OpenAPI

zio-blocks-openapi is a complete, type-safe OpenAPI 3.1 data model for building API documentation programmatically. It provides immutable case classes and sealed traits representing every OpenAPI concept—operations, parameters, security schemes, and components—enabling you to construct OpenAPI documents in compile-time-safe Scala and export them as JSON for consumption by tools like Swagger UI, Redoc, and API validators.

Core types: OpenAPI, Info, Paths, PathItem, Operation, Parameter, RequestBody, Response, Components, SchemaObject, SecurityScheme, ReferenceOr.

final case class OpenAPI(
  openapi: String,
  info: Info,
  servers: Option[Chunk[Server]] = None,
  paths: Option[Paths] = None,
  components: Option[Components] = None,
  security: Option[Chunk[SecurityRequirement]] = None
)

Introduction

OpenAPI documents are the lingua franca for API specifications. They define request/response contracts, authentication methods, and data schemas in a standardized JSON or YAML format that external tools consume. Building these documents manually in JSON is error-prone; maintaining them as your API evolves is tedious.

The OpenAPI module bridges the gap by letting you author API specs as Scala code—leveraging the type system for compile-time correctness—then export to standard JSON that any OpenAPI tool understands. You get type safety during authoring plus interoperability with the entire OpenAPI ecosystem.

Installation

libraryDependencies += "dev.zio" %% "zio-blocks-openapi" % "0.0.56"

// You'll also need the schema module for Schema[A] integration:
libraryDependencies += "dev.zio" %% "zio-blocks-schema" % "0.0.56"

For Scala.js:

libraryDependencies += "dev.zio" %%% "zio-blocks-openapi" % "0.0.56"

Supported Scala versions: 2.13.x and 3.x.

How They Work Together

The OpenAPI module follows a clear workflow:

1. Define your data types using ZIO Blocks Schema:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._

import zio.blocks.schema._

case class User(id: Int, name: String, email: String)
object User {
  implicit val schema: Schema[User] = Schema.derived
}

case class ErrorResponse(code: Int, message: String)
object ErrorResponse {
  implicit val schema: Schema[ErrorResponse] = Schema.derived
}

2. Create an OpenAPI document by composing types:

val api = OpenAPI(
  openapi = "3.1.0",
  info = Info(
    title = "User API",
    version = "1.0.0",
    description = Some(md"API for managing users")
  ),
  paths = Some(Paths(ChunkMap(
    "/users" -> PathItem(
      get = Some(Operation(
        summary = Some(md"List all users"),
        description = Some(md"Returns a paginated list of users"),
        responses = Responses(ChunkMap(
          "200" -> ReferenceOr.Value(Response(
            description = md"Successful response",
            content = ChunkMap(
              "application/json" -> MediaType(
                schema = Some(ReferenceOr.Value(
                  Schema[List[User]].toOpenAPISchema
                ))
              )
            )
          ))
        ))
      ))
    ),
    "/users/{id}" -> PathItem(
      get = Some(Operation(
        summary = Some(md"Get a user by ID"),
        parameters = Chunk(
          ReferenceOr.Value(Parameter(
            name = "id",
            in = ParameterLocation.Path,
            required = true,
            schema = Some(ReferenceOr.Value(
              Schema[Int].toOpenAPISchema
            ))
          ))
        ),
        responses = Responses(ChunkMap(
          "200" -> ReferenceOr.Value(Response(
            description = md"User found",
            content = ChunkMap(
              "application/json" -> MediaType(
                schema = Some(ReferenceOr.Value(
                  Schema[User].toOpenAPISchema
                ))
              )
            )
          )),
          "404" -> ReferenceOr.Value(Response(
            description = md"User not found",
            content = ChunkMap(
              "application/json" -> MediaType(
                schema = Some(ReferenceOr.Value(
                  Schema[ErrorResponse].toOpenAPISchema
                ))
              )
            )
          ))
        ))
      ))
    )
  ))),
  components = Some(Components(
    schemas = ChunkMap(
      Schema[User].toRefSchema._2._1 -> ReferenceOr.Value(Schema[User].toRefSchema._2._2),
      Schema[ErrorResponse].toRefSchema._2._1 -> ReferenceOr.Value(Schema[ErrorResponse].toRefSchema._2._2)
    )
  ))
)

