Hooks

Hooks are a way to add custom code to your SDK or Terraform provider to hook into the API invocation lifecycle. This document will guide you through extending the liblab generated SDK with your custom logic using our Hooks framework.

Supported SDK languages and versions:

TypeScript	Java	Python v1	Python v2	C#	Go	Terraform
✅	✅	✅	✅	✅	✅	✅

What are Hooks?

In some use cases, you need to extend the SDK created by liblab, and add your own custom code into the SDK at the generation process. Examples of such use cases include custom authentication or auditing requirements, or providing Terraform plan modifiers.

liblab can extend your SDKs in each of the languages generated, using our Hooks framework. The SDK hooks framework lets you hook in your code into three events in the API invocation lifecycle:

• Before Request - Code implemented in this section will run before the request. You can use the request object and update the request itself before it goes out to your API.
• After Response - Code implemented in this section will run after the call returns from your API. You can use the request objects to get context for the API call made and the response object for the response provided.
• On Error - Code implemented in this section will run in case of an API call error. You can use the request objects to get context for the API call and the exception object for information about the error that accrued.

Happy path

Error path

For Terraform you can hook into the terraform plan command to modify the plan before it is applied. You can read more on this in our Terraform provider hooks and custom plan modifiers documentation.

To implement hooks, you need to implement one or more of the three hooks - before request, after response or on error.

TypeScript v1

src/index.ts

export default class CustomHook implements Hook {
  async beforeRequest(request: Request): Promise<void> {
    // Your code goes here
  }

  async afterResponse(request: Request, response: Response): Promise<void> {
    // Your code goes here
  }

  async onError(error: Exception): Promise<void> {
    // Your code goes here
  }
}

TypeScript v2

src/index.ts

export default class CustomHook implements Hook {
  async beforeRequest(request: Request): Promise<void> {
    // Your code goes here
  }

  async afterResponse(request: Request, response: Response): Promise<void> {
    // Your code goes here
  }

  async onError(error: Exception): Promise<void> {
    // Your code goes here
  }
}

Python v1

src/hook.py

class CustomHook:
    def before_request(self, request: Request, **kwargs):
        # Your code goes here

    def after_response(self, request: Request, response: Response, **kwargs):
        # Your code goes here

    def on_error(self, error: Exception, request: Request, response: Response, **kwargs):
        # Your code goes here

Python v2

src/hook.py

class CustomHook:
    def before_request(self, request: Request, **kwargs):
        # Your code goes here

    def after_response(self, request: Request, response: Response, **kwargs):
        # Your code goes here

    def on_error(self, error: Exception, request: Request, response: Response, **kwargs):
        # Your code goes here

Java

src/main/java/com/liblab/hook/CustomHook.java

public class CustomHook implements Hook {
    @Override
    public void beforeRequest(Request request) {
        // Your code goes here
    }

    @Override
    public void afterResponse(Request request, Response response) {
        // Your code goes here
    }

    @Override
    public void onError(Request request, Exception exception) {
        // Your code goes here
    }
}

C#

CustomHook.cs

public class CustomHook : IHook
{
    public async Task<HttpRequestMessage> BeforeRequestAsync(HttpRequestMessage request)
    {
    }

    public async Task<HttpResponseMessage> AfterResponseAsync(HttpResponseMessage response)
    {
    }

    public async Task OnErrorAsync(HttpResponseMessage response)
    {
    }
}

Go

hooks/custom_hook.go

type Hook interface {
    BeforeRequest(req Request) Request
    AfterResponse(req Request, resp Response) Response
    OnError(req Request, resp ErrorResponse) ErrorResponse
}

PHP

CustomHook.php

class CustomHook implements HookInterface
{
    public function beforeRequest(RequestInterface &$request): void
    {
        // Your code goes here
    }

    public function afterResponse(RequestInterface $request, ResponseInterface &$response): void
    {
        // Your code goes here
    }

    public function onError(RequestInterface $request, Exception $exception): void
    {
        // Your code goes here
    }
}

note

If you are generating a Terraform provider as well as a standalone Go SDK, hooks are not shared between the Go SDK generated for the terraform provider and the standalone Go SDK.

Add hooks to your liblab project

To add the hooks framework, run the following command:

liblab hooks add

This will generate a hooks folder which you can modify to extend the SDK. To be included in our SDK, this hooks folder must live in the same folder as your liblab config file.

