learner-it-support: improve nullability declarations

Author: mtf90

test-support/learner-it-support/pom.xml

@@ -60,6 +60,12 @@ limitations under the License.
             <artifactId>learnlib-util</artifactId>
         </dependency>
 
+        <!-- build -->
+        <dependency>
+            <groupId>org.checkerframework</groupId>
+            <artifactId>checker-qual</artifactId>
+        </dependency>
+
         <!-- external -->
         <dependency>
             <groupId>net.automatalib</groupId>

test-support/learner-it-support/src/main/java/de/learnlib/testsupport/it/learner/AbstractLearnerVariantITCase.java

@@ -29,6 +29,7 @@
 import net.automatalib.automaton.concept.Output;
 import net.automatalib.common.util.random.RandomUtil;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.testng.Assert;
@@ -104,6 +105,6 @@ public String getTestName() {
         return variant.getLearnerName() + "[" + variant.getName() + "]/" + example.getClass().getSimpleName();
     }
 
-    protected abstract Word<I> checkEquivalence(M hypothesis);
+    protected abstract @Nullable Word<I> checkEquivalence(M hypothesis);
 
 }

test-support/learner-it-support/src/main/java/de/learnlib/testsupport/it/learner/OneSEVPALearnerITCase.java

@@ -20,6 +20,7 @@
 import net.automatalib.automaton.vpa.OneSEVPA;
 import net.automatalib.util.automaton.vpa.OneSEVPAs;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class OneSEVPALearnerITCase<I> extends AbstractLearnerVariantITCase<I, Boolean, OneSEVPA<?, I>> {
 
@@ -33,7 +34,7 @@ public class OneSEVPALearnerITCase<I> extends AbstractLearnerVariantITCase<I, Bo
     }
 
     @Override
-    protected Word<I> checkEquivalence(OneSEVPA<?, I> hypothesis) {
+    protected @Nullable Word<I> checkEquivalence(OneSEVPA<?, I> hypothesis) {
         return OneSEVPAs.findSeparatingWord(this.example.getReferenceAutomaton(),
                                             hypothesis,
                                             this.example.getAlphabet());

test-support/learner-it-support/src/main/java/de/learnlib/testsupport/it/learner/SBALearnerITCase.java

@@ -20,6 +20,7 @@
 import net.automatalib.automaton.procedural.SBA;
 import net.automatalib.util.automaton.procedural.SBAs;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class SBALearnerITCase<I> extends AbstractLearnerVariantITCase<I, Boolean, SBA<?, I>> {
 
@@ -33,7 +34,7 @@ public class SBALearnerITCase<I> extends AbstractLearnerVariantITCase<I, Boolean
     }
 
     @Override
-    protected Word<I> checkEquivalence(SBA<?, I> hypothesis) {
+    protected @Nullable Word<I> checkEquivalence(SBA<?, I> hypothesis) {
         return SBAs.findSeparatingWord(this.example.getReferenceAutomaton(),
                                        hypothesis,
                                        this.example.getAlphabet());

test-support/learner-it-support/src/main/java/de/learnlib/testsupport/it/learner/SPALearnerITCase.java

@@ -20,6 +20,7 @@
 import net.automatalib.automaton.procedural.SPA;
 import net.automatalib.util.automaton.procedural.SPAs;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class SPALearnerITCase<I> extends AbstractLearnerVariantITCase<I, Boolean, SPA<?, I>> {
 
@@ -33,7 +34,7 @@ public class SPALearnerITCase<I> extends AbstractLearnerVariantITCase<I, Boolean
     }
 
     @Override
-    protected Word<I> checkEquivalence(SPA<?, I> hypothesis) {
+    protected @Nullable Word<I> checkEquivalence(SPA<?, I> hypothesis) {
         return SPAs.findSeparatingWord(this.example.getReferenceAutomaton(),
                                        hypothesis,
                                        this.example.getAlphabet());

test-support/learner-it-support/src/main/java/de/learnlib/testsupport/it/learner/SPMMLearnerITCase.java

@@ -20,6 +20,7 @@
 import net.automatalib.automaton.procedural.SPMM;
 import net.automatalib.util.automaton.procedural.SPMMs;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class SPMMLearnerITCase<I, O> extends AbstractLearnerVariantITCase<I, Word<O>, SPMM<?, I, ?, O>> {
 
@@ -33,7 +34,7 @@ public class SPMMLearnerITCase<I, O> extends AbstractLearnerVariantITCase<I, Wor
     }
 
     @Override
-    protected Word<I> checkEquivalence(SPMM<?, I, ?, O> hypothesis) {
+    protected @Nullable Word<I> checkEquivalence(SPMM<?, I, ?, O> hypothesis) {
         return SPMMs.findSeparatingWord(this.example.getReferenceAutomaton(),
                                         hypothesis,
                                         this.example.getAlphabet());

test-support/learner-it-support/src/main/java/de/learnlib/testsupport/it/learner/UniversalDeterministicLearnerITCase.java

@@ -21,6 +21,7 @@
 import net.automatalib.automaton.concept.Output;
 import net.automatalib.util.automaton.Automata;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class UniversalDeterministicLearnerITCase<I, D, M extends UniversalDeterministicAutomaton<?, I, ?, ?, ?> & Output<I, D>>
         extends AbstractLearnerVariantITCase<I, D, M> {
@@ -35,7 +36,7 @@ public class UniversalDeterministicLearnerITCase<I, D, M extends UniversalDeterm
     }
 
     @Override
-    protected Word<I> checkEquivalence(M hypothesis) {
+    protected @Nullable Word<I> checkEquivalence(M hypothesis) {
         return Automata.findSeparatingWord(this.example.getReferenceAutomaton(),
                                            hypothesis,
                                            this.example.getAlphabet());

test-support/learner-it-support/src/main/java/module-info.java

@@ -42,5 +42,7 @@
     requires org.slf4j;
     requires org.testng;
 
+    requires static org.checkerframework.checker.qual;
+
     exports de.learnlib.testsupport.it.learner;
 }