Gatsby version 2.18.0 revealed problems in several plugins which mutate data after createNode call. When they do so - mutated fields are not registered by gatsby internal data tracking and are not added to the GraphQL schema.

After gatsby 2.18.5 things work closer to how they did in 2.17.x so those issues are hidden again. But they still exist and must be addressed in every affected plugin. Otherwise, various new features including incremental builds may break.

We should do an audit for data-mutation patterns in plugins, address them (for gatsby own plugins), and help authors of community plugins to fix them too. We should also ensure we don't encourage data mutation practice in our docs.

The list of plugins which are probably affected:

• gatsby-remark-relative-images (After npm update, suddenly getting GRAPHQL ERROR - "featuredimage" must not have a selection since type "String" has no subfields #19748)
• gatsby-source-airtable (already fixed)
• gatsby-plugin-remote-images (Broken with Gatsby 2.18.0 graysonhicks/gatsby-plugin-remote-images#28)
• gatsby-source-contentful (ContentfulAssets localFile node is missing in the graphql query result with gatsby v2.18.0+ #19716)