diff options
| -rw-r--r-- | LICENSE | 73 | ||||
| -rw-r--r-- | README.md | 4 | ||||
| -rw-r--r-- | go.mod | 3 | ||||
| -rw-r--r-- | internal/test/helpers.go | 24 | ||||
| -rw-r--r-- | option/option.go | 362 | ||||
| -rw-r--r-- | option/option_test.go | 174 | ||||
| -rw-r--r-- | options/options.go | 22 | ||||
| -rw-r--r-- | options/options_test.go | 19 |
8 files changed, 681 insertions, 0 deletions
@@ -0,0 +1,73 @@ +Apache License +Version 2.0, January 2004 +http://www.apache.org/licenses/ + +TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + +1. Definitions. + +"License" shall mean the terms and conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document. + +"Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License. + +"Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. For the purposes of this definition, "control" means (i) the power, direct or indirect, to cause the direction or management of such entity, whether by contract or otherwise, or (ii) ownership of fifty percent (50%) or more of the outstanding shares, or (iii) beneficial ownership of such entity. + +"You" (or "Your") shall mean an individual or Legal Entity exercising permissions granted by this License. + +"Source" form shall mean the preferred form for making modifications, including but not limited to software source code, documentation source, and configuration files. + +"Object" form shall mean any form resulting from mechanical transformation or translation of a Source form, including but not limited to compiled object code, generated documentation, and conversions to other media types. + +"Work" shall mean the work of authorship, whether in Source or Object form, made available under the License, as indicated by a copyright notice that is included in or attached to the work (an example is provided in the Appendix below). + +"Derivative Works" shall mean any work, whether in Source or Object form, that is based on (or derived from) the Work and for which the editorial revisions, annotations, elaborations, or other modifications represent, as a whole, an original work of authorship. For the purposes of this License, Derivative Works shall not include works that remain separable from, or merely link (or bind by name) to the interfaces of, the Work and Derivative Works thereof. + +"Contribution" shall mean any work of authorship, including the original version of the Work and any modifications or additions to that Work or Derivative Works thereof, that is intentionally submitted to Licensor for inclusion in the Work by the copyright owner or by an individual or Legal Entity authorized to submit on behalf of the copyright owner. For the purposes of this definition, "submitted" means any form of electronic, verbal, or written communication sent to the Licensor or its representatives, including but not limited to communication on electronic mailing lists, source code control systems, and issue tracking systems that are managed by, or on behalf of, the Licensor for the purpose of discussing and improving the Work, but excluding communication that is conspicuously marked or otherwise designated in writing by the copyright owner as "Not a Contribution." + +"Contributor" shall mean Licensor and any individual or Legal Entity on behalf of whom a Contribution has been received by Licensor and subsequently incorporated within the Work. + +2. Grant of Copyright License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare Derivative Works of, publicly display, publicly perform, sublicense, and distribute the Work and such Derivative Works in Source or Object form. + +3. Grant of Patent License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Work, where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution(s) alone or by combination of their Contribution(s) with the Work to which such Contribution(s) was submitted. If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Work or a Contribution incorporated within the Work constitutes direct or contributory patent infringement, then any patent licenses granted to You under this License for that Work shall terminate as of the date such litigation is filed. + +4. Redistribution. You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications, and