feat: add remove unused imports

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Commit, tag and push the choco source files to the chocolatey-bucket repository during the release process
 - Added formatter [`clean-that`](https://github.com/diffplug/spotless/tree/main/plugin-gradle#cleanthat)
+- Added formatter [`remove-unused-imports`](https://github.com/diffplug/spotless/tree/main/plugin-gradle#removeunusedimports)
 
 ## [0.1.1] - 2025-06-02
 

README.md

@@ -152,14 +152,15 @@ or apply the formatting to the files.
   -V, --version              Print version information and exit.
 
 Available formatting steps:
-  clang-format          Runs clang-format
-  clean-that            CleanThat enables automatic refactoring of Java code.
-  format-annotations    Corrects line break formatting of type annotations in
-                          java files.
-  google-java-format    Runs google java format
-  license-header        Runs license header
-  palantir-java-format  Runs palantir java format
-  prettier              Runs prettier, the opinionated code formatter.
+  clang-format           Runs clang-format
+  clean-that             CleanThat enables automatic refactoring of Java code.
+  format-annotations     Corrects line break formatting of type annotations in
+                           java files.
+  google-java-format     Runs google java format
+  license-header         Runs license header
+  palantir-java-format   Runs palantir java format
+  prettier               Runs prettier, the opinionated code formatter.
+  remove-unused-imports  Removes unused imports from Java files.
 
 Possible exit codes:
   0    Successful formatting.

app/src/main/java/com/diffplug/spotless/cli/SpotlessCLI.java

@@ -50,6 +50,7 @@
 import com.diffplug.spotless.cli.steps.LicenseHeader;
 import com.diffplug.spotless.cli.steps.PalantirJavaFormat;
 import com.diffplug.spotless.cli.steps.Prettier;
+import com.diffplug.spotless.cli.steps.RemoveUnusedImports;
 import com.diffplug.spotless.cli.version.SpotlessCLIVersionProvider;
 
 import picocli.CommandLine;
@@ -100,7 +101,8 @@
             GoogleJavaFormat.class,
             LicenseHeader.class,
             PalantirJavaFormat.class,
-            Prettier.class
+            Prettier.class,
+            RemoveUnusedImports.class
         })
 public class SpotlessCLI implements SpotlessAction, SpotlessCommand, SpotlessActionContextProvider {
 

app/src/main/java/com/diffplug/spotless/cli/steps/RemoveUnusedImports.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2025 DiffPlug
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 com.diffplug.spotless.cli.steps;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.jetbrains.annotations.NotNull;
+
+import com.diffplug.spotless.FormatterStep;
+import com.diffplug.spotless.cli.core.SpotlessActionContext;
+import com.diffplug.spotless.cli.help.AdditionalInfoLinks;
+import com.diffplug.spotless.cli.help.OptionConstants;
+import com.diffplug.spotless.cli.help.SupportedFileTypes;
+import com.diffplug.spotless.java.RemoveUnusedImportsStep;
+
+import picocli.CommandLine;
+
+@CommandLine.Command(name = "remove-unused-imports", description = "Removes unused imports from Java files.")
+@SupportedFileTypes("Java")
+@AdditionalInfoLinks("https://github.com/diffplug/spotless/tree/main/plugin-gradle#removeunusedimports")
+public class RemoveUnusedImports extends SpotlessFormatterStep {
+
+    @CommandLine.Option(
+            names = {"--engine", "-e"},
+            defaultValue = "GOOGLE_JAVA_FORMAT",
+            description = "The backing engine to use for detecting and removing unused imports."
+                    + OptionConstants.VALID_AND_DEFAULT_VALUES_SUFFIX)
+    Engine engine;
+
+    public enum Engine {
+        GOOGLE_JAVA_FORMAT {
+            @Override
+            String formatterName() {
+                return RemoveUnusedImportsStep.defaultFormatter();
+            }
+        },
+        CLEAN_THAT {
+            @Override
+            String formatterName() {
+                return "cleanthat-javaparser-unnecessaryimport";
+            }
+        };
+
+        abstract String formatterName();
+    }
+
+    @Override
+    public @NotNull List<FormatterStep> prepareFormatterSteps(SpotlessActionContext context) {
+        return Collections.singletonList(RemoveUnusedImportsStep.create(engine.formatterName(), context.provisioner()));
+    }
+}

