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Query Functions
Query FunctionsField Response Removal

Field Response Removal

Included in the “Power Extensions” bundle

Addition of the @remove directive to the GraphQL schema, which removes the output of a field from the response.

Description

The GraphQL spec indicates that the GraphQL response needs to match exactly the shape of the query. However, in certain circumstances we'd rather avoid sending back the response of the field, because:

  • We already know what it is, and by not sending it again we can boost performance
  • It contains sensitive information (such as login credentials)
  • An empty field can be distinguished from a null value

By adding @remove to the field, it will not be printed in the response.

In the query below (that uses the PHP Functions via Schema and HTTP Client extensions), we generate the URL to send an HTTP request to, by concatenating the site domain and the REST API endpoint. As the values of these "components" are not of interest to us, there is no need to print them in the response, and we can @remove them:

query {
  siteURL: optionValue(name: "siteurl")
    @remove
 
  requestURL: _sprintf(
    string: "%s/wp-json/wp/v2/comments/11/?_fields=id,content,date",
    values: [$__siteURL]
  )
    @remove
 
  _sendJSONObjectItemHTTPRequest(
    input: {
      url: $__requestURL
    }
  )
}

...producing (notice that fields siteURL and requestURL are not in the response):

{
  "data": {
    "_sendJSONObjectItemHTTPRequest": {
      "id": 11,
      "date": "2020-12-12T04:07:36",
      "content": {
        "rendered": "<p>Btw, I really like this stuff<\/p>\n"
      }
    }
  }
}

We can also tell directive @remove to conditionally remove the value, if a condition is met. Argument condition can receive 3 possible values:

  • ALWAYS (default value): Remove it always
  • IS_NULL: Remove it whenever the value is null
  • IS_EMPTY: Remove it whenever the value is empty

For instance, in the query below, when a post does not have a featured image, field featuredImage will have value null. By adding @remove(condition: IS_NULL), this value will not be added to the response:

query {
  posts {
    title
    featuredImage @remove(condition: IS_NULL) {
      src
    }
  }
}

...producing:

{
  "data": {
    "posts": [
      {
        "title": "Hello world!"
      },
      {
        "title": "Nested mutations are a must have",
        "featuredImage": {
          "src": "https:\/\/gato-graphql.lndo.site\/wp-content\/uploads\/2022\/05\/graphql-voyager-public.jpg"
        }
      },
      {
        "title": "Customize the schema for each client"
      }
    ]
  }
}

Examples

Remove unneeded data from an external API

Let's say we want to retrieve some specific data from an external REST API endpoint, and we don't need the rest of the data. We can then use @remove to make the response payload smaller, thus boosting performance:

  • Use field _sendJSONObjectItemHTTPRequest (from the HTTP Client extension) to connect to the REST API
  • Process this data to extract the needed piece of information (via Field to Input and the _objectProperty field from PHP Function via Schema)
  • @remove the original data from the REST endpoint

This query ties everything together:

{
  postData: _sendJSONObjectItemHTTPRequest(input: {
    url: "https://newapi.getpop.org/wp-json/wp/v2/posts/1"
  }) @remove
  renderedTitle: _objectProperty(
    object: $__postData,
    by: {
      path: "title.rendered"
    }
  )
}

In the response to this query, field postData has been removed:

{
  "data": {
    "renderedTitle": "Hello world!"
  }
}

Avoid printing user credentials

This example connects to the GitHub API to retrieve the artifacts available in a private repository, and avoids printing the user's credentials in the response:

query RetrieveGitHubActionArtifacts(
  $repoOwner: String!
  $repoProject: String!
) {
  githubAccessToken: _env(name: "GITHUB_ACCESS_TOKEN")
    @remove
 
  # Create the authorization header to send to GitHub
  authorizationHeader: _sprintf(
    string: "Bearer %s"
    # "Field to Input" feature to access value from the field above
    values: [$__githubAccessToken]
  )
    @remove
 
  # Create the authorization header to send to GitHub
  githubRequestHeaders: _echo(
    value: [
      { name: "Accept", value: "application/vnd.github+json" }
      { name: "Authorization", value: $__authorizationHeader }
    ]
  )
    @remove
 
  githubAPIEndpoint: _sprintf(
    string: "https://api.github.com/repos/%s/%s/actions/artifacts"
    values: [$repoOwner, $repoProject]
  )
 
  # Use the field from "Send HTTP Request Fields" to connect to GitHub
  gitHubArtifactData: _sendJSONObjectItemHTTPRequest(
    input: {
      url: $__githubAPIEndpoint
      options: { headers: $__githubRequestHeaders }
    }
  )
}

GraphQL spec

This functionality is currently not part of the GraphQL spec, but it has been requested: