Fetch Commands

Fetch commands provide advanced network request handling and interception capabilities using the Fetch API domain.

Overview

The fetch commands module enables sophisticated network request management, including request modification, response interception, and authentication handling.

pydoll.commands.fetch_commands

FetchCommands

This class encapsulates the fetch commands of the Chrome DevTools Protocol (CDP).

CDP's Fetch domain allows interception and modification of network requests at the application layer. This enables developers to examine, modify, and control network traffic, which is particularly useful for testing, debugging, and advanced automation scenarios.

The commands defined in this class provide functionality for: - Enabling and disabling fetch request interception - Continuing, fulfilling, or failing intercepted requests - Handling authentication challenges - Retrieving and modifying response bodies - Processing response data as streams

continue_request `staticmethod`

continue_request(request_id, url=None, method=None, post_data=None, headers=None, intercept_response=None)

Creates a command to continue a paused fetch request.

This command allows the browser to resume a fetch operation that has been intercepted. You can modify the fetch request URL, method, headers, and body before continuing.

PARAMETER	DESCRIPTION
`request_id`	The ID of the fetch request to continue. TYPE: `str`
`url`	The new URL for the fetch request. Defaults to None. TYPE: `Optional[str]` DEFAULT: `None`
`method`	The HTTP method to use (e.g., 'GET', 'POST'). Defaults to None. TYPE: `Optional[RequestMethod]` DEFAULT: `None`
`post_data`	The body data to send with the fetch request. Defaults to None. TYPE: `Optional[dict]` DEFAULT: `None`
`headers`	A list of HTTP headers to include in the fetch request. Defaults to None. TYPE: `Optional[list[HeaderEntry]]` DEFAULT: `None`
`intercept_response`	Indicates if the response should be intercepted. Defaults to None. TYPE: `Optional[bool]` DEFAULT: `None`

RETURNS	DESCRIPTION
`Command[Response]`	Command[Response]: A command for continuing the fetch request.

continue_request_with_auth `staticmethod`

continue_request_with_auth(request_id, auth_challenge_response, proxy_username=None, proxy_password=None)

Creates a command to continue a paused fetch request with authentication.

This command is used when the fetch operation requires authentication. It provides the necessary credentials to continue the request.

PARAMETER	DESCRIPTION
`request_id`	The ID of the fetch request to continue. TYPE: `str`
`auth_challenge_response`	The authentication challenge response type. TYPE: `AuthChallengeResponseValues`
`proxy_username`	The username for proxy authentication. Defaults to None. TYPE: `Optional[str]` DEFAULT: `None`
`proxy_password`	The password for proxy authentication. Defaults to None. TYPE: `Optional[str]` DEFAULT: `None`

RETURNS	DESCRIPTION
`Command[Response]`	Command[Response]: A command for continuing the fetch request with authentication.

disable `staticmethod`

disable()

Creates a command to disable fetch interception.

This command stops the browser from intercepting fetch requests.

RETURNS	DESCRIPTION
`Command[Response]`	Command[Response]: A command for disabling fetch interception.

enable `staticmethod`

enable(handle_auth_requests, url_pattern='*', resource_type=None, request_stage=None)

Creates a command to enable fetch interception.

This command allows the browser to start intercepting fetch requests. You can specify whether to handle authentication challenges and the types of resources to intercept.

PARAMETER	DESCRIPTION
`handle_auth_requests`	Indicates if authentication requests should be handled. TYPE: `bool`
`url_pattern`	Pattern to match URLs for interception. Defaults to ''. TYPE:* `str` DEFAULT: `'*'`
`resource_type`	The type of resource to intercept. Defaults to None. TYPE: `Optional[ResourceType]` DEFAULT: `None`
`request_stage`	The stage of the request to intercept. Defaults to None. TYPE: `Optional[RequestStage]` DEFAULT: `None`

RETURNS	DESCRIPTION
`Command[Response]`	Command[Response]: A command for enabling fetch interception.

fail_request `staticmethod`

fail_request(request_id, error_reason)

Creates a command to simulate a failure in a fetch request.

This command allows you to simulate a failure for a specific fetch operation, providing a reason for the failure.

PARAMETER	DESCRIPTION
`request_id`	The ID of the fetch request to fail. TYPE: `str`
`error_reason`	The reason for the failure. TYPE: `NetworkErrorReason`

RETURNS	DESCRIPTION
`Command[Response]`	Command[Response]: A command for failing the fetch request.

fulfill_request `staticmethod`

fulfill_request(request_id, response_code, response_headers=None, body=None, response_phrase=None)

Creates a command to fulfill a fetch request with a custom response.

This command allows you to provide a custom response for a fetch operation, including the HTTP status code, headers, and body content.

PARAMETER	DESCRIPTION
`request_id`	The ID of the fetch request to fulfill. TYPE: `str`
`response_code`	The HTTP status code to return. TYPE: `int`
`response_headers`	A list of response headers. Defaults to None. TYPE: `Optional[list[HeaderEntry]]` DEFAULT: `None`
`body`	The body content of the response. Defaults to None. TYPE: `Optional[dict]` DEFAULT: `None`
`response_phrase`	The response phrase (e.g., 'OK', 'Not Found'). Defaults to None. TYPE: `Optional[str]` DEFAULT: `None`

RETURNS	DESCRIPTION
`Command[Response]`	Command[Response]: A command for fulfilling the fetch request.

get_response_body `staticmethod`

get_response_body(request_id)

Creates a command to retrieve the response body of a fetch request.

