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| 1 | +/* |
| 2 | + * Copyright 2025 the original author or authors. |
| 3 | + * <p> |
| 4 | + * Licensed under the Moderne Source Available License (the "License"); |
| 5 | + * you may not use this file except in compliance with the License. |
| 6 | + * You may obtain a copy of the License at |
| 7 | + * <p> |
| 8 | + * https://docs.moderne.io/licensing/moderne-source-available-license |
| 9 | + * <p> |
| 10 | + * Unless required by applicable law or agreed to in writing, software |
| 11 | + * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | + * See the License for the specific language governing permissions and |
| 14 | + * limitations under the License. |
| 15 | + */ |
| 16 | +package org.openrewrite.java.migrate.lang; |
| 17 | + |
| 18 | +import lombok.EqualsAndHashCode; |
| 19 | +import lombok.Value; |
| 20 | +import org.jspecify.annotations.Nullable; |
| 21 | +import org.openrewrite.*; |
| 22 | +import org.openrewrite.internal.ListUtils; |
| 23 | +import org.openrewrite.java.JavaIsoVisitor; |
| 24 | +import org.openrewrite.java.JavaTemplate; |
| 25 | +import org.openrewrite.java.search.SemanticallyEqual; |
| 26 | +import org.openrewrite.java.search.UsesJavaVersion; |
| 27 | +import org.openrewrite.java.tree.*; |
| 28 | +import org.openrewrite.marker.Markers; |
| 29 | +import org.openrewrite.staticanalysis.InlineVariable; |
| 30 | +import org.openrewrite.staticanalysis.groovy.GroovyFileChecker; |
| 31 | +import org.openrewrite.staticanalysis.kotlin.KotlinFileChecker; |
| 32 | + |
| 33 | +import java.util.List; |
| 34 | +import java.util.concurrent.atomic.AtomicBoolean; |
| 35 | +import java.util.concurrent.atomic.AtomicReference; |
| 36 | + |
| 37 | +import static java.util.Collections.singletonList; |
| 38 | +import static java.util.Objects.requireNonNull; |
| 39 | +import static org.openrewrite.Tree.randomId; |
| 40 | + |
| 41 | +@Value |
| 42 | +@EqualsAndHashCode(callSuper = false) |
| 43 | +public class SwitchCaseAssignmentsToSwitchExpression extends Recipe { |
| 44 | + @Override |
| 45 | + public String getDisplayName() { |
| 46 | + return "Convert assigning Switch statements to Switch expressions"; |
| 47 | + } |
| 48 | + |
| 49 | + @Override |
| 50 | + public String getDescription() { |
| 51 | + return "Switch statements for which each case is assigning a value to the same variable can be converted to a switch expression that returns the value of the variable. " + |
| 52 | + "This is only applicable for Java 17 and later."; |
| 53 | + } |
| 54 | + |
| 55 | + @Override |
| 56 | + public TreeVisitor<?, ExecutionContext> getVisitor() { |
| 57 | + TreeVisitor<?, ExecutionContext> preconditions = Preconditions.and( |
| 58 | + new UsesJavaVersion<>(17), |
| 59 | + Preconditions.not(new KotlinFileChecker<>()), |
| 60 | + Preconditions.not(new GroovyFileChecker<>()) |
| 61 | + ); |
| 62 | + return Preconditions.check(preconditions, new JavaIsoVisitor<ExecutionContext>() { |
| 63 | + @Override |
| 64 | + public J.Block visitBlock(J.Block originalBlock, ExecutionContext ctx) { |
| 65 | + J.Block block = super.visitBlock(originalBlock, ctx); |
| 66 | + |
| 67 | + AtomicReference<J.@Nullable Switch> originalSwitch = new AtomicReference<>(); |
| 68 | + |
| 69 | + int lastIndex = block.getStatements().size() - 1; |
