review: feature Parameter remove refactoring

src/main/java/spoon/refactoring/CtParameterRemoveRefactoring.java

@@ -0,0 +1,328 @@
+/**
+ * Copyright (C) 2006-2017 INRIA and contributors
+ * Spoon - http://spoon.gforge.inria.fr/
+ *
+ * This software is governed by the CeCILL-C License under French law and
+ * abiding by the rules of distribution of free software. You can use, modify
+ * and/or redistribute the software under the terms of the CeCILL-C license as
+ * circulated by CEA, CNRS and INRIA at http://www.cecill.info.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the CeCILL-C License for more details.
+ *
+ * The fact that you are presently reading this means that you have had
+ * knowledge of the CeCILL-C license and that you accept its terms.
+ */
+package spoon.refactoring;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import spoon.SpoonException;
+import spoon.reflect.code.CtAnnotationFieldAccess;
+import spoon.reflect.code.CtArrayRead;
+import spoon.reflect.code.CtExpression;
+import spoon.reflect.code.CtFieldRead;
+import spoon.reflect.code.CtInvocation;
+import spoon.reflect.code.CtLiteral;
+import spoon.reflect.code.CtNewArray;
+import spoon.reflect.code.CtThisAccess;
+import spoon.reflect.code.CtVariableRead;
+import spoon.reflect.declaration.CtElement;
+import spoon.reflect.declaration.CtExecutable;
+import spoon.reflect.declaration.CtParameter;
+import spoon.reflect.reference.CtExecutableReference;
+import spoon.reflect.reference.CtParameterReference;
+import spoon.reflect.visitor.CtAbstractVisitor;
+import spoon.reflect.visitor.chain.CtConsumer;
+import spoon.reflect.visitor.filter.AllMethodsSameSignatureFunction;
+import spoon.reflect.visitor.filter.ExecutableReferenceFilter;
+import spoon.reflect.visitor.filter.ParameterReferenceFunction;
+
+/**
+ * Removes target {@link CtParameter} from the parent target {@link CtExecutable}
+ * and from all overriding/overridden methods of related type hierarchies
+ * and from all lambda expressions (if any) implementing the modified interface.
+ * It removes arguments from all invocations of refactored executables too.<br>
+ *
+ * Before the refactoring is started it checks that:
+ * <ul>
+ * <li>to be removed parameter is NOT used in any refactored implementation
+ * <li>to be removed argument contains read only expression, which can be safely removed
+ * </ul>
+ * If one of the validation constraints fails, then {@link RefactoringException} is thrown and nothing is changed.
+ * You can override `#create*Issue(...)` methods to handle such exceptions individually.
+ * <br>
+ */
+public class CtParameterRemoveRefactoring implements CtRefactoring {
+
+	private CtParameter<?> target;
+	private int parameterIndex;
+	/**
+	 * List of all {@link CtExecutable}s whose parameter has to be removed
+	 */
+	private List<CtExecutable<?>> targetExecutables;
+	/**
+	 * List of all {@link CtInvocation}s whose argument has to be removed
+	 */
+	private List<CtInvocation<?>> targetInvocations;
+
+	public CtParameterRemoveRefactoring() {
+	}
+
+	/**
+	 * @return the {@link CtParameter} which has to be removed by this refactoring function
+	 */
+	public CtParameter<?> getTarget() {
+		return target;
+	}
+
+	/**
+	 * @param target the {@link CtParameter} which has to be removed by this refactoring function
+	 * @return this to support fluent API
+	 */
+	public CtParameterRemoveRefactoring setTarget(CtParameter<?> target) {
+		if (this.target == target) {
+			return this;
+		}
+		this.target = target;
+		this.parameterIndex = target.getParent().getParameters().indexOf(target);
+		targetExecutables = null;
+		targetInvocations = null;
+		return this;
+	}
+
+	/**
+	 * @return computes and returns all executables, which will be modified by this refactoring
+	 */
+	public List<CtExecutable<?>> getTargetExecutables() {
+		if (targetExecutables == null) {
+			computeAllExecutables();
+		}
+		return targetExecutables;
+	}
+
+	/**
+	 * @return computes and returns all invocations, which will be modified by this refactoring
+	 */
+	public List<CtInvocation<?>> getTargetInvocations() {
+		if (targetInvocations == null) {
+			computeAllInvocations();
+		}
+		return targetInvocations;
+	}
+
+	@Override
+	public void refactor() {
+		if (getTarget() == null) {
+			throw new SpoonException("The target of refactoring is not defined");
+		}
+		detectIssues();
+		refactorNoCheck();
+	}
+
+	/**
+	 * validates whether this refactoring can be done without changing behavior of the refactored code.
