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Let all change-to-var recipes use a created var-Identifier instead of using a JavaTemplate #793

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merged 5 commits into from
Jul 14, 2025
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Let all change-to-var recipes use a created var-Identifier instead of using a JavaTemplate #793

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Let all change-to-var recipes use a created var-Identifier instead of…
jevanlingen Jul 9, 2025
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44 changes: 38 additions & 6 deletions src/main/java/org/openrewrite/java/migrate/lang/var/DeclarationCheck.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,20 +15,27 @@
*/
package org.openrewrite.java.migrate.lang.var;

import lombok.experimental.UtilityClass;
import org.jspecify.annotations.Nullable;
import org.openrewrite.Cursor;
import org.openrewrite.internal.ListUtils;
import org.openrewrite.java.tree.*;
import org.openrewrite.marker.Markers;

import java.util.List;
import java.util.function.UnaryOperator;

import static java.util.Collections.emptyList;
import static java.util.Collections.singleton;
import static java.util.Objects.requireNonNull;
import static org.openrewrite.Tree.randomId;
import static org.openrewrite.java.tree.Space.EMPTY;

@UtilityClass
final class DeclarationCheck {

private DeclarationCheck() {

}

/**
* Determine if var is applicable with regard to location and decleation type.
* Determine if var is applicable with regard to location and declaration type.
* <p>
* Var is applicable inside methods and initializer blocks for single variable definition.
* Var is *not* applicable to method definitions.
Expand Down Expand Up @@ -119,7 +126,7 @@ public static boolean useGenerics(J.VariableDeclarations vd) {
}

/**
* Determin if the initilizer uses the ternary operator <code>Expression ? if-then : else</code>
* Determine if the initializer uses the ternary operator <code>Expression ? if-then : else</code>
*
* @param vd variable declaration at hand
* @return true iff the ternary operator is used in the initialization
Expand Down Expand Up @@ -225,4 +232,29 @@ public static boolean initializedByStaticMethod(@Nullable Expression initializer

return invocation.getMethodType().hasFlags(Flag.Static);
}

public static J.VariableDeclarations transformToVar(J.VariableDeclarations vd) {
return transformToVar(vd, it -> it);
}

public static <T extends Expression> J.VariableDeclarations transformToVar(J.VariableDeclarations vd, UnaryOperator<T> transformerInitializer) {
T initializer = (T) vd.getVariables().get(0).getInitializer();
if (initializer == null) {
return vd;
}

Expression transformedInitializer = transformerInitializer.apply(initializer);

List<J.VariableDeclarations.NamedVariable> variables = ListUtils.mapFirst(vd.getVariables(), it -> {
JavaType.Variable variableType = it.getVariableType() == null ? null : it.getVariableType().withOwner(null);
return it
.withName(it.getName().withType(transformedInitializer.getType()).withFieldType(variableType))
.withInitializer(transformedInitializer)
.withVariableType(variableType);
});
J.Identifier typeExpression = new J.Identifier(randomId(), vd.getTypeExpression() == null ? EMPTY : vd.getTypeExpression().getPrefix(),
Markers.build(singleton(JavaVarKeyword.build())), emptyList(), "var", transformedInitializer.getType(), null);

return vd.withVariables(variables).withTypeExpression(typeExpression);
}
}
75 changes: 21 additions & 54 deletions src/main/java/org/openrewrite/java/migrate/lang/var/UseVarForGenericMethodInvocations.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,18 +15,15 @@
*/
package org.openrewrite.java.migrate.lang.var;

import org.openrewrite.*;
import org.openrewrite.ExecutionContext;
import org.openrewrite.Preconditions;
import org.openrewrite.Recipe;
import org.openrewrite.TreeVisitor;
import org.openrewrite.java.JavaIsoVisitor;
import org.openrewrite.java.JavaParser;
import org.openrewrite.java.JavaTemplate;
import org.openrewrite.java.search.UsesJavaVersion;
import org.openrewrite.java.tree.*;
import org.openrewrite.marker.Markers;

