Make UnusedVariable an error

ExecutableTransform's logger, StringWrapper's endLine and the stderr
two MainTest tests read after the process had exited were never read.
They are gone, and Error Prone now fails the build on the next one.

Author: abashev

buildSrc/src/main/groovy/open-java-format.error-prone-conventions.gradle

@@ -51,3 +51,10 @@ tasks.withType(JavaCompile).configureEach {
         //disable('NonStaticImport')
     }
 }
+
+// Checks whose findings have been fixed, build-breaking so that new ones are fixed too rather than read past.
+tasks.withType(JavaCompile).configureEach {
+    options.errorprone {
+        error('UnusedVariable')
+    }
+}

gradle-open-java-format/src/main/java/com/palantir/javaformat/gradle/ExecutableTransform.java

@@ -31,8 +31,6 @@
 import org.gradle.api.artifacts.transform.TransformOutputs;
 import org.gradle.api.artifacts.transform.TransformParameters;
 import org.gradle.api.file.FileSystemLocation;
-import org.gradle.api.logging.Logger;
-import org.gradle.api.logging.Logging;
 import org.gradle.api.provider.Provider;
 import org.gradle.api.tasks.PathSensitive;
 import org.gradle.api.tasks.PathSensitivity;
@@ -47,8 +45,6 @@
         because = "Only copies one file and sets its executable bit; caching would cost more than it saves")
 public abstract class ExecutableTransform implements TransformAction<TransformParameters.None> {
 
-    private static Logger logger = Logging.getLogger(ExecutableTransform.class);
-
     @InputArtifact
     @PathSensitive(PathSensitivity.NAME_ONLY)
     public abstract Provider<FileSystemLocation> getInputArtifact();

open-java-format/src/main/java/com/palantir/javaformat/java/StringWrapper.java

@@ -448,7 +448,6 @@ private String computePrefixIndentation(
                 int startLine = lineMap.getLineNumber(startingPos);
                 int lineStartPosition = lineMap.getStartPosition(startLine);
                 int endPos = getEndPosition(unit, expression);
-                int endLine = lineMap.getLineNumber(endPos);
                 int parentLine = shouldUseStartLineParent ? startParentLine : endParentLine;
                 // ignore indentation if the current argument is on the same line as the parent
                 if (startLine == parentLine) {

open-java-format/src/test/java/com/palantir/javaformat/java/MainTest.java

@@ -483,7 +483,6 @@ void exitIfChangedStdin() throws Exception {
         Files.write(path, "class Test {\n}\n".getBytes(UTF_8));
         Process process = formatterMain("-").redirectInput(path.toFile()).start();
         process.waitFor();
-        String err = new String(ByteStreams.toByteArray(process.getErrorStream()), UTF_8);
         String out = new String(ByteStreams.toByteArray(process.getInputStream()), UTF_8);
         assertThat(out).isEqualTo("<stdin>" + System.lineSeparator());
         assertThat(process.exitValue()).isEqualTo(1);
@@ -495,7 +494,6 @@ void exitIfChangedFiles() throws Exception {
         Files.write(path, "class Test {\n}\n".getBytes(UTF_8));
         Process process = formatterMain(path.toAbsolutePath().toString()).start();
         process.waitFor();
-        String err = new String(ByteStreams.toByteArray(process.getErrorStream()), UTF_8);
         String out = new String(ByteStreams.toByteArray(process.getInputStream()), UTF_8);
         assertThat(out).isEqualTo(path.toAbsolutePath().toString() + System.lineSeparator());
         assertThat(process.exitValue()).isEqualTo(1);