| 70 | + return block.withStatements(ListUtils.map(block.getStatements(), (index, statement) -> { |
| 71 | + if (statement == originalSwitch.getAndSet(null)) { |
| 72 | + doAfterVisit(new InlineVariable().getVisitor()); |
| 73 | + // We've already converted the switch/assignments to an assignment with a switch expression. |
| 74 | + return null; |
| 75 | + } |
| 76 | + |
| 77 | + if (index < lastIndex && |
| 78 | + statement instanceof J.VariableDeclarations && |
| 79 | + ((J.VariableDeclarations) statement).getVariables().size() == 1 && |
| 80 | + !canHaveSideEffects(((J.VariableDeclarations) statement).getVariables().get(0).getInitializer()) && |
| 81 | + block.getStatements().get(index + 1) instanceof J.Switch) { |
| 82 | + J.VariableDeclarations vd = (J.VariableDeclarations) statement; |
| 83 | + J.Switch nextStatementSwitch = (J.Switch) block.getStatements().get(index + 1); |
| 84 | + |
| 85 | + J.VariableDeclarations.NamedVariable originalVariable = vd.getVariables().get(0); |
| 86 | + J.SwitchExpression newSwitchExpression = buildNewSwitchExpression(nextStatementSwitch, originalVariable); |
| 87 | + if (newSwitchExpression != null) { |
| 88 | + originalSwitch.set(nextStatementSwitch); |
| 89 | + return vd |
| 90 | + .withVariables(singletonList(originalVariable.getPadding().withInitializer( |
| 91 | + JLeftPadded.<Expression>build(newSwitchExpression).withBefore(Space.SINGLE_SPACE)))) |
| 92 | + .withComments(ListUtils.concatAll(vd.getComments(), nextStatementSwitch.getComments())); |
| 93 | + } |
| 94 | + } |
| 95 | + return statement; |
| 96 | + })); |
| 97 | + } |
| 98 | + |
| 99 | + private J.@Nullable SwitchExpression buildNewSwitchExpression(J.Switch originalSwitch, J.VariableDeclarations.NamedVariable originalVariable) { |
| 100 | + J.Identifier originalVariableId = originalVariable.getName(); |
| 101 | + AtomicBoolean isQualified = new AtomicBoolean(true); |
| 102 | + AtomicBoolean isDefaultCaseAbsent = new AtomicBoolean(true); |
| 103 | + AtomicBoolean isUsingArrows = new AtomicBoolean(true); |
| 104 | + AtomicBoolean isLastCaseEmpty = new AtomicBoolean(false); |
| 105 | + |
| 106 | + List<Statement> updatedCases = ListUtils.map(originalSwitch.getCases().getStatements(), (index, s) -> { |
| 107 | + if (!isQualified.get()) { |
| 108 | + return null; |
| 109 | + } |
| 110 | + |
| 111 | + J.Case caseItem = (J.Case) s; |
| 112 | + if (caseItem.getCaseLabels().get(0) instanceof J.Identifier && |
| 113 | + "default".equals(((J.Identifier) caseItem.getCaseLabels().get(0)).getSimpleName())) { |
| 114 | + isDefaultCaseAbsent.set(false); |
| 115 | + } |
| 116 | + |
| 117 | + if (caseItem.getBody() != null) { // arrow cases |
| 118 | + J caseBody = caseItem.getBody(); |
| 119 | + if (caseBody instanceof J.Block && ((J.Block) caseBody).getStatements().size() == 1) { |
| 120 | + caseBody = ((J.Block) caseBody).getStatements().get(0); |
| 121 | + } |
| 122 | + J.Assignment assignment = extractAssignmentOfVariable(caseBody, originalVariableId); |
| 123 | + if (assignment != null) { |
| 124 | + return caseItem.withBody(assignment.getAssignment()); |
| 125 | + } |
| 126 | + } else { // colon cases |
| 127 | + isUsingArrows.set(false); |
| 128 | + boolean isLastCase = index + 1 == originalSwitch.getCases().getStatements().size(); |
| 129 | + |
