Add ArbitraryBuilder set value lazily (#307)

fixture-monkey/src/main/java/com/navercorp/fixturemonkey/ArbitraryBuilder.java

@@ -51,6 +51,7 @@
 import com.navercorp.fixturemonkey.arbitrary.ArbitraryNullity;
 import com.navercorp.fixturemonkey.arbitrary.ArbitrarySet;
 import com.navercorp.fixturemonkey.arbitrary.ArbitrarySetArbitrary;
+import com.navercorp.fixturemonkey.arbitrary.ArbitrarySetLazyValue;
 import com.navercorp.fixturemonkey.arbitrary.ArbitrarySetPostCondition;
 import com.navercorp.fixturemonkey.arbitrary.ArbitrarySpecAny;
 import com.navercorp.fixturemonkey.arbitrary.ArbitraryTraverser;
@@ -246,6 +247,12 @@ public ArbitraryBuilder<T> set(String expression, @Nullable Object value) {
 		return this;
 	}
 
+	public ArbitraryBuilder<T> setLazy(String expression, Supplier<T> supplier) {
+		ArbitraryExpression arbitraryExpression = ArbitraryExpression.from(expression);
+		this.builderManipulators.add(new ArbitrarySetLazyValue<>(arbitraryExpression, supplier));
+		return this;
+	}
+
 	public ArbitraryBuilder<T> set(String expression, Object value, long limit) {
 		ArbitraryExpression arbitraryExpression = ArbitraryExpression.from(expression);
 		this.builderManipulators.add(new ArbitrarySet<>(arbitraryExpression, value, limit));

fixture-monkey/src/main/java/com/navercorp/fixturemonkey/arbitrary/ArbitrarySetLazyValue.java

@@ -0,0 +1,80 @@
+/*
+ * Fixture Monkey
+ *
+ * Copyright (c) 2021-present NAVER Corp.
+ *
+ * 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.
+ */
+
+package com.navercorp.fixturemonkey.arbitrary;
+
+import java.util.Objects;
+import java.util.function.Supplier;
+
+import net.jqwik.api.Arbitraries;
+import net.jqwik.api.Arbitrary;
+
+public final class ArbitrarySetLazyValue<T> extends AbstractArbitrarySet<T> {
+	private final Supplier<T> supplier;
+	private long limit;
+
+	public ArbitrarySetLazyValue(ArbitraryExpression arbitraryExpression, Supplier<T> supplier, long limit) {
+		super(arbitraryExpression);
+		this.supplier = supplier;
+		this.limit = limit;
+	}
+
+	public ArbitrarySetLazyValue(ArbitraryExpression arbitraryExpression, Supplier<T> supplier) {
+		this(arbitraryExpression, supplier, Long.MAX_VALUE);
+	}
+
+	@Override
+	public T getValue() {
+		return supplier.get();
+	}
+
+	@Override
+	public Arbitrary<T> apply(Arbitrary<T> from) {
+		if (this.limit > 0) {
+			limit--;
+			return Arbitraries.just(getValue());
+		} else {
+			return from;
+		}
+	}
+
+	@Override
+	public ArbitrarySetLazyValue<T> copy() {
+		return new ArbitrarySetLazyValue<>(this.getArbitraryExpression(), this.supplier, this.limit);
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj) {
+			return true;
+		}
+		if (obj == null || getClass() != obj.getClass()) {
+			return false;
+		}
+		if (!super.equals(obj)) {
+			return false;
+		}
+		ArbitrarySetLazyValue<?> that = (ArbitrarySetLazyValue<?>)obj;
+		return getValue().equals(that.getValue());
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(super.hashCode(), getValue());
+	}
+}

fixture-monkey/src/test/java/com/navercorp/fixturemonkey/test/SimpleManipulatorTest.java

@@ -30,6 +30,7 @@
 import net.jqwik.api.Property;
 import net.jqwik.api.domains.Domain;
 
+import com.navercorp.fixturemonkey.ArbitraryBuilder;
 import com.navercorp.fixturemonkey.customizer.ExpressionSpec;
 import com.navercorp.fixturemonkey.test.SimpleManipulatorTestSpecs.IntValue;
 import com.navercorp.fixturemonkey.test.SimpleManipulatorTestSpecs.IntegerList;
@@ -856,4 +857,32 @@ void giveMeIncludeFixedArbitrarySize() {
 
 		then(actual.getValues()).hasSizeBetween(0, 4);
 	}
+
+	@Property
+	void giveMeSetLazyValue() {
+		// given
+		ArbitraryBuilder<String> variable = SUT.giveMeBuilder(String.class);
+		ArbitraryBuilder<String> builder = SUT.giveMeBuilder(String.class)
+			.setLazy("$", () -> variable.sample());
+		variable.set("test");
+
+		// when
+		String actual = builder.sample();
+
+		then(actual).isEqualTo("test");
+	}
+
+	@Property(tries = 1)
+	void giveMeSetLazyValueSampleGivesDifferentValue() {
+		// given
+		ArbitraryBuilder<String> variable = SUT.giveMeBuilder(String.class);
+		ArbitraryBuilder<String> builder = SUT.giveMeBuilder(String.class)
+			.setLazy("$", () -> variable.sample());
+		String expected = builder.sample();
+
+		// when
+		String actual = builder.sample();
+
+		then(actual).isNotEqualTo(expected);
+	}
 }