236 var for methods

src/main/java/org/openrewrite/java/migrate/lang/var/UseVarForGenericMethodInvocations.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright 2021 the original author or authors.
+ * <p>
+ * 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
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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 org.openrewrite.java.migrate.lang.var;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.openrewrite.*;
+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;
+
+public class UseVarForGenericMethodInvocations extends Recipe {
+    @Override
+    public String getDisplayName() {
+        //language=markdown
+        return "Apply `var` to Generic Method Invocations";
+    }
+
+    @Override
+    public String getDescription() {
+        //language=markdown
+        return "Apply `var` to variables initialized by invocations of Generic Methods. " +
+               "This recipe ignores generic factory methods without parameters, because open rewrite cannot handle them correctly ATM.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(
+                new UsesJavaVersion<>(10),
+                new UseVarForGenericMethodInvocations.UseVarForGenericsVisitor());
+    }
+
+    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);
+
+            boolean isGeneralApplicable = DeclarationCheck.isVarApplicable(this.getCursor(), vd);
+            if (!isGeneralApplicable) return vd;
+
+            // 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
+            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
+            boolean hasNoTypeParams = ((J.MethodInvocation) initializer).getTypeParameters() == null;
+            boolean argumentsEmpty = ((J.MethodInvocation) initializer).getArguments().stream().allMatch(p -> p instanceof J.Empty);
+            if (hasNoTypeParams && argumentsEmpty) return vd;
+
+            return transformToVar(vd, new ArrayList<>(), new ArrayList<>());
+        }
+
+        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 = leftTypes.stream()
+                        .map(t ->
+                                new J.Identifier(Tree.randomId(), Space.EMPTY, Markers.EMPTY, ((JavaType.Class)t).getClassName(), t, null))
+                        .collect(Collectors.toList());
+                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;
+        }
+    }
+}

src/main/java/org/openrewrite/java/migrate/lang/var/UseVarForGenericsConstructors.java

@@ -0,0 +1,147 @@
+/*
+ * Copyright 2021 the original author or authors.
+ * <p>
+ * 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
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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 org.openrewrite.java.migrate.lang.var;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+import org.openrewrite.*;
+import org.openrewrite.internal.lang.Nullable;
+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;
+
+public class UseVarForGenericsConstructors extends Recipe {
+    @Override
+    public String getDisplayName() {
+        //language=markdown
+        return "Apply `var` to Generic Constructors";
+    }
+
+    @Override
+    public String getDescription() {
+        //language=markdown
+        return "Apply `var` to generics variables initialized by constructor calls.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(
+                new UsesJavaVersion<>(10),
+                new UseVarForGenericsConstructors.UseVarForGenericsVisitor());
+    }
+
+    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);
+
+            boolean isGeneralApplicable = DeclarationCheck.isVarApplicable(this.getCursor(), vd);
+            if (!isGeneralApplicable) return vd;
+
+            // 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
+            J.VariableDeclarations.NamedVariable variable = vd.getVariables().get(0);
+            List<JavaType> leftTypes = extractParameters(variable.getVariableType());
+            List<JavaType> rightTypes = extractParameters(variable.getInitializer());
+            if (rightTypes == null || (leftTypes.isEmpty() && rightTypes.isEmpty())) return vd;
+
+            return transformToVar(vd, leftTypes, rightTypes);
+        }
+
+        /**
+         * Tries to extract the genric parameters from the expression,
+         * if the Initializer is no new class or not of a parameterized type, returns null to signale "no info".
+         * if the initializer uses empty diamonds use an empty list to signale no type information
+         * @param initializer to extract parameters from
+         * @return null or list of type parameters in diamond
+         */
+        private @Nullable List<JavaType> extractParameters(@Nullable Expression initializer) {
+            if (initializer instanceof J.NewClass) {
+                TypeTree clazz = ((J.NewClass) initializer).getClazz();
+                if (clazz instanceof J.ParameterizedType) {
+                    List<Expression> typeParameters = ((J.ParameterizedType) clazz).getTypeParameters();
+                    if (typeParameters != null) {
+                        return typeParameters
+                                .stream()
+                                .map(Expression::getType)
+                                .filter(Objects::nonNull)
+                                .collect(Collectors.toList());
+                    } else {
+                        return new ArrayList<>();
+                    }
+                }
+            }
+            return null;
+        }
+
+        private List<JavaType> extractParameters(@Nullable JavaType.Variable variableType) {
+            if (variableType != null && variableType.getType() instanceof JavaType.Parameterized) {
+                return ((JavaType.Parameterized) variableType.getType()).getTypeParameters();
+            } else {
+                return new ArrayList<>();
+            }
+        }
+
+        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 = leftTypes.stream()
+                        .map(t ->
+                                new J.Identifier(Tree.randomId(), Space.EMPTY, Markers.EMPTY, ((JavaType.Class)t).getClassName(), t, null))
+                        .collect(Collectors.toList());
+                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;
+        }
+    }
+}

src/main/resources/META-INF/rewrite/java-lang-var.yml

@@ -17,11 +17,14 @@
 type: specs.openrewrite.org/v1beta/recipe
 name: org.openrewrite.java.migrate.lang.UseVar
 displayName: Use local variable type inference
-description: Apply local variable type inference (`var`) for primitives and objects.
+description: Apply local variable type inference (`var`) for primitives and objects. These recipes can cause unused
+  imports, be advised to run `org.openrewrite.java.RemoveUnusedImports afterwards.
 tags:
   - refactoring
   - java10
   - var
 recipeList:
   - org.openrewrite.java.migrate.lang.var.UseVarForObject
   - org.openrewrite.java.migrate.lang.var.UseVarForPrimitive
+  - org.openrewrite.java.migrate.lang.var.UseVarForGenericsConstructors
+  - org.openrewrite.java.migrate.lang.var.UseVarForGenericMethodInvocations