3. Serialize to JSON for tools to consume:

import zio.blocks.openapi.OpenAPICodec._

val json = openAPICodec.encodeValue(api)

4. Render or serve the JSON (e.g., to Swagger UI):

import zio.blocks.schema.json._

val jsonString = Json.jsonCodec.encodeToString(json, WriterConfig.withIndentionStep2)
// jsonString: String = """{
//   "openapi": "3.1.0",
//   "info": {
//     "title": "User API",
//     "version": "1.0.0",
//     "description": "API for managing users\n\n"
//   },
//   "paths": {
//     "/users": {
//       "get": {
//         "responses": {
//           "200": {
//             "description": "Successful response\n\n",
//             "content": {
//               "application/json": {
//                 "schema": {
//                   "items": {
//                     "properties": {
//                       "id": {
//                         "type": "integer",
//                         "maximum": 2147483647,
//                         "minimum": -2147483648
//                       },
//                       "name": {
//                         "type": "string"
//                       },
//                       "email": {
//                         "type": "string"
//                       }
//                     },
//                     "type": "object",
//                     "required": [
//                       "id",
//                       "name",
//                       "email"
//                     ],
//                     "title": "User"
//                   },
//                   "type": [
//                     "array",
//                     "null"
//                   ],
//                   "title": "List[User]"
//                 }
//               }
//             }
//           }
//         },
//         "summary": "List all users\n\n",
// ...

Type Relationships Diagram

OpenAPI (root document)
├─ info: Info (metadata)
├─ servers: Option[Chunk[Server]]
├─ paths: Option[Paths] (map of path strings to PathItem)
│  └─ PathItem
│     ├─ get: Operation
│     ├─ post: Operation
│     ├─ put: Operation
│     └─ ... (other HTTP methods)
│        ├─ parameters: Chunk[ReferenceOr[Parameter]]
│        ├─ requestBody: ReferenceOr[RequestBody]
│        │  └─ content: Map[String, MediaType]
│        │     └─ schema: ReferenceOr[SchemaObject]
│        └─ responses: Responses
│           └─ Map[statusCode, ReferenceOr[Response]]
│              └─ content: Map[String, MediaType]
│                 └─ schema: ReferenceOr[SchemaObject]
├─ components: Option[Components]
│  ├─ schemas: ChunkMap[String, ReferenceOr[SchemaObject]]
│  ├─ responses: ChunkMap[String, ReferenceOr[Response]]
│  ├─ parameters: ChunkMap[String, ReferenceOr[Parameter]]
│  └─ securitySchemes: ChunkMap[String, ReferenceOr[SecurityScheme]]
└─ security: Option[Chunk[SecurityRequirement]]

Common Patterns

Building Reusable Schema Components

Avoid duplicating schema definitions by moving them to components.schemas:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

case class User(id: Int, name: String, email: String)
object User {
  implicit val schema: Schema[User] = Schema.derived
}

val userSchemaComponent = Schema[User].toRefSchema
// Returns: (ReferenceOr.Ref(...), ("User", SchemaObject(...)))
// Use the ref in operations, store the component in components.schemas

Using `ReferenceOr` for Inline vs. Referenced Schemas

ReferenceOr[A] is a sealed trait with two cases:

ReferenceOr.Ref: Points to a schema in #/components/schemas/<name>
ReferenceOr.Value: Inline schema definition

Prefer Ref for reusable schemas; use Value for simple, one-off schemas:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

// Reusable: use Ref
val userRef = ReferenceOr.Ref(Reference(`$ref` = "#/components/schemas/User"))

// One-off: use Value
val simpleString = ReferenceOr.Value(Schema[String].toOpenAPISchema)

Security Schemes

Define authentication methods in components.securitySchemes:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val apiKeyScheme = SecurityScheme.APIKey(
  name = "X-API-Key",
  in = APIKeyLocation.Header,
  description = Some(md"API key for authentication")
)

val oauthScheme = SecurityScheme.OAuth2(
  flows = OAuthFlows(
    authorizationCode = Some(OAuthFlow(
      authorizationUrl = Some("https://example.com/oauth/authorize"),
      tokenUrl = Some("https://example.com/oauth/token"),
      scopes = ChunkMap("read" -> "Read access", "write" -> "Write access")
    ))
  ),
  description = Some(md"OAuth 2.0 authorization")
)

val components = Components(
  securitySchemes = ChunkMap(
    "api_key" -> ReferenceOr.Value(apiKeyScheme),
    "oauth2" -> ReferenceOr.Value(oauthScheme)
  )
)

