feat: set canonical header for file

plone/namedfile/browser.py

@@ -127,6 +127,13 @@ def handle_request_range(self, file):
         except ValueError:
             return default
 
+    def get_canonical(self, file):
+        filename = getattr(file, "filename", None)
+        if filename is None:
+            return f"{self.context.absolute_url()}/@@download/{self.fieldname}"
+        else:
+            return f"{self.context.absolute_url()}/@@download/{self.fieldname}/filename"
+
     def set_headers(self, file):
         # With filename None, set_headers will not add the download headers.
         if not self.filename:
@@ -135,7 +142,8 @@ def set_headers(self, file):
                 self.filename = self.fieldname
                 if self.filename is None:
                     self.filename = "file.ext"
-        set_headers(file, self.request.response, filename=self.filename)
+        canonical =  self.get_canonical(file)
+        set_headers(file, self.request.response, filename=self.filename, canonical=canonical)
 
     def _getFile(self):
         if not self.fieldname:
@@ -185,4 +193,5 @@ def set_headers(self, file):
                 if mimetype not in self.allowed_inline_mimetypes:
                     # Let the Download view handle this.
                     return super().set_headers(file)
-        set_headers(file, self.request.response)
+        canonical =  self.get_canonical(file)
+        set_headers(file, self.request.response, canonical=canonical)

plone/namedfile/tests/test_display_file.py

@@ -49,6 +49,15 @@ def get_disposition_header(browser):
     return browser.headers.get(name, None)
 
 
+def get_canonical_header(browser):
+    name = "Link"
+    for header, value in browser.headers.items():
+        if header == name or header == name.lower():
+            if 'rel="canonical"' in map(str.strip, value.split(";")):
+                return value
+    return None
+
+
 def custom_available_sizes():
     # Define available image scales.
     return {"custom": (10, 10)}
@@ -96,12 +105,16 @@ def assert_download_works(self, base_url):
         self.assertIsNotNone(header)
         self.assertIn("attachment", header)
         self.assertIn("filename", header)
+        header = get_canonical_header(browser)
+        self.assertTrue(header.startswith(f"<{base_url}/@@download/{self.field_name}>"))
 
     def assert_display_inline_works(self, base_url):
         # Test that displaying this file inline works.
         browser = self.get_anon_browser()
         browser.open(base_url + f"/@@display-file/{self.field_name}")
         self.assertIsNone(get_disposition_header(browser))
+        header = get_canonical_header(browser)
+        self.assertTrue(header.startswith(f"<{base_url}/@@download/{self.field_name}>"))
 
     def assert_display_inline_is_download(self, base_url):
         # Test that displaying this file inline turns into a download.
@@ -111,6 +124,8 @@ def assert_display_inline_is_download(self, base_url):
         self.assertIsNotNone(header)
         self.assertIn("attachment", header)
         self.assertIn("filename", header)
+        header = get_canonical_header(browser)
+        self.assertTrue(header.startswith(f"<{base_url}/@@download/{self.field_name}>"))
 
     def assert_scale_view_works(self, base_url):
         # Test that accessing a scale view shows the image inline.

plone/namedfile/utils/__init__.py

@@ -130,7 +130,7 @@ def get_contenttype(file=None, filename=None, default="application/octet-stream"
     return default
 
 
-def set_headers(file, response, filename=None):
+def set_headers(file, response, filename=None, canonical=None):
     """Set response headers for the given file. If filename is given, set
     the Content-Disposition to attachment.
     """
@@ -149,6 +149,8 @@ def set_headers(file, response, filename=None):
             "Content-Disposition", