Treat all packages as @NullMarked

* For NullAway, the config is now in the build setup because it doesn't
  yet support module descriptors (see uber/NullAway#1083)
* For IntelliJ, the config is now in the module descriptors

Author: marcphilipp

CONTRIBUTING.md

@@ -120,6 +120,17 @@ See [`ExtensionContext`](junit-jupiter-api/src/main/java/org/junit/jupiter/api/e
 [`ParameterContext`](junit-jupiter-api/src/main/java/org/junit/jupiter/api/extension/ParameterContext.java) for example Javadoc.
 
 
+### Nullability
+
+This project uses JSpecify's annotation to indicate nullability. In general, the approach
+is as follows:
+
+- The Gradle build is set up to treat all code as being `@NullMarked`
+- The descriptor of each module is annotated with `@NullMarked` for IDEs such as IntelliJ
+  IDEA to treat code correctly.
+- Fields, parameters, return types etc. may be annotated with `@Nullable`
+- A package can be excluded (temporarily) using `@NullUnmarked`
+
 ### Tests
 
 #### Naming

gradle/plugins/common/src/main/kotlin/junitbuild.java-nullability-conventions.gradle.kts

@@ -13,7 +13,7 @@ dependencies {
 }
 
 nullaway {
-	onlyNullMarked = true
+	annotatedPackages.add("org.junit")
 }
 
 tasks.withType<JavaCompile>().configureEach {

junit-platform-commons/src/main/java/module-info.java

@@ -8,11 +8,14 @@
  * https://www.eclipse.org/legal/epl-v20.html
  */
 
+import org.jspecify.annotations.NullMarked;
+
 /**
  * Common APIs and support utilities for the JUnit Platform.
  *
  * @since 1.0
  */
+@NullMarked
 module org.junit.platform.commons {
 	requires java.logging;
 	requires java.management; // needed by RuntimeUtils to determine input arguments

junit-platform-commons/src/main/java/org/junit/platform/commons/annotation/package-info.java

@@ -2,7 +2,4 @@
  * Common annotations for the JUnit Platform.
  */
 
-@NullMarked
 package org.junit.platform.commons.annotation;
-
-import org.jspecify.annotations.NullMarked;

junit-platform-commons/src/main/java/org/junit/platform/commons/function/package-info.java

@@ -2,7 +2,4 @@
  * Functional interfaces and support classes.
  */
 
-@NullMarked
 package org.junit.platform.commons.function;
-
-import org.jspecify.annotations.NullMarked;

junit-platform-commons/src/main/java/org/junit/platform/commons/logging/package-info.java

@@ -8,7 +8,4 @@
  * Use at your own risk!
  */
 
-@NullMarked
 package org.junit.platform.commons.logging;
-
-import org.jspecify.annotations.NullMarked;

junit-platform-commons/src/main/java/org/junit/platform/commons/package-info.java

@@ -8,7 +8,4 @@
  * APIs by external parties is not supported!</strong>
  */
 
-@NullMarked
 package org.junit.platform.commons;
-
-import org.jspecify.annotations.NullMarked;

junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/package-info.java

@@ -2,7 +2,4 @@
  * Conversion APIs provided by the JUnit Platform.
  */
 
-@NullMarked
 package org.junit.platform.commons.support.conversion;
-
-import org.jspecify.annotations.NullMarked;

junit-platform-commons/src/main/java/org/junit/platform/commons/support/package-info.java

@@ -8,7 +8,4 @@
  * extensions with the same semantics as within the JUnit Platform itself.
  */
 
-@NullMarked
 package org.junit.platform.commons.support;
-
-import org.jspecify.annotations.NullMarked;

junit-platform-commons/src/main/java/org/junit/platform/commons/support/scanning/package-info.java

@@ -2,7 +2,4 @@
  * Classpath scanning APIs provided by the JUnit Platform.
  */
 
-@NullMarked
 package org.junit.platform.commons.support.scanning;
-
-import org.jspecify.annotations.NullMarked;