Path Parameters vs. Query Parameters

Distinguish parameter locations using ParameterLocation:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val pathParam = Parameter(
  name = "id",
  in = ParameterLocation.Path,
  required = true,
  schema = Some(ReferenceOr.Value(Schema[Int].toOpenAPISchema))
)

val queryParam = Parameter(
  name = "limit",
  in = ParameterLocation.Query,
  required = false,
  schema = Some(ReferenceOr.Value(Schema[Int].toOpenAPISchema))
)

val headerParam = Parameter(
  name = "X-Custom-Header",
  in = ParameterLocation.Header,
  required = false,
  schema = Some(ReferenceOr.Value(Schema[String].toOpenAPISchema))
)

Integration Points

The OpenAPI module integrates tightly with other ZIO Blocks components:

Schema Integration: All OpenAPI types have Schema.derived instances, enabling round-trip serialization via DynamicValue. Use Schema[A].toOpenAPISchema to convert any schema to an OpenAPI component.
Markdown Support: Description fields use the in-house Doc type, which supports CommonMark rendering. This ensures markdown descriptions round-trip correctly.
JSON AST: All codecs operate on the Json AST from zio-blocks-schema, not external JSON libraries. To render as YAML, pipe the Json through zio-blocks-schema-yaml separately.

OpenAPI

OpenAPI is the root document object representing a complete OpenAPI 3.1 specification.

Definition

Every OpenAPI document requires:

openapi: Version string (typically "3.1.0")
info: Metadata about the API (Info)

Optional top-level fields include:

servers: Server definitions for the API (Chunk[Server])
paths: Map of endpoint paths to operations (Paths)
components: Reusable schemas, responses, parameters, and other components (Components)
security: Security requirements applied to the API (Chunk[SecurityRequirement])

Response definitions are modeled per Operation, not as a top-level field on OpenAPI.

Creating an OpenAPI Document

To construct an OpenAPI document:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val minimalApi = OpenAPI(
  openapi = "3.1.0",
  info = Info(title = "My API", version = "1.0.0")
)

Add paths, operations, and components as shown in the "How They Work Together" section above.

Serialization

Encode an OpenAPI document to Json AST:

import zio.blocks.openapi._
import zio.blocks.openapi.OpenAPICodec._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

import zio.blocks.schema.json._

val myApi = OpenAPI(openapi = "3.1.0", info = Info(title = "My API", version = "1.0.0"))
val encoded: Json = openAPICodec.encodeValue(myApi)

Decode from Json AST back to an OpenAPI instance:

import zio.blocks.openapi._
import zio.blocks.openapi.OpenAPICodec._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

import zio.blocks.schema.json._

val myApi = OpenAPI(openapi = "3.1.0", info = Info(title = "My API", version = "1.0.0"))
val encoded: Json = openAPICodec.encodeValue(myApi)
val decoded: OpenAPI = openAPICodec.decodeValue(encoded)

Info

Info contains metadata about the API: title, version, contact, and license.

Definition

Required fields:

title: API name (e.g., "User API")
version: API version (e.g., "1.0.0")

Optional fields:

description: Markdown-formatted description (Doc)
termsOfService: Terms of service URL
contact: Contact information (Contact)
license: License information (License)

Creating Info

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val info = Info(
  title = "Pet Store API",
  version = "3.0.0",
  description = Some(md"API for managing a pet store"),
  contact = Some(Contact(
    name = Some("API Support"),
    url = Some("https://example.com/support"),
    email = Some("support@example.com")
  )),
  license = Some(License(
    name = "Apache 2.0",
    identifier = Some("Apache-2.0")
  ))
)

Paths & PathItem

Paths represents the collection of URL paths and their operations. PathItem groups HTTP methods (GET, POST, PUT, etc.) on a single path.

