Added plugin for formatting Java sources using Palantir (#3531)

Added `contrib.palantir.JavafmtModule` for formatting Java sources using
[Palantir](https://github.com/palantir/palantir-java-format/).
The plugin also supports command line arguments for
- checking for formatting errors with `--check` flag
- formatting specific files or folders

Resolves #3448.

example/javalib/linting/3-palantirformat/build.mill

@@ -0,0 +1,26 @@
+package build
+
+import mill._
+import mill.javalib.palantirformat._
+
+object `package` extends RootModule with PalantirFormatModule {
+}
+
+/** See Also: src/A.java */
+
+/** Usage
+
+> ./mill palantirformat --check                                         # check should fail initially
+...checking format in java sources ...
+...src/A.java
+error: ...palantirformat aborted due to format error(s) (or invalid plugin settings/palantirformat options)
+
+> ./mill palantirformat                                                 # format all Java source files
+...formatting java sources ...
+
+> ./mill palantirformat --check                                         # check should succeed now
+...checking format in java sources ...
+
+> ./mill mill.javalib.palantirformat.PalantirFormatModule/ __.sources   # alternatively, use external module to check/format
+...formatting java sources ...
+*/

example/javalib/linting/3-palantirformat/src/A.java

@@ -0,0 +1,6 @@
+public class A {
+
+    public static void main(String[] args) {
+    System.out.println("hello"); // indentation should be fixed
+    }
+}

