[RFC] many: add types.Option generic and use in customizations
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| Copyright 2021 Taiki Kawakami (a.k.a. moznion) https://moznion.net | ||
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| Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: | ||
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| The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. | ||
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| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | ||
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| Original file line number | Diff line number | Diff line change |
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| package types | ||
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| import ( | ||
| "bytes" | ||
| "encoding/json" | ||
| "fmt" | ||
| ) | ||
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| // Option is a more constrained subset of the code in | ||
| // https://github.com/moznion/go-optional | ||
| // | ||
| // It is not using an external go-optional lib directly because none | ||
| // has toml unmarshal support and also because there is no support for | ||
| // complex types in UnmarshalTOML (it only gives a single | ||
| // reflect.Value of type any) so our optional "lib" must come with | ||
| // limitations for this. | ||
| // | ||
| // Unfortunately there is no way I could find to import the code and | ||
| // limit the supported types. So this is a copy of the subset. | ||
| // Fortunatly the code is small, targeted and easy to follow so it | ||
| // should not be too bad. | ||
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| type OptionTomlTypes interface { | ||
| ~int | ~bool | ~string | ||
| } | ||
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| // Option is a subset of github.com/moznion/go-optional for use with toml | ||
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| // Option is a data type that must be Some (i.e. having a value) or None (i.e. doesn't have a value). | ||
| // This type implements database/sql/driver.Valuer and database/sql.Scanner. | ||
| type Option[T OptionTomlTypes] []T | ||
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| const ( | ||
| value = iota | ||
| ) | ||
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| // Some is a function to make an Option type value with the actual value. | ||
| func Some[T OptionTomlTypes](v T) Option[T] { | ||
|
There was a problem hiding this comment. Fwiw, we could call this differently, e.g. |
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| return Option[T]{ | ||
| value: v, | ||
| } | ||
| } | ||
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| // None is a function to make an Option type value that doesn't have a value. | ||
| func None[T OptionTomlTypes]() Option[T] { | ||
| return nil | ||
| } | ||
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| // IsNone returns True if the Option *doesn't* have a value | ||
| func (o Option[T]) IsNone() bool { | ||
| return o == nil | ||
| } | ||
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| // IsSome returns whether the Option has a value or not. | ||
| func (o Option[T]) IsSome() bool { | ||
| return o != nil | ||
| } | ||
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| // Unwrap returns the value regardless of Some/None status. | ||
| // If the Option value is Some, this method returns the actual value. | ||
| // On the other hand, if the Option value is None, this method returns the *default* value according to the type. | ||
| func (o Option[T]) Unwrap() T { | ||
| if o.IsNone() { | ||
| var defaultValue T | ||
| return defaultValue | ||
| } | ||
| return o[value] | ||
| } | ||
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| // TakeOr returns the actual value if the Option has a value. | ||
| // On the other hand, this returns fallbackValue. | ||
| func (o Option[T]) TakeOr(fallbackValue T) T { | ||
| if o.IsNone() { | ||
| return fallbackValue | ||
| } | ||
| return o[value] | ||
| } | ||
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| var jsonNull = []byte("null") | ||
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| func (o Option[T]) MarshalJSON() ([]byte, error) { | ||
| if o.IsNone() { | ||
| return jsonNull, nil | ||
| } | ||
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| marshal, err := json.Marshal(o.Unwrap()) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return marshal, nil | ||
| } | ||
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| func (o *Option[T]) UnmarshalJSON(data []byte) error { | ||
| if len(data) <= 0 || bytes.Equal(data, jsonNull) { | ||
| *o = None[T]() | ||
| return nil | ||
| } | ||
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| var v T | ||
| err := json.Unmarshal(data, &v) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| *o = Some(v) | ||
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| return nil | ||
| } | ||
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| // not part of github.com/moznion/go-optional | ||
| func (o *Option[T]) UnmarshalTOML(data any) error { | ||
| b, ok := data.(T) | ||
| if !ok { | ||
| return fmt.Errorf("cannot use %[1]v (%[1]T) as bool", data) | ||
| } | ||
| *o = Some(b) | ||
| return nil | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,80 @@ | ||
| package types_test | ||
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| import ( | ||
| "testing" | ||
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| "github.com/BurntSushi/toml" | ||
| "github.com/stretchr/testify/assert" | ||
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| "github.com/osbuild/images/internal/types" | ||
| ) | ||
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| type s1 struct { | ||
| Name string `toml:"name"` | ||
| Sub s2 `toml:"sub"` | ||
| } | ||
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| type s2 struct { | ||
| ValBool types.Option[bool] `toml:"val-bool"` | ||
| ValString types.Option[string] `toml:"val-string"` | ||
| ValString2 types.Option[string] `toml:"val-string2"` | ||
| } | ||
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| func TestTomlParseOption(t *testing.T) { | ||
| testTomlStr := ` | ||
| name = "some-name" | ||
| [sub] | ||
| val-bool = true | ||
| val-string = "opt-string" | ||
| ` | ||
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| var bp s1 | ||
| err := toml.Unmarshal([]byte(testTomlStr), &bp) | ||
| assert.NoError(t, err) | ||
| assert.Equal(t, bp.Name, "some-name") | ||
| assert.Equal(t, types.Some(true), bp.Sub.ValBool) | ||
| assert.Equal(t, types.Some("opt-string"), bp.Sub.ValString) | ||
| assert.EqualValues(t, types.None[string](), bp.Sub.ValString2) | ||
| } | ||
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| func TestTomlParseOptionBad(t *testing.T) { | ||
| testTomlStr := ` | ||
| [sub] | ||
| val-bool = 1234 | ||
| ` | ||
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| var bp s1 | ||
| err := toml.Unmarshal([]byte(testTomlStr), &bp) | ||
| assert.ErrorContains(t, err, "cannot use 1234 (int64) as bool") | ||
| } | ||
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| // taken from https://github.com/moznion/go-optional | ||
| func TestOption_IsNone(t *testing.T) { | ||
| assert.True(t, types.None[int]().IsNone()) | ||
| assert.False(t, types.Some[int](123).IsNone()) | ||
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| var nilValue types.Option[int] = nil | ||
| assert.True(t, nilValue.IsNone()) | ||
| } | ||
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| func TestOption_IsSome(t *testing.T) { | ||
| assert.False(t, types.None[int]().IsSome()) | ||
| assert.True(t, types.Some[int](123).IsSome()) | ||
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| var nilValue types.Option[int] = nil | ||
| assert.False(t, nilValue.IsSome()) | ||
| } | ||
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| func TestOption_Unwrap(t *testing.T) { | ||
| assert.Equal(t, "foo", types.Some[string]("foo").Unwrap()) | ||
| assert.Equal(t, "", types.None[string]().Unwrap()) | ||
| assert.Equal(t, false, types.None[bool]().Unwrap()) | ||
| } | ||
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| func TestOption_TakeOr(t *testing.T) { | ||
| v := types.Some[int](123).TakeOr(666) | ||
| assert.Equal(t, 123, v) | ||
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| v = types.None[int]().TakeOr(666) | ||
| assert.Equal(t, 666, v) | ||
| } |
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Fwiw, we could call this
Optionaltoo which I actually slightly prefer but thenOptionis what rust uses and lots of people are familar with this terminology now.