feat(lang): add example validation checks

2 files changed, 58 insertions, 1 deletions

diff --git a/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java b/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java
index 56186bc9..7525dfc6 100644
--- a/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java
+++ b/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java
@@ -16,7 +16,15 @@ public class ReferenceCounter {
         @Inject
         private IResourceScopeCache cache;
 
-        public Map<EObject, Integer> getReferenceCounts(Problem problem) {
+        public int countReferences(Problem problem, EObject eObject) {
+                var count = getReferenceCounts(problem).get(eObject);
+                if (count == null) {
+                        return 0;
+                }
+                return count;
+        }
+
+        protected Map<EObject, Integer> getReferenceCounts(Problem problem) {
                 var resource = problem.eResource();
                 if (resource == null) {
                         return doGetReferenceCounts(problem);
diff --git a/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java b/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
index f2378df6..dfd386f5 100644
--- a/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
+++ b/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
@@ -3,6 +3,19 @@
  */
 package tools.refinery.language.validation;
 
+import org.eclipse.xtext.EcoreUtil2;
+import org.eclipse.xtext.validation.Check;
+
+import com.google.inject.Inject;
+
+import tools.refinery.language.model.ProblemUtil;
+import tools.refinery.language.model.problem.Node;
+import tools.refinery.language.model.problem.Problem;
+import tools.refinery.language.model.problem.ProblemPackage;
+import tools.refinery.language.model.problem.Variable;
+import tools.refinery.language.model.problem.VariableOrNodeArgument;
+import tools.refinery.language.resource.ReferenceCounter;
+
 /**
  * This class contains custom validation rules.
  *
@@ -10,4 +23,40 @@ package tools.refinery.language.validation;
  * https://www.eclipse.org/Xtext/documentation/303_runtime_concepts.html#validation
  */
 public class ProblemValidator extends AbstractProblemValidator {
+        private static final String ISSUE_PREFIX = "tools.refinery.language.validation.ProblemValidator.";
+
+        public static final String SINGLETON_VARIABLE_ISSUE = ISSUE_PREFIX + "SINGLETON_VARIABLE";
+
+        public static final String NON_UNIQUE_NODE_ISSUE = ISSUE_PREFIX + "NON_UNIQUE_NODE";
+
+        @Inject
+        private ReferenceCounter referenceCounter;
+
+        @Check
+        public void checkUniqueVariable(VariableOrNodeArgument argument) {
+                var variableOrNode = argument.getVariableOrNode();
+                if (variableOrNode instanceof Variable variable && ProblemUtil.isImplicitVariable(variable)
+                                && !ProblemUtil.isSingletonVariable(variable)) {
+                        var problem = EcoreUtil2.getContainerOfType(variable, Problem.class);
+                        if (problem != null && referenceCounter.countReferences(problem, variable) <= 1) {
+                                var name = variable.getName();
+                                var message = "Variable '%s' has only a single reference. Add another reference or mark is as a singleton variable: '_%s'"
+                                                .formatted(name, name);
+                                warning(message, argument, ProblemPackage.Literals.VARIABLE_OR_NODE_ARGUMENT__VARIABLE_OR_NODE,
+                                                INSIGNIFICANT_INDEX, SINGLETON_VARIABLE_ISSUE);
+                        }
+                }
+        }
+
+        @Check
+        public void checkNonUniqueNode(VariableOrNodeArgument argument) {
+                var variableOrNode = argument.getVariableOrNode();
+                if (variableOrNode instanceof Node node && !ProblemUtil.isUniqueNode(node)) {
+                        var name = node.getName();
+                        var message = "Only unique nodes can be referenced in predicates. Mark '%s' as unique with the declaration 'unique %s.'"
+                                        .formatted(name, name);
+                        error(message, argument, ProblemPackage.Literals.VARIABLE_OR_NODE_ARGUMENT__VARIABLE_OR_NODE,
+                                        INSIGNIFICANT_INDEX, NON_UNIQUE_NODE_ISSUE);
+                }
+        }
 }