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Introduce AggregationVariable type.
This commit introduces a new AggregationVariable type that is intended to better identify variables within a pipeline to avoid mapping failures caused by invalid field names. Closes #4070 Original pull request: #4242
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‎spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationVariable.java‎

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/*
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* Copyright 2022 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.data.mongodb.core.aggregation;
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import org.springframework.lang.Nullable;
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import org.springframework.util.Assert;
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import org.springframework.util.ObjectUtils;
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/**
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* A special field that points to a variable {@code $$} expression.
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*
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* @author Christoph Strobl
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* @since 4.1
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*/
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public interface AggregationVariable extends Field {
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String PREFIX = "$$";
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/**
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* @return {@literal true} if the fields {@link #getName() name} does not match the defined {@link #getTarget()
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* target}.
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*/
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default boolean isAliased() {
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return !ObjectUtils.nullSafeEquals(getName(), getTarget());
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}
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@Override
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default String getName() {
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return getTarget();
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}
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default boolean isInternal() {
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return false;
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}
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/**
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* Create a new {@link AggregationVariable} for the given name.
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* <p>
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* Variables start with {@code $$}. If not, the given value gets prefixed with {@code $$}.
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*
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* @param value must not be {@literal null}.
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* @return new instance of {@link AggregationVariable}.
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* @throws IllegalArgumentException if given value is {@literal null}.
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*/
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static AggregationVariable variable(String value) {
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Assert.notNull(value, "Value must not be null");
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return new AggregationVariable() {
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private final String val = AggregationVariable.prefixVariable(value);
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@Override
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public String getTarget() {
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return val;
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}
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};
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}
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/**
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* Create a new {@link #isInternal() local} {@link AggregationVariable} for the given name.
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* <p>
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* Variables start with {@code $$}. If not, the given value gets prefixed with {@code $$}.
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*
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* @param value must not be {@literal null}.
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* @return new instance of {@link AggregationVariable}.
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* @throws IllegalArgumentException if given value is {@literal null}.
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*/
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static AggregationVariable localVariable(String value) {
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Assert.notNull(value, "Value must not be null");
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return new AggregationVariable() {
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private final String val = AggregationVariable.prefixVariable(value);
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@Override
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public String getTarget() {
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return val;
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}
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@Override
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public boolean isInternal() {
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return true;
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}
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};
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}
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/**
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* Check if the given field name reference may be variable.
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*
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* @param fieldRef can be {@literal null}.
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* @return true if given value matches the variable identification pattern.
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*/
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static boolean isVariable(@Nullable String fieldRef) {
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return fieldRef != null && fieldRef.stripLeading().matches("^\\$\\$\\w.*");
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}
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/**
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* Check if the given field may be variable.
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*
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* @param field can be {@literal null}.
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* @return true if given {@link Field field} is an {@link AggregationVariable} or if its value is a
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* {@link #isVariable(String) variable}.
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*/
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static boolean isVariable(Field field) {
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if (field instanceof AggregationVariable) {
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return true;
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}
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return isVariable(field.getTarget());
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}
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private static String prefixVariable(String variable) {
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var trimmed = variable.stripLeading();
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return trimmed.startsWith(PREFIX) ? trimmed : (PREFIX + trimmed);
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}
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}

‎spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ArrayOperators.java‎

Lines changed: 16 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -1515,52 +1515,39 @@ public interface AsBuilder {
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}
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}
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public enum Variable implements Field {
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public enum Variable implements AggregationVariable {
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THIS {
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@Override
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public String getName() {
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return "$$this";
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}
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@Override
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public String getTarget() {
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return "$$this";
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}
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@Override
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public boolean isAliased() {
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return false;
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}
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@Override
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public String toString() {
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return getName();
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}
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},
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VALUE {
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@Override
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public String getName() {
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return "$$value";
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}
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@Override
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public String getTarget() {
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return "$$value";
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}
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1553-
@Override
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public boolean isAliased() {
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return false;
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}
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@Override
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public String toString() {
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return getName();
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}
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};
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@Override
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public boolean isInternal() {
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return true;
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}
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/**
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* Create a {@link Field} reference to a given {@literal property} prefixed with the {@link Variable} identifier.
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* eg. {@code $$value.product}
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}
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};
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}
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public static boolean isVariable(Field field) {
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for (Variable var : values()) {
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if (field.getTarget().startsWith(var.getTarget())) {
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return true;
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}
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}
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return false;
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}
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}
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}
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‎spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Fields.java‎