import java.util.ArrayList;
import java.util.List;

import static java.util.Collections.emptyList;
import org.openrewrite.java.tree.Expression;
import org.openrewrite.java.tree.J;
import org.openrewrite.java.tree.JavaType;

public class UseVarForGenericMethodInvocations extends Recipe {
@Override
Expand All @@ -50,9 +47,6 @@ public TreeVisitor<?, ExecutionContext> getVisitor() {
}

static final class UseVarForGenericsVisitor extends JavaIsoVisitor<ExecutionContext> {
private final JavaTemplate template = JavaTemplate.builder("var #{} = #{any()}")
.javaParser(JavaParser.fromJavaVersion()).build();

@Override
public J.VariableDeclarations visitVariableDeclarations(J.VariableDeclarations vd, ExecutionContext ctx) {
vd = super.visitVariableDeclarations(vd, ctx);
Expand All @@ -62,34 +56,42 @@ public J.VariableDeclarations visitVariableDeclarations(J.VariableDeclarations v
return vd;
}

// recipe specific
// Recipe specific
boolean isPrimitive = DeclarationCheck.isPrimitive(vd);
boolean usesNoGenerics = !DeclarationCheck.useGenerics(vd);
boolean usesTernary = DeclarationCheck.initializedByTernary(vd);
if (isPrimitive || usesTernary || usesNoGenerics) {
return vd;
}

//now we deal with generics, check for method invocations
// Now we deal with generics, check for method invocations
Expression initializer = vd.getVariables().get(0).getInitializer();
boolean isMethodInvocation = initializer != null && initializer.unwrap() instanceof J.MethodInvocation;
if (!isMethodInvocation) {
return vd;
}

//if no type paramters are present and no arguments we assume the type is hard to determine a needs manual action
// If no type parameters and no arguments are present, we assume the type is too hard to determine
boolean hasNoTypeParams = ((J.MethodInvocation) initializer).getTypeParameters() == null;
boolean argumentsEmpty = allArgumentsEmpty((J.MethodInvocation) initializer);
if (hasNoTypeParams && argumentsEmpty) {
return vd;
}

// mark imports for removal if unused
if (vd.getType() instanceof JavaType.FullyQualified) {
maybeRemoveImport( (JavaType.FullyQualified) vd.getType() );
maybeRemoveImport((JavaType.FullyQualified) vd.getType());
}

return transformToVar(vd, new ArrayList<>(), new ArrayList<>());
return DeclarationCheck.transformToVar(vd);
// TODO implement to support cases like `var strs = List.<String>of();`
/*J.VariableDeclarations finalVd = vd;
return DeclarationCheck.<J.MethodInvocation>transformToVar(vd, it -> {
// If left has generics but right has not, copy types parameters
if (finalVd.getTypeExpression() instanceof J.ParameterizedType && !((J.ParameterizedType) finalVd.getTypeExpression()).getTypeParameters().isEmpty() && it.getTypeParameters() == null) {
return it.withTypeParameters(((J.ParameterizedType) finalVd.getTypeExpression()).getPadding().getTypeParameters());
}
return it;
});*/
}

private static boolean allArgumentsEmpty(J.MethodInvocation invocation) {
Expand All @@ -100,40 +102,5 @@ private static boolean allArgumentsEmpty(J.MethodInvocation invocation) {
}
return true;
}

private J.VariableDeclarations transformToVar(J.VariableDeclarations vd, List<JavaType> leftTypes, List<JavaType> rightTypes) {
Expression initializer = vd.getVariables().get(0).getInitializer();
String simpleName = vd.getVariables().get(0).getSimpleName();