+	 */
+	protected void detectIssues() {
+		checkAllExecutables();
+		checkAllInvocations();
+	}
+
+	/**
+	 * search for all methods and lambdas which has to be refactored together with target method
+	 */
+	private void computeAllExecutables() {
+		if (getTarget() == null) {
+			throw new SpoonException("The target of refactoring is not defined");
+		}
+		final List<CtExecutable<?>> executables = new ArrayList<>();
+		CtExecutable<?> targetExecutable = target.getParent();
+		//all the executables, which belongs to same inheritance tree
+		executables.add(targetExecutable);
+		targetExecutable.map(new AllMethodsSameSignatureFunction()).forEach(new CtConsumer<CtExecutable<?>>() {
+			@Override
+			public void accept(CtExecutable<?> executable) {
+				executables.add(executable);
+			}
+		});
+		targetExecutables = Collections.unmodifiableList(executables);
+	}
+
+	/**
+	 * search for all methods and lambdas which has to be refactored together with target method
+	 */
+	private void computeAllInvocations() {
+		ExecutableReferenceFilter execRefFilter = new ExecutableReferenceFilter();
+		for (CtExecutable<?> exec : getTargetExecutables()) {
+			execRefFilter.addExecutable(exec);
+		}
+		//all the invocations, which belongs to same inheritance tree
+		final List<CtInvocation<?>> invocations = new ArrayList<>();
+		target.getFactory().getModel().getRootPackage().filterChildren(execRefFilter).forEach(new CtConsumer<CtExecutableReference<?>>() {
+			@Override
+			public void accept(CtExecutableReference<?> t) {
+				CtElement parent = t.getParent();
+				if (parent instanceof CtInvocation<?>) {
+					invocations.add((CtInvocation<?>) parent);
+				} //else ignore other hits, which are not in context of invocation
+			}
+		});
+		targetInvocations = Collections.unmodifiableList(invocations);
+	}
+
+	private void checkAllExecutables() {
+		for (CtExecutable<?> executable : getTargetExecutables()) {
+			checkExecutable(executable);
+		}
+	}
+
+	private void checkExecutable(CtExecutable<?> executable) {
+		final CtParameter<?> toBeRemovedParam = executable.getParameters().get(this.parameterIndex);
+		toBeRemovedParam.map(new ParameterReferenceFunction()).forEach(new CtConsumer<CtParameterReference<?>>() {
+			@Override
+			public void accept(CtParameterReference<?> paramRef) {
+				//some parameter uses are acceptable
+				//e.g. parameter in invocation of super of method, which is going to be removed too.
+				if (isAllowedParameterUsage(paramRef)) {
+					return;
+				}
+				createParameterUsedIssue(toBeRemovedParam, paramRef);
+			}
+		});
+	}
+
+	private void checkAllInvocations() {
+		for (CtInvocation<?> invocation : getTargetInvocations()) {
+			checkInvocation(invocation);
+		}
+	}
+
+	private void checkInvocation(CtInvocation<?> invocation) {
+		final CtExpression<?> toBeRemovedExpression = invocation.getArguments().get(this.parameterIndex);
+		if (canRemoveExpression(toBeRemovedExpression) == false) {
+			createExpressionCannotBeRemovedIssue(invocation, toBeRemovedExpression);
+		}
+	}
+
+	/**
+	 * Detects whether found usage of removed parameter is acceptable
+	 * @param paramRef the found reference to
+	 * @return true if it is allowed parameter use
+	 */
+	protected boolean isAllowedParameterUsage(CtParameterReference<?> paramRef) {
+		if (isRemovedParamOfRefactoredInvocation(paramRef)) {
+			return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Detects whether `toBeRemovedExpression` can be safely removed during the refactoring
+	 *
+	 * @param toBeRemovedExpression the {@link CtExpression}, which will be removed by this refactoring
+	 * @return true if the expression used to deliver argument of removed parameter can be removed
+	 * false if cannot be removed and this refactoring has to be avoided.
