Drupal Commerce: revised related Products Guide using Views and Entity Reference

There's a great tutorial on drupal.org, written by Jim Bova, explaining how to create a "related products" block in Drupal Commerce.

In his tutorial, Jim is building the relations between the product nodes with Entity Reference moudle and is using Views PHP module in order to filter the correct relations based on the currently viewed node. While I was building a similar Views block based on this tutorial, I've found some improvements that are imho both cleaner and more performant, completely relinguishing the use of Views PHP module.

As I don't want to make that kind of major changes to his original article, I will copy and paste his tutorial here in our blog, adjust it to my approach and propose the changes to Jim afterwards:

Install the necessary modules

• Download, Install, and Enable the "Entity Reference" module. http://drupal.org/project/entityreference

Creating the Reference Field

1. Create your product types and product display content types. For this example, the product display content types is labeled "Product Display".
2. Navigate to Structure -> Content Types -> Product Display -> Manage fields
3. Add a new Entity Reference field. For this example, the field is labeled "Related Products", and named "pd_related_products". The widget type is Autocomplete.
4. Choose the number of values. For this example, this is set to "Unlimited".
5. Select the "Target type" of "Node".
6. Select the target bundles. For this example, there is only one product display. Therefore, we highlight "Product Display".
7. Optionally, set the sort options. For this example, the field is sorted by the Title property in ascending order.

Configure the "Related Products" field in the display

1. Navigate to Structure -> Content Types -> Product Display -> Manage display
2. For this example, the Related Products are shown in a block. Therefore, we hide this field from the display.

Add one or more Related Products to a Product Display

1. If it hasn't already been done, add a few sample products, and the accompanying product displays.
2. On at least one product display edit screen, choose the references to the product displays that will be listed as Related Products.

Initial View Creation

1. Navigate to Structure -> Add new view
2. Choose a view name. In this example, the name is "Related Products".
3. Choose Show: "Content", of type "Product Display", sorted by "Newest first".
4. Uncheck the box reading "Create a page"
5. Check the box reading "Create a block".
6. Give the block a title, for this example the title is "Related Products".
7. Select the desired number of items to display and pager settings.
8. Click "Continue & edit".

Configure Filter Criteria

This section differs from the original post:

1. Expand the "Advanced" settings of the view configuration.
2. In the "Relationships" heading, add a new relationship to "Entity Reference: Referencing entity" for your related product field
3. In the "Contextual filters" heading, add a new contextual filter to "Content: Nid"
4. In the opening dialog choose your relationship you've just created in step 2.
5. In section "When the filter value is NOT available" of the dialog, choose "Provide default value" and further "Content ID from URL" as type

Configure Relationship from the Product Display to its Products

1. Expand the "Advanced" settings of the view configuration.
2. In the "Relationships" heading, add a new relationship to "Content: Referenced product".
3. Give this reference an identifier, for this example "Product Reference" was used.
4. Apply this setting. Fields from the product entity will now be available as fields in the view.

Configure the Format

1. In the "Format" heading, choose Format: "Unformatted list", Show: "Fields".

Configure the Fields

In the "Fields" heading, add the following fields:

1. Content: Nid
   Choose "Exclude from display" for this field. The Node ID is only needed for the filter settings above.
2. Content: Title
3. Commerce Product: Image
   Choose Relationship: "Product".
   Uncheck Create a label.
   Formatter: "Image"
   Image Style: [your desired image style]
   Link image to: "Content"
4. Commerce Product: Price
   Choose Relationship: "Product".
   Formatter: Formatted amount
   Choose "Display the calculated sell price for the current user.".

Configure Aggregation Settings

I skipped this step because I didn't need id (maybe it's necessary when operating with Views PHP?)

Disable SQL Query Rewriting or set Permission

Due to issue #1276450: Views results empty for unprivileged user when using Relationship: Content: Referenced Product, you must either disable SQL Rewriting in the view, or allow all roles access to "View any [ProductType] Product" permission. To disable the SQL Rewriting, navigate to the Advanced -> Other -> Query Settings and check "Disable SQL Rewriting". If you choose to set the permission, then navigate to People -> Permissions and check all roles to grant access to "View any [ProductType] Product". Keep an eye on the issue to see if a better solution arises.

Save the View

Configure the Block

1. Navigate to Structure -> Blocks.
2. Locate the "View: Related Products" block.
3. Choose the desired display region for this block.
4. While this would be enough to show the block only on article pages, on which product relations are defined, I'd recommend to restrict the block's appearance in the "Visibility settings" area to content type "Product display" (or whatever your node type(s) are named that have such a product relationship). So Views doesn't have to query for related products on any other page, where definitely no results would appear.

Finally, you can navigate to your product display, that has related products to confirm everything works as desired.