Replace derive4j with a sealed interface and records

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

@@ -16,7 +16,7 @@ nullaway {
 
 tasks.withType(JavaCompile).configureEach {
     options.errorprone {
-        // Annotation processor output (derive4j, Immutables) is not ours to fix.
+        // Annotation processor output (Immutables) is not ours to fix.
         excludedPaths = '.*/build/generated/.*'
     }
 }

gradle/libs.versions.toml

@@ -26,8 +26,6 @@ compileTesting = { module = "com.google.testing.compile:compile-testing", versio
 errorprone-core = { module = "com.google.errorprone:error_prone_core", version = "2.50.0" }
 errorProneSupport-contrib = { module = "tech.picnic.error-prone-support:error-prone-contrib", version = "0.30.0" }
 nullaway = { module = "com.uber.nullaway:nullaway", version = "0.14.2" }
-derive4j = { module = "org.derive4j:derive4j", version = "1.1.1" }
-derive4j-annotation = { module = "org.derive4j:derive4j-annotation", version = "1.1.1" }
 functionaljava = { module = "org.functionaljava:functionaljava", version = "5.0" }
 guava = { module = "com.google.guava:guava", version = "33.7.1-jre" }
 guava-testlib = { module = "com.google.guava:guava-testlib", version = "33.5.0-jre" }

open-java-format/build.gradle

@@ -26,8 +26,6 @@ dependencies {
     compileOnly variantOf(libs.immutables.value) { classifier('annotations') }
     annotationProcessor libs.immutables.value
 
-    compileOnly libs.derive4j.annotation
-    annotationProcessor libs.derive4j
     implementation libs.jsr305
 }
 

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

@@ -23,96 +23,99 @@
 import com.palantir.javaformat.doc.Doc;
 import com.palantir.javaformat.doc.Level;
 import java.io.IOException;
-import java.io.UncheckedIOException;
-import org.derive4j.ArgOption;
-import org.derive4j.Data;
 
-@Data(arguments = ArgOption.checkedNotNull)
+/**
+ * How a {@link Level} is broken when it does not fit on one line. Each case's {@code toString()} is what
+ * {@link com.palantir.javaformat.doc.LevelDelimitedFlatValueDocVisitor} prints for it.
+ */
 @Immutable
 @JsonSerialize(using = BreakBehaviour.Json.class)
-public abstract class BreakBehaviour {
-    public interface Cases<R> {
+public sealed interface BreakBehaviour {
 
-        R breakThisLevel();
+    static BreakBehaviour breakThisLevel() {
+        return new BreakThisLevel();
+    }
 
-        /**
-         * If the last level is breakable, prefer breaking it if it will keep the rest of this level on line line.
-         *
-         * @param keepIndentWhenInlined whether to keep this level's indent when inlined as a recursive level (when
-         *     reached via a previous `preferBreakingLastInnerLevel` whose breakability was
-         *     {@link LastLevelBreakability#CHECK_INNER})
-         */
-        R preferBreakingLastInnerLevel(boolean keepIndentWhenInlined);
+    static BreakBehaviour preferBreakingLastInnerLevel(boolean keepIndentWhenInlined) {
+        return new PreferBreakingLastInnerLevel(keepIndentWhenInlined);
+    }
 
-        /**
-         * Attempt to inline the suffix of this level (which must be a {@link Level} and the last doc), recursing into
-         * the {@link Level} just before the last {@link Level} (if there is such a level) to see if that can be broken
-         * instead.
-         *
-         * <p>This behaves like {@link #breakThisLevel()} if we couldn't recurse into such an inner level, or if the
-         * suffix level doesn't fit on the last line.
-         */
-        R inlineSuffix();
+    static BreakBehaviour inlineSuffix() {
+        return new InlineSuffix();
+    }
 