scalalib/src/mill/javalib/palantirformat/PalantirFormatModule.scala

@@ -0,0 +1,190 @@
+package mill
+package javalib.palantirformat
+
+import mill.api.{Loose, PathRef}
+import mill.define.{Discover, ExternalModule}
+import mill.main.Tasks
+import mill.scalalib.{CoursierModule, DepSyntax, JavaModule}
+import mill.util.Jvm
+
+trait PalantirFormatBaseModule extends CoursierModule {
+
+  /**
+   * Classpath for running Palantir Java Format.
+   */
+  def palantirformatClasspath: T[Loose.Agg[PathRef]] = T {
+    defaultResolver().resolveDeps(
+      Agg(ivy"com.palantir.javaformat:palantir-java-format:${palantirformatVersion()}")
+    )
+  }
+
+  /**
+   * JVM arguments for running Palantir Java Format. Defaults to values prescribed in
+   * "[[https://github.com/palantir/palantir-java-format/issues/548 Broken on Java 16]]".
+   */
+  def palantirformatJvmArgs: T[Seq[String]] = T {
+    Seq(
+      "--add-exports",
+      "jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED",
+      "--add-exports",
+      "jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED",
+      "--add-exports",
+      "jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED",
+      "--add-exports",
+      "jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED",
+      "--add-exports",
+      "jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED"
+    )
+  }
+
+  /**
+   * Path to options file for Palantir Java Format CLI. Defaults to `millSourcePath` `/` `palantirformat.options`.
+   */
+  def palantirformatOptions: T[PathRef] = Task.Source(
+    millSourcePath / "palantirformat.options"
+  )
+
+  /**
+   * Palantir Java Format version. Defaults to `2.50.0`.
+   */
+  def palantirformatVersion: T[String] = T {
+    "2.50.0"
+  }
+}
+
+/**
+ * Formats Java source files using [[https://github.com/palantir/palantir-java-format Palantir Java Format]].
+ */
+trait PalantirFormatModule extends JavaModule with PalantirFormatBaseModule {
+
+  /**
+   * Formats Java source files.
+   *
+   * @param check if an exception should be raised when formatting errors are found
+   *              - when set, files are not formatted
+   * @param sources list of file or folder path(s) to be processed
+   *                - path must be relative to [[millSourcePath]]
+   *                - when empty, all [[sources]] are processed
+   */
+  def palantirformat(
+      check: mainargs.Flag = mainargs.Flag(value = false),
+      sources: mainargs.Leftover[String]
+  ): Command[Unit] = Task.Command {
+
+    val _sources =
+      if (sources.value.isEmpty) this.sources()
+      else sources.value.iterator.map(rel => PathRef(millSourcePath / os.RelPath(rel)))
+
+    PalantirFormatModule.palantirAction(
+      _sources,
+      check.value,
+      palantirformatOptions(),
+      palantirformatClasspath(),
+      palantirformatJvmArgs()
+    )
+  }
+}
+object PalantirFormatModule extends ExternalModule with PalantirFormatBaseModule with TaskModule {
+
+  override def defaultCommandName(): String = "formatAll"
+
+  /**
+   * Formats Java source files.
+   *
+   * @param check if an exception should be raised when formatting errors are found
+   *              - when set, files are not formatted
+   * @param sources list of [[JavaModule]] sources to process
+   */
+  def formatAll(
+      check: mainargs.Flag = mainargs.Flag(value = false),
+      @mainargs.arg(positional = true) sources: Tasks[Seq[PathRef]]
+  ): Command[Unit] = Task.Command {
+
+    val _sources = T.sequence(sources.value)().iterator.flatten
+
+    palantirAction(
+      _sources,
+      check.value,
+      palantirformatOptions(),
+      palantirformatClasspath(),
+      palantirformatJvmArgs()
+    )
+  }
+
+  lazy val millDiscover: Discover = Discover[this.type]
+
+  private[palantirformat] def palantirAction(
+      sources: IterableOnce[PathRef],
+      check: Boolean,
+      options: PathRef,
+      classPath: Loose.Agg[PathRef],
+      jvmArgs: Seq[String]
+  )(implicit ctx: api.Ctx): Unit = {
+
+    if (check) {
+      ctx.log.info("checking format in java sources ...")
+    } else {
+      ctx.log.info("formatting java sources ...")
+    }
+
+    val mainArgs = palantirArgs(sources, check, options)
+
+    ctx.log.debug(s"running palantirformat with $mainArgs")
+
+    val exitCode = Jvm.callSubprocess(
+      mainClass = "com.palantir.javaformat.java.Main",
+      classPath = classPath.map(_.path),
+      jvmArgs = jvmArgs,
+      mainArgs = mainArgs,
+      workingDir = ctx.dest,
+      check = false
+    ).exitCode
+
+    if (check && exitCode != 0) {
+      ctx.log.error(
+        "palantirformat aborted due to format error(s) (or invalid plugin settings/palantirformat options)"
+      )
+      throw new RuntimeException(s"palantirformat exit($exitCode)")
+    }
+  }
+
+  private def palantirArgs(
+      sources: IterableOnce[PathRef],
+      check: Boolean,
+      options: PathRef
+  ): Seq[String] = {
+
+    val args = Seq.newBuilder[String]
+
+    // https://github.com/palantir/palantir-java-format/blob/dae9be4b84e2bd4d7ea346c6374fda47eee7118f/palantir-java-format/src/main/java/com/palantir/javaformat/java/CommandLineOptionsParser.java#L199
+    if (os.exists(options.path)) args += s"@${options.path}"
+
+    // https://github.com/palantir/palantir-java-format/blob/dae9be4b84e2bd4d7ea346c6374fda47eee7118f/palantir-java-format/src/main/java/com/palantir/javaformat/java/CommandLineOptions.java#L27
+    if (check) {
+      // do not overwrite files and exit(1) if formatting changes were detected
+      args += "--dry-run" += "--set-exit-if-changed"
+    } else {
+      // format in place
+      args += "--replace"
+    }
+
+    // https://github.com/palantir/palantir-java-format/blob/dae9be4b84e2bd4d7ea346c6374fda47eee7118f/palantir-java-format/src/main/java/com/palantir/javaformat/java/CommandLineOptionsParser.java#L49
+    args ++=
+      sources
+        .iterator
+        .map(_.path)
+        .flatMap(os.walk(_, includeTarget = true))
+        .filter(os.isFile)
+        .filter(_.ext == "java")
+        .map(_.toString())
+
+    args.result()
+  }
+
+  /**
+   * Path to options file for Palantir Java Format CLI at `T.workspace` `/` `palantirformat.options`.
+   */
+  override def palantirformatOptions: T[PathRef] = Task.Source(
+    T.workspace / "palantirformat.options"
+  )
+}

