Implement DistinctFieldView

Author: yevhenii-nadtochii

model/src/main/kotlin/io/spine/validation/DistinctFieldView.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2025, TeamDev. All rights reserved.
+ *
+ * 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
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package io.spine.validation
+
+import io.spine.core.Subscribe
+import io.spine.protodata.ast.FieldRef
+import io.spine.protodata.plugin.View
+import io.spine.server.entity.alter
+import io.spine.validation.event.DistinctFieldDiscovered
+
+/**
+ * A view of a field that is marked with `(distinct) = true` option.
+ */
+internal class DistinctFieldView : View<FieldRef, DistinctField, DistinctField.Builder>() {
+
+    @Subscribe
+    fun on(e: DistinctFieldDiscovered) = alter {
+        errorMessage = e.errorMessage
+        subject = e.subject
+    }
+}

model/src/main/kotlin/io/spine/validation/ValidationPlugin.kt

@@ -48,6 +48,7 @@ public abstract class ValidationPlugin(renderers: List<Renderer<*>> = emptyList(
         RequiredFieldView::class.java,
         PatternFieldView::class.java,
         GoesFieldView::class.java,
+        DistinctFieldView::class.java,
     ),
     viewRepositories = setOf<ViewRepository<*, *, *>>(
         CompiledMessageRepository(),