// if left is defined but not right, copy types to initializer
if (rightTypes.isEmpty() && !leftTypes.isEmpty()) {
// we need to switch type infos from left to right here
List<Expression> typeArgument = new ArrayList<>();
for (JavaType t : leftTypes) {
typeArgument.add(new J.Identifier(Tree.randomId(), Space.EMPTY, Markers.EMPTY, emptyList(), ((JavaType.Class) t).getClassName(), t, null));
}
J.ParameterizedType typedInitializerClazz = ((J.ParameterizedType) ((J.NewClass) initializer).getClazz()).withTypeParameters(typeArgument);
initializer = ((J.NewClass) initializer).withClazz(typedInitializerClazz);
}

J.VariableDeclarations result = template.<J.VariableDeclarations>apply(getCursor(), vd.getCoordinates().replace(), simpleName, initializer)
.withPrefix(vd.getPrefix());

// apply modifiers like final
List<J.Modifier> modifiers = vd.getModifiers();
boolean hasModifiers = !modifiers.isEmpty();
if (hasModifiers) {
result = result.withModifiers(modifiers);
}

// apply prefix to type expression
TypeTree resultingTypeExpression = result.getTypeExpression();
boolean resultHasTypeExpression = resultingTypeExpression != null;
if (resultHasTypeExpression) {
result = result.withTypeExpression(resultingTypeExpression.withPrefix(vd.getTypeExpression().getPrefix()));
}

return result;
}
}
}
49 changes: 14 additions & 35 deletions src/main/java/org/openrewrite/java/migrate/lang/var/UseVarForGenericsConstructors.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,19 +20,15 @@
import org.openrewrite.Preconditions;
import org.openrewrite.Recipe;
import org.openrewrite.TreeVisitor;
import org.openrewrite.internal.ListUtils;
import org.openrewrite.java.JavaIsoVisitor;
import org.openrewrite.java.search.UsesJavaVersion;
import org.openrewrite.java.tree.*;
import org.openrewrite.marker.Markers;
import org.openrewrite.java.tree.Expression;
import org.openrewrite.java.tree.J;
import org.openrewrite.java.tree.JavaType;
import org.openrewrite.java.tree.TypeTree;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

import static java.util.Collections.emptyList;
import static java.util.Collections.singleton;
import static org.openrewrite.Tree.randomId;

public class UseVarForGenericsConstructors extends Recipe {
@Override
Expand Down Expand Up @@ -87,12 +83,20 @@ public J.VariableDeclarations visitVariableDeclarations(J.VariableDeclarations v
return vd;
}

// Mark imports for removal if unused
if (vd.getType() instanceof JavaType.FullyQualified) {
maybeRemoveImport((JavaType.FullyQualified) vd.getType());
}

return transformToVar(vd, leftTypes, rightTypes);
J.VariableDeclarations finalVd = vd;
return DeclarationCheck.<J.NewClass>transformToVar(vd, it -> {
// If left is defined but right is not, copy types from typeExpression to initializer
if (rightTypes.isEmpty() && !leftTypes.isEmpty() && finalVd.getTypeExpression() instanceof J.ParameterizedType && it.getClazz() instanceof J.ParameterizedType) {
J.ParameterizedType typedInitializerClazz = ((J.ParameterizedType) it.getClazz())
.withTypeParameters(((J.ParameterizedType) finalVd.getTypeExpression()).getTypeParameters());
return it.withClazz(typedInitializerClazz);
}
return it;
});
}

private static Boolean anyTypeHasBounds(List<JavaType> leftTypes) {
Expand Down Expand Up @@ -141,30 +145,5 @@ private List<JavaType> extractTypeParameters(JavaType.@Nullable Variable variabl
}
return new ArrayList<>();
}

private J.VariableDeclarations transformToVar(J.VariableDeclarations vd, List<JavaType> leftTypes, List<JavaType> rightTypes) {
J.NewClass initializer = Objects.requireNonNull((J.NewClass) vd.getVariables().get(0).getInitializer());

// If left is defined but right is not, copy types from typeExpression to initializer
if (rightTypes.isEmpty() && !leftTypes.isEmpty() && vd.getTypeExpression() instanceof J.ParameterizedType && initializer.getClazz() instanceof J.ParameterizedType) {
J.ParameterizedType typedInitializerClazz = ((J.ParameterizedType) initializer.getClazz())
.withTypeParameters(((J.ParameterizedType) vd.getTypeExpression()).getTypeParameters());
initializer = initializer.withClazz(typedInitializerClazz);
}

// Replace actual type by `var` keyword and replace the first variable's name, initializer and type
J.NewClass finalInitializer = initializer;
List<J.VariableDeclarations.NamedVariable> variables = ListUtils.mapFirst(vd.getVariables(), it -> {
JavaType.Variable variableType = it.getVariableType() == null ? null : it.getVariableType().withOwner(null);
return it
.withName(it.getName().withType(finalInitializer.getType()).withFieldType(variableType))
.withInitializer(finalInitializer)
.withVariableType(variableType);
});
J.Identifier typeExpression = new J.Identifier(randomId(), vd.getTypeExpression().getPrefix(),
Markers.build(singleton(JavaVarKeyword.build())), emptyList(), "var", initializer.getType(), null);

return vd.withVariables(variables).withTypeExpression(typeExpression);
}
}
}
29 changes: 1 addition & 28 deletions src/main/java/org/openrewrite/java/migrate/lang/var/UseVarForObject.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,13 +22,10 @@
import org.openrewrite.Recipe;
import org.openrewrite.TreeVisitor;
import org.openrewrite.java.JavaIsoVisitor;
import org.openrewrite.java.JavaParser;
import org.openrewrite.java.JavaTemplate;
import org.openrewrite.java.search.UsesJavaVersion;
import org.openrewrite.java.tree.Expression;
import org.openrewrite.java.tree.J;
import org.openrewrite.java.tree.JavaType;
import org.openrewrite.java.tree.TypeTree;

@EqualsAndHashCode(callSuper = false)
@Value
Expand Down Expand Up @@ -58,11 +55,6 @@ public TreeVisitor<?, ExecutionContext> getVisitor() {


static final class UseVarForObjectVisitor extends JavaIsoVisitor<ExecutionContext> {
private final JavaTemplate template = JavaTemplate.builder("var #{} = #{any()};")
.contextSensitive()
.javaParser(JavaParser.fromJavaVersion()).build();


@Override
public J.VariableDeclarations visitVariableDeclarations(J.VariableDeclarations vd, ExecutionContext ctx) {
vd = super.visitVariableDeclarations(vd, ctx);
Expand All @@ -82,30 +74,11 @@ public J.VariableDeclarations visitVariableDeclarations(J.VariableDeclarations v
return vd;
}

// mark imports for removal if unused
if (vd.getType() instanceof JavaType.FullyQualified) {
maybeRemoveImport( (JavaType.FullyQualified) vd.getType() );
}

return transformToVar(vd);
}


private J.VariableDeclarations transformToVar(J.VariableDeclarations vd) {
Expression initializer = vd.getVariables().get(0).getInitializer();
String simpleName = vd.getVariables().get(0).getSimpleName();

if (vd.getModifiers().isEmpty()) {
return template.apply(getCursor(), vd.getCoordinates().replace(), simpleName, initializer)
.withPrefix(vd.getPrefix());
} else {
J.VariableDeclarations result = template.<J.VariableDeclarations>apply(getCursor(), vd.getCoordinates().replace(), simpleName, initializer)
.withModifiers(vd.getModifiers())
.withPrefix(vd.getPrefix());
TypeTree typeExpression = result.getTypeExpression();
//noinspection DataFlowIssue
return typeExpression != null ? result.withTypeExpression(typeExpression.withPrefix(vd.getTypeExpression().getPrefix())) : vd;
}
return DeclarationCheck.transformToVar(vd);
}
}
}
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