in Source or Object form, provided that You meet the following conditions: + + (a) You must give any other recipients of the Work or Derivative Works a copy of this License; and + + (b) You must cause any modified files to carry prominent notices stating that You changed the files; and + + (c) You must retain, in the Source form of any Derivative Works that You distribute, all copyright, patent, trademark, and attribution notices from the Source form of the Work, excluding those notices that do not pertain to any part of the Derivative Works; and + + (d) If the Work includes a "NOTICE" text file as part of its distribution, then any Derivative Works that You distribute must include a readable copy of the attribution notices contained within such NOTICE file, excluding those notices that do not pertain to any part of the Derivative Works, in at least one of the following places: within a NOTICE text file distributed as part of the Derivative Works; within the Source form or documentation, if provided along with the Derivative Works; or, within a display generated by the Derivative Works, if and wherever such third-party notices normally appear. The contents of the NOTICE file are for informational purposes only and do not modify the License. You may add Your own attribution notices within Derivative Works that You distribute, alongside or as an addendum to the NOTICE text from the Work, provided that such additional attribution notices cannot be construed as modifying the License. + + You may add Your own copyright statement to Your modifications and may provide additional or different license terms and conditions for use, reproduction, or distribution of Your modifications, or for any such Derivative Works as a whole, provided Your use, reproduction, and distribution of the Work otherwise complies with the conditions stated in this License. + +5. Submission of Contributions. Unless You explicitly state otherwise, any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License, without any additional terms or conditions. Notwithstanding the above, nothing herein shall supersede or modify the terms of any separate license agreement you may have executed with Licensor regarding such Contributions. + +6. Trademarks. This License does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor, except as required for reasonable and customary use in describing the origin of the Work and reproducing the content of the NOTICE file. + +7. Disclaimer of Warranty. Unless required by applicable law or agreed to in writing, Licensor provides the Work (and each Contributor provides its Contributions) on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are solely responsible for determining the appropriateness of using or redistributing the Work and assume any risks associated with Your exercise of permissions under this License. + +8. Limitation of Liability. In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall any Contributor be liable to You for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising as a result of this License or out of the use or inability to use the Work (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if such Contributor has been advised of the possibility of such damages. + +9. Accepting Warranty or Additional Liability. While redistributing the Work or Derivative Works thereof, You may choose to offer, and charge a fee for, acceptance of support, warranty, indemnity, or other liability obligations and/or rights consistent with this License. However, in accepting such obligations, You may act only on Your own behalf and on Your sole responsibility, not on behalf of any other Contributor, and only if You agree to indemnify, defend, and hold each Contributor harmless for any liability incurred by, or claims asserted against, such Contributor by reason of your accepting any such warranty or additional liability. + +END OF TERMS AND CONDITIONS + +APPENDIX: How to apply the Apache License to your work. + +To apply the Apache License to your work, attach the following boilerplate notice, with the fields enclosed by brackets "[]" replaced with your own identifying information. (Don't