Fix drush_version field in env:info command

Author: pwtyler

src/Models/Environment.php

@@ -621,7 +621,7 @@ public function getPrimaryDomainModel()
      */
     public function getDrushVersion()
     {
-        return $this->settings('drush_version');
+        return $this->settings('appserver_runtime')->drush_version;
     }
 
     /**
@@ -957,6 +957,7 @@ public function serialize()
             'initialized' => $this->isInitialized(),
             'connection_mode' => $this->get('connection_mode'),
             'php_version' => $this->getPHPVersion(),
+            'drush_version' => $this->getDrushVersion(),
             'php_runtime_generation' => $this->getPHPRuntimeGeneration(),
         ];
     }

tests/Functional/EnvCommandsTest.php

@@ -317,6 +317,29 @@ public function testInfoCommand()
         );
     }
 
+    /**
+     * @test
+     * @covers \Pantheon\Terminus\Commands\Env\InfoCommand
+     *
+     * @group env
+     * @group short
+     */
+    public function testInfoCommandWithDrushVersion()
+    {
+        $envInfo = $this->terminusJsonResponse(
+            sprintf('env:info %s --field=drush_version', $this->getSiteEnv())
+        );
+        $this->assertArrayHasKey(
+            'drush_version',
+            $envInfo,
+            'Environment info should have "drush_version" field when explicitly requested.'
+        );
+        $this->assertNotEmpty(
+            $envInfo['drush_version'],
+            'Environment info "drush_version" should not be empty.'
+        );
+    }
+
     /**
      * @test
      * @covers \Pantheon\Terminus\Commands\Env\MetricsCommand