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@@ -245,7 +245,7 @@ public AggregationField(String name, @Nullable String target) {
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private static String cleanUp(String source) {
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if (SystemVariable.isReferingToSystemVariable(source)) {
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if (AggregationVariable.isVariable(source)) {
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return source;
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}
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‎spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/SystemVariable.java‎

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* @author Christoph Strobl
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* @see <a href="https://docs.mongodb.com/manual/reference/aggregation-variables">Aggregation Variables</a>.
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*/
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public enum SystemVariable {
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public enum SystemVariable implements AggregationVariable {
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/**
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* Variable for the current datetime.
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*/
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SEARCH_META;
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private static final String PREFIX = "$$";
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/**
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* Return {@literal true} if the given {@code fieldRef} denotes a well-known system variable, {@literal false}
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* otherwise.
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*/
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public static boolean isReferingToSystemVariable(@Nullable String fieldRef) {
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if (fieldRef == null || !fieldRef.startsWith(PREFIX) || fieldRef.length() <= 2) {
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String candidate = variableNameFrom(fieldRef);
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if (candidate == null) {
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return false;
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}
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int indexOfFirstDot = fieldRef.indexOf('.');
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String candidate = fieldRef.substring(2, indexOfFirstDot == -1 ? fieldRef.length() : indexOfFirstDot);
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candidate = candidate.startsWith(PREFIX) ? candidate.substring(2) : candidate;
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for (SystemVariable value : values()) {
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if (value.name().equals(candidate)) {
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return true;
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public String toString() {
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return PREFIX.concat(name());
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}
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@Override
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public String getTarget() {
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return toString();
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}
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@Nullable
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static String variableNameFrom(@Nullable String fieldRef) {
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if (fieldRef == null || !fieldRef.startsWith(PREFIX) || fieldRef.length() <= 2) {
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return null;
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}
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int indexOfFirstDot = fieldRef.indexOf('.');
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return indexOfFirstDot == -1 ? fieldRef : fieldRef.substring(2, indexOfFirstDot);
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}
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}

‎spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/TypeBasedAggregationOperationContext.java‎

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Original file line numberDiff line numberDiff line change
@@ -133,7 +133,7 @@ public AggregationOperationContext continueOnMissingFieldReference(Class<?> type
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protected FieldReference getReferenceFor(Field field) {
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136-
if(entity.getNullable() == null) {
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if(entity.getNullable() == null || AggregationVariable.isVariable(field)) {
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return new DirectFieldReference(new ExposedField(field, true));
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}
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‎spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/AggregationVariableUnitTests.java‎

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/*
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* Copyright 2022 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.data.mongodb.core.aggregation;
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import static org.assertj.core.api.Assertions.*;
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import org.junit.jupiter.api.Test;
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import org.mockito.Mockito;
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/**
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* @author Christoph Strobl
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*/
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class AggregationVariableUnitTests {
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@Test // GH-4070
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void variableErrorsOnNullValue() {
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assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> AggregationVariable.variable(null));
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}
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@Test // GH-4070
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void createsVariable() {
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var variable = AggregationVariable.variable("$$now");
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assertThat(variable.getTarget()).isEqualTo("$$now");
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assertThat(variable.isInternal()).isFalse();
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}
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@Test // GH-4070
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void prefixesVariableIfNeeded() {
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var variable = AggregationVariable.variable("this");
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assertThat(variable.getTarget()).isEqualTo("$$this");
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}
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@Test // GH-4070
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void localVariableErrorsOnNullValue() {
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assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> AggregationVariable.localVariable(null));
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}
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@Test // GH-4070
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void localVariable() {
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var variable = AggregationVariable.localVariable("$$this");
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assertThat(variable.getTarget()).isEqualTo("$$this");
61+
assertThat(variable.isInternal()).isTrue();
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}
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@Test // GH-4070
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void prefixesLocalVariableIfNeeded() {
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var variable = AggregationVariable.localVariable("this");
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assertThat(variable.getTarget()).isEqualTo("$$this");
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}
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@Test // GH-4070
73+
void isVariableReturnsTrueForAggregationVariableTypes() {
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var variable = Mockito.mock(AggregationVariable.class);
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assertThat(AggregationVariable.isVariable(variable)).isTrue();
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}
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@Test // GH-4070
81+
void isVariableReturnsTrueForFieldThatTargetsVariable() {
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var variable = Fields.field("value", "$$this");
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85+
assertThat(AggregationVariable.isVariable(variable)).isTrue();
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}
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@Test // GH-4070
89+
void isVariableReturnsFalseForFieldThatDontTargetsVariable() {
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var variable = Fields.field("value", "$this");
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assertThat(AggregationVariable.isVariable(variable)).isFalse();
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}
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}

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