| 130 | + List<Statement> caseStatements = caseItem.getStatements(); |
| 131 | + if (caseStatements.isEmpty()) { |
| 132 | + if (isLastCase) { |
| 133 | + isLastCaseEmpty.set(true); |
| 134 | + } |
| 135 | + return caseItem; |
| 136 | + } |
| 137 | + |
| 138 | + J.Assignment assignment = extractAssignmentFromColonCase(caseStatements, isLastCase, originalVariableId); |
| 139 | + if (assignment != null) { |
| 140 | + J.Yield yieldStatement = new J.Yield( |
| 141 | + randomId(), |
| 142 | + assignment.getPrefix().withWhitespace(" "), |
| 143 | + Markers.EMPTY, |
| 144 | + false, |
| 145 | + assignment.getAssignment() |
| 146 | + ); |
| 147 | + return caseItem.withStatements(singletonList(yieldStatement)); |
| 148 | + } |
| 149 | + } |
| 150 | + |
| 151 | + isQualified.set(false); |
| 152 | + return null; |
| 153 | + }); |
| 154 | + if (!isQualified.get()) { |
| 155 | + return null; |
| 156 | + } |
| 157 | + |
| 158 | + boolean shouldAddDefaultCase = isDefaultCaseAbsent.get() && !SwitchUtils.coversAllPossibleValues(originalSwitch); |
| 159 | + Expression originalInitializer = originalVariable.getInitializer(); |
| 160 | + if ((originalInitializer == null && shouldAddDefaultCase) || |
| 161 | + (isLastCaseEmpty.get() && !shouldAddDefaultCase)) { |
| 162 | + return null; |
| 163 | + } |
| 164 | + |
| 165 | + if (shouldAddDefaultCase) { |
| 166 | + updatedCases.add(createDefaultCase(originalSwitch, originalInitializer.withPrefix(Space.SINGLE_SPACE), isUsingArrows.get())); |
| 167 | + } |
| 168 | + |
| 169 | + return new J.SwitchExpression( |
| 170 | + randomId(), |
| 171 | + Space.SINGLE_SPACE, |
| 172 | + Markers.EMPTY, |
| 173 | + originalSwitch.getSelector(), |
| 174 | + originalSwitch.getCases().withStatements(updatedCases), |
| 175 | + originalVariable.getType()); |
| 176 | + } |
| 177 | + |
| 178 | + private J.@Nullable Assignment extractAssignmentFromColonCase(List<Statement> caseStatements, boolean isLastCase, J.Identifier variableId) { |
| 179 | + if (caseStatements.size() == 1 && caseStatements.get(0) instanceof J.Block) { |
| 180 | + caseStatements = ((J.Block) caseStatements.get(0)).getStatements(); |
| 181 | + } |
| 182 | + if ((caseStatements.size() == 2 && caseStatements.get(1) instanceof J.Break) || (caseStatements.size() == 1 && isLastCase)) { |
| 183 | + return extractAssignmentOfVariable(caseStatements.get(0), variableId); |
| 184 | + } |
| 185 | + return null; |
| 186 | + } |
| 187 | + |
| 188 | + private J.@Nullable Assignment extractAssignmentOfVariable(J maybeAssignment, J.Identifier variableId) { |
| 189 | + if (maybeAssignment instanceof J.Assignment) { |
| 190 | + J.Assignment assignment = (J.Assignment) maybeAssignment; |
| 191 | + if (assignment.getVariable() instanceof J.Identifier) { |
| 192 | + J.Identifier variable = (J.Identifier) assignment.getVariable(); |
| 193 | + if (SemanticallyEqual.areEqual(variable, variableId) && |
| 194 | + !containsIdentifier(variableId, assignment.getAssignment())) { |
| 195 | + return assignment; |
| 196 | + } |
| 197 | + } |
| 198 | + } |
| 199 | + return null; |
| 200 | + } |
| 201 | + |
| 202 | + private J.Case createDefaultCase(J.Switch originalSwitch, Expression returnedExpression, boolean arrow) { |
| 203 | + J.Switch switchStatement = JavaTemplate.apply( |
