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feat(decoder-configs): add flag to force decoding nil input in decode…
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…r config (#42)

* Add ForceDecoding Flag To Decoder Config

* Add Test Cases

* Fix Documentation

* Remove Extra Check

* Do Not Override Zero Fields Check

* Use Map As Input For Tests

* Rename Flag And Simplify godoc

* Fix Test Name

* Fix Wording of godoc

* Use interface{} Instead of map[string]interface{}

* Fix Test Case

* Fix Variable Name

* Fix godoc

* Address Feedback From PR Review

* Change Logic To Set InputVal And Not Erase OutputVal

* Add Additional Test With Type Hook

* Add Extra Test Case And Extract Bool Expression Into Variable

* Fix Typo

* Add More Test Cases

* Rename Variable

* Fix Test Case

* Address Feedback From PR Review

* Simplify Test Strings

* Use More Descriptive Test Name

* Add Test Cases For Append Hook

Signed-off-by: Mahad Zaryab <mahadzaryab1@gmail.com>

* Run Linter

Signed-off-by: Mahad Zaryab <mahadzaryab1@gmail.com>

* Remove Debug Statement

Signed-off-by: Mahad Zaryab <mahadzaryab1@gmail.com>

---------

Signed-off-by: Mahad Zaryab <mahadzaryab1@gmail.com>
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@mahadzaryab1
mahadzaryab1 committed Sep 20, 2024
1 parent c97971d commit ff5d967
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Showing 2 changed files with 188 additions and 7 deletions.
30 changes: 23 additions & 7 deletions mapstructure.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -278,6 +278,10 @@ type DecoderConfig struct {
// field name or tag. Defaults to `strings.EqualFold`. This can be used
// to implement case-sensitive tag values, support snake casing, etc.
MatchName func(mapKey, fieldName string) bool

// DecodeNil, if set to true, will cause the DecodeHook (if present) to run
// even if the input is nil. This can be used to provide default values.
DecodeNil bool
}

// A Decoder takes a raw interface value and turns it into structured
Expand Down Expand Up @@ -451,6 +455,8 @@ func (d *Decoder) decode(name string, input interface{}, outVal reflect.Value) e
}
}

decodeNil := d.config.DecodeNil && d.config.DecodeHook != nil

if input == nil {
// If the data is nil, then we don't set anything, unless ZeroFields is set
// to true.
Expand All @@ -461,17 +467,27 @@ func (d *Decoder) decode(name string, input interface{}, outVal reflect.Value) e
d.config.Metadata.Keys = append(d.config.Metadata.Keys, name)
}
}
return nil

if !decodeNil {
return nil
}
}

if !inputVal.IsValid() {
// If the input value is invalid, then we just set the value
// to be the zero value.
outVal.Set(reflect.Zero(outVal.Type()))
if d.config.Metadata != nil && name != "" {
d.config.Metadata.Keys = append(d.config.Metadata.Keys, name)
if !decodeNil {
// If the input value is invalid, then we just set the value
// to be the zero value.
outVal.Set(reflect.Zero(outVal.Type()))
if d.config.Metadata != nil && name != "" {
d.config.Metadata.Keys = append(d.config.Metadata.Keys, name)
}
return nil
}
return nil

// If we get here, we have an untyped nil so the type of the input is assumed.
// We do this because all subsequent code requires a valid value for inputVal.
var mapVal map[string]interface{}
inputVal = reflect.MakeMap(reflect.TypeOf(mapVal))
}

if d.cachedDecodeHook != nil {
Expand Down
165 changes: 165 additions & 0 deletions mapstructure_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3083,6 +3083,171 @@ func TestDecoder_IgnoreUntaggedFieldsWithStruct(t *testing.T) {
}
}

func TestDecoder_CanPerformDecodingForNilInputs(t *testing.T) {
t.Parallel()

type Transformed struct {
Message string
When string
}

helloHook := func(reflect.Type, reflect.Type, interface{}) (interface{}, error) {
return Transformed{Message: "hello"}, nil
}
goodbyeHook := func(reflect.Type, reflect.Type, interface{}) (interface{}, error) {
return Transformed{Message: "goodbye"}, nil
}
appendHook := func(from reflect.Value, to reflect.Value) (interface{}, error) {
if from.Kind() == reflect.Map {
stringMap := from.Interface().(map[string]interface{})
stringMap["when"] = "see you later"
return stringMap, nil
}
return from.Interface(), nil
}