scalalib/test/resources/javalib/palantirformat/after/example/A.java

@@ -0,0 +1,6 @@
+public class A {
+
+  public static void main(String[] args) {
+    System.out.println("hello"); // indentation should be fixed
+  }
+}

scalalib/test/resources/javalib/palantirformat/after/google/A.java

@@ -0,0 +1,76 @@
+package com.google.googlejavaformat.java.test;
+
+/**
+ * Tests for AbstractTypeDeclarations, AnnotationTypeDeclarations, AnnotationTypeMemberDeclarations,
+ * Annotations, AnonymousClassDeclarations, ArrayAccesses, ArrayCreations, ArrayInitializers,
+ * ArrayTypes, AssertStatements, and Assignments.
+ */
+class A {
+  public @interface X {
+    int x();
+
+    int y() default
+        1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1
+            + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1;
+  }
+
+  @X(x = 1)
+  private @interface Y {}
+
+  // TODO(jdd): Add annotation declaration with empty body.
+
+  @X(x = 1)
+  @Y
+  protected @interface Z {}
+
+  // TODO(jdd): Include type annotations once we can include a higher language level.
+
+  int[] array1 = new int[5];
+  int[] array2 = new int[] {
+    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+    26, 27, 28, 29, 30, 31
+  };
+  int[] array3 = {
+    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+    26, 27, 28, 29, 30, 31
+  };
+  int[][] array4 = {
+    {0, 1}, {2, 3}, {4, 5}, {6, 7}, {8, 9}, {10, 11}, {12, 13}, {14, 15}, {16, 17}, {18, 19},
+    {20, 21}, {22, 23}
+  };
+  int[][][] arrayWithLongName = new int
+      [0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0
+          + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0]
+      [0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0
+          + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0]
+      [];
+
+  A a1 = new A() {
+    int x = array1[
+            0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0
+                + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0]
+        + array2[
+            0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0
+                + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0]
+        + array3[
+            0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0
+                + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0]
+        + array4[0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0][
+            0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0];
+  };
+
+  void f(int something) {
+    assert 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1
+        == 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1;
+    assert 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1
+            == 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1
+        : "that was certainly unexpected!";
+    arrayWithLongName[
+            0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0] =
+        arrayWithLongName[
+            0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0];
+    something = 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2
+        + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2
+        + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2;
+  }
+}

scalalib/test/resources/javalib/palantirformat/after/google/A.scala

@@ -0,0 +1,7 @@
+package com.google.googlejavaformat.java.test
+
+object A {
+
+// plugin should ignore non Java file
+// introduce a compile error to trigger failure in case this file is processed
+//}

scalalib/test/resources/javalib/palantirformat/after/palantir/Main.java

@@ -0,0 +1,33 @@
+package a;
+
+// imports should be sorted
+// unsed imports should be removed
+import some.Configuration;
+import some.GradleException;
+import some.MavenPublication;
+import some.Project;
+import some.PublishingExtension;
+import some.VariantVersionMappingStrategy;
+
+public class Main {
+
+    private static void configureResolvedVersionsWithVersionMapping(Project project) {
+        project.getPluginManager().withPlugin("maven-publish", plugin -> {
+            project.getExtensions()
+                    .getByType(PublishingExtension.class)
+                    .getPublications()
+                    .withType(MavenPublication.class)
+                    .configureEach(publication -> publication.versionMapping(mapping -> {
+                        mapping.allVariants(VariantVersionMappingStrategy::fromResolutionResult);
+                    }));
+        });
+    }
+
+    private static GradleException notFound(String group, String name, Configuration configuration) {
+        String actual = configuration.getIncoming().getResolutionResult().getAllComponents().stream()
+                .map(ResolvedComponentResult::getModuleVersion)
+                .map(mvi -> String.format("\t- %s:%s:%s", mvi.getGroup(), mvi.getName(), mvi.getVersion()))
+                .collect(Collectors.joining("\n"));
+        // ...
+    }
+}

scalalib/test/resources/javalib/palantirformat/before/example/src/A.java

@@ -0,0 +1,6 @@
+public class A {
+
+    public static void main(String[] args) {
+    System.out.println("hello"); // indentation should be fixed
+    }
+}