Definition

Paths is a wrapper case class with two fields:

paths: ChunkMap[String, PathItem], where keys are path strings (e.g., "/users/{id}")
extensions: ChunkMap[String, Json], for OpenAPI specification extensions

PathItem contains optional fields for each HTTP method:

get, post, put, delete, patch, head, options, trace: Operation instances
parameters: Path-level parameters shared by all methods on this path
servers: Optional server overrides for this path

Creating Path Items

To define a path with multiple operations:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val userPaths = Paths(ChunkMap(
  "/users" -> PathItem(
    get = Some(Operation(
      summary = Some(md"List users"),
      responses = Responses(ChunkMap(
        "200" -> ReferenceOr.Value(Response(
          description = md"User list",
          content = ChunkMap(
            "application/json" -> MediaType(schema = None)
          )
        ))
      ))
    )),
    post = Some(Operation(
      summary = Some(md"Create user"),
      requestBody = Some(ReferenceOr.Value(RequestBody(
        description = Some(md"User data"),
        content = ChunkMap(
          "application/json" -> MediaType(schema = None)
        ),
        required = true
      ))),
      responses = Responses(ChunkMap(
        "201" -> ReferenceOr.Value(Response(
          description = md"User created",
          content = ChunkMap(
            "application/json" -> MediaType(schema = None)
          )
        ))
      ))
    ))
  ),
  "/users/{id}" -> PathItem(
    parameters = Chunk(
      ReferenceOr.Value(Parameter(
        name = "id",
        in = ParameterLocation.Path,
        required = true,
        schema = Some(ReferenceOr.Value(Schema[String].toOpenAPISchema))
      ))
    ),
    get = Some(Operation(
      summary = Some(md"Get user by ID"),
      responses = Responses(ChunkMap(
        "200" -> ReferenceOr.Value(Response(
          description = md"User found",
          content = ChunkMap(
            "application/json" -> MediaType(schema = None)
          )
        )),
        "404" -> ReferenceOr.Value(Response(
          description = md"User not found",
          content = ChunkMap(
            "application/json" -> MediaType(schema = None)
          )
        ))
      ))
    ))
  )
))

Operation

Operation represents a single HTTP operation (GET, POST, etc.) on a path.

Definition

Key fields:

responses: Required. Map of status codes to response definitions
operationId: Unique operation identifier
summary: Short description
description: Detailed markdown description
parameters: Path, query, header, and cookie parameters
requestBody: Request payload definition
deprecated: Whether the operation is deprecated
tags: Group operations in documentation (e.g., "users", "products")

Defining an Operation

With summary, description, and parameters:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val getUser = Operation(
  tags = Chunk("users"),
  summary = Some(md"Retrieve user"),
  description = Some(md"Fetches a single user by ID"),
  operationId = Some("getUserById"),
  parameters = Chunk(
    ReferenceOr.Value(Parameter(
      name = "id",
      in = ParameterLocation.Path,
      required = true,
      schema = Some(ReferenceOr.Value(Schema[String].toOpenAPISchema)),
      description = Some(md"User ID")
    ))
  ),
  responses = Responses(ChunkMap(
    "200" -> ReferenceOr.Value(Response(
      description = md"User found",
      content = ChunkMap(
        "application/json" -> MediaType(schema = None)
      )
    )),
    "404" -> ReferenceOr.Value(Response(
      description = md"User not found",
      content = ChunkMap(
        "application/json" -> MediaType(schema = None)
      )
    ))
  ))
)

Parameter

Parameter represents query, path, header, or cookie parameters in a request.

Definition

Required fields:

name: Parameter name (e.g., "id", "limit")
in: Location—Path, Query, Header, or Cookie (ParameterLocation)
schema: Data type of the parameter (ReferenceOr[SchemaObject])

Optional fields:

description: Markdown description
required: Whether the parameter is mandatory (default: false)
deprecated: Whether the parameter is deprecated
allowEmptyValue: Whether empty string values are allowed

Creating Parameters

Path parameter (required):

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val idPathParam = Parameter(
  name = "id",
  in = ParameterLocation.Path,
  required = true,
  schema = Some(ReferenceOr.Value(Schema[String].toOpenAPISchema)),
  description = Some(md"User identifier")
)

Query parameter (optional with default):

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val limitQueryParam = Parameter(
  name = "limit",
  in = ParameterLocation.Query,
  required = false,
  schema = Some(ReferenceOr.Value(Schema[Int].toOpenAPISchema)),
  description = Some(md"Maximum number of results (default: 20)")
)

Header parameter:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val authHeaderParam = Parameter(
  name = "X-API-Key",
  in = ParameterLocation.Header,
  required = true,
  schema = Some(ReferenceOr.Value(Schema[String].toOpenAPISchema)),
  description = Some(md"API key for authentication")
)

RequestBody & Response

RequestBody defines the structure of a request payload. Response defines the structure and status of a response.