app/src/test/java/com/diffplug/spotless/cli/steps/RemoveUnusedImportsTest.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2025 DiffPlug
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 com.diffplug.spotless.cli.steps;
+
+import org.junit.jupiter.api.Test;
+
+import com.diffplug.spotless.cli.CLIIntegrationHarness;
+import com.diffplug.spotless.tag.CliNativeTest;
+import com.diffplug.spotless.tag.CliProcessTest;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@CliProcessTest
+@CliNativeTest
+class RemoveUnusedImportsTest extends CLIIntegrationHarness {
+
+    @Test
+    void itRemovesUnusedImportsWithDefaultEngine() {
+        setFile("Java.java").toResource("java/removeunusedimports/JavaCodeWithLicensePackageUnformatted.test");
+
+        cliRunner().withTargets("Java.java").withStep(RemoveUnusedImports.class).run();
+
+        assertFile("Java.java")
+                .notSameSasResource("java/removeunusedimports/JavaCodeWithLicensePackageUnformatted.test")
+                .hasNotContent("Unused");
+
+        selfie().expectResource("Java.java").toMatchDisk();
+    }
+
+    @Test
+    void itRemovesWithExplicitDefaultEngine() {
+        setFile("Java.java").toResource("java/removeunusedimports/JavaCodeWithLicensePackageUnformatted.test");
+
+        cliRunner()
+                .withTargets("Java.java")
+                .withStep(RemoveUnusedImports.class)
+                .withOption("--engine", "GOOGLE_JAVA_FORMAT")
+                .run();
+
+        assertFile("Java.java")
+                .notSameSasResource("java/removeunusedimports/JavaCodeWithLicensePackageUnformatted.test")
+                .hasNotContent("Unused");
+
+        selfie().expectResource("Java.java").toMatchDisk();
+    }
+
+    @Test
+    void itRemovesWithExplicitCleanThatEngine() {
+        setFile("Java.java").toResource("java/removeunusedimports/JavaCodeWithLicensePackageUnformatted.test");
+
+        cliRunner()
+                .withTargets("Java.java")
+                .withStep(RemoveUnusedImports.class)
+                .withOption("--engine", "CLEAN_THAT")
+                .run();
+
+        assertFile("Java.java")
+                .notSameSasResource("java/removeunusedimports/JavaCodeWithLicensePackageUnformatted.test")
+                .hasNotContent("Unused");
+
+        selfie().expectResource("Java.java").toMatchDisk();
+    }
+}

app/src/test/resources/com/diffplug/spotless/cli/steps/RemoveUnusedImportsTest.ss

@@ -0,0 +1,52 @@
+╔═ itRemovesUnusedImportsWithDefaultEngine ═╗
+/*
+ * Some license stuff.
+ * Very official.
+ */
+package hello.world;
+
+import mylib.UsedB;
+import mylib.UsedA;
+
+public class Java {
+public static void main(String[] args) {
+System.out.println("hello");
+UsedB.someMethod();
+UsedA.someMethod();
+}
+}
+╔═ itRemovesWithExplicitCleanThatEngine ═╗
+/*
+ * Some license stuff.
+ * Very official.
+ */
+package hello.world;
+
+import mylib.UsedB;
+import mylib.UsedA;
+
+public class Java {
+public static void main(String[] args) {
+System.out.println("hello");
+UsedB.someMethod();
+UsedA.someMethod();
+}
+}
+╔═ itRemovesWithExplicitDefaultEngine ═╗
+/*
+ * Some license stuff.
+ * Very official.
+ */
+package hello.world;
+
+import mylib.UsedB;
+import mylib.UsedA;
+
+public class Java {
+public static void main(String[] args) {
+System.out.println("hello");
+UsedB.someMethod();
+UsedA.someMethod();
+}
+}
+╔═ [end of file] ═╗

build-logic/src/main/groovy/com/diffplug/spotless/cli/picocli/usage/DocumentedUsages.groovy

