Issue #3261847: Add helpful methods to compute the difference between two ComposerUtility objects

package_manager/src/ComposerUtility.php

@@ -157,33 +157,29 @@ class ComposerUtility {
   /**
    * Returns the packages added in another directory.
    *
-   * @param self $other
+   * @param self $that
    *   A Composer utility wrapper around a different directory.
    *
    * @return \Composer\Package\PackageInterface[]
    *   The packages that were added in the other directory, keyed by name.
    */
-  public function getPackagesAddedBy(self $other): array {
-    return array_diff_key(
-      $other->getInstalledPackages(),
-      $this->getInstalledPackages()
-    );
+  public function getPackagesAddedBy(self $that): array {
+    // Return the packages that are there, but not here.
+    return array_diff_key($that->getInstalledPackages(), $this->getInstalledPackages());
   }
 
   /**
    * Returns the packages that were removed in another directory.
    *
-   * @param self $other
+   * @param self $that
    *   A Composer utility wrapper around a different directory.
    *
    * @return \Composer\Package\PackageInterface[]
    *   The packages that were removed in the other directory, keyed by name.
    */
-  public function getPackagesRemovedBy(self $other): array {
-    return array_diff_key(
-      $this->getInstalledPackages(),
-      $other->getInstalledPackages()
-    );
+  public function getPackagesRemovedBy(self $that): array {
+    // Return the packages that are here, but not there.
+    return array_diff_key($this->getInstalledPackages(), $that->getInstalledPackages());
   }
 
   /**
@@ -192,19 +188,18 @@ class ComposerUtility {
    * A package will be considered "updated" if its version in the other
    * directory has changed *at all*.
    *
-   * @param self $other
+   * @param self $that
    *   A Composer utility wrapper around a different directory.
    *
    * @return \Composer\Package\PackageInterface[]
    *   The packages in the current directory that were updated in the other
    *   directory, keyed by name.
    */
-  public function getPackagesUpdatedBy(self $other): array {
-    $mine = $this->getInstalledPackages();
-    $theirs = $other->getInstalledPackages();
+  public function getPackagesUpdatedBy(self $that): array {
+    $theirs = $that->getInstalledPackages();
 
-    // Only compare packages that are installed in both places.
-    $packages = array_intersect_key($mine, $theirs);
+    // Only compare packages that are both here and there.
+    $packages = array_intersect_key($this->getInstalledPackages(), $theirs);
 
     $filter = function (PackageInterface $package, string $name) use ($theirs): bool {
       return Comparator::notEqualTo($package->getVersion(), $theirs[$name]->getVersion());