WordPress 5.6 introduces a number of changes to the REST APIREST API The REST API is an acronym for the RESTful Application Program Interface (API) that uses HTTP requests to GET, PUT, POST and DELETE data. It is how the front end of an application (think “phone app” or “website”) can communicate with the data store (think “database” or “file system”) https://developer.wordpress.org/rest-api/., some of which have been covered in other dev notesdev note Each important change in WordPress Core is documented in a developers note, (usually called dev note). Good dev notes generally include: a description of the change; the decision that led to this change a description of how developers are supposed to work with that change. Dev notes are published on Make/Core blog during the beta phase of WordPress release cycle. Publishing dev notes is particularly important when plugin/theme authors and WordPress developers need to be aware of those changes.In general, all dev notes are compiled into a Field Guide at the beginning of the release candidate phase..

Below are some other noteworthy changes that deserve a call out.

Search

The wp/v2/search endpoint introduced in WordPress 5.0 provides a unified interface for searching across multiple content types. WordPress 5.6 adds a terms and post formats search handler. For example, to search across terms in all taxonomies, make the following request: https://example.org/wp-json/wp/v2/search?type=term&search=my-term. To search post-formats, use the post-format type: https://example.org/wp-json/wp/v2/search?type=post-format&search=aside.

Additionally, the REST API search infrastructure no longer requires that the id for each item is an integer. Strings are now an acceptable id type.

See #51458, #51459, #51131.

JSONJSON JSON, or JavaScript Object Notation, is a minimal, readable format for structuring data. It is used primarily to transmit data between a server and web application, as an alternative to XML. Schema

multipleOf keyword

The multipleOf keyword allows for asserting that an integer or number type is a multiple of the given number. For example, this schema will only accept even integers.

{
  "type": "integer",
  "multipleOf": 2
}

multipleOf also supports decimals. For example, this schema could be used to accept a percentage with a maximum of 1 decimal point.

{
  "type": "number",
  "minimum": 0,
  "maximum": 100,
  "multipleOf": 0.1
}

See #51022.

minProperties and maxProperties

The minItems and maxItems keywords can be used for the array type. The minProperties and maxProperties introduces this same functionality for the object type. This is helpful when using additionalProperties to have a list of objects with unique keys.

This schema requires an object that specifies at least 1, and at most 3, colors.

{
  "type": "object",
  "additionalProperties": {
    "type": "string",
    "format": "hex-color"
  },
  "minProperties": 1,
  "maxProperties": 3
}

{
  "primary": "#52accc",
  "secondary": "#096484"
}

See #51023.

patternProperties

The patternProperties keyword is similar to the additionalProperties keyword, but allows for asserting that the property matches a regex pattern. The keyword is an object where each property is a regex pattern and its value is the JSON Schema used to validate properties that match that pattern.

For example, this schema requires that each value is a hex color and the property must only contain “word” characters.

{
  "type": "object",
  "patternProperties": {
    "^\\w+$": {
      "type": "string",
      "format": "hex-color"
    }
  },
  "additionalProperties": false
}

When the REST API validates the patternProperties schema, if a property doesn’t match any of the patterns, the property will be allowed and not have any validation applied to its contents. This behaves the same as the properties keyword. If this logic isn’t desired, add additionalProperties to the schema to disallow non-matching properties. See #51024.

oneOf and anyOf

These are advanced keywords that allow for the JSON Schema validator to choose one of many schemas to use when validating a value. The anyOf keyword allows for a value to match at least one of the given schemas. Whereas, the oneOf keyword requires the value match exactly one schema.

For example, this schema allows for submitting an array of “operations” to an endpoint. Each operation can either be a “crop” or a “rotation”.

{
  "type": "array",
  "items": {
    "oneOf": [
      {
        "title": "Crop",
        "type": "object",
        "properties": {
          "operation": {
            "type": "string",
            "enum": [
              "crop"
            ]
          },
          "x": {
            "type": "integer"
          },
          "y": {
            "type": "integer"
          }
        }
      },
      {
        "title": "Rotation",
        "type": "object",
        "properties": {
          "operation": {
            "type": "string",
            "enum": [
              "rotate"
            ]
          },
          "degrees": {
            "type": "integer",
            "minimum": 0,
            "maximum": 360
          }
        }
      }
    ]
  }
}

The REST API will loopLoop The Loop is PHP code used by WordPress to display posts. Using The Loop, WordPress processes each post to be displayed on the current page, and formats it according to how it matches specified criteria within The Loop tags. Any HTML or PHP code in the Loop will be processed on each post. https://codex.wordpress.org/The_Loop. over each schema specified in the oneOf array and look for a match. If exactly one schema matches, then validation will succeed. If more than one schema matches, validation will fail. If no schemas match, then the validator will try to find the closest matching schema and return an appropriate error message.

operations[0] is not a valid Rotation. Reason: operations[0][degrees] must be between 0 (inclusive) and 360 (inclusive)

See #51025.

Expose all JSON Schema keywords in the index

When making an OPTIONS request to an endpoint, the REST API will return the args that the route accepts. Previously, only a limited subset of JSON Schema keywords were exposed. In WordPress 5.6, now the full list of JSON Schema keywords that the REST API supports will be exposed. See #51020.

More specific validation error codes

When the type of a value is incorrect, rest_validate_value_from_schema now returns rest_invalid_type instead of the generic rest_invalid_param. The validation error code is not currently exposed to REST API clients. This would only effect direct usages of the validation function.

Miscellaneous

The apiRequest library now supports using the PUT and DELETE HTTPHTTP HTTP is an acronym for Hyper Text Transfer Protocol. HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. methods with servers that didn’t support those methods. This is done by making the request a POST request and passing the original HTTP method in the X-HTTP-Method-Override headerHeader The header of your site is typically the first thing people will experience. The masthead or header art located across the top of your page is part of the look and feel of your website. It can influence a visitor’s opinion about your content and you/ your organization’s brand. It may also look different on different screen sizes.. #43605.

The comments controller now uses the rest_get_route_for_post function introduced in WordPress 5.5 to generate the up response link. This function is filterable to allow for custom controllers to properly define their REST API route. #44152.

The REST API now supports a broader range of JSON media types. Previously, only application/json was supported which prevented using subtypes like application/activity+json. The REST API will now json_decode the body of requests using a JSON subtype Content-Type. Additionally, wp_die() now properly sends the error as JSON when a JSON subtype is specified in the Accept header. #49404.

Props @m_butcher for reviewing.

#5-6, #dev-notes, #rest-api