RequestBody Definition

Key fields:

content: Map of MIME types to MediaType definitions
description: Optional markdown description
required: Whether the request body is mandatory (default: false)

Creating a RequestBody

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._
import zio.blocks.schema.json._

case class User(name: String, email: String)
object User { implicit val schema: Schema[User] = Schema.derived }

val createUserBody = RequestBody(
  description = Some(md"User data to create"),
  content = ChunkMap(
    "application/json" -> MediaType(
      schema = Some(ReferenceOr.Value(Schema[User].toOpenAPISchema)),
      example = Some(Json.Object(Chunk(
        "name" -> Json.String("John Doe"),
        "email" -> Json.String("john@example.com")
      )))
    )
  ),
  required = true
)

Response Definition

Key fields:

description: Required. Markdown description of the response
content: Map of MIME types to MediaType definitions
headers: Optional response headers
links: Optional links to related operations

Creating a Response

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

case class User2(id: Int, name: String, email: String)
object User2 { implicit val schema: Schema[User2] = Schema.derived }
case class ErrorResponse2(code: Int, message: String)
object ErrorResponse2 { implicit val schema: Schema[ErrorResponse2] = Schema.derived }

val successResponse = Response(
  description = md"User successfully created",
  content = ChunkMap(
    "application/json" -> MediaType(
      schema = Some(ReferenceOr.Value(Schema[User2].toOpenAPISchema))
    )
  )
)

val errorResponse = Response(
  description = md"Request validation failed",
  content = ChunkMap(
    "application/json" -> MediaType(
      schema = Some(ReferenceOr.Value(Schema[ErrorResponse2].toOpenAPISchema))
    )
  )
)

Responses

Responses is a map of HTTP status codes to ReferenceOr[Response]:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val ok = Response(description = md"Created", content = ChunkMap())
val err = Response(description = md"Bad request", content = ChunkMap())

val responses = Responses(ChunkMap(
  "201" -> ReferenceOr.Value(ok),
  "400" -> ReferenceOr.Value(err),
  "401" -> ReferenceOr.Value(Response(
    description = md"Unauthorized",
    content = ChunkMap()
  )),
  "500" -> ReferenceOr.Value(Response(
    description = md"Internal server error",
    content = ChunkMap()
  ))
))

MediaType

MediaType specifies the schema and encoding for a particular MIME type in a request or response.

Definition

Key fields:

schema: Data type for this MIME type (ReferenceOr[SchemaObject])
example: Example value as Json
encoding: Encoding rules for multipart form data
extensions: Custom vendor extensions (x-* fields)

Creating MediaType

With schema and example:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._
import zio.blocks.schema.json._

case class User(id: Int, name: String, email: String)
object User { implicit val schema: Schema[User] = Schema.derived }

val jsonMedia = MediaType(
  schema = Some(ReferenceOr.Value(Schema[User].toOpenAPISchema)),
  example = Some(Json.Object(
    "id" -> Json.Number(1),
    "name" -> Json.String("Alice"),
    "email" -> Json.String("alice@example.com")
  ))
)

For form data:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val formMedia = MediaType(
  schema = Some(ReferenceOr.Value(Schema[Map[String, String]].toOpenAPISchema)),
  encoding = ChunkMap(
    "file" -> Encoding(
      contentType = Some("application/octet-stream")
    )
  )
)

Components

Components stores reusable schema and security definitions referenced throughout the document.

