Merge pull request #440 from JWCook/immutable

Add support for Cache-Control: immutable

4 files changed, 12 insertions, 5 deletions

diff --git a/HISTORY.md b/HISTORY.md
index d76f567..b00c478 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -5,7 +5,8 @@
 
 **Expiration & Headers:**
 * Use `Cache-Control` **request** headers by default
-* Support immediate expiration + revalidation for `Cache-Control: max-age=0` and `Expires: 0`
+* Add support for `Cache-Control: immutable`
+* Add support for immediate expiration + revalidation with `Cache-Control: max-age=0` and `Expires: 0`
 
 **Backends:**
 * Filesystem and SQLite backends: Add better error message if parent path exists but isn't a directory
diff --git a/docs/user_guide/headers.md b/docs/user_guide/headers.md
index a1c7e2f..8373214 100644
--- a/docs/user_guide/headers.md
+++ b/docs/user_guide/headers.md
@@ -56,6 +56,7 @@ The following headers are currently supported:
 **Response headers:**
 - `Cache-Control: max-age`: Used as the expiration time in seconds
 - `Cache-Control: no-store` Skips writing response data to the cache
+- `Cache-Control: immutable`: Caches the response with no expiration
 - `Expires`: Used as an absolute expiration time
 - `ETag`: Returns expired cache data if the remote content has not changed (`304 Not Modified` response)
 - `Last-Modified`: Returns expired cache data if the remote content has not changed (`304 Not Modified` response)
diff --git a/requests_cache/cache_control.py b/requests_cache/cache_control.py
index 604820f..5b238d8 100644
--- a/requests_cache/cache_control.py
+++ b/requests_cache/cache_control.py
@@ -28,7 +28,7 @@ __all__ = ['DO_NOT_CACHE', 'CacheActions']
 # May be set by either headers or expire_after param to disable caching
 DO_NOT_CACHE = 0
 # Supported Cache-Control directives
-CACHE_DIRECTIVES = ['max-age', 'no-cache', 'no-store']
+CACHE_DIRECTIVES = ['immutable', 'max-age', 'no-cache', 'no-store']
 
 CacheDirective = Tuple[str, Union[None, int, bool]]
 ExpirationTime = Union[None, int, float, str, datetime, timedelta]
@@ -136,9 +136,12 @@ class CacheActions:
         logger.debug(f'Cache directives from response headers: {directives}')
 
         # Check headers for expiration, validators, and other cache directives
-        self.expire_after = coalesce(
-            directives.get('max-age'), directives.get('expires'), self.expire_after
-        )
+        if directives.get('immutable'):
+            self.expire_after = -1
+        else:
+            self.expire_after = coalesce(
+                directives.get('max-age'), directives.get('expires'), self.expire_after
+            )
         has_validator = response.headers.get('ETag') or response.headers.get('Last-Modified')
         no_store = 'no-store' in directives or 'no-store' in self.request_directives
 
diff --git a/tests/unit/test_cache_control.py b/tests/unit/test_cache_control.py
index cb8ea96..54182e3 100644
--- a/tests/unit/test_cache_control.py
+++ b/tests/unit/test_cache_control.py
@@ -206,6 +206,8 @@ def test_update_from_cached_response__ignored():
         ({'Cache-Control': 'public, max-age=60'}, 60),
         ({'Cache-Control': 'max-age=0'}, DO_NOT_CACHE),
         ({'Cache-Control': 'no-store'}, DO_NOT_CACHE),
+        ({'Cache-Control': 'immutable'}, -1),
+        ({'Cache-Control': 'immutable, max-age=60'}, -1),  # Immutable should take precedence
         ({'Expires': HTTPDATE_STR}, HTTPDATE_STR),
         ({'Expires': HTTPDATE_STR, 'Cache-Control': 'max-age=60'}, 60),
     ],