This hooks folder will contain a folder for each of the languages specified in your config file.

.
├── hooks
│   ├── go
│   ├── csharp
│   ├── java
│   ├── python
│   ├── terraform
│   └── typescript
├── customPlanModifiers // hooks that are triggered on the `terraform plan` command
│   ├── attributes
│   └── resources
└── liblab.config.json

Each folder will contain a full code project that you can add your custom hook code to. This code is then sent to liblab when your SDK is generated. The presence of the hooks folder is all liblab needs to generate hooks in your SDK.

You can also add hooks for a single language by running:

liblab hooks add --language=<language>

If you are creating hooks for a Terraform provider, you will get an additional folder called customPlanModifiers which contains the hooks for the internal Go SDK that is used by the Terraform provider. You can read more on this in our Terraform provider hooks and custom plan modifiers documentation.

Hooks can be written for the underlying Go SDK that is used by the Terraform provider by updating the code in the hooks/terraform folder. These hooks are written in the same way as writing hooks for the Go SDK.

You can read more about adding hooks in our CLI hooks documentation.

Implement hooks

In the hooks folder, you will find hooks code for each of the languages you have generated.

TypeScript v1

typescript
├── src
│   └── index.ts
├── tests
│   └── hook.spec.ts
├── package-lock.json
├── package.json
├── prettier.config.js
├── tsconfig.eslint.json
└── tsconfig.json

TypeScript v2

typescript
├── src
│   └── index.ts
├── tests
│   └── hook.spec.ts
├── package-lock.json
├── package.json
├── prettier.config.js
├── tsconfig.eslint.json
└── tsconfig.json

Python v1

python
├── src
│   └── hook.py
├── test
│   └── test_hook.py
└── requirements.txt

Python v2

python
├── src
│   └── hook.py
├── test
│   └── test_hook.py
└── requirements.txt

Java

java
├── src
│   ├── main/java/<namespace>
│   │   └── hook
│   │       ├── CustomHook.java
│   │       └── model
│   │           ├── Hook.java
│   │           ├── Request.java
│   │           └── Response.java
│   └── test/java/<namespace>
│       └── hook
│           └── CustomHookTest.java
└── pom.xml

C#

csharp
└── CustomHook.cs

Go

go
├── hooks
│   ├── custom_hook.go
│   └── hook.go
└── go.mod

PHP

php
├── CustomHook.php
├── HookInterface.php
└── composer.json

Hook dependencies

Each hook project has relevant files to add dependencies, for example in a Python hook there is a requirements.txt file, in Java there is a pom.xml. If you want to add any dependencies to your hooks code, for example an SDK to add telemetry, you must add them to the relevant file so that they can be picked up during the SDK generation process.

note

If you do not add dependencies to these files, the SDK generation will not know to add them and your final SDK may not build or run

Before request

The before request hook is called just before the request is sent to your API. The hook receives a request object with the URL being called, the relevant verb (GET, POST etc.), the body as JSON, and the headers.

In this hook, you can modify the request object or the headers, and the changes will be sent to your API.

TypeScript v1

The Request class lives in the src/index.ts file:

src/index.ts

export interface Request {
  method: string;
  url: string;
  input?: object;
  headers: object;
}

The beforeRequest method is implemented in the CustomHook class in the src/index.ts file:

src/index.ts

export default class CustomHook implements Hook {
  async beforeRequest(request: Request): Promise<void> {
    // Your code goes here
  }
}

TypeScript v2

The Request class lives in the src/index.ts file:

src/index.ts

export interface Request {
  method: string;
  url: string;
  input?: object;
  headers: object;
}

The beforeRequest method is implemented in the CustomHook class in the src/index.ts file:

src/index.ts

export default class CustomHook implements Hook {
  async beforeRequest(request: Request): Promise<void> {
    // Your code goes here
  }
}

Python v1

The Request class lives in the src/hook.py file:

src/hook.py

class Request:
    def __init__(self, method, url, headers, body=""):
        self.method = method
        self.url = url
        self.headers = headers
        self.body = body

The before_request method is implemented in the CustomHook class in the src/hook.py file:

src/hook.py

class CustomHook:
    def before_request(self, request: Request, **kwargs):
        # Your code goes here

