Unify user update methods (#28733)

Fixes #28660
Fixes an admin api bug related to `user.LoginSource`
Fixed `/user/emails` response not identical to GitHub api

This PR unifies the user update methods. The goal is to keep the logic
only at one place (having audit logs in mind). For example, do the
password checks only in one method not everywhere a password is updated.

After that PR is merged, the user creation should be next.

2 files changed, 93 insertions, 0 deletions

diff --git a/modules/optional/option.go b/modules/optional/option.go
new file mode 100644
index 0000000000..af9e5ac852
--- /dev/null
+++ b/modules/optional/option.go
@@ -0,0 +1,45 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package optional
+
+type Option[T any] []T
+
+func None[T any]() Option[T] {
+	return nil
+}
+
+func Some[T any](v T) Option[T] {
+	return Option[T]{v}
+}
+
+func FromPtr[T any](v *T) Option[T] {
+	if v == nil {
+		return None[T]()
+	}
+	return Some(*v)
+}
+
+func FromNonDefault[T comparable](v T) Option[T] {
+	var zero T
+	if v == zero {
+		return None[T]()
+	}
+	return Some(v)
+}
+
+func (o Option[T]) Has() bool {
+	return o != nil
+}
+
+func (o Option[T]) Value() T {
+	var zero T
+	return o.ValueOrDefault(zero)
+}
+
+func (o Option[T]) ValueOrDefault(v T) T {
+	if o.Has() {
+		return o[0]
+	}
+	return v
+}
diff --git a/modules/optional/option_test.go b/modules/optional/option_test.go
new file mode 100644
index 0000000000..7ec345b6ba
--- /dev/null
+++ b/modules/optional/option_test.go
@@ -0,0 +1,48 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package optional
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/util"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestOption(t *testing.T) {
+	var uninitialized Option[int]
+	assert.False(t, uninitialized.Has())
+	assert.Equal(t, int(0), uninitialized.Value())
+	assert.Equal(t, int(1), uninitialized.ValueOrDefault(1))
+
+	none := None[int]()
+	assert.False(t, none.Has())
+	assert.Equal(t, int(0), none.Value())
+	assert.Equal(t, int(1), none.ValueOrDefault(1))
+
+	some := Some[int](1)
+	assert.True(t, some.Has())
+	assert.Equal(t, int(1), some.Value())
+	assert.Equal(t, int(1), some.ValueOrDefault(2))
+
+	var ptr *int
+	assert.False(t, FromPtr(ptr).Has())
+
+	opt1 := FromPtr(util.ToPointer(1))
+	assert.True(t, opt1.Has())
+	assert.Equal(t, int(1), opt1.Value())
+
+	assert.False(t, FromNonDefault("").Has())
+
+	opt2 := FromNonDefault("test")
+	assert.True(t, opt2.Has())
+	assert.Equal(t, "test", opt2.Value())
+
+	assert.False(t, FromNonDefault(0).Has())
+
+	opt3 := FromNonDefault(1)
+	assert.True(t, opt3.Has())
+	assert.Equal(t, int(1), opt3.Value())
+}