include the brackets!) The text should be enclosed in the appropriate comment syntax for the file format. We also recommend that a file or class name and description of purpose be included on the same "printed page" as the copyright notice for easier identification within third-party archives. + +Copyright 2025 stefan + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + +http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. diff --git a/README.md b/README.md new file mode 100644 index 0000000..e86b816 --- /dev/null +++ b/README.md @@ -0,0 +1,4 @@ +# gg (Generic Generics) + +A Go library for the generic types that should be in the standard library, but aren't. +Currently, this includes [Option](./option/), but `Result` or `Either` could also be added once there is a compelling usecase for myself. @@ -0,0 +1,3 @@ +module github.com/majewsky/gg + +go 1.23 diff --git a/internal/test/helpers.go b/internal/test/helpers.go new file mode 100644 index 0000000..a93aa9e --- /dev/null +++ b/internal/test/helpers.go @@ -0,0 +1,24 @@ +/******************************************************************************* +* Copyright 2025 Stefan Majewsky <majewsky@gmx.net> +* SPDX-License-Identifier: Apache-2.0 +* Refer to the file "LICENSE" for details. +*******************************************************************************/ + +package option + +import ( + "reflect" + "testing" +) + +func AssertEqual[V any](t *testing.T, actual, expected V) { + if reflect.DeepEqual(actual, expected) { + return + } + t.Helper() + t.Errorf("expected %#v, but got %#v", expected, actual) +} + +func PointerTo[V any](value V) *V { + return &value +} diff --git a/option/option.go b/option/option.go new file mode 100644 index 0000000..1ea2e79 --- /dev/null +++ b/option/option.go @@ -0,0 +1,362 @@ +/******************************************************************************* +* Copyright 2025 Stefan Majewsky <majewsky@gmx.net> +* SPDX-License-Identifier: Apache-2.0 +* Refer to the file "LICENSE" for details. +*******************************************************************************/ + +// Package optional provides an Option type for Go. +// A value of the Option type will be in one of two states: "Some" (containing a value) or "None" (containing no value). +// +// The purpose of the Option type is to more clearly distinguish the two situations that standard Go uses pointer types for: +// - to provide a way to edit the inside of a value without changing the value itself +// - to allow for a value to be either present or absent (with absence being represented as "nil") +// +// Using the Option type, pointers may be reserved for the first purpose. +// For instance, a type like *int32 would clearly represent an editable value, whereas Option[int32] clearly represents an optional value. +// +// # Clean import guarantee +// +// This package is supposed to be used as a dot-import: +// +// import . "github.com/majewsky/go-option" +// +// To avoid backwards incompatibilities, we guarantee that, at least throughout the 1.x series, +// newer versions of this package will never export any more names than it currently does ("None", "Option" and "Some"). +// +// # Marshalling considerations +// +// Marshaling into and from YAML using https://github.com/go-yaml/yaml is supported. +// The "omitempty" flag works as expected. +// +// Marshaling into and from JSON using encoding/json is supported, but the "omitempty" flag does not work. +// You must use the "omitzero" flag to get the same effect, but note that this flag is only supported by Go 1.24 and newer. +// +// # How to replace pointer types with Option types +// +// This abridged example shows the most common ways to interact with pointer types that represent optional values: +// +// type ServerConfiguration struct { +// CrashLogPath *string +// ListenAddress *string +// ThreadCount *uint64 +// } +// +// func RunServer(cfg ServerConfiguration) { +// // inform about a value being absent +// if cfg.CrashLogPath == nil { +// log.Print("crash logging disabled because no CrashLogPath is given") +// } +// +// // fill a default value if nil is given +// listenAddress := "127.0.0.1:8080" +// if cfg.ListenAddress != nil { +// listenAddress = *listenAddress +// } +// +// // access contained value if present, or proceed without contained value if absent +// if cfg.ThreadCount != nil { +// startMultiThreadedServer(listenAddress, *cfg.ThreadCount) +// } else { +// startSingleThreadedServer(listenAddress) +// } +// } +// +// This is how the same code snippet looks when replacing the pointer types with Option types and taking advantage of the methods on type Option: +// +// type ServerConfiguration struct { +// CrashLogPath Option[string] +// ListenAddress Option[string] +// ThreadCount Option[uint64] +// } +// +// func RunServer(cfg ServerConfiguration) { +// // "if x == nil" becomes "if x.IsNone()"; the opposite check is called IsSome() +// if cfg.CrashLogPath.IsNone() { +// log.Print("crash logging disabled because no CrashLogPath is given") +// } +// +// // default values can be filled with UnwrapOr() +// listenAddress := cfg.ListenAddress.UnwrapOr("127.0.0.1:8080") +// +// // Unpack() provides the contained value and a success flag, similar to the double-return-value form of map indexing +// if threadCount, ok := cfg.ThreadCount.Unpack(); ok { +// startMultiThreadedServer(listenAddress, *cfg.ThreadCount) +// } else { +// startSingleThreadedServer(listenAddress) +// } +// } +// +// # Differences to Rust +// +// This package's API is obviously modeled after the Option type in the Rust standard library, but with some exceptions. +// +// - Go does not allow to introduce additional type parameters for individual methods. +// Any methods that, in Rust, introduce the second type parameter U, cannot be represented in Go. +// Some methods like and() or zip() could be allowed if the argument is restricted to Option[T] instead of Option[U], +// but this restriction degrades their usefulness beyond reasonable limits. +// - Go does not allow to introduce additional type restrictions in individual methods. +// This makes methods like unzip() or cloned() unrepresentable in Go. +// We might make these available as free-standing functions in the future, but if we do, +// they will definitely not be in this package (see "Clean import guarantee" above). +// - Mixing of struct receiver methods and pointer receiver methods on the same type is discouraged to avoid unintentional copies and data races. +// Since most of the useful methods require only a struct receiver, we forego those that require a pointer receiver, like get_or_insert() or take(). +// The only exception to this is the methods implementing Unmarshaler interfaces, where concurrency bugs are very unlikely. +// +// Finally, the unwrap() function is not provided since its meaningless error message is not helpful in most contexts. +// We only provide expect(), but under the different name UnwrapOrPanic(), since expect() reads terribly in context. Consider the following example: +// +// dbURL := GetDatabaseURLFromEnvironment().Expect("no DB connection found") +// // ^ This reads like we *expect* to not find a DB connection, even though the opposite is true. +// +// dbURL := GetDatabaseURLFromEnvironment().UnwrapOrPanic("no DB connection found") +// // ^ This is a much clearer phrasing. +package option + +import ( + "encoding/json" + "fmt" + "iter" +) + +// Option is a type that contains either one or no instances of T. +type Option[T any] struct { + value T + isSome bool +} + +//////////////////////////////////////////////////////////////////////////////// +// constructors + +// None constructs an Option instance that contains no value. +func None[T any]() Option[T] { + var empty T + return Option[T]{empty, false} +} + +// Some constructs an Option instance that contains the provided value. +func Some[T any](value T) Option[T] { + return Option[T]{value, true} +} + +// NOTE: Cannot use options.FromPointer() here because of import cycle. +func fromPointer[T any](value *T) Option[T] { + if value == nil { + return None[T]() + } else { + return Some(*value) + } +} + +//////////////////////////////////////////////////////////////////////////////// +// core API (methods sorted by name) + +// AsPointer converts this Option into a pointer type. +// +// Usage of this function is discouraged because it breaks the clear distinction +// between interior mutability (pointer) vs. optionality (Option). +// It is provided for when an Option value needs to be passed to a library +// function that requires a pointer value. +func (o Option[T]) AsPointer() *T { + if o.isSome { + return &o.value + } else { + return nil + } +} + +// AsSlice returns a slice with either the contained value or nothing in it. +func (o Option[T]) AsSlice() []T { + if o.isSome { + return []T{o.value} + } else { + return nil + } +} + +// Filter removes the contained value (if any) from the Option if it does not match the predicate. +func (o Option[T]) Filter(predicate func(T) bool) Option[T] { + if o.isSome && predicate(o.value) { + return o + } else { + return None[T]() + } +} + +// IsNone returns whether the Option contains no value. +// Its inverse is IsSome(). +func (o Option[T]) IsNone() bool { + return !o.isSome +} + +// IsSome returns whether the Option contains a value. +// Its inverse is IsNone(). +func (o Option[T]) IsSome() bool { + return o.isSome +} + +// IsSomeAnd returns whether the Option contains a value that matches the given predicate. +func (o Option[T]) IsSomeAnd(predicate func(T) bool) bool { + return o.isSome && predicate(o.value) +} + +// IsNoneOr returns whether the Option is either empty, or contains a value that matches the given predicate. +func (o Option[T]) IsNoneOr(predicate func(T) bool) bool { + return !o.isSome || predicate(o.value) +} + +// Iter returns an iterator that yields the contained value once (if any). +// If the Option is empty, the iterator yields nothing. +func (o Option[T]) Iter() iter.Seq[T] { + if o.isSome { + return func(yield func(T) bool) { yield(o.value) } + } else { + return func(yield func(T) bool) {} + } +} + +// Or returns the option itself if it contains a value, or otherwise returns "other". +// +// If you are passing the result of a function call, consider using OrElse() to avoid calling the function unless necessary. +func (o Option[T]) Or(other Option[T]) Option[T] { + if o.isSome { + return o + } else { + return other + } +} + +// Or returns the option itself if it contains a value, or otherwise runs the provided closure to produce the return value. +func (o Option[T]) OrElse(closure func() Option[T]) Option[T] { + if o.isSome { + return o + } else { + return closure() + } +} + +// Unpack returns the contained value (or the zero value if None), as well as if there was a contained value. +func (o Option[T]) Unpack() (T, bool) { + return o.value, o.isSome +} + +// UnwrapOr returns the contained value. +// If the Option is empty, the provided fallback value is returned instead. +func (o Option[T]) UnwrapOr(fallback T) T { + if o.isSome { + return o.value + } else { + return fallback + } +} + +// UnwrapOrElse returns the contained value. +// If the Option is empty, the provided closure is used to produce the return value. +func (o Option[T]) UnwrapOrElse(closure func() T) T { + if o.isSome { + return o.value + } else { + return closure() + } +} + +// UnwrapOrPanic returns the contained value, or panics with the given error message if it is empty. +func (o Option[T]) UnwrapOrPanic(msg any) T { + if o.isSome { + return o.value + } else { + panic(msg) + } +} + +// UnwrapOrPanicf is a shorthand for UnwrapOrPanic(fmt.Sprintf(msg, args...)). +func (o Option[T]) UnwrapOrPanicf(msg string, args ...any) T { + if o.isSome { + return o.value + } else { + panic(fmt.Sprintf(msg, args...)) + } +} + +// Xor returns an option containing a value if exactly one of the two given options contains a value, or None otherwise. +func (o Option[T]) Xor(other Option[T]) Option[T] { + if o.isSome == other.isSome { + return None[T]() + } else { + return o.Or(other) + } +} + +//////////////////////////////////////////////////////////////////////////////// +// formatting/marshalling support + +// Format implements the fmt.Formatter interface. +// +// If there is a contained value, it will be formatted as if it was given directly. +// Otherwise, the string "<none>" will be formatted according to the specified width and flags. +func (o Option[T]) Format(f fmt.State, verb rune) { + if o.isSome { + fmt.Fprintf(f, fmt.FormatString(f, verb), o.value) + } else { + fmt.Fprintf(f, fmt.FormatString(f, 's'), "<none>") + } +} + +// IsZero implements the IsZeroer interface as understood by encoding/json and github.com/go-yaml/yaml. +// It is an alias of IsNone(). +func (o Option[T]) IsZero() bool { + return !o.isSome +} + +type yamlMarshaler interface { + MarshalYAML() (any, error) +} + +// MarshalJSON implements the json.Marshaler interface. +func (o Option[T]) MarshalJSON() ([]byte, error) { + if o.isSome { + return json.Marshal(o.value) + } else { + return []byte("null"), nil + } +} + +// UnmarshalJSON implements the json.Unmarshaler interface. +func (o *Option[T]) UnmarshalJSON(buf []byte) error { + var data *T + err := json.Unmarshal(buf, &data) + if err != nil { + return err + } + *o = fromPointer(data) + return nil +} + +// MarshalYAML implements the yaml.Marshaler interface. +func (o Option[T]) MarshalYAML() (any, error) { + if o.isSome { + // If we just return o.value directly here, MarshalYAML will not be called + // on the value even if it exists. For this one specific case, we have to + // take care ourselves. + if m, ok := any(o.value).(yamlMarshaler); ok { + return m.MarshalYAML() + } else { + return o.value, nil + } + } else { + return nil, nil + } +} + +// UnmarshalYAML implements the yaml.Unmarshaler interface. +// +// This function signature is compatible with both v2 and v3 of github.com/go-yaml/yaml, +// so we intentionally do not use the v3-only signature that refers to the yaml.Node type. +func (o *Option[T]) UnmarshalYAML(unmarshal func(any) error) error { + var data *T + err := unmarshal(&data) + if err != nil { + return err + } + *o = fromPointer(data) + return nil +} diff --git a/option/option_test.go b/option/option_test.go new file mode 100644 index 0000000..2bac4f5 --- /dev/null +++ b/option/option_test.go @@ -0,0 +1,174 @@ +/******************************************************************************* +* Copyright 2025 Stefan Majewsky <majewsky@gmx.net> +* SPDX-License-Identifier: Apache-2.0 +* Refer to the file "LICENSE" for details. +*******************************************************************************/ + +package option + +import ( + "encoding/json" + "fmt" + "slices" + "testing" + + . "github.com/majewsky/gg/internal/test" +) + +//////////////////////////////////////////////////////////////////////////////// +// core API (methods sorted by name) + +func TestAsPointer(t *testing.T) { + AssertEqual(t, None[int]().AsPointer(), nil) + AssertEqual(t, Some(42).AsPointer(), PointerTo(42)) +} + +func TestAsSlice(t *testing.T) { + AssertEqual(t, None[int]().AsSlice(), []int(nil)) + AssertEqual(t, Some(42).AsSlice(), []int{42}) +} + +func TestFilter(t *testing.T) { + isEven := func(x int) bool { + return x%2 == 0 + } + + AssertEqual(t, None[int]().Filter(isEven), None[int]()) + AssertEqual(t, Some(41).Filter(isEven), None[int]()) + AssertEqual(t, Some(42).Filter(isEven), Some(42)) +} + +func TestIsNone(t *testing.T) { + AssertEqual(t, None[int]().IsNone(), true) + AssertEqual(t, Some(42).IsNone(), false) +} + +func TestIsSome(t *testing.T) { + AssertEqual(t, None[int]().IsSome(), false) + AssertEqual(t, Some(42).IsSome(), true) +} + +func TestIsZero(t *testing.T) { + AssertEqual(t, None[int]().IsZero(), true) + AssertEqual(t, Some(42).IsZero(), false) +} + +func TestIter(t *testing.T) { + AssertEqual(t, slices.Collect(None[int]().Iter()), []int(nil)) + AssertEqual(t, slices.Collect(Some(42).Iter()), []int{42}) +} + +func TestOr(t *testing.T) { + none := None[int]() + AssertEqual(t, none.Or(none), None[int]()) + AssertEqual(t, Some(42).Or(none), Some(42)) + AssertEqual(t, none.Or(Some(43)), Some(43)) + AssertEqual(t, Some(42).Or(Some(43)), Some(42)) +} + +func TestOrElse(t *testing.T) { + callCount := 0 + makeNone := func() Option[int] { + callCount++ + return None[int]() + } + makeSome := func() Option[int] { + callCount++ + return Some(43) + } + + AssertEqual(t, None[int]().OrElse(makeNone), None[int]()) + AssertEqual(t, callCount, 1) + AssertEqual(t, Some(42).OrElse(makeNone), Some(42)) + AssertEqual(t, callCount, 1) + AssertEqual(t, None[int]().OrElse(makeSome), Some(43)) + AssertEqual(t, callCount, 2) + AssertEqual(t, Some(42).OrElse(makeSome), Some(42)) + AssertEqual(t, callCount, 