This command allows you to access the body of a completed fetch operation, which can be useful for analyzing the response data.

PARAMETER	DESCRIPTION
`request_id`	The ID of the fetch request to retrieve the body from. TYPE: `str`

RETURNS	DESCRIPTION
`Command[GetResponseBodyResponse]`	Command[GetResponseBodyResponse]: A command for getting the response body.

continue_response `staticmethod`

continue_response(request_id, response_code=None, response_headers=None, response_phrase=None)

Creates a command to continue a fetch response for an intercepted request.

This command allows the browser to continue the response flow for a specific fetch request, including customizing the HTTP status code, headers, and response phrase.

PARAMETER	DESCRIPTION
`request_id`	The ID of the fetch request to continue the response for. TYPE: `str`
`response_code`	The HTTP status code to send. Defaults to None. TYPE: `Optional[int]` DEFAULT: `None`
`response_headers`	A list of response headers. Defaults to None. TYPE: `Optional[list[HeaderEntry]]` DEFAULT: `None`
`response_phrase`	The response phrase (e.g., 'OK'). Defaults to None. TYPE: `Optional[str]` DEFAULT: `None`

RETURNS	DESCRIPTION
`Command[Response]`	Command[Response]: A command for continuing the fetch response.

take_response_body_as_stream `staticmethod`

take_response_body_as_stream(request_id)

Creates a command to take the response body as a stream.

This command allows you to receive the response body as a stream which can be useful for handling large responses.

PARAMETER	DESCRIPTION
`request_id`	The ID of the fetch request to take the response body stream from. TYPE: `str`

RETURNS	DESCRIPTION
`Command[TakeResponseBodyAsStreamResponse]`	Command[TakeResponseBodyAsStreamResponse]: A command for taking the response body as a stream.

Usage

Fetch commands are used for advanced network interception and request handling:

from pydoll.commands.fetch_commands import enable, request_paused, continue_request
from pydoll.connection.connection_handler import ConnectionHandler

# Enable fetch domain
connection = ConnectionHandler()
await enable(connection, patterns=[{
    "urlPattern": "*",
    "requestStage": "Request"
}])

# Handle paused requests
async def handle_paused_request(request_id, request):
    # Modify request or continue as-is
    await continue_request(connection, request_id=request_id)

Key Functionality

The fetch commands module provides functions for:

Request Interception

enable() - Enable fetch domain with patterns
disable() - Disable fetch domain
continue_request() - Continue intercepted requests
fail_request() - Fail requests with specific errors

Request Modification

Modify request headers
Change request URLs
Alter request methods (GET, POST, etc.)
Modify request bodies

Response Handling

fulfill_request() - Provide custom responses
get_response_body() - Get response content
Response header modification
Response status code control

Authentication

continue_with_auth() - Handle authentication challenges
Basic authentication support
Custom authentication flows

Advanced Features

Pattern-Based Interception

# Intercept specific URL patterns
patterns = [
    {"urlPattern": "*/api/*", "requestStage": "Request"},
    {"urlPattern": "*.js", "requestStage": "Response"},
    {"urlPattern": "https://example.com/*", "requestStage": "Request"}
]

await enable(connection, patterns=patterns)

Request Modification

# Modify intercepted requests
async def modify_request(request_id, request):
    # Add authentication header
    headers = request.headers.copy()
    headers["Authorization"] = "Bearer token123"

    # Continue with modified headers
    await continue_request(
        connection,
        request_id=request_id,
        headers=headers
    )

Response Mocking

# Mock API responses
await fulfill_request(
    connection,
    request_id=request_id,
    response_code=200,
    response_headers=[
        {"name": "Content-Type", "value": "application/json"},
        {"name": "Access-Control-Allow-Origin", "value": "*"}
    ],
    body='{"status": "success", "data": {"mocked": true}}'
)

Authentication Handling

# Handle authentication challenges
await continue_with_auth(
    connection,
    request_id=request_id,
    auth_challenge_response={
        "response": "ProvideCredentials",
        "username": "user",
        "password": "pass"
    }
)

Request Stages

Fetch commands can intercept requests at different stages:

Stage	Description	Use Cases
Request	Before request is sent	Modify headers, URL, method
Response	After response received	Mock responses, modify content

Error Handling

# Fail requests with specific errors
await fail_request(
    connection,
    request_id=request_id,
    error_reason="ConnectionRefused"  # or "AccessDenied", "TimedOut", etc.
)

Integration with Network Commands

Fetch commands work alongside network commands but provide more granular control:

Network Commands: Broader network monitoring and control
Fetch Commands: Specific request/response interception and modification

Performance Considerations

Fetch interception can impact page loading performance. Use specific URL patterns and disable when not needed to minimize overhead.

Fetch Commands

Overview

pydoll.commands.fetch_commands

FetchCommands

continue_request staticmethod

continue_request_with_auth staticmethod

disable staticmethod

enable staticmethod

fail_request staticmethod

fulfill_request staticmethod

get_response_body staticmethod

continue_response staticmethod

take_response_body_as_stream staticmethod

Usage

Key Functionality

Request Interception

Request Modification

Response Handling

Authentication

Advanced Features

Pattern-Based Interception

Request Modification

Response Mocking

Authentication Handling

Request Stages

Error Handling

Integration with Network Commands

continue_request `staticmethod`

continue_request_with_auth `staticmethod`

disable `staticmethod`

enable `staticmethod`

fail_request `staticmethod`

fulfill_request `staticmethod`

get_response_body `staticmethod`

continue_response `staticmethod`

take_response_body_as_stream `staticmethod`