-        /**
-         * Break if by doing so all inner levels then fit on a single line. However, don't break if we can fit in the
-         * {@link Doc docs} up to the first break (which might be nested inside the next doc if it's a {@link Level}),
-         * in order to prevent exceeding the maxLength accidentally.
-         */
-        R breakOnlyIfInnerLevelsThenFitOnOneLine(boolean keepIndentWhenInlined);
+    static BreakBehaviour breakOnlyIfInnerLevelsThenFitOnOneLine(boolean keepIndentWhenInlined) {
+        return new BreakOnlyIfInnerLevelsThenFitOnOneLine(keepIndentWhenInlined);
     }
 
-    public abstract <R> R match(Cases<R> cases);
+    /** Break this level. */
+    record BreakThisLevel() implements BreakBehaviour {
+        @Override
+        public String toString() {
+            return "breakThisLevel()";
+        }
+    }
 
-    /** For {@link com.palantir.javaformat.doc.LevelDelimitedFlatValueDocVisitor}. */
-    @Override
-    public abstract String toString();
+    /**
+     * If the last level is breakable, prefer breaking it if it will keep the rest of this level on line line.
+     *
+     * @param keepIndentWhenInlined whether to keep this level's indent when inlined as a recursive level (when
+     *     reached via a previous `preferBreakingLastInnerLevel` whose breakability was
+     *     {@link LastLevelBreakability#CHECK_INNER})
+     */
+    record PreferBreakingLastInnerLevel(boolean keepIndentWhenInlined) implements BreakBehaviour {
+        @Override
+        public String toString() {
+            return "preferBreakingLastInnerLevel(" + keepIndentWhenInlined + ")";
+        }
+    }
+
+    /**
+     * Attempt to inline the suffix of this level (which must be a {@link Level} and the last doc), recursing into the
+     * {@link Level} just before the last {@link Level} (if there is such a level) to see if that can be broken instead.
+     *
+     * <p>This behaves like {@link BreakThisLevel} if we couldn't recurse into such an inner level, or if the suffix
+     * level doesn't fit on the last line.
+     */
+    record InlineSuffix() implements BreakBehaviour {
+        @Override
+        public String toString() {
+            return "inlineSuffix()";
+        }
+    }
 
     /**
-     * This is gross but just wanted to get something working. See https://github.com/derive4j/derive4j/issues/51 for a
-     * potential better implementation.
+     * Break if by doing so all inner levels then fit on a single line. However, don't break if we can fit in the
+     * {@link Doc docs} up to the first break (which might be nested inside the next doc if it's a {@link Level}), in
+     * order to prevent exceeding the maxLength accidentally.
+     *
+     * @param keepIndentWhenInlined whether to keep this level's indent when inlined as a recursive level
      */
-    static class Json extends JsonSerializer<BreakBehaviour> {
+    record BreakOnlyIfInnerLevelsThenFitOnOneLine(boolean keepIndentWhenInlined) implements BreakBehaviour {
+        @Override
+        public String toString() {
+            return "breakOnlyIfInnerLevelsThenFitOnOneLine(" + keepIndentWhenInlined + ")";
+        }
+    }
 