Python v2

The Request class lives in the src/hook.py file:

src/hook.py

class Request:
    def __init__(self, method, url, headers, body=""):
        self.method = method
        self.url = url
        self.headers = headers
        self.body = body

The before_request method is implemented in the CustomHook class in the src/hook.py file:

src/hook.py

class CustomHook:
    def before_request(self, request: Request, **kwargs):
        # Your code goes here

Java

The Request class lives in the src/main/<namespace>/hook/model/Request.java file:

src/main/java/com/liblab/hook/model/Request.java

public class Request {
    public Request(String method, String url, String body, Map<String, String> headers) {}

    public String getMethod() {}
    public void setMethod(String method) {}

    public String getUrl() {}
    public void setUrl(String url) {}

    public String getBody() {}
    public void setBody(String body) {}

    public Map<String, String> getHeaders() {}
    public void setHeaders(Map<String, String> headers) {}
}

The beforeRequest method is implemented in the CustomHook class in the src/main/<namespace>/hook/CustomHook.java file:

src/main/java/com/liblab/hook/CustomHook.java

public class CustomHook implements Hook {
    @Override
    public void beforeRequest(Request request) {
        // Your code goes here
    }
}

C#

The BeforeRequestAsync method is implemented in the CustomHook class in the CustomHook.cs file:

CustomHook.cs

public async Task<HttpRequestMessage> BeforeRequestAsync(HttpRequestMessage request)
{
    // Your code goes here
}

The request type used is an instance of System.Net.Http.HttpRequestMessage.

Go

The Request type lives in the hooks/hook.go file:

hooks/hook.go

type Request interface {
    GetMethod() string
    SetMethod(method string)
    GetBaseUrl() string
    SetBaseUrl(baseUrl string)
    GetPath() string
    SetPath(path string)
    GetHeader(header string) string
    SetHeader(header string, value string)
    GetPathParam(param string) string
    SetPathParam(param string, value any)
    GetQueryParam(param string) string
    SetQueryParam(param string, value any)
    GetBody() any
    SetBody(body any)
}

The BeforeRequest method is implemented in the hooks package in the custom_hook.go file:

hooks/custom_hook.go

type CustomHook struct{}

func (h *CustomHook) BeforeRequest(req Request) Request {
    // Your code goes here
    return req
}

PHP

The request type used is an instance of Psr\Http\Message\RequestInterface.

The beforeRequest method is implemented in the CustomHook class in the CustomHook.php file:

CustomHook.php

class CustomHook implements HookInterface
{
    public function beforeRequest(RequestInterface &$request): void
    {
        // Your code goes here
    }
}

After response

The after response hook is called once the response has been received from the SDK. The hook receives the request object, and the response object. The response object contains the response body as JSON, the headers, and the status code.

In this hook you can modify the response body or headers, and the changes will be returned to the SDK caller.

TypeScript v1

The Response class lives in the src/index.ts file:

src/index.ts

export interface Response {
  data: object;
  headers: object;
  status: number;
}

The afterResponse method is implemented in the CustomHook class in the src/index.ts file:

src/index.ts

export default class CustomHook implements Hook {
  async afterResponse(request: Request, response: Response): Promise<void> {
    // Your code goes here
  }
}

TypeScript v2

The Response class lives in the src/index.ts file:

src/index.ts

export interface Response {
  data: object;
  headers: object;
  status: number;
}

The afterResponse method is implemented in the CustomHook class in the src/index.ts file:

src/index.ts

export default class CustomHook implements Hook {
  async afterResponse(request: Request, response: Response): Promise<void> {
    // Your code goes here
  }
}

Python v1

The Response class lives in the src/hook.py file:

src/hook.py

class Response:
    def __init__(self, status, headers, body):
        self.status = status
        self.headers = headers
        self.body = body

The after_response method is implemented in the CustomHook class in the src/hook.py file:

src/hook.py

class CustomHook:
     def after_response(self, request: Request, response: Response, **kwargs):
        # Your code goes here

Python v2

The Response class lives in the src/hook.py file:

src/hook.py

class Response:
    def __init__(self, status, headers, body):
        self.status = status
        self.headers = headers
        self.body = body

The after_response method is implemented in the CustomHook class in the src/hook.py file:

src/hook.py

class CustomHook:
     def after_response(self, request: Request, response: Response, **kwargs):
        # Your code goes here