| 204 | + "switch(1) { default" + (arrow ? " ->" : ": yield") + " #{any()}; }", |
| 205 | + new Cursor(getCursor(), originalSwitch), |
| 206 | + originalSwitch.getCoordinates().replace(), |
| 207 | + returnedExpression |
| 208 | + ); |
| 209 | + return (J.Case) switchStatement.getCases().getStatements().get(0); |
| 210 | + } |
| 211 | + |
| 212 | + private boolean containsIdentifier(J.Identifier identifier, Expression expression) { |
| 213 | + return new JavaIsoVisitor<AtomicBoolean>() { |
| 214 | + @Override |
| 215 | + public J.Identifier visitIdentifier(J.Identifier id, AtomicBoolean found) { |
| 216 | + if (SemanticallyEqual.areEqual(id, identifier)) { |
| 217 | + found.set(true); |
| 218 | + return id; |
| 219 | + } |
| 220 | + return super.visitIdentifier(id, found); |
| 221 | + } |
| 222 | + }.reduce(expression, new AtomicBoolean()).get(); |
| 223 | + } |
| 224 | + |
| 225 | + // Might the initializer affect the input or output of the switch expression? |
| 226 | + private boolean canHaveSideEffects(@Nullable Expression expression) { |
| 227 | + if (expression == null) { |
| 228 | + return false; |
| 229 | + } |
| 230 | + |
| 231 | + return new JavaIsoVisitor<AtomicBoolean>() { |
| 232 | + @Override |
| 233 | + public J.Assignment visitAssignment(J.Assignment assignment, AtomicBoolean found) { |
| 234 | + found.set(true); |
| 235 | + return super.visitAssignment(assignment, found); |
| 236 | + } |
| 237 | + |
| 238 | + @Override |
| 239 | + public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, AtomicBoolean found) { |
| 240 | + found.set(true); |
| 241 | + return method; |
| 242 | + } |
| 243 | + |
| 244 | + @Override |
| 245 | + public J.NewClass visitNewClass(J.NewClass newClass, AtomicBoolean found) { |
| 246 | + found.set(true); |
| 247 | + return newClass; |
| 248 | + } |
| 249 | + |
| 250 | + @Override |
| 251 | + public J.Unary visitUnary(J.Unary unary, AtomicBoolean found) { |
| 252 | + found.set(true); |
| 253 | + return super.visitUnary(unary, found); |
| 254 | + } |
| 255 | + |
| 256 | + private boolean isToStringImplicitlyCalled(Expression a, Expression b) { |
| 257 | + // Assuming an implicit `.toString()` call could have a side effect, but excluding |
| 258 | + // the java.lang.* classes from that rule. |
| 259 | + if (TypeUtils.isAssignableTo("java.lang.String", a.getType()) && |
| 260 | + TypeUtils.isAssignableTo("java.lang.String", b.getType())) { |
| 261 | + return false; |
| 262 | + } |
| 263 | + |
| 264 | + return a.getType() == JavaType.Primitive.String && |
| 265 | + (!(b.getType() instanceof JavaType.Primitive || requireNonNull(b.getType()).toString().startsWith("java.lang")) && |
| 266 | + !TypeUtils.isAssignableTo("java.lang.String", b.getType())); |
| 267 | + } |
| 268 | + |
| 269 | + @Override |
| 270 | + public J.Binary visitBinary(J.Binary binary, AtomicBoolean found) { |
| 271 | + if (isToStringImplicitlyCalled(binary.getLeft(), binary.getRight()) || |
| 272 | + isToStringImplicitlyCalled(binary.getRight(), binary.getLeft())) { |
| 273 | + found.set(true); |
| 274 | + return binary; |
| 275 | + } |
| 276 | + return super.visitBinary(binary, found); |
| 277 | + } |
| 278 | + }.reduce(expression, new AtomicBoolean()).get(); |
| 279 | + } |
| 280 | + } |
| 281 | + ); |
| 282 | + } |
| 283 | +} |
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