+    /** Writes the case as {@code type} and its flag, if it has one. */
+    final class Json extends JsonSerializer<BreakBehaviour> {
         @Override
         public void serialize(BreakBehaviour value, JsonGenerator gen, SerializerProvider serializers)
                 throws IOException {
             gen.writeStartObject();
-            BreakBehaviours.caseOf(value)
-                    .breakThisLevel(() -> {
-                        try {
-                            gen.writeObjectField("type", "breakThisLevel");
-                        } catch (IOException e) {
-                            throw new UncheckedIOException(e);
-                        }
-                        return null;
-                    })
-                    .preferBreakingLastInnerLevel(keepIndentWhenInlined -> {
-                        try {
-                            gen.writeObjectField("type", "preferBreakingLastInnerLevel");
-                            gen.writeObjectField("keepIndentWhenInlined", keepIndentWhenInlined);
-                        } catch (IOException e) {
-                            throw new UncheckedIOException(e);
-                        }
-                        return null;
-                    })
-                    .inlineSuffix(() -> {
-                        try {
-                            gen.writeObjectField("type", "inlineSuffix");
-                        } catch (IOException e) {
-                            throw new UncheckedIOException(e);
-                        }
-                        return null;
-                    })
-                    .breakOnlyIfInnerLevelsThenFitOnOneLine(keepIndentWhenInlined -> {
-                        try {
-                            gen.writeObjectField("type", "breakOnlyIfInnerLevelsThenFitOnOneLine");
-                            gen.writeObjectField("keepIndentWhenInlined", keepIndentWhenInlined);
-                        } catch (IOException e) {
-                            throw new UncheckedIOException(e);
-                        }
-                        return null;
-                    });
+            switch (value) {
+                case BreakThisLevel() -> gen.writeObjectField("type", "breakThisLevel");
+                case PreferBreakingLastInnerLevel(boolean keepIndentWhenInlined) -> {
+                    gen.writeObjectField("type", "preferBreakingLastInnerLevel");
+                    gen.writeObjectField("keepIndentWhenInlined", keepIndentWhenInlined);
+                }
+                case InlineSuffix() -> gen.writeObjectField("type", "inlineSuffix");
+                case BreakOnlyIfInnerLevelsThenFitOnOneLine(boolean keepIndentWhenInlined) -> {
+                    gen.writeObjectField("type", "breakOnlyIfInnerLevelsThenFitOnOneLine");
+                    gen.writeObjectField("keepIndentWhenInlined", keepIndentWhenInlined);
+                }
+            }
             gen.writeEndObject();
         }
     }

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

@@ -20,25 +20,25 @@
 
 /**
  * How to decide whether to break the last inner level ("this level") of a parent level with
- * {@link BreakBehaviour.Cases#preferBreakingLastInnerLevel}.
+ * {@link BreakBehaviour.PreferBreakingLastInnerLevel}.
  */
 public enum LastLevelBreakability {
     /**
-     * Default behaviour. When processing a {@link BreakBehaviour.Cases#preferBreakingLastInnerLevel} chain, if we've
+     * Default behaviour. When processing a {@link BreakBehaviour.PreferBreakingLastInnerLevel} chain, if we've
      * arrived at a level with this breakability, then we should abort the chain.
      */
     ABORT,
     /**
      * Unconditionally allow ending an inline chain at this level, after which this level may be broken as usual, or a
      * prefix thereof could be inlined further (if it has the appropriate break behaviour of
-     * {@link BreakBehaviour.Cases#preferBreakingLastInnerLevel}). This should only be used when you know that the first
+     * {@link BreakBehaviour.PreferBreakingLastInnerLevel}). This should only be used when you know that the first
      * non-Level {@link Doc} inside this level, if you flatten it, is a {@link Break}.
      */
     ACCEPT_INLINE_CHAIN,
     /**
      * Delegate to the {@link LastLevelBreakability} of _this_ level's last inner level. Typically, this will be true if
      * this level is not immediately followed by a break (see StartsWithBreakVisitor). Behaves the same as
-     * {@link #ABORT} if this level is not {@link BreakBehaviour.Cases#preferBreakingLastInnerLevel}.
+     * {@link #ABORT} if this level is not {@link BreakBehaviour.PreferBreakingLastInnerLevel}.
      */
     CHECK_INNER,
     /**

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

@@ -41,7 +41,7 @@ public abstract class OpenOp extends HasUniqueId implements Op {
      */
     @Default
     public BreakBehaviour breakBehaviour() {
-        return BreakBehaviours.breakThisLevel();
+        return BreakBehaviour.breakThisLevel();
     }
 
     /** If it's the last level of its parent, when to inline this level rather than break the parent. */

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

@@ -20,7 +20,7 @@
 
 /**
  * What are the conditions for a level to be partially inlineable. Partial inlining refers to the behaviour of
- * {@link BreakBehaviours#breakOnlyIfInnerLevelsThenFitOnOneLine} where a level is too large to fit on the current line,
+ * {@link BreakBehaviour.BreakOnlyIfInnerLevelsThenFitOnOneLine} where a level is too large to fit on the current line,
  * but a prefix thereof is partially inlined onto the current line.
  *
  * <p>Specifically, when inlining a level with the above behaviour, the partial inlineability of its first