[source-contentful] node deletions bug

[Khaledgarbaya]

If you hook up your project with a Contentful space that has deleted blog posts, they are still being fetched by GraphQL. It seems like CF doesn't delete the nodes once they are created--they just get returned with null values:

The issue this presents is in the index page (src/pages/index.js) because the code is looping through each node and creating a div for it (so a user could end up with empty white space on their blog if they have deleted entries--I was able to recreate):

            {posts.map(({ node }) => {
              return (
                <div className="article" key={node.slug}>
                  <ArticlePreview article={node} />
                </div>
              )
            })}

I was looking at this issue with another engineer and the easiest solution we could come up with is to only use nodes that have a valid title. So instead of this:

const posts = get(this, 'props.data.allContentfulBlogPost.edges')

You can filter for only posts that have a title (or any other field):

const allPosts = get(this, 'props.data.allContentfulBlogPost.edges')
const posts = allPosts.filter(post => post.node.title)

Question: Is it expected behavior to have phantom nodes even after posts are deleted? And should I create a PR to filter out these nodes if you agree with my assessment?

@zcei Had a theory

From what I found, there might a bug here, as deleted entries are handled by gatsby-source-contentful.

I haven't worked a lot with the source, but it looks like we're using the (maybe c-prefixed) entity ID to delete a node, while a different format is used to create the node.

[KyleAMathews]

Ooooo that's definitely it! I think I added that deleting code early and then later added the id padding code and forgot to update the deleting code.

[ryanditjia]

Could this be the same bug? #5348 (comment)

In that comment, I mentioned there being 1036 nodes, close to 70% were nulls.

[axe312ger]

Opened a PR which should fix this issue :)