Implement implicit ID

bosk-core/src/main/java/io/vena/bosk/SerializationPlugin.java

@@ -192,7 +192,23 @@ public final List<Object> parameterValueList(Class<?> nodeClass, Map<String, Obj
 				} else if (Phantom.class.equals(type)) {
 					parameterValues.add(Phantom.empty());
 				} else {
-					throw new DeserializationException("Missing field: " + name);
+					Path path = currentScope.get().path();
+					if ("id".equals(name) && !path.isEmpty()) {
+						// If the object is an entry in a Catalog or a key in a SideTable, we can determine its ID
+						Reference<Object> enclosingRef;
+						try {
+							enclosingRef = bosk.rootReference().then(Object.class, path.truncatedBy(1));
+						} catch (InvalidTypeException e) {
+							throw new AssertionError("Non-empty path must have an enclosing reference: " + path, e);
+						}
+						if (AddressableByIdentifier.class.isAssignableFrom(enclosingRef.targetClass())) {
+							parameterValues.add(Identifier.from(path.lastSegment()));
+						} else {
+							throw new DeserializationException("Missing id field for object at " + path);
+						}
+					} else {
+						throw new DeserializationException("Missing field \"" + name + "\" at " + path);
+					}
 				}
 			} else if (implicitReference == null) {
 				parameterValues.add(value);

docs/USERS.md

@@ -801,6 +801,13 @@ A field of type `Optional<T>` is simply serialized as a `T`, unless the optional
 
 A field of type `Phantom<T>` is not serialized (just like `Optional.empty()`).
 
+The `id` field of a Catalog entry or a SideTable key may be omitted,
+and will be inferred during deserialization if possible from context,
+including any `@DeserializationPath` annotations.
+This inference process takes some time, though,
+so for best performance, it's better for the JSON input to include the `id` field,
+just as it does when serialized.
+
 #### DeserializationScope
 
 Fields marked as `@Self` or `@Enclosing` are not serialized.
@@ -825,6 +832,9 @@ try (var __ = jacksonPlugin.newDeserializationScope(ref)) {
 For this to work, you will need access to the `JacksonPlugin` object,
 typically from your dependency injection framework.
 
+For an object whose _fields_ represent specific nodes of the bosk state,
+use the `@DeserializationPath` annotation; see the javadocs for more info.
+
 #### DerivedRecord
 
 In inner-loop, high-performance code, it can be too costly to use `Reference.value()` to access node objects, and it is definitely too costly to create new `Reference` objects.