Definition

Key fields:

schemas: Reusable schema objects (ChunkMap[String, ReferenceOr[SchemaObject]])
responses: Reusable response definitions
parameters: Reusable parameter definitions
securitySchemes: Authentication method definitions
examples, requestBodies, headers, links, callbacks: Additional reusable components

Creating Components

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

case class User(id: Int, name: String, email: String)
object User { implicit val schema: Schema[User] = Schema.derived }
case class ErrorResponse(code: Int, message: String)
object ErrorResponse { implicit val schema: Schema[ErrorResponse] = Schema.derived }

val components = Components(
  schemas = ChunkMap(
    Schema[User].toRefSchema._2._1 -> ReferenceOr.Value(Schema[User].toRefSchema._2._2),
    Schema[ErrorResponse].toRefSchema._2._1 -> ReferenceOr.Value(Schema[ErrorResponse].toRefSchema._2._2)
  ),
  parameters = ChunkMap(
    "id" -> ReferenceOr.Value(Parameter(
      name = "id",
      in = ParameterLocation.Path,
      required = true,
      schema = Some(ReferenceOr.Value(Schema[String].toOpenAPISchema))
    ))
  ),
  responses = ChunkMap(
    "NotFound" -> ReferenceOr.Value(Response(
      description = md"Resource not found",
      content = ChunkMap(
        "application/json" -> MediaType(
          schema = Some(ReferenceOr.Value(
            Schema[ErrorResponse].toOpenAPISchema
          ))
        )
      )
    )),
    "Unauthorized" -> ReferenceOr.Value(Response(
      description = md"Unauthorized access",
      content = ChunkMap()
    ))
  ),
  securitySchemes = ChunkMap(
    "api_key" -> ReferenceOr.Value(SecurityScheme.APIKey(
      name = "X-API-Key",
      in = APIKeyLocation.Header,
      description = Some(md"API key header")
    ))
  )
)

SchemaObject

SchemaObject wraps a JSON Schema 2020-12 definition with OpenAPI-specific extensions like discriminator, XML metadata, and examples.

Definition

SchemaObject contains:

jsonSchema: Raw JSON Schema 2020-12 as Json AST
discriminator: Polymorphism discriminator for oneOf/anyOf
xml: XML serialization metadata
example: Example value for documentation
extensions: Custom x-* fields

Creating SchemaObject

Directly from a Schema[A]:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

case class User(id: Int, name: String, email: String)
object User { implicit val schema: Schema[User] = Schema.derived }

val userSchema = Schema[User].toOpenAPISchema
// Returns a SchemaObject with the User type's JSON Schema

Or with additional OpenAPI metadata:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._
import zio.blocks.schema.json._

case class User(id: Int, name: String, email: String)
object User { implicit val schema: Schema[User] = Schema.derived }

val enrichedSchema = SchemaObject(
  jsonSchema = Schema[User].toJsonSchema.toJson,
  discriminator = None,
  xml = Some(XML(
    name = Some("user"),
    namespace = None,
    prefix = None,
    attribute = false,
    wrapped = false
  )),
  example = Some(Json.Object(
    "id" -> Json.Number(1),
    "name" -> Json.String("John")
  )),
  extensions = ChunkMap(
    "x-generated" -> Json.String("true"),
    "x-version" -> Json.String("1.0.0")
  )
)

Converting Schemas to SchemaObject

Use the SchemaOps extension methods on any Schema[A]:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

case class User(id: Int, name: String, email: String)
object User { implicit val schema: Schema[User] = Schema.derived }

val schemaObj: SchemaObject = Schema[User].toOpenAPISchema
val (ref, component) = Schema[User].toRefSchema
// ref = ReferenceOr.Ref pointing to #/components/schemas/User
// component = ("User", SchemaObject(...))

ReferenceOr

ReferenceOr[A] is a sealed trait representing the OpenAPI pattern of choosing between a $ref and an inline value.

