Detect loops in namespace dependencies

1 files changed, 40 insertions, 0 deletions

diff --git a/src/test/java/org/shedlang/compiler/typechecker/NamespaceDependencyLineariserTests.java b/src/test/java/org/shedlang/compiler/typechecker/NamespaceDependencyLineariserTests.java
index efbeeeaf..0492ce5d 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/NamespaceDependencyLineariserTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/NamespaceDependencyLineariserTests.java
@@ -3,11 +3,13 @@ package org.shedlang.compiler.typechecker;
 import org.junit.jupiter.api.Test;
 import org.shedlang.compiler.ast.untyped.Untyped;
 import org.shedlang.compiler.ast.untyped.UntypedNamespaceNode;
+import org.shedlang.compiler.typechecker.errors.CircularNamespaceDependencyError;
 import org.shedlang.compiler.types.NamespaceName;
 import org.zwobble.precisely.Matcher;
 
 import java.util.List;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.zwobble.precisely.AssertThat.assertThat;
 import static org.zwobble.precisely.Matchers.*;
 
@@ -53,6 +55,44 @@ public class NamespaceDependencyLineariserTests {
         ));
     }
 
+    @Test
+    public void whenNamespaceDirectlyDependsOnItselfThenErrorIsThrown() {
+        var namespaces = List.of(
+            namespaceNode("A", List.of("A"))
+        );
+
+        var error = assertThrows(
+            CircularNamespaceDependencyError.class,
+            () -> NamespaceDependencyLineariser.orderNamespaces(namespaces)
+        );
+
+        assertThat(error.namespaceNames(), isSequence(
+            equalTo(NamespaceName.of("A")),
+            equalTo(NamespaceName.of("A"))
+        ));
+    }
+
+    @Test
+    public void whenNamespaceIndirectlyDependsItselfThenErrorIsThrown() {
+        var namespaces = List.of(
+            namespaceNode("A", List.of("B")),
+            namespaceNode("B", List.of("C")),
+            namespaceNode("C", List.of("A"))
+        );
+
+        var error = assertThrows(
+            CircularNamespaceDependencyError.class,
+            () -> NamespaceDependencyLineariser.orderNamespaces(namespaces)
+        );
+
+        assertThat(error.namespaceNames(), isSequence(
+            equalTo(NamespaceName.of("A")),
+            equalTo(NamespaceName.of("B")),
+            equalTo(NamespaceName.of("C")),
+            equalTo(NamespaceName.of("A"))
+        ));
+    }
+
     private static UntypedNamespaceNode namespaceNode(
         String namespaceName,
         List<String> dependencies