@@ -9,7 +9,8 @@ enum DocumentedUsages {
 	GOOGLE_JAVA_FORMAT(),
 	LICENSE_HEADER(),
 	PALANTIR_JAVA_FORMAT(),
-	PRETTIER()
+	PRETTIER(),
+	REMOVE_UNUSED_IMPORTS(),
 
 	private final String fileName
 

testlib/src/main/java/com/diffplug/spotless/ResourceHarness.java

@@ -201,47 +201,50 @@ private ReadAsserter(File file) {
             this.file = file;
         }
 
-        public void hasContent(String expected) {
-            hasContent(expected, StandardCharsets.UTF_8);
+        public ReadAsserter hasContent(String expected) {
+            return hasContent(expected, StandardCharsets.UTF_8);
         }
 
-        public void hasNotContent(String notExpected) {
-            notHasContent(notExpected, StandardCharsets.UTF_8);
+        public ReadAsserter hasNotContent(String notExpected) {
+            return notHasContent(notExpected, StandardCharsets.UTF_8);
         }
 
-        public void hasContent(String expected, Charset charset) {
+        public ReadAsserter hasContent(String expected, Charset charset) {
             assertThat(file).usingCharset(charset).hasContent(expected);
+            return this;
         }
 
-        public void notHasContent(String notExpected, Charset charset) {
+        public ReadAsserter notHasContent(String notExpected, Charset charset) {
             assertThat(file).usingCharset(charset).content().isNotEqualTo(notExpected);
+            return this;
         }
 
-        public void hasLines(String... lines) {
-            hasContent(String.join("\n", Arrays.asList(lines)));
+        public ReadAsserter hasLines(String... lines) {
+            return hasContent(String.join("\n", Arrays.asList(lines)));
         }
 
-        public void sameAsResource(String resource) {
-            hasContent(getTestResource(resource));
+        public ReadAsserter sameAsResource(String resource) {
+            return hasContent(getTestResource(resource));
         }
 
-        public void notSameSasResource(String resource) {
-            hasNotContent(getTestResource(resource));
+        public ReadAsserter notSameSasResource(String resource) {
+            return hasNotContent(getTestResource(resource));
         }
 
-        public void matches(Consumer<AbstractCharSequenceAssert<?, String>> conditions) throws IOException {
+        public ReadAsserter matches(Consumer<AbstractCharSequenceAssert<?, String>> conditions) throws IOException {
             String content = new String(Files.readAllBytes(file.toPath()), StandardCharsets.UTF_8);
             conditions.accept(assertThat(content));
+            return this;
         }
 
-        public void sameAsFile(File otherFile) throws IOException {
+        public ReadAsserter sameAsFile(File otherFile) throws IOException {
             String otherFileContent = Files.readString(otherFile.toPath());
-            hasContent(otherFileContent, StandardCharsets.UTF_8);
+            return hasContent(otherFileContent, StandardCharsets.UTF_8);
         }
 
-        public void notSameAsFile(File otherFile) throws IOException {
+        public ReadAsserter notSameAsFile(File otherFile) throws IOException {
             String otherFileContent = Files.readString(otherFile.toPath());
-            notHasContent(otherFileContent, StandardCharsets.UTF_8);
+            return notHasContent(otherFileContent, StandardCharsets.UTF_8);
         }
     }
 

testlib/src/main/resources/java/removeunusedimports/JavaCodeWithLicensePackageUnformatted.test

@@ -0,0 +1,17 @@
+/*
+ * Some license stuff.
+ * Very official.
+ */
+package hello.world;
+
+import mylib.Unused;
+import mylib.UsedB;
+import mylib.UsedA;
+
+public class Java {
+public static void main(String[] args) {
+System.out.println("hello");
+UsedB.someMethod();
+UsedA.someMethod();
+}
+}