Definition

Two cases:

ReferenceOr.Ref: Points to a definition at #/components/<type>/<name>
ReferenceOr.Value: Inline definition without reference

Using ReferenceOr

Prefer Ref for reusable components:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val userRef = ReferenceOr.Ref(Reference(`$ref` = "#/components/schemas/User"))

val responseRef = ReferenceOr.Ref(Reference(
  `$ref` = "#/components/responses/NotFound"
))

Use Value for inline, one-off definitions:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

case class User(id: Int, name: String, email: String)
object User { implicit val schema: Schema[User] = Schema.derived }

val inlineUser = ReferenceOr.Value(Schema[User].toOpenAPISchema)

val inlineError = ReferenceOr.Value(Response(
  description = md"Quick error",
  content = ChunkMap()
))

Pattern Matching on ReferenceOr

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

def describeRef[A](ref: ReferenceOr[A]): String = ref match {
  case ReferenceOr.Ref(r)   => s"Reference to ${r.`$ref`}"
  case ReferenceOr.Value(_) => "Inline value"
}

SecurityScheme

SecurityScheme is a sealed trait representing different authentication methods. Variants include API Key, HTTP Basic/Bearer, OAuth 2.0, OpenID Connect, and Mutual TLS.

Definition

Sealed trait variants:

APIKey: API key in header, query, or cookie
HTTP: HTTP authentication (Basic, Bearer, etc.)
OAuth2: OAuth 2.0 authorization flows
OpenIdConnect: OpenID Connect discovery
MutualTLS: Mutual TLS certificate-based

Creating Security Schemes

API Key authentication:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val apiKeySecurity = SecurityScheme.APIKey(
  name = "X-API-Key",
  in = APIKeyLocation.Header,
  description = Some(md"API key required in header")
)

HTTP Bearer token:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val bearerSecurity = SecurityScheme.HTTP(
  scheme = "bearer",
  bearerFormat = Some("JWT"),
  description = Some(md"JWT bearer token")
)

OAuth 2.0:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val oauthSecurity = SecurityScheme.OAuth2(
  flows = OAuthFlows(
    authorizationCode = Some(OAuthFlow(
      authorizationUrl = Some("https://example.com/oauth/authorize"),
      tokenUrl = Some("https://example.com/oauth/token"),
      scopes = ChunkMap(
        "read:users" -> "Read user data",
        "write:users" -> "Modify user data"
      )
    ))
  ),
  description = Some(md"OAuth 2.0 authorization")
)

note

The OAuthFlows type supports multiple flow types: implicit, password, clientCredentials, and authorizationCode. Choose the flow that matches your OAuth 2.0 configuration.

OpenID Connect:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val oidcSecurity = SecurityScheme.OpenIdConnect(
  openIdConnectUrl = "https://example.com/.well-known/openid-configuration",
  description = Some(md"OpenID Connect discovery")
)

Discriminator

Discriminator specifies how to distinguish between different variants in a polymorphic schema (using oneOf or anyOf).

Definition

Key fields:

propertyName: Field name used to discriminate (e.g., "type", "kind")
mapping: Optional explicit mapping of discriminator values to schema references

Creating a Discriminator

Simple discriminator by property name:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val discriminator = Discriminator(propertyName = "type")

With explicit value-to-schema mapping:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val mappedDiscriminator = Discriminator(
  propertyName = "kind",
  mapping = ChunkMap(
    "user" -> "#/components/schemas/User",
    "admin" -> "#/components/schemas/Admin",
    "guest" -> "#/components/schemas/Guest"
  )
)

Server & ServerVariable

Server specifies base URLs and server-specific variables. ServerVariable allows parameterization of server URLs.

Definition

Server contains:

url: Server URL (may contain variable placeholders like {base_path})
description: Optional description
variables: Map of variable names to ServerVariable

ServerVariable contains:

enum: List of allowed values
default: Default value
description: Description of the variable

Creating Servers

Single static server:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val server = Server(
  url = "https://api.example.com",
  description = Some(md"Production API")
)

Server with variables:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val variableServer = Server(
  url = "https://{host}:{port}/{basePath}",
  description = Some(md"Development API with variables"),
  variables = ChunkMap(
    "host" -> ServerVariable(
      default = "localhost",
      `enum` = Chunk("localhost", "staging.example.com", "api.example.com"),
      description = Some(md"API host")
    ),
    "port" -> ServerVariable(
      default = "8080",
      `enum` = Chunk("8080", "443"),
      description = Some(md"Port number")
    ),
    "basePath" -> ServerVariable(
      default = "v1",
      `enum` = Chunk("v1", "v2"),
      description = Some(md"API version path")
    )
  )
)

note

ServerVariable contains enumerable values for each variable. The field is named to avoid the reserved enum keyword in Scala.

