Regression: Optional context values may throw exceptions if unsatisfied

Thanks, for creating the issue setting it RTBC as per original issue.

@larowlan asked in slack if

+++ b/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php
@@ -110,19 +110,30 @@ public function applyContextMapping(ContextAwarePluginInterface $plugin, $contex
+      catch (\Exception $e) {

we can catch a more specific context. @tim.plunkett can we catch \Drupal\Component\Plugin\Exception\PluginException instead?

Quick thought. why not update the getContext method then we can catch the '\Drupal\Component\Plugin\Exception\PluginException' from there.

  /**
   * {@inheritdoc}
   *
   * This code is identical to the Component in order to pick up a different
   * Context class.
   *
   * @return \Drupal\Core\Plugin\Context\ContextInterface
   *   The context object.
   */
  public function getContext($name) {
    // Check for a valid context value.
    if (!isset($this->context[$name])) {
      $this->context[$name] = new Context($this->getContextDefinition($name));
    }
    return $this->context[$name];
  }

Based on thoughts in #8, check the $context is an instance of ContextInterface, otherwise, it is NULL

  /**
   * {@inheritdoc}
   *
   * This code is identical to the Component in order to pick up a different
   * Context class.
   *
   * @return \Drupal\Core\Plugin\Context\ContextInterface
   *   The context object.
   */
  public function getContext($name) {
    // Check for a valid context value.
    if (!isset($this->context[$name])) {
      $this->context[$name] = NULL;
      $context = new Context($this->getContextDefinition($name));
      if ($context instanceof ContextInterface) {
        $this->context[$name] = new Context($this->getContextDefinition($name));
      }
    }
    return $this->context[$name];
  }

'getContext' always return an instance of ContextInerface or NULL instead of any exception.

@tim.plunkett++ thanks the new patch looks much better than catching \Exception - if it is not rtbc tomorrow I'll do that otherwise I'll commit it if it is :)

I agree patch looks much better now. Thanks!

Cross-linking #2677162: Context::getContextValue() violates ContextInterface by throwing an unexpected exception and #2620126: No way to handle 'optional' contexts without try/catch.

Committed/pushed to 8.8.x and cherry-picked to 8.7.x, thanks!

Correcting the tag.