fix (core): Merge lists in ThingMerger

java/dev/enola/common/collect/BUILD

@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: Apache-2.0
+#
+# Copyright 2023 The Enola <https://enola.dev> Authors
+#
+# 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
+#
+#     https://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.
+
+load("@rules_java//java:defs.bzl", "java_library")
+
+java_library(
+    name = "collect",
+    srcs = glob(
+        ["*.java"],
+        exclude = ["*Test.java"],
+    ),
+    visibility = ["//:__subpackages__"],
+    deps = [
+        "@maven//:com_google_errorprone_error_prone_annotations",
+        "@maven//:com_google_guava_guava",
+        "@maven//:org_jspecify_jspecify",
+    ],
+)

java/dev/enola/common/collect/Immutables.java

@@ -0,0 +1,32 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright 2024 The Enola <https://enola.dev> Authors
+ *
+ * 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
+ *
+ *     https://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 dev.enola.common.collect;
+
+import com.google.common.collect.ImmutableList;
+
+import java.util.List;
+
+public final class Immutables {
+
+    public static <T> ImmutableList<T> join(List<T> a, List<T> b) {
+        var builder = ImmutableList.<T>builderWithExpectedSize(a.size() + b.size());
+        return builder.addAll(a).addAll(b).build();
+    }
+
+    private Immutables() {}
+}

java/dev/enola/thing/BUILD

@@ -71,6 +71,7 @@ java_library(
     deps = [
         ":thing_java_proto",
         "//java/dev/enola/common",
+        "//java/dev/enola/common/collect",
         "//java/dev/enola/common/convert",
         "//java/dev/enola/common/function",
         "//java/dev/enola/common/io",

java/dev/enola/thing/io/Loader.java

@@ -28,6 +28,7 @@
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
+import java.util.List;
 import java.util.stream.Stream;
 
 public class Loader implements ConverterInto<Stream<ReadableResource>, Store<?, Thing>> {
@@ -58,7 +59,7 @@ private void load(ReadableResource resource, Store<?, Thing> store) {
             things.get()
                     .forEach(
                             thingBuilder -> {
-                                thingBuilder.set(KIRI.E.ORIGIN, resource.uri());
+                                thingBuilder.set(KIRI.E.ORIGIN, List.of(resource.uri()));
                                 var thing = thingBuilder.build();
                                 store.merge(thing);
                             });

java/dev/enola/thing/repo/ThingMerger.java

@@ -17,38 +17,42 @@
  */
 package dev.enola.thing.repo;
 
+import static dev.enola.common.collect.Immutables.join;
+
 import dev.enola.thing.KIRI;
 import dev.enola.thing.Thing;
 
+import java.util.List;
+
 class ThingMerger {
     // TODO Implement missing ThingMergerTest coverage!
 
-    public static Thing merge(Thing existing, Thing update) {
-        if (!existing.iri().equals(update.iri())) throw new IllegalArgumentException();
+    public static Thing merge(Thing t1, Thing t2) {
+        if (!t1.iri().equals(t2.iri())) throw new IllegalArgumentException();
 
-        if (existing.predicateIRIs().isEmpty()) return update;
-        if (update.predicateIRIs().isEmpty()) return existing;
+        if (t1.predicateIRIs().isEmpty()) return t2;
+        if (t2.predicateIRIs().isEmpty()) return t1;
 
-        var merged = existing.copy();
-        var properties = update.properties();
+        var merged = t1.copy();
+        var properties = t2.properties();
         properties.forEach(
-                (predicate, value) -> {
-                    var old = existing.get(predicate);
-                    if (old == null) merged.set(predicate, value, update.datatype(predicate));
-                    else if (old.equals(value)) {
+                (predicate, t2obj) -> {
+                    var t1obj = t1.get(predicate);
+                    if (t1obj == null) merged.set(predicate, t2obj, t2.datatype(predicate));
+                    else if (t1obj.equals(t2obj)) {
                         // That's fine!
-                    } else if (predicate.equals(KIRI.E.ORIGIN)) {
-                        // TODO Implement merging both into a List, with test coverage!
+                    } else if (t1obj instanceof List t1list && t2obj instanceof List t2list) {
+                        merged.set(predicate, join(t1list, t2list));
                     } else
                         throw new IllegalStateException(
                                 "Cannot merge "
                                         + predicate
                                         + " of an "
-                                        + existing.iri()
+                                        + t1.iri()
                                         + " from "
-                                        + existing.getString(KIRI.E.ORIGIN)
+                                        + t1.getString(KIRI.E.ORIGIN)
                                         + " and "
-                                        + update.getString(KIRI.E.ORIGIN));
+                                        + t2.getString(KIRI.E.ORIGIN));
                 });
         return merged.build();
     }