File Cache Control Headers Support (#2447)

Co-authored-by: Adam Hopkins <adam@amhopkins.com>

sanic/response.py

@@ -1,9 +1,12 @@
 from __future__ import annotations
 
+from datetime import datetime
+from email.utils import formatdate
 from functools import partial
 from mimetypes import guess_type
 from os import path
-from pathlib import PurePath
+from pathlib import Path, PurePath
+from time import time
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -23,7 +26,12 @@ from sanic.compat import Header, open_async
 from sanic.constants import DEFAULT_HTTP_CONTENT_TYPE
 from sanic.cookies import CookieJar
 from sanic.exceptions import SanicException, ServerError
-from sanic.helpers import has_message_body, remove_entity_headers
+from sanic.helpers import (
+    Default,
+    _default,
+    has_message_body,
+    remove_entity_headers,
+)
 from sanic.http import Http
 from sanic.models.protocol_types import HTMLProtocol, Range
 
@@ -309,6 +317,9 @@ async def file(
     mime_type: Optional[str] = None,
     headers: Optional[Dict[str, str]] = None,
     filename: Optional[str] = None,
+    last_modified: Optional[Union[datetime, float, int, Default]] = _default,
+    max_age: Optional[Union[float, int]] = None,
+    no_store: Optional[bool] = None,
     _range: Optional[Range] = None,
 ) -> HTTPResponse:
     """Return a response object with file data.
@@ -317,6 +328,9 @@ async def file(
     :param mime_type: Specific mime_type.
     :param headers: Custom Headers.
     :param filename: Override filename.
+    :param last_modified: The last modified date and time of the file.
+    :param max_age: Max age for cache control.
+    :param no_store: Any cache should not store this response.
     :param _range:
     """
     headers = headers or {}
@@ -324,6 +338,33 @@ async def file(
         headers.setdefault(
             "Content-Disposition", f'attachment; filename="{filename}"'
         )
+
+    if isinstance(last_modified, datetime):
+        last_modified = last_modified.timestamp()
+    elif isinstance(last_modified, Default):
+        last_modified = Path(location).stat().st_mtime
+
+    if last_modified:
+        headers.setdefault(
+            "last-modified", formatdate(last_modified, usegmt=True)
+        )
+
+    if no_store:
+        cache_control = "no-store"
+    elif max_age:
+        cache_control = f"public, max-age={max_age}"
+        headers.setdefault(
+            "expires",
+            formatdate(
+                time() + max_age,
+                usegmt=True,
+            ),
+        )
+    else:
+        cache_control = "no-cache"
+
+    headers.setdefault("cache-control", cache_control)
+
     filename = filename or path.split(location)[-1]
 
     async with await open_async(location, mode="rb") as f:

tests/test_response.py

@@ -3,10 +3,13 @@ import inspect
 import os
 
 from collections import namedtuple
+from datetime import datetime
+from email.utils import formatdate
 from logging import ERROR, LogRecord
 from mimetypes import guess_type
+from pathlib import Path
 from random import choice
-from typing import Callable, List
+from typing import Callable, List, Union
 from urllib.parse import unquote
 
 import pytest
@@ -328,12 +331,27 @@ def static_file_directory():
     return static_directory
 
 
-def get_file_content(static_file_directory, file_name):
+def path_str_to_path_obj(static_file_directory: Union[Path, str]):
+    if isinstance(static_file_directory, str):
+        static_file_directory = Path(static_file_directory)
+    return static_file_directory
+
+
+def get_file_content(static_file_directory: Union[Path, str], file_name: str):
     """The content of the static file to check"""
-    with open(os.path.join(static_file_directory, file_name), "rb") as file:
+    static_file_directory = path_str_to_path_obj(static_file_directory)
+    with open(static_file_directory / file_name, "rb") as file:
         return file.read()
 
 
+def get_file_last_modified_timestamp(
+    static_file_directory: Union[Path, str], file_name: str
+):
+    """The content of the static file to check"""
+    static_file_directory = path_str_to_path_obj(static_file_directory)
+    return (static_file_directory / file_name).stat().st_mtime
+
+
 @pytest.mark.parametrize(
     "file_name", ["test.file", "decode me.txt", "python.png"]
 )
@@ -711,3 +729,84 @@ def send_response_after_eof_should_fail(
         assert "foo, " in response.text
         assert message_in_records(caplog.records, error_msg1)
         assert message_in_records(caplog.records, error_msg2)
+
+
+@pytest.mark.parametrize(
+    "file_name", ["test.file", "decode me.txt", "python.png"]
+)
+def test_file_response_headers(
+    app: Sanic, file_name: str, static_file_directory: str
+):
+    test_last_modified = datetime.now()
+    test_max_age = 10
+    test_expires = test_last_modified.timestamp() + test_max_age
+
+    @app.route("/files/cached/<filename>", methods=["GET"])
+    def file_route_cache(request, filename):
+        file_path = (Path(static_file_directory) / file_name).absolute()
+        return file(
+            file_path, max_age=test_max_age, last_modified=test_last_modified
+        )
+
+    @app.route(
+        "/files/cached_default_last_modified/<filename>", methods=["GET"]
+    )
+    def file_route_cache_default_last_modified(request, filename):
+        file_path = (Path(static_file_directory) / file_name).absolute()
+        return file(file_path, max_age=test_max_age)
+
+    @app.route("/files/no_cache/<filename>", methods=["GET"])
+    def file_route_no_cache(request, filename):
+        file_path = (Path(static_file_directory) / file_name).absolute()
+        return file(file_path)
+
+    @app.route("/files/no_store/<filename>", methods=["GET"])
+    def file_route_no_store(request, filename):
+        file_path = (Path(static_file_directory) / file_name).absolute()
+        return file(file_path, no_store=True)
+
+    _, response = app.test_client.get(f"/files/cached/{file_name}")
+    assert response.body == get_file_content(static_file_directory, file_name)
+    headers = response.headers
+    assert (
+        "cache-control" in headers
+        and f"max-age={test_max_age}" in headers.get("cache-control")
+        and f"public" in headers.get("cache-control")
+    )
+    assert (
+        "expires" in headers
+        and headers.get("expires")[:-6]
+        == formatdate(test_expires, usegmt=True)[:-6]
+        # [:-6] to allow at most 1 min difference
+        # It's minimal for cases like:
+        # Thu, 26 May 2022 05:36:49 GMT
+        # AND
+        # Thu, 26 May 2022 05:36:50 GMT
+    )
+
+    assert "last-modified" in headers and headers.get(
+        "last-modified"
+    ) == formatdate(test_last_modified.timestamp(), usegmt=True)
+
+    _, response = app.test_client.get(
+        f"/files/cached_default_last_modified/{file_name}"
+    )
+    file_last_modified = get_file_last_modified_timestamp(
+        static_file_directory, file_name
+    )
+    headers = response.headers
+    assert "last-modified" in headers and headers.get(
+        "last-modified"
+    ) == formatdate(file_last_modified, usegmt=True)
+
+    _, response = app.test_client.get(f"/files/no_cache/{file_name}")
+    headers = response.headers
+    assert "cache-control" in headers and f"no-cache" == headers.get(
+        "cache-control"
+    )
+
+    _, response = app.test_client.get(f"/files/no_store/{file_name}")
+    headers = response.headers
+    assert "cache-control" in headers and f"no-store" == headers.get(
+        "cache-control"
+    )