+	 */
+	protected boolean canRemoveExpression(CtExpression<?> toBeRemovedExpression) {
+		class Context {
+			boolean canBeRemoved = false;
+		}
+		final Context context = new Context();
+		toBeRemovedExpression.accept(new CtAbstractVisitor() {
+			@Override
+			public <T> void visitCtVariableRead(CtVariableRead<T> variableRead) {
+				context.canBeRemoved = true;
+			}
+			@Override
+			public <T> void visitCtArrayRead(CtArrayRead<T> arrayRead) {
+				context.canBeRemoved = true;
+			}
+			@Override
+			public <T> void visitCtFieldRead(CtFieldRead<T> fieldRead) {
+				context.canBeRemoved = true;
+			}
+			@Override
+			public <T> void visitCtParameterReference(CtParameterReference<T> reference) {
+				context.canBeRemoved = true;
+			}
+			@Override
+			public <T> void visitCtLiteral(CtLiteral<T> literal) {
+				context.canBeRemoved = true;
+			}
+			@Override
+			public <T> void visitCtNewArray(CtNewArray<T> newArray) {
+				context.canBeRemoved = true;
+			}
+			@Override
+			public <T> void visitCtAnnotationFieldAccess(CtAnnotationFieldAccess<T> annotationFieldAccess) {
+				context.canBeRemoved = true;
+			}
+			@Override
+			public <T> void visitCtThisAccess(CtThisAccess<T> thisAccess) {
+				context.canBeRemoved = true;
+			}
+			//There are more expression which is save to remove. Including tree of unary/binary operators, conditional, etc.
+			//It would be good to have a Filter, which matches read only expressions
+		});
+		return context.canBeRemoved;
+	}
+
+	protected boolean isRemovedParamOfRefactoredInvocation(CtParameterReference<?> paramRef) {
+		CtInvocation<?> invocation = paramRef.getParent(CtInvocation.class);
+		if (invocation == null) {
+			return false;
+		}
+		return getTargetInvocations().contains(invocation);
+	}
+
+	/**
+	 * Override this method to get access to details about this refactoring issue
+	 * @param usedParameter to be removed parameter, which is used by `parameterUsage`
+	 * @param parameterUsage the usage of parameter, which avoids it's remove
+	 */
+	protected void createParameterUsedIssue(CtParameter<?> usedParameter, CtParameterReference<?> parameterUsage) {
+		throw new RefactoringException("The parameter " + usedParameter.getSimpleName()
+		+ " of method: " + parameterUsage.getDeclaringExecutable() + " cannot be removed because it is used (" + parameterUsage.getPosition() + ")");
+	}
+
+	/**
+	 * Override this method to get access to details about this refactoring issue.
+	 * @param toBeRemovedExpression is the expression which delivers value for the argument of the removed parameter,
+	 * where {@link #canRemoveExpression(CtExpression)} returned false.
+	 */
+	protected void createExpressionCannotBeRemovedIssue(CtInvocation<?> invocation, CtExpression<?> toBeRemovedExpression) {
+		throw new RefactoringException("The expression " + toBeRemovedExpression
+		+ ", which creates argument of the to be removed parameter in invocation " + invocation + " cannot be removed."
+		+ " Override method `canRemoveExpression` to customize this behavior.");
+	}
+
+	protected void refactorNoCheck() {
+		removeInvocationArguments();
+		removeMethodParameters();
+	}
+
+	protected void removeInvocationArguments() {
+		List<CtInvocation<?>> invocations = getTargetInvocations();
+		for (CtInvocation<?> invocation : invocations) {
+			removeInvocationArgument(invocation);
+		}
+	}
+
+	protected void removeInvocationArgument(CtInvocation<?> invocation) {
+		invocation.removeArgument(invocation.getArguments().get(this.parameterIndex));
+	}
+
+	protected void removeMethodParameters() {
+		List<CtExecutable<?>> executables = getTargetExecutables();
+		for (CtExecutable<?> executable : executables) {
+			removeParameter(executable);
+		}
+	}
+
+	protected void removeParameter(CtExecutable<?> executable) {
+		executable.removeParameter(executable.getParameters().get(this.parameterIndex));
+	}
+}