Convert Guava Iterables.transform and Collections2.transform (#917)

* Convert Guava `Iterables.transform` and `Collections2.transform`

* Remove unused import

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Use `Collectors.toList()` while we support older Java versions still

---------

Co-authored-by: Tim te Beek <[email protected]>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Tim te Beek <[email protected]>

Author: 3 people

src/main/java/org/openrewrite/java/migrate/guava/NoGuavaCollections2Transform.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (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://docs.moderne.io/licensing/moderne-source-available-license
+ * <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.guava;
+
+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.JavaTemplate;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.search.UsesMethod;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.TypeUtils;
+
+import java.util.Set;
+
+import static java.util.Collections.singleton;
+
+public class NoGuavaCollections2Transform extends Recipe {
+    private static final MethodMatcher COLLECTIONS2_TRANSFORM = new MethodMatcher("com.google.common.collect.Collections2 transform(java.util.Collection, com.google.common.base.Function)");
+
+    @Override
+    public String getDisplayName() {
+        return "Prefer `Collection.stream().map(Function)` over `Collections2.transform`";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Prefer `Collection.stream().map(Function)` over `Collections2.transform(Collection, Function)`.";
+    }
+
+    @Override
+    public Set<String> getTags() {
+        return singleton("guava");
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(
+                new UsesMethod<>(COLLECTIONS2_TRANSFORM),
+                new JavaIsoVisitor<ExecutionContext>() {
+                    @Override
+                    public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx) {
+                        if (COLLECTIONS2_TRANSFORM.matches(method)) {
+                            maybeRemoveImport("com.google.common.base.Function");
+                            maybeRemoveImport("com.google.common.collect.Collections2");
+                            maybeAddImport("java.util.function.Function");
+                            maybeAddImport("java.util.stream.Collectors");
+
+                            if (TypeUtils.isAssignableTo("java.util.Collection", method.getArguments().get(0).getType())) {
+                                return JavaTemplate.builder("#{any(java.util.Collection)}.stream().map(#{any(java.util.function.Function)}).collect(Collectors.toList())")
+                                        .imports("java.util.stream.Collectors")
+                                        .build()
+                                        .apply(getCursor(),
+                                                method.getCoordinates().replace(),
+                                                method.getArguments().get(0),
+                                                method.getArguments().get(1));
+                            }
+                            return method;
+                        }
+                        return super.visitMethodInvocation(method, ctx);
+                    }
+                }
+        );
+    }
+}

src/main/java/org/openrewrite/java/migrate/guava/NoGuavaIterablesTransform.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (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://docs.moderne.io/licensing/moderne-source-available-license
+ * <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.guava;
+
+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.JavaTemplate;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.search.UsesMethod;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.TypeUtils;
+
+import java.util.Set;
+
+import static java.util.Collections.singleton;
+
+public class NoGuavaIterablesTransform extends Recipe {
+    private static final MethodMatcher ITERABLES_TRANSFORM = new MethodMatcher("com.google.common.collect.Iterables transform(java.lang.Iterable, com.google.common.base.Function)");
+
+    @Override
+    public String getDisplayName() {
+        return "Prefer `Collection.stream().map(Function)` over `Iterables.transform`";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Prefer `Collection.stream().map(Function)` over `Iterables.transform(Collection, Function)`.";
+    }
+
+    @Override
+    public Set<String> getTags() {
+        return singleton("guava");
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(
+                new UsesMethod<>(ITERABLES_TRANSFORM),
+                new JavaIsoVisitor<ExecutionContext>() {
+                    @Override
+                    public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx) {
+                        if (ITERABLES_TRANSFORM.matches(method)) {
+                            maybeRemoveImport("com.google.common.base.Function");
+                            maybeRemoveImport("com.google.common.collect.Iterables");
+                            maybeAddImport("java.util.function.Function");
+                            maybeAddImport("java.util.stream.Collectors");
+
+                            if (TypeUtils.isAssignableTo("java.util.Collection", method.getArguments().get(0).getType())) {
+                                return JavaTemplate.builder("#{any(java.util.Collection)}.stream().map(#{any(java.util.function.Function)}).collect(Collectors.toList())")
+                                        .imports("java.util.stream.Collectors")
+                                        .build()
+                                        .apply(getCursor(),
+                                                method.getCoordinates().replace(),
+                                                method.getArguments().get(0),
+                                                method.getArguments().get(1));
+                            }
+                            return method;
+                        }
+                        return super.visitMethodInvocation(method, ctx);
+                    }
+                }
+        );
+    }
+}