2) +} + +func TestUnpack(t *testing.T) { + val, ok := None[int]().Unpack() + AssertEqual(t, val, 0) + AssertEqual(t, ok, false) + + val, ok = Some(42).Unpack() + AssertEqual(t, val, 42) + AssertEqual(t, ok, true) +} + +func TestUnwrapOr(t *testing.T) { + AssertEqual(t, None[int]().UnwrapOr(5), 5) + AssertEqual(t, Some(42).UnwrapOr(5), 42) +} + +func TestUnwrapOrElse(t *testing.T) { + callCount := 0 + five := func() int { + callCount++ + return 5 + } + + AssertEqual(t, None[int]().UnwrapOrElse(five), 5) + AssertEqual(t, callCount, 1) + AssertEqual(t, Some(42).UnwrapOrElse(five), 42) + AssertEqual(t, callCount, 1) +} + +func TestXor(t *testing.T) { + none := None[int]() + AssertEqual(t, none.Xor(none), None[int]()) + AssertEqual(t, Some(42).Xor(none), Some(42)) + AssertEqual(t, none.Xor(Some(43)), Some(43)) + AssertEqual(t, Some(42).Xor(Some(43)), None[int]()) +} + +//////////////////////////////////////////////////////////////////////////////// +// formatting/marshalling support + +func TestFormat(t *testing.T) { + none := None[int]() + some := Some(42) + + AssertEqual(t, fmt.Sprintf("value is %d", none), "value is <none>") + AssertEqual(t, fmt.Sprintf("value is %d", some), "value is 42") + AssertEqual(t, fmt.Sprintf("value is %010d", none), "value is 0000<none>") + AssertEqual(t, fmt.Sprintf("value is %010d", some), "value is 0000000042") + + noneList := None[[]int]() + someList := Some([]int{4, 2}) + AssertEqual(t, fmt.Sprintf("value is %v", noneList), "value is <none>") + AssertEqual(t, fmt.Sprintf("value is %v", someList), "value is [4 2]") + AssertEqual(t, fmt.Sprintf("value is %#v", noneList), "value is <none>") + AssertEqual(t, fmt.Sprintf("value is %#v", someList), "value is []int{4, 2}") + + listOfOptions := []Option[int]{none, some} + AssertEqual(t, fmt.Sprintf("value is %#v", listOfOptions), "value is []option.Option[int]{<none>, 42}") +} + +func TestMarshalAndUnmarshalJSON(t *testing.T) { + type payload struct { + N1 Option[int] `json:"n1"` + N2 Option[int] `json:"n2,omitempty"` + N3 Option[int] `json:"n3,omitzero"` + S1 Option[int] `json:"s1"` + S2 Option[int] `json:"s2,omitempty"` + S3 Option[int] `json:"s3,omitzero"` + } + original := payload{ + N1: None[int](), + N2: None[int](), + N3: None[int](), + S1: Some(1), + S2: Some(2), + S3: Some(3), + } + buf, err := json.Marshal(original) + AssertEqual(t, err, nil) + AssertEqual(t, string(buf), `{"n1":null,"n2":null,"s1":1,"s2":2,"s3":3}`) + + var decoded payload + err = json.Unmarshal(buf, &decoded) + AssertEqual(t, err, nil) + AssertEqual(t, decoded, original) +} diff --git a/options/options.go b/options/options.go new file mode 100644 index 0000000..e058559 --- /dev/null +++ b/options/options.go @@ -0,0 +1,22 @@ +/******************************************************************************* +* Copyright 2025 Stefan Majewsky <majewsky@gmx.net> +* SPDX-License-Identifier: Apache-2.0 +* Refer to the file "LICENSE" for details. +*******************************************************************************/ + +// Package options provides additional functions for type option.Option +// that cannot be expressed as methods on the Option type itself. +package options + +import . "github.com/majewsky/gg/option" + +// NOTE: Keep functions sorted by name. + +// FromPointer converts a *T into an Option[T]. +func FromPointer[T any](value *T) Option[T] { + if value == nil { + return None[T]() + } else { + return Some(*value) + } +} diff --git a/options/options_test.go b/options/options_test.go new file mode 100644 index 0000000..69a4b43 --- /dev/null +++ b/options/options_test.go @@ -0,0 +1,19 @@ +/******************************************************************************* +* Copyright 2025 Stefan Majewsky <majewsky@gmx.net> +* SPDX-License-Identifier: Apache-2.0 +* Refer to the file "LICENSE" for details. +*******************************************************************************/ + +package options + +import ( + "testing" + + . "github.com/majewsky/gg/internal/test" + . "github.com/majewsky/gg/option" +) + +func TestFromPointer(t *testing.T) { + AssertEqual(t, FromPointer[int](nil), None[int]()) + AssertEqual(t, FromPointer(PointerTo[int](42)), Some(42)) +} |