Reset contexts before evaluation. (#932)

* Reset contexts before evaluation.
* Only reset when Islandora's ContextProviders are being used.

src/IslandoraContextManager.php

@@ -13,6 +13,14 @@
  */
 class IslandoraContextManager extends ContextManager {
 
+  /**
+   * Allow the contexts to be reset before evaluation.
+   */
+  protected function resetContextEvaluation() {
+    $this->contexts = [];
+    $this->contextConditionsEvaluated = FALSE;
+  }
+
   /**
    * Evaluate all context conditions.
    *
@@ -22,7 +30,11 @@ class IslandoraContextManager extends ContextManager {
   public function evaluateContexts(array $provided = []) {
 
     $this->activeContexts = [];
-
+    // XXX: Ensure that no earlier executed contexts in the request are still
+    // present when being triggered via Islandora's ContextProviders.
+    if (!empty($provided)) {
+      $this->resetContextEvaluation();
+    }
     /** @var \Drupal\context\ContextInterface $context */
     foreach ($this->getContexts() as $context) {
       if ($this->evaluateContextConditions($context, $provided) && !$context->disabled()) {