src/main/resources/META-INF/rewrite/no-guava.yml

@@ -32,6 +32,8 @@ recipeList:
   - org.openrewrite.java.migrate.guava.NoGuavaFunctionsCompose
   - org.openrewrite.java.migrate.guava.NoGuavaInlineMeMethods
   - org.openrewrite.java.migrate.guava.NoGuavaIterablesAnyFilter
+  - org.openrewrite.java.migrate.guava.NoGuavaIterablesTransform
+  - org.openrewrite.java.migrate.guava.NoGuavaCollections2Transform
   - org.openrewrite.java.migrate.guava.NoGuavaListsNewArrayList
   - org.openrewrite.java.migrate.guava.NoGuavaListsNewCopyOnWriteArrayList
   - org.openrewrite.java.migrate.guava.NoGuavaListsNewLinkedList

src/test/java/org/openrewrite/java/migrate/guava/NoGuavaCollections2TransformTest.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (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://docs.moderne.io/licensing/moderne-source-available-license
+ * <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.guava;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.DocumentExample;
+import org.openrewrite.InMemoryExecutionContext;
+import org.openrewrite.java.JavaParser;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+class NoGuavaCollections2TransformTest implements RewriteTest {
+
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec
+          .recipe(new NoGuavaCollections2Transform())
+          .parser(JavaParser.fromJavaVersion().classpathFromResources(new InMemoryExecutionContext(), "guava"));
+    }
+
+    @DocumentExample
+    @Test
+    void replaceCollections2Transform() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              import java.util.Collection;
+
+              import com.google.common.base.Function;
+              import com.google.common.collect.Collections2;
+
+              class Test {
+                  Iterable<Integer> test(Collection<String> collection, Function<String, Integer> toSize) {
+                      return Collections2.transform(collection, toSize);
+                  }
+              }
+              """,
+            """
+              import java.util.Collection;
+              import java.util.stream.Collectors;
+
+              import com.google.common.base.Function;
+
+              class Test {
+                  Iterable<Integer> test(Collection<String> collection, Function<String, Integer> toSize) {
+                      return collection.stream().map(toSize).collect(Collectors.toList());
+                  }
+              }
+              """
+          )
+        );
+    }
+}

src/test/java/org/openrewrite/java/migrate/guava/NoGuavaIterablesTransformTest.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (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://docs.moderne.io/licensing/moderne-source-available-license
+ * <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.guava;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.DocumentExample;
+import org.openrewrite.InMemoryExecutionContext;
+import org.openrewrite.java.JavaParser;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+class NoGuavaIterablesTransformTest implements RewriteTest {
+
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec
+          .recipe(new NoGuavaIterablesTransform())
+          .parser(JavaParser.fromJavaVersion().classpathFromResources(new InMemoryExecutionContext(), "guava"));
+    }
+
+    @DocumentExample
+    @Test
+    void replaceIterablesTransform() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              import java.util.Collection;
+
+              import com.google.common.base.Function;
+              import com.google.common.collect.Iterables;
+
+              class Test {
+                  Iterable<Integer> test(Collection<String> collection, Function<String, Integer> toSize) {
+                      return Iterables.transform(collection, toSize);
+                  }
+              }
+              """,
+            """
+              import java.util.Collection;
+              import java.util.stream.Collectors;
+
+              import com.google.common.base.Function;
+
+              class Test {
+                  Iterable<Integer> test(Collection<String> collection, Function<String, Integer> toSize) {
+                      return collection.stream().map(toSize).collect(Collectors.toList());
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void doNotReplaceIterablesTransformWithIterable() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              import com.google.common.base.Function;
+              import com.google.common.collect.Iterables;
+
+              class Test {
+                  Iterable<Integer> test(Iterable<String> iterable, Function<String, Integer> toSize) {
+                      return Iterables.transform(iterable, toSize);
+                  }
+              }
+              """
+          )
+        );
+    }
+}