect.Value, value string) error {
 			out := setter.Call([]reflect.Value{reflect.ValueOf(value)})

unpack_test.go

@@ -30,13 +30,18 @@ func (bp *Bar) Set(s string) error {
 	*bp = Bar(s + "/e")
 	return nil
 }
+
 func (bp Bar) String() string {
 	return "b/" + string(bp)
 }
 
 var _ flag.Value = func() *Bar { var x Bar; return &x }()
 
 func TestStringSetter(t *testing.T) {
+	type J struct {
+		A int
+		B string
+	}
 	type tsType struct {
 		Int        int             `value:"38"`
 		Int8       int8            `value:"-9"`
@@ -75,7 +80,7 @@ func TestStringSetter(t *testing.T) {
 		FooP       *Foo            `value:"foo"      want:"~foo~"`
 		Dur        time.Duration   `value:"30m"      want:"30m0s"`
 		DurP       *time.Duration  `value:"15m"      want:"15m0s"`
-		DurArray   []time.Duration `value:"15m,45m"      want:"[15m0s 45m0s]"`
+		DurArray   []time.Duration `value:"15m,45m"  want:"[15m0s 45m0s]"`
 		Bar        Bar             `value:"bar"      want:"b/bar/e"`
 		BarArray   [2]Bar          `value:"a,b,c"    want:"[b/a/e b/b,c/e]"`
 		BarP       *Bar            `value:"bar"      want:"b/bar/e"`
@@ -89,6 +94,7 @@ func TestStringSetter(t *testing.T) {
 		SS5        []string        `value:"foo"      want:"[foo bar]"   value2:"bar"`
 		SS6        []string        `value:"foo"      want:"[bar]"       value2:"bar" sa:"f"`
 		RG01       *[]int          `value:"823:29"   want:"[823 29]"    split:":"`
+		S          *J              `value:"{\"A\":10,\"B\":\"bar\"}"  want:"{A:10 B:bar}" fj:"t"`
 	}
 	var ts tsType
 	vp := reflect.ValueOf(&ts)
@@ -116,6 +122,12 @@ func TestStringSetter(t *testing.T) {
 				t.Log("  slice append", b)
 				opts = append(opts, reflectutils.SliceAppend(b))
 			}
+			if fj, ok := f.Tag.Lookup("fj"); ok {
+				b, err := strconv.ParseBool(fj)
+				require.NoError(t, err, "parse fj")
+				t.Log("  force JSON", b)
+				opts = append(opts, reflectutils.ForceJSON(b))
+			}
 
 			fn, err := reflectutils.MakeStringSetter(f.Type, opts...)
 			if !assert.NoErrorf(t, err, "make string setter for %s", f.Name) {