engineering/resources/tooling/format/Format.java

import com.palantir.javaformat.java.Formatter;
import com.palantir.javaformat.java.JavaFormatterOptions;
import java.nio.file.*;
import java.security.MessageDigest;
import java.util.*;
import org.openrewrite.*;
import org.openrewrite.internal.InMemoryLargeSourceSet;
import org.openrewrite.text.*;

/** Source-launcher bootstrap: no project-specific artifact is resolved or installed. */
public class Format {
    /**
     * Checks or atomically formats configured handwritten Java sources with the pinned formatter.
     *
     * @param args consumer repository root followed by either {@code check} or {@code apply}
     * @throws Exception if configuration, parsing or formatting fails, or check mode finds differences
     */
    public static void main(final String... args) throws Exception {
        Path root = Path.of(args[0]).toAbsolutePath().normalize();
        boolean check = switch (args[1]) {
            case "check" -> true;
            case "apply" -> false;
            default -> throw new IllegalArgumentException("format.mode must be apply or check");
        };
        Path cacheFile = root.resolve("target/palantir-cache.properties");
        var cache = new Properties();
        if (Files.exists(cacheFile)) {
            try (var input = Files.newInputStream(cacheFile)) {
                cache.load(input);
            }
        }
        String configuration = digest(Files.readString(root.resolve("pom.xml"))
                + Files.readString(root.resolve("generated/tooling/format/Format.java"))
                + System.getProperty("java.version")
                + System.getProperty("java.class.path"));
        if (!configuration.equals(cache.getProperty("configuration"))) cache.clear();
        cache.setProperty("configuration", configuration);
        List<SourceFile> sources = new ArrayList<>();
        var settings = new Properties();
        try (var input = Files.newInputStream(root.resolve("engineering.properties"))) {
            settings.load(input);
        }
        for (String directory :
                settings.getProperty("FORMAT_DIRECTORIES", "backend/src").split(",")) {
            if (!Files.isDirectory(root.resolve(directory))) continue;
            try (var paths = Files.walk(root.resolve(directory))) {
                for (Path path : paths.filter(p -> p.toString().endsWith(".java"))
                        .sorted()
                        .toList()) {
                    try {
                        String content = Files.readString(path);
                        String key = root.relativize(path).toString();
                        if (!digest(content).equals(cache.getProperty(key))) {
                            sources.add(PlainText.builder()
                                    .sourcePath(root.relativize(path))
                                    .text(content)
                                    .build());
                        }
                    } catch (Exception error) {
                        throw new IllegalStateException(path + ": " + error.getMessage(), error);
                    }
                }
            }
        }
        var context = new InMemoryExecutionContext(error -> {
            throw new IllegalStateException("Formatting failed: " + error.getMessage(), error);
        });
        var results = new PalantirRecipe()
                .run(new InMemoryLargeSourceSet(sources), context)
                .getChangeset()
                .getAllResults();
        for (Result result : results) {
            IO.println((check ? "Needs formatting: " : "Formatted: ")
                    + result.getAfter().getSourcePath());
        }
        if (check && !results.isEmpty()) {
            throw new IllegalStateException("Run mvn -N exec:exec@format to apply Palantir formatting.");
        }
        // Complete parsing/formatting before writing any maintained file. Each replacement is atomic.
        if (!check) {
            for (Result result : results) {
                Path destination = root.resolve(result.getAfter().getSourcePath());
                Path temporary = Files.createTempFile(destination.getParent(), ".palantir-", ".tmp");
                try {
                    Files.writeString(temporary, result.getAfter().printAll());
                    Files.setPosixFilePermissions(temporary, Files.getPosixFilePermissions(destination));
                    Files.move(
                            temporary,
                            destination,
                            StandardCopyOption.ATOMIC_MOVE,
                            StandardCopyOption.REPLACE_EXISTING);
                } finally {
                    Files.deleteIfExists(temporary);
                }
            }
        }
        for (SourceFile source : sources) {
            cache.setProperty(
                    source.getSourcePath().toString(), digest(Files.readString(root.resolve(source.getSourcePath()))));
        }
        Files.createDirectories(cacheFile.getParent());
        try (var output = Files.newOutputStream(cacheFile)) {
            cache.store(output, "Successfully formatted content only");
        }
        IO.println("Palantir " + args[1] + ": " + sources.size() + " Java files, " + results.size() + " differences");
    }

    static String digest(String value) throws Exception {
        return HexFormat.of()
                .formatHex(MessageDigest.getInstance("SHA-256")
                        .digest(value.getBytes(java.nio.charset.StandardCharsets.UTF_8)));
    }

    public static final class PalantirRecipe extends Recipe {
        public String getDisplayName() {
            return "Palantir Java Format";
        }

        public String getDescription() {
            return "Apply the pinned Palantir engine and its native import handling.";
        }

        public TreeVisitor<?, ExecutionContext> getVisitor() {
            return new PlainTextVisitor<ExecutionContext>() {
                final Formatter formatter = Formatter.createFormatter(JavaFormatterOptions.builder()
                        .style(JavaFormatterOptions.Style.PALANTIR)
                        .formatJavadoc(false)
                        .build());

                @Override
                public PlainText visitText(PlainText text, ExecutionContext context) {
                    try {
                        return text.withText(formatter.formatSourceAndFixImports(text.getText()));
                    } catch (Exception | LinkageError error) {
                        throw new IllegalStateException(text.getSourcePath() + ": " + error, error);
                    }
                }
            };
        }
    }
}