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Add codec method to retrieve a Go type registered name #316

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Add codec method to retrieve a Go type registered name #316

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af9b7d6
add codec method to retrieve a Go type registered name
gsora May 12, 2020
d963179
add tests
gsora May 12, 2020
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24 changes: 24 additions & 0 deletions codec.go
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Original file line number Diff line number Diff line change
Expand Up @@ -308,6 +308,30 @@ func (cdc *Codec) PrintTypes(out io.Writer) error {
return nil
}

// ConcreteRegisteredName returns the name under which i has been registered.
func (cdc *Codec) ConcreteRegisteredName(i interface{}) (string, error) {
cdc.mtx.RLock()
defer cdc.mtx.RUnlock()

if i == nil {
return "", errors.New("argument must not be nil")
}

gt := reflect.TypeOf(i)

// if i is a non-nil pointer, dereference it and grab its inner Elem
if gt.Kind() == reflect.Ptr {
gt = gt.Elem()
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What happens if this a **SomeType? (pointer to pointer)

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@gsora gsora May 13, 2020 •
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Uhm, **SomeType would return error even though the struct type has been registered previously.

I could add a check on the inner gt.Elem(), this way it would dereference 2 times and get to the concrete instance.

Thoughts?

Something like:

gt := reflect.TypeOf(i)

for gt.Kind() == reflect.Ptr {
	gt = gt.Elem()
}

}

ct, ok := cdc.typeInfos[gt]
if !ok {
return "", fmt.Errorf("no type registered for %s", gt.String())
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This should probably be a sentinel error, such that callers can switch over a returned error to see if the type wasn't registered or if any other error occurred.

And independent of that: I think %s already calls String() on the type (no need to explicitly call it here).

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Would those two errors be okay for the purpose?

  • ErrNilPointer, when i is nil;
  • ErrTypeNotRegistered, when the concrete type of i is not registered;

Yup, String() will be removed :-)

}

return ct.Name, nil
}

// A heuristic to guess the size of a registered type and return it as a string.
// If the size is not fixed it returns "variable".
func getLengthStr(info *TypeInfo) string {
Expand Down
32 changes: 31 additions & 1 deletion codec_test.go
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Expand Up @@ -10,7 +10,7 @@ import (
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"

amino "github.com/tendermint/go-amino"
"github.com/tendermint/go-amino"
)

type SimpleStruct struct {
Expand Down Expand Up @@ -250,3 +250,33 @@ func TestCodecSeal(t *testing.T) {
assert.Panics(t, func() { cdc.RegisterInterface((*Bar)(nil), nil) })
assert.Panics(t, func() { cdc.RegisterConcrete(int(0), "int", nil) })
}

func TestCodec_RegisteredName(t *testing.T) {
aminoStructType := "tendermint/SimpleStruct"

// Struct is registered
cdc := amino.NewCodec()
cdc.RegisterConcrete(SimpleStruct{}, aminoStructType, nil)
rn, err := cdc.ConcreteRegisteredName(SimpleStruct{})
require.NoError(t, err)
require.Equal(t, aminoStructType, rn)

// Struct is not registered
cdc = amino.NewCodec()
rn, err = cdc.ConcreteRegisteredName(SimpleStruct{})
require.Error(t, err)
require.Empty(t, rn)

// Struct is pointer
cdc = amino.NewCodec()
cdc.RegisterConcrete(SimpleStruct{}, aminoStructType, nil)
rn, err = cdc.ConcreteRegisteredName(&SimpleStruct{})
require.NoError(t, err)
require.Equal(t, aminoStructType, rn)

// Struct is nil pointer
cdc = amino.NewCodec()
rn, err = cdc.ConcreteRegisteredName(nil)
require.Error(t, err)
require.Empty(t, rn)
}