tessl/pypi-hishel

Persistent cache implementation for httpx and httpcore following RFC 9111 specification

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HTTP Cache Validator Implementation

Name: tessl/pypi-hishel
Rating: 0.74 (1 reviews)
Author: tessl

Build a simple HTTP caching client that properly handles conditional requests using cache validators (ETags and Last-Modified timestamps).

Requirements

Your task is to implement a caching HTTP client that:

Makes an initial request to an API endpoint and caches the response along with its validator headers (ETag and/or Last-Modified)
On subsequent requests to the same endpoint, sends conditional request headers based on the cached validators
Handles 304 Not Modified responses by serving the cached content
Updates the cache when receiving a 200 OK response with new content

Implementation Details

Create a module cache_client.py with a CachedClient class that:

Stores responses in memory with their ETag and Last-Modified values
Automatically includes If-None-Match header when an ETag is cached
Automatically includes If-Modified-Since header when a Last-Modified value is cached
Returns cached content when the server responds with 304 Not Modified
Updates the cache when receiving fresh content (200 OK)

Your implementation should handle:

Endpoints that provide ETag headers
Endpoints that provide Last-Modified headers
Endpoints that provide both validator types
Proper conditional request formation

Test Cases

Test Case 1: ETag Validation { @test }

# test_cache_client.py
def test_etag_conditional_request():
    """Test that cached responses with ETags trigger conditional requests."""
    client = CachedClient()

    # First request - cache the response with ETag
    response1 = client.get("https://api.example.com/data")
    assert response1.status_code == 200
    assert "ETag" in response1.headers

    # Second request - should send If-None-Match
    response2 = client.get("https://api.example.com/data")
    # If server returns 304, client should serve cached content
    assert response2.content == response1.content

Test Case 2: Last-Modified Validation { @test }

def test_last_modified_conditional_request():
    """Test that cached responses with Last-Modified trigger conditional requests."""
    client = CachedClient()

    # First request - cache the response with Last-Modified
    response1 = client.get("https://api.example.com/resource")
    assert response1.status_code == 200
    assert "Last-Modified" in response1.headers

    # Second request - should send If-Modified-Since
    response2 = client.get("https://api.example.com/resource")
    # Client should handle 304 by serving cached content
    assert response2.content == response1.content

Test Case 3: Cache Update on Fresh Content { @test }

def test_cache_update_on_new_content():
    """Test that cache is updated when server returns new content."""
    client = CachedClient()

    # First request
    response1 = client.get("https://api.example.com/mutable")
    original_content = response1.content

    # Simulate time passing and content changing
    # Second request gets new content (200 OK instead of 304)
    response2 = client.get("https://api.example.com/mutable")

    # If content changed, new content should be cached and returned
    if response2.status_code == 200:
        assert response2.content != original_content

Dependencies { .dependencies }

hishel { .dependency }

An elegant HTTP caching library for Python that implements RFC 9111 specifications. Provides built-in support for cache validators including ETag and Last-Modified headers with automatic conditional request generation.

Install with Tessl CLI

npx tessl i tessl/pypi-hishel