Tag

Tag groups related operations under a heading in generated documentation.

Definition

Key fields:

name: Tag identifier (e.g., "users", "products")
description: Markdown description of the tag
externalDocs: Link to external documentation

Creating Tags

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val userTag = Tag(
  name = "users",
  description = Some(md"User management operations")
)

val productsTag = Tag(
  name = "products",
  description = Some(md"Product catalog operations"),
  externalDocs = Some(ExternalDocumentation(
    url = "https://docs.example.com/products",
    description = Some(md"Full product API documentation")
  ))
)

Common Extension Fields

All types support custom x-* extension fields for vendor-specific metadata. These extensions are preserved during encoding/decoding:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._
import zio.blocks.schema.json._

val operationWithExtensions = Operation(
  summary = Some(md"Get user"),
  responses = Responses(ChunkMap(
    "200" -> ReferenceOr.Value(Response(
      description = md"User found",
      content = ChunkMap()
    ))
  )),
  extensions = ChunkMap(
    "x-internal" -> Json.Boolean(true),
    "x-rate-limit" -> Json.Number(100),
    "x-deprecated-at" -> Json.String("2024-01-01")
  )
)

Round-Tripping with Schema

All OpenAPI types have Schema.derived instances, enabling serialization through DynamicValue:

import zio.blocks.openapi._
import zio.blocks.docs._
import zio.blocks.chunk._
import zio.blocks.schema._

val myApi = OpenAPI(openapi = "3.1.0", info = Info(title = "My API", version = "1.0.0"))
val openAPISchema = Schema[OpenAPI]

val apiDynamic = openAPISchema.toDynamicValue(myApi)

val apiRestored = openAPISchema.fromDynamicValue(apiDynamic)

This enables integration with other ZIO Blocks modules that work with DynamicValue.

Introduction​

Installation​

How They Work Together​

Type Relationships Diagram​

Common Patterns​

Building Reusable Schema Components​

Using ReferenceOr for Inline vs. Referenced Schemas​

Security Schemes​

Path Parameters vs. Query Parameters​

Integration Points​

OpenAPI​

Definition​

Creating an OpenAPI Document​

Serialization​

Info​

Definition​

Creating Info​

Paths & PathItem​

Definition​

Creating Path Items​

Operation​

Definition​

Defining an Operation​

Parameter​

Definition​

Creating Parameters​

RequestBody & Response​

RequestBody Definition​

Creating a RequestBody​

Response Definition​

Creating a Response​

Responses​

MediaType​

Definition​

Creating MediaType​

Components​

Definition​

Creating Components​

SchemaObject​

Definition​

Creating SchemaObject​

Converting Schemas to SchemaObject​

ReferenceOr​

Definition​

Using ReferenceOr​

Pattern Matching on ReferenceOr​

SecurityScheme​

Definition​

Creating Security Schemes​

Discriminator​

Definition​

Creating a Discriminator​

Server & ServerVariable​

Definition​

Creating Servers​

Tag​

Definition​

Creating Tags​

Common Extension Fields​

Round-Tripping with Schema​

Introduction

Installation

How They Work Together

Type Relationships Diagram

Common Patterns

Building Reusable Schema Components

Using `ReferenceOr` for Inline vs. Referenced Schemas

Security Schemes

Path Parameters vs. Query Parameters

Integration Points

OpenAPI

Definition

Creating an OpenAPI Document

Serialization

Info

Definition

Creating Info

Paths & PathItem

Definition

Creating Path Items

Operation

Definition

Defining an Operation

Parameter

Definition

Creating Parameters

RequestBody & Response

RequestBody Definition

Creating a RequestBody

Response Definition

Creating a Response

Responses

MediaType

Definition

Creating MediaType

Components

Definition

Creating Components

SchemaObject

Definition

Creating SchemaObject

Converting Schemas to SchemaObject

ReferenceOr

Definition

Using ReferenceOr

Pattern Matching on ReferenceOr

SecurityScheme

Definition

Creating Security Schemes

Discriminator

Definition

Creating a Discriminator

Server & ServerVariable

Definition

Creating Servers

Tag

Definition

Creating Tags

Common Extension Fields

Round-Tripping with Schema