zdm/event-bus
zdm/event-bus
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Fix several edge cases in EventProcessor

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When encountering an event handler with an invalid signature, the
processor doesn't crash anymore. Also, event parameters that aren't
objects are now reported as errors.
This commit is contained in:
Kai S. K. Engelbart 2021-02-17 08:22:48 +01:00
parent 1dd9e05c38
commit ff35e7f37d
Signed by: kske
GPG Key ID: 8BEB13EC5DF7EF13
2 changed files with 36 additions and 22 deletions
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4
README.md
View File

@ -157,9 +157,9 @@ If you intend to use event handlers that are inaccessible to Event Bus by means
opens my.module to dev.kske.eventbus.core;
```
## Compile-Time Error Checking with Event Bus AP
## Compile-Time Error Checking with Event Bus Proc
To assist you with writing event listeners, the Event Bus AP (Annotation Processor) module enforces correct usage of the `@Event` annotation during compile time.
To assist you with writing event listeners, the Event Bus Proc (Annotation Processor) module enforces correct usage of the `@Event` annotation during compile time.
This reduces difficult-to-debug bugs that occur during runtime to compile-time errors which can be easily fixed.
The event annotation processor detects invalid event handlers and event type issues with more to come in future versions.

54
event-bus-proc/src/main/java/dev/kske/eventbus/proc/EventProcessor.java
View File

@ -34,9 +34,10 @@ public class EventProcessor extends AbstractProcessor {
private void processRound(Set<ExecutableElement> eventHandlers) {
for (ExecutableElement eventHandler : eventHandlers) {
Event eventAnnotation = eventHandler.getAnnotation(Event.class);
Event eventAnnotation = eventHandler.getAnnotation(Event.class);
TypeMirror eventType;
// Determine how the event type is defined
// Determine the event type and how it is defined
boolean useParameter;
try {
eventAnnotation.value();
@ -45,36 +46,49 @@ public class EventProcessor extends AbstractProcessor {
} catch (MirroredTypeException e) {
// Task failed successfully
useParameter = processingEnv.getTypeUtils().isSameType(e.getTypeMirror(),
eventType = e.getTypeMirror();
useParameter = processingEnv.getTypeUtils().isSameType(eventType,
getTypeMirror(Event.USE_PARAMETER.class));
}
// Check for correct method signature and return type
if (eventHandler.getParameters().size() == 0 && useParameter)
// Check handler signature
boolean pass = false;
if (useParameter && eventHandler.getParameters().size() == 0)
error(eventHandler, "The method or the annotation must define the event type");
if (eventHandler.getParameters().size() == 1 && !useParameter)
else if (!useParameter && eventHandler.getParameters().size() == 1)
error(eventHandler,
"Either the method or the annotation must define the event type");
if (eventHandler.getParameters().size() > 1)
else if (eventHandler.getParameters().size() > 1)
error(eventHandler, "Method must not have more than one parameter");
if (eventHandler.getReturnType().getKind() != TypeKind.VOID)
else if (eventHandler.getReturnType().getKind() != TypeKind.VOID)
error(eventHandler, "Method must return void");
else
pass = true;
// Get first parameter as type and element
var paramElement = eventHandler.getParameters().get(0);
var paramType = paramElement.asType();
// Abort checking if the handler signature is incorrect
if (!pass)
continue;
// Additional checks if parameter is used
if (useParameter) {
VariableElement paramElement = eventHandler.getParameters().get(0);
eventType = paramElement.asType();
// Check if parameter is object
// Abort checking otherwise
if (eventType.getKind() != TypeKind.DECLARED) {
error(paramElement, "Event must be an object");
continue;
}
}
// Check for handlers for abstract types that aren't polymorphic
Element eventElement = ((DeclaredType) eventType).asElement();
if (eventHandler.getAnnotation(Polymorphic.class) == null
&& paramType.getKind() == TypeKind.DECLARED) {
var declaredElement = ((DeclaredType) paramType).asElement();
if (declaredElement.getKind() == ElementKind.INTERFACE
|| declaredElement.getModifiers().contains(Modifier.ABSTRACT))
warning(paramElement,
"Parameter should be instantiable or handler should use @Polymorphic");
&& (eventElement.getKind() == ElementKind.INTERFACE
|| eventElement.getModifiers().contains(Modifier.ABSTRACT))) {
warning(eventHandler,
"Parameter should be instantiable or handler should use @Polymorphic");
}
}
}