Issue #3230235: Validate that an update is supported before an update begins and after staged

src/Event/PreStartEvent.php

@@ -9,4 +9,32 @@ class PreStartEvent extends UpdateEvent {
 
   use ExcludedPathsTrait;
 
+  /**
+   * The desired package versions to update to, keyed by package name.
+   *
+   * @var string[]
+   */
+  protected $packageVersions;
+
+  /**
+   * Constructs a PreStartEvent.
+   *
+   * @param string[] $package_versions
+   *   (optional) The desired package versions to update to, keyed by package
+   *   name.
+   */
+  public function __construct(array $package_versions = []) {
+    $this->packageVersions = $package_versions;
+  }
+
+  /**
+   * Returns the desired package versions to update to.
+   *
+   * @return string[]
+   *   The desired package versions to update to, keyed by package name.
+   */
+  public function getPackageVersions(): array {
+    return $this->packageVersions;
+  }
+
 }