Adds the ability to remove a relationship from the workspace.

Author: simonbrowndotje

structurizr-core/src/main/java/com/structurizr/Workspace.java

@@ -310,6 +310,36 @@ void remove(DeploymentNode deploymentNode) {
         }
     }
 
+    /**
+     * Removes a relationship from the workspace.
+     *
+     * @param relationship      the Relationship to remove
+     */
+    public void remove(Relationship relationship) {
+        if (relationship == null) {
+            throw new IllegalArgumentException("A relationship must be specified.");
+        }
+
+        // remove the relationship from views
+        for (View view : viewSet.getViews()) {
+            if (view instanceof ModelView) {
+                ModelView modelView = (ModelView)view;
+                if (modelView.isRelationshipInView(relationship)) {
+                    modelView.remove(relationship);
+                }
+            }
+        }
+
+        // now remove the relationship itself
+        try {
+            Method method = Model.class.getDeclaredMethod("remove", Relationship.class);
+            method.setAccessible(true);
+            method.invoke(model, relationship);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     private boolean isElementAssociatedWithAnyViews(Element element) {
         boolean result = false;
 

structurizr-core/src/main/java/com/structurizr/model/Model.java

@@ -1171,13 +1171,22 @@ private void removeElement(Element element) {
         // remove any relationships to/from the element
         for (Relationship relationship : getRelationships()) {
             if (relationship.getSource() == element || relationship.getDestination() == element) {
-                removeRelationshipFromInternalStructures(relationship);
-                relationship.getSource().remove(relationship);
+                remove(relationship);
             }
         }
 
         elementsById.remove(element.getId());
         elements.remove(element);
     }
 
+    /**
+     * Removes a relationship from the model.
+     *
+     * @param relationship      the Relationship to remove
+     */
+    void remove(Relationship relationship) {
+        removeRelationshipFromInternalStructures(relationship);
+        relationship.getSource().remove(relationship);
+    }
+
 }

structurizr-core/src/main/java/com/structurizr/view/ModelView.java

@@ -272,10 +272,26 @@ protected RelationshipView addRelationship(Relationship relationship) {
         return null;
     }
 
+    /**
+     * Determines whether the specified element exists in this view.
+     *
+     * @param element       the Element to look for
+     * @return      true if the element exists in the view, false otherwise
+     */
     public boolean isElementInView(Element element) {
         return this.elementViews.stream().anyMatch(ev -> ev.getElement().equals(element));
     }
 
+    /**
+     * Determines whether the specified relationship exists in this view.
+     *
+     * @param relationship      the Relationship to look for
+     * @return      true if the relationship exists in the view, false otherwise
+     */
+    public boolean isRelationshipInView(Relationship relationship) {
+        return this.relationshipViews.stream().anyMatch(rv -> rv.getRelationship().equals(relationship));
+    }
+
     /**
      * Removes a relationship from this view.
      *

structurizr-core/src/test/java/com/structurizr/WorkspaceTests.java

@@ -300,4 +300,32 @@ void trim_WhenTheDestinationOfAnElementIsRemoved() {
         assertEquals(0, a.getRelationships().size());
     }
 
+    @Test
+    void removeRelationship_ThrowsAnException_WhenNoRelationshipIsSpecified() {
+        Workspace workspace = new Workspace("Name", "Description");
+        try {
+            workspace.remove((Relationship)null);
+            fail();
+        } catch (Exception e) {
+            assertEquals("A relationship must be specified.", e.getMessage());
+        }
+    }
+
+    @Test
+    void removeRelationship() {
+        Workspace workspace = new Workspace("Name", "Description");
+        SoftwareSystem a = workspace.getModel().addSoftwareSystem("A");
+        SoftwareSystem b = workspace.getModel().addSoftwareSystem("B");
+        Relationship relationship = a.uses(b, "Uses");
+
+        SystemLandscapeView view = workspace.getViews().createSystemLandscapeView("key", "Description");
+        view.addDefaultElements();
+
+        workspace.remove(relationship);
+
+        assertEquals(0, a.getRelationships().size());
+        assertFalse(a.hasEfferentRelationshipWith(b));
+        assertFalse(view.isRelationshipInView(relationship));
+    }
+
 }