tests := []struct {
name string
decodeNil bool
input interface{}
result Transformed
expectedResult Transformed
decodeHook DecodeHookFunc
}{
{
name: "decodeNil=true for nil input with hook",
decodeNil: true,
input: nil,
decodeHook: helloHook,
expectedResult: Transformed{Message: "hello"},
},
{
name: "decodeNil=true for nil input without hook",
decodeNil: true,
input: nil,
expectedResult: Transformed{Message: ""},
},
{
name: "decodeNil=false for nil input with hook",
decodeNil: false,
input: nil,
decodeHook: helloHook,
expectedResult: Transformed{Message: ""},
},
{
name: "decodeNil=false for nil input without hook",
decodeNil: false,
input: nil,
expectedResult: Transformed{Message: ""},
},
{
name: "decodeNil=true for non-nil input without hook",
decodeNil: true,
input: map[string]interface{}{"message": "bar"},
expectedResult: Transformed{Message: "bar"},
},
{
name: "decodeNil=true for non-nil input with hook",
decodeNil: true,
input: map[string]interface{}{"message": "bar"},
decodeHook: goodbyeHook,
expectedResult: Transformed{Message: "goodbye"},
},
{
name: "decodeNil=false for non-nil input without hook",
decodeNil: false,
input: map[string]interface{}{"message": "bar"},
expectedResult: Transformed{Message: "bar"},
},
{
name: "decodeNil=false for non-nil input with hook",
decodeNil: false,
input: map[string]interface{}{"message": "bar"},
decodeHook: goodbyeHook,
expectedResult: Transformed{Message: "goodbye"},
},
{
name: "decodeNil=true for nil input without hook and non-empty result",
decodeNil: true,
input: nil,
result: Transformed{Message: "foo"},
expectedResult: Transformed{Message: "foo"},
},
{
name: "decodeNil=true for nil input with hook and non-empty result",
decodeNil: true,
input: nil,
result: Transformed{Message: "foo"},
decodeHook: helloHook,
expectedResult: Transformed{Message: "hello"},
},
{
name: "decodeNil=false for nil input without hook and non-empty result",
decodeNil: false,
input: nil,
result: Transformed{Message: "foo"},
expectedResult: Transformed{Message: "foo"},
},
{
name: "decodeNil=false for nil input with hook and non-empty result",
decodeNil: false,
input: nil,
result: Transformed{Message: "foo"},
decodeHook: helloHook,
expectedResult: Transformed{Message: "foo"},
},
{
name: "decodeNil=false for non-nil input with hook that appends a value",
decodeNil: false,
input: map[string]interface{}{"message": "bar"},
decodeHook: appendHook,
expectedResult: Transformed{Message: "bar", When: "see you later"},
},
{
name: "decodeNil=true for non-nil input with hook that appends a value",
decodeNil: true,
input: map[string]interface{}{"message": "bar"},
decodeHook: appendHook,
expectedResult: Transformed{Message: "bar", When: "see you later"},
},
{
name: "decodeNil=true for nil input with hook that appends a value",
decodeNil: true,
decodeHook: appendHook,
expectedResult: Transformed{When: "see you later"},
},
{
name: "decodeNil=false for nil input with hook that appends a value",
decodeNil: false,
decodeHook: appendHook,
expectedResult: Transformed{},
},
}

for _, test := range tests {
t.Run(test.name, func(t *testing.T) {
config := &DecoderConfig{
Result: &test.result,
DecodeNil: test.decodeNil,
DecodeHook: test.decodeHook,
}

decoder, err := NewDecoder(config)
if err != nil {
t.Fatalf("err: %s", err)
}

if err := decoder.Decode(test.input); err != nil {
t.Fatalf("got an err: %s", err)
}

if test.result != test.expectedResult {
t.Errorf("result should be: %#v, got %#v", test.expectedResult, test.result)
}
})
}
}

func testSliceInput(t *testing.T, input map[string]interface{}, expected *Slice) {
var result Slice
err := Decode(input, &result)
Expand Down

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