bpo-29654 : Support If-Modified-Since HTTP header (browser cache) (#298)

Return 304 response if file was not modified.

Lib/test/test_httpservers.py

@@ -14,11 +14,14 @@
 import base64
 import ntpath
 import shutil
-import urllib.parse
+import email.message
+import email.utils
 import html
 import http.client
+import urllib.parse
 import tempfile
 import time
+import datetime
 from io import BytesIO
 
 import unittest
@@ -333,6 +336,13 @@ def setUp(self):
         self.base_url = '/' + self.tempdir_name
         with open(os.path.join(self.tempdir, 'test'), 'wb') as temp:
             temp.write(self.data)
+            mtime = os.fstat(temp.fileno()).st_mtime
+        # compute last modification datetime for browser cache tests
+        last_modif = datetime.datetime.fromtimestamp(mtime,
+            datetime.timezone.utc)
+        self.last_modif_datetime = last_modif.replace(microsecond=0)
+        self.last_modif_header = email.utils.formatdate(
+            last_modif.timestamp(), usegmt=True)
 
     def tearDown(self):
         try:
@@ -444,6 +454,44 @@ def test_head(self):
         self.assertEqual(response.getheader('content-type'),
                          'application/octet-stream')
 
+    def test_browser_cache(self):
+        """Check that when a request to /test is sent with the request header
+        If-Modified-Since set to date of last modification, the server returns
+        status code 304, not 200
+        """
+        headers = email.message.Message()
+        headers['If-Modified-Since'] = self.last_modif_header
+        response = self.request(self.base_url + '/test', headers=headers)
+        self.check_status_and_reason(response, HTTPStatus.NOT_MODIFIED)
+
+        # one hour after last modification : must return 304
+        new_dt = self.last_modif_datetime + datetime.timedelta(hours=1)
+        headers = email.message.Message()
+        headers['If-Modified-Since'] = email.utils.format_datetime(new_dt,
+            usegmt=True)
+        response = self.request(self.base_url + '/test', headers=headers)
+        self.check_status_and_reason(response, HTTPStatus.NOT_MODIFIED)        
+
+    def test_browser_cache_file_changed(self):
+        # with If-Modified-Since earlier than Last-Modified, must return 200
+        dt = self.last_modif_datetime
+        # build datetime object : 365 days before last modification
+        old_dt = dt - datetime.timedelta(days=365)
+        headers = email.message.Message()
+        headers['If-Modified-Since'] = email.utils.format_datetime(old_dt,
+            usegmt=True)
+        response = self.request(self.base_url + '/test', headers=headers)
+        self.check_status_and_reason(response, HTTPStatus.OK)
+
+    def test_browser_cache_with_If_None_Match_header(self):
+        # if If-None-Match header is present, ignore If-Modified-Since
+
+        headers = email.message.Message()
+        headers['If-Modified-Since'] = self.last_modif_header
+        headers['If-None-Match'] = "*"
+        response = self.request(self.base_url + '/test', headers=headers)
+        self.check_status_and_reason(response, HTTPStatus.OK)        
+
     def test_invalid_requests(self):
         response = self.request('/', method='FOO')
         self.check_status_and_reason(response, HTTPStatus.NOT_IMPLEMENTED)
@@ -453,6 +501,15 @@ def test_invalid_requests(self):
         response = self.request('/', method='GETs')
         self.check_status_and_reason(response, HTTPStatus.NOT_IMPLEMENTED)
 
+    def test_last_modified(self):
+        """Checks that the datetime returned in Last-Modified response header
+        is the actual datetime of last modification, rounded to the second
+        """
+        response = self.request(self.base_url + '/test')
+        self.check_status_and_reason(response, HTTPStatus.OK, data=self.data)
+        last_modif_header = response.headers['Last-modified']
+        self.assertEqual(last_modif_header, self.last_modif_header)
+
     def test_path_without_leading_slash(self):
         response = self.request(self.tempdir_name + '/test')
         self.check_status_and_reason(response, HTTPStatus.OK, data=self.data)