Java

The Response class lives in the src/main/<namespace>/hook/model/Response.java file:

src/main/java/com/liblab/hook/model/Response.java

public class Response {
    public Response(int statusCode, String body, Map<String, String> headers) {}

    public int getStatusCode() {}
    public void setStatusCode(int statusCode) {}

    public String getBody() {}
    public void setBody(String body) {}

    public Map<String, String> getHeaders() {}
    public void setHeaders(Map<String, String> headers) {}
}

The afterResponse method is implemented in the CustomHook class in the src/main/<namespace>/hook/CustomHook.java file:

src/main/java/com/liblab/hook/CustomHook.java

public class CustomHook implements Hook {
    @Override
    public void afterResponse(Request request, Response response) {
        // Your code goes here
    }
}

C#

The AfterResponseAsync method is implemented in the CustomHook class in the CustomHook.cs file:

CustomHook.cs

public async Task<HttpResponseMessage> AfterResponseAsync(HttpResponseMessage response)
{
    // Your code goes here
}

The response parameter is an instance of System.Net.Http.HttpResponseMessage.

Go

The Response type lives in the hooks/hook.go file:

hooks/hook.go

type Response interface {
    GetStatusCode() int
    SetStatusCode(statusCode int)
    GetHeader(header string) string
    SetHeader(header string, value string)
    GetBody() []byte
    SetBody(body []byte)
}

The AfterResponse method is implemented in the hooks package in the custom_hook.go file:

hooks/custom_hook.go

func (h *CustomHook) AfterResponse(req Request, resp Response) Response {
    fmt.Printf("AfterResponse: %#v\n", resp)
    return resp
}

PHP

The afterResponse method is implemented in the CustomHook class in the CustomHook.php file:

CustomHook.php

class CustomHook implements HookInterface
{
    public function afterResponse(RequestInterface $request, ResponseInterface &$response): void
    {
        // Your code goes here
    }
}

The response parameter is an instance of Psr\Http\Message\ResponseInterface.

On error

The on error hook is called if the API returns an error, such as a 4xx status code. This hook passes the original request object for reference, along with details of the error.

TypeScript v1

The Exception class lives in the src/index.ts file:

src/index.ts

export interface Exception extends Error {
  title: string;
  type?: string;
  detail?: string;
  instance?: string;
  statusCode: number;
}

The onError method is implemented in the CustomHook class in the src/index.ts file:

src/index.ts

export default class CustomHook implements Hook {
  async onError(error: Exception): Promise<void> {
    // Your code goes here
  }
}

TypeScript v2

The Exception class lives in the src/index.ts file:

src/index.ts

export interface Exception extends Error {
  title: string;
  type?: string;
  detail?: string;
  instance?: string;
  statusCode: number;
}

The onError method is implemented in the CustomHook class in the src/index.ts file:

src/index.ts

export default class CustomHook implements Hook {
  async onError(error: Exception): Promise<void> {
    // Your code goes here
  }
}

Python v1

The on_error method is implemented in the CustomHook class in the src/hook.py file:

src/hook.py

class CustomHook:
    def on_error(self, error: Exception, request: Request, response: Response, **kwargs):
        # Your code goes here

The error is provided in the error parameter. For example, if the API call returns a status of 401, this will be a http_exceptions.client_exceptions.UnauthorizedException.

The original request is passed to this hook in the request parameter. The response from the call is passed in the response parameter.

After this hook is called, the SDK code will throw the exception so that the SDK caller can handle it.

Python v2

The on_error method is implemented in the CustomHook class in the src/hook.py file:

src/hook.py

class CustomHook:
    def on_error(self, error: Exception, request: Request, response: Response, **kwargs):
        # Your code goes here

The error is provided in the error parameter. For example, if the API call returns a status of 401, this will be a http_exceptions.client_exceptions.UnauthorizedException.

The original request is passed to this hook in the request parameter. The response from the call is passed in the response parameter.

After this hook is called, the SDK code will throw the exception so that the SDK caller can handle it.

Java

The onError method is implemented in the CustomHook class in the src/main/<namespace>/hook/CustomHook.java file:

src/main/java/com/liblab/hook/CustomHook.java

public class CustomHook implements Hook {
    @Override
    public void onError(Request request, Exception exception) {
        // Your code goes here
    }
}

The original request is passed to this hook in the request parameter.

