Steps to reproduce

1. Duplicate https://demo.magnolia-cms.com/.magnolia/admincentral#app:groovy:browser;/samples/commands/GroovyMailCommand:null:
2. https://demopublic.magnolia-cms.com/.magnolia/admincentral#app:groovy:detail;/samples/commands/GroovyMailCommand0:edit Edit the duplicated script and add this content:

3. package samples.commands;
   
   import info.magnolia.rendering.engine.*;
   import info.magnolia.rendering.context.*;
   import info.magnolia.objectfactory.Components;
   import info.magnolia.commands.CommandsManager;
   import info.magnolia.commands.impl.*;
   import org.apache.commons.lang3.text.StrBuilder;
   
   public class ProgrammaticRenderCommand extends BaseRepositoryCommand {
   
       @Override
       public boolean execute(Context context) throws Exception {
   
           def node = context.getJCRSession("website").getNode("/travel/about");
   
           final StrBuilder out = new StrBuilder();
           AppendableOnlyOutputProvider outputProvider = new AppendableOnlyOutputProvider(out);
   
           RenderingEngine renderingEngine = Components.getComponent(RenderingEngine.class);
           renderingEngine.render(node, outputProvider);
           
           def resources = context.getJCRSession("resources");
           def rendered = NodeUtil.createPath(resources.getRootNode(), "rendered", "mgnl:content");
           rendered.setProperty("text", out.toString());
           resources.save();
           return true;
       }
   }
   

1. Save changes.
2. Set https://demopublic.magnolia-cms.com/.magnolia/admincentral#app:configuration:browser;/modules/publishing-core/commands/default/publish@class:treeview: to samples.commands.ProgrammaticRenderCommand (we misuse the publication command for simplicity but we are on public instance so the command shouldn't be used)
3. Publish something (e.g. https://demopublic.magnolia-cms.com/.magnolia/admincentral#app:configuration:browser;/modules/publishing-core/commands/default/publish:treeview:)
4. The page is rendered and saved to the resources workspace. This is working fine as we reuse the request created when clicking the action. See https://demopublic.magnolia-cms.com/.magnolia/admincentral#app:resources:view;/rendered:edit.
5. Try to do the step 3. but this time Publish recursively. (this action  is configured to run asynchronously)
6. This fails with NullPointerException as rendering misses a request.

Expected results

I can render content without a web request (asynchronously).

Actual results

The process fails on missing web context.

Workaround

Programmatically create http request with all that information against Magnolia and capture rendered content.

Development notes

• Rendering engine needs renderingContext from request
• Renderer doesn't check if WebContext is null since MAGNOLIA-6452
• FreemarkerRenderer doesn't check if WebContext is null since MAGNOLIA-4165 (Magnolia 4.5)
• Area element needs WebContext since SCRUM-517 (Magnolia 4.5)
• even assuming all the above is worked around, site renderer still needs request by its nature
• we can't be sure no template script is accessing web context / request / aggregationState...