refactor!: create math go sub module

[alexanderbez]

Description

Closes: #11784

• Create math go sub-module
• Move Int, and Uint types to math
• Add aliases to types/math.go
• Removed Int#ToDec (API breaking)

A beta release/tag of math will be made along with the replace directive being removed once this PR is merged.

---

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[alexanderbez]

@aaronc we need to duplicate proto.go which defines the CustomProtobufType interface, which is easy to handle as we can duplicate it. However, the following causes another issue:

// ToDec converts Int to Dec
func (i Int) ToDec() Dec {
	return NewDecFromInt(i)
}

Should we:

1. include Dec as part of math too OR
2. create ToDec(i Int) in types (i.e. w/o the receiver -- this is a breaking API change)?

(1) allows use to avoid copying proto.go and is cleaner, but I don't know if this is what you intended in the original issue.

[tac0turtle]

should we alias the math package from types for a release and mark as deprecated, similar to errors

[alexanderbez]

should we alias the math package from types for a release and mark as deprecated, similar to errors

Yes :)

[aaronc]

should we alias the math package from types for a release and mark as deprecated, similar to errors

I chatted with @alexanderbez about this a bit, but the idea is to keep the gogo proto and amino serialization in types.Int and math.Int will only include serialization logic for cosmos/cosmos-proto#2 (if needed). So likely types.Int will need to be a wrapper of math.Int with those additional serialization methods

[aaronc]

@aaronc we need to duplicate proto.go which defines the CustomProtobufType interface, which is easy to handle as we can duplicate it. However, the following causes another issue:

// ToDec converts Int to Dec
func (i Int) ToDec() Dec {
	return NewDecFromInt(i)
}

Should we:

1. include Dec as part of math too OR
2. create ToDec(i Int) in types (i.e. w/o the receiver -- this is a breaking API change)?

(1) allows use to avoid copying proto.go and is cleaner, but I don't know if this is what you intended in the original issue.

What I'd propose for ToDec() is the same as what I'm proposing for all the marshaling logic/CustomProtoType - we leave those methods in types.Int for now but on a wrapper.

So in types/int.go we'd have:

type Int math.Int

func (i Int) ToDec() Dec {
  return NewDecFromInt(i)
}

I'd prefer to avoid API breakage in types/ but it's okay to have a slightly different API in math (because it's effectively a new package)

[aaronc]

What I'd propose is (for now at least) to leave all of this stuff in types/int.go on the types.Int wrapper type:

cosmos-sdk/types/int.go

Lines 335 to 434 in 019444a

	func (i Int) MarshalJSON() ([]byte, error) {
	if i.i == nil { // Necessary since default Uint initialization has i.i as nil
	i.i = new(big.Int)
	}
	return marshalJSON(i.i)
	}
	// UnmarshalJSON defines custom decoding scheme
	func (i *Int) UnmarshalJSON(bz []byte) error {
	if i.i == nil { // Necessary since default Int initialization has i.i as nil
	i.i = new(big.Int)
	}
	return unmarshalJSON(i.i, bz)
	}
	// MarshalJSON for custom encoding scheme
	// Must be encoded as a string for JSON precision
	func marshalJSON(i encoding.TextMarshaler) ([]byte, error) {
	text, err := i.MarshalText()
	if err != nil {
	return nil, err
	}
	return json.Marshal(string(text))
	}
	// UnmarshalJSON for custom decoding scheme
	// Must be encoded as a string for JSON precision
	func unmarshalJSON(i *big.Int, bz []byte) error {
	var text string
	if err := json.Unmarshal(bz, &text); err != nil {
	return err
	}
	return unmarshalText(i, text)
	}
	// MarshalYAML returns the YAML representation.
	func (i Int) MarshalYAML() (interface{}, error) {
	return i.String(), nil
	}
	// Marshal implements the gogo proto custom type interface.
	func (i Int) Marshal() ([]byte, error) {
	if i.i == nil {
	i.i = new(big.Int)
	}
	return i.i.MarshalText()
	}
	// MarshalTo implements the gogo proto custom type interface.
	func (i *Int) MarshalTo(data []byte) (n int, err error) {
	if i.i == nil {
	i.i = new(big.Int)
	}
	if i.i.BitLen() == 0 { // The value 0
	copy(data, []byte{0x30})
	return 1, nil
	}
	bz, err := i.Marshal()
	if err != nil {
	return 0, err
	}
	copy(data, bz)
	return len(bz), nil
	}
	// Unmarshal implements the gogo proto custom type interface.
	func (i *Int) Unmarshal(data []byte) error {
	if len(data) == 0 {
	i = nil
	return nil
	}
	if i.i == nil {
	i.i = new(big.Int)
	}
	if err := i.i.UnmarshalText(data); err != nil {
	return err
	}
	if i.i.BitLen() > maxBitLen {
	return fmt.Errorf("integer out of range; got: %d, max: %d", i.i.BitLen(), maxBitLen)
	}
	return nil
	}
	// Size implements the gogo proto custom type interface.
	func (i *Int) Size() int {
	bz, _ := i.Marshal()
	return len(bz)
	}
	// Override Amino binary serialization by proxying to protobuf.
	func (i Int) MarshalAmino() ([]byte, error) { return i.Marshal() }
	func (i *Int) UnmarshalAmino(bz []byte) error { return i.Unmarshal(bz) }

To avoid carrying all the gogo/amino baggage

[aaronc]

Why did you decide to not create an Int wrapper type with the Dec method defined?

Otherwise LGTM

[alexanderbez]

Why did you decide to not create an Int wrapper type with the Dec method defined?

Yes, correct. That one API was just not worth it -- a caller can and should just call NewDecFromInt.