The error is provided in the exception parameter. For example, this could be a java.io.IOException if the request failed due to a network error, or an io.swagger.exceptions.ApiException if the request failed due to an HTTP error response.

After this hook is called, the SDK code will throw the exception so that the SDK caller can handle it.

C#

The OnErrorAsync method is implemented in the CustomHook class in the CustomHook.cs file:

CustomHook.cs

public async Task OnErrorAsync(HttpResponseMessage response)
{
    // Your code goes here
}

The response from the call is passed in the response parameter, and is an instance of System.Net.Http.HttpResponseMessage.

After this hook is called, the SDK code will throw an exception so that the SDK caller can handle it.

Go

The OnError method is implemented in the hooks package in the custom_hook.go file:

hooks/custom_hook.go

func (h *CustomHook) OnError(req Request, resp ErrorResponse) ErrorResponse {
    fmt.Printf("On Error: %#v\n", resp)
    return resp
}

The original request is passed to this hook in the req parameter.

The error is provided in the resp parameter. This has the following type:

hooks/hook.go

type ErrorResponse interface {
    Error() string
    GetError() error
    GetStatusCode() int
    SetStatusCode(statusCode int)
    GetHeader(header string) string
    SetHeader(header string, value string)
    GetBody() []byte
    SetBody(body []byte)
}

After this hook is called, the SDK code will return the error.

PHP

The onError method is implemented in the CustomHook class in the CustomHook.php file:

CustomHook.php

class CustomHook implements HookInterface
{
    public function onError(RequestInterface $request, Exception $exception): void
    {
        // Your code goes here
    }
}

The original request is passed to this hook in the $request parameter.

The error is provided in the $exception parameter.

After this hook is called, the SDK code will throw the exception so that the SDK caller can handle it.

Additional constructor parameters

Supported SDK languages and versions:

TypeScript v1	TypeScript v2	Java	Python v1	Python v2	C#	Go	PHP	Terraform
❌	❌	❌	✅	❌	❌	❌	❌	❌

If you need to pass additional data from the code that calls your SDK into hooks, you can enable this by adding additional constructor parameters to your SDK client. These are defined in your liblab config file.

TypeScript v1

Additional constructor parameters are not supported in v1 of the TypeScript SDK generation.

TypeScript v2

This feature is not currently supported in TypeScript SDK generation.

Python v1

Additional constructor parameters are not supported in v1 of the Python SDK generation.

Python v2

For example, if you wanted to define a client Id and client secret for oAuth that is used by your custom hooks code to authenticate requests, you could set this option in your config file like this:

{
    ...
    "languageOptions": {
        "python": {
            "additionalConstructorParameters": [
                {
                    "name": "client_id",
                    "example": "myClientId"
                },
                {
                    "name": "client_secret",
                    "example": "myClientSecret"
                }
            ]
        }
    }
    ...
}

This would add the following parameters to the SDK client constructor:

class MyClient:
    def __init__(
        self,
        client_id: str = None,
        client_secret: str = None,
    ):

These parameters are passed to the kwargs parameter of the hooks before_request, after_request, and on_error methods. For example, in the before_request method, you could access these parameters like this:

def before_request(self, request: Request, **kwargs):
    # Get the client Id and secret from the kwargs
    client_id = kwargs.get("client_id")
    client_secret = kwargs.get("client_secret")

Java

This feature is not currently supported in Java SDK generation.

C#

This feature is not currently supported during the C# beta.

Go

This feature is not currently supported during the Go beta.

PHP

This feature is not currently supported in PHP SDK generation.

Build your SDK with hooks

When you next run the liblab build command, liblab will send the code in the hooks folder to our servers, and the resulting SDKs will have your code integrated automatically into the SDKs. Any package dependencies that your hooks have will be merged with the SDK dependencies.

Remember to add the hooks folder to your source control, so that your hooks code is always available when you build your SDKs. It should live in the same folder in the same repo as your liblab config file.

Remove hooks

To remove hooks you can use the command liblab hooks remove, or manually delete your hooks folder. Once this is done, the next time you run liblab build, your SDK will be generated without your custom hook code.

note

If you have terraform as one of the languages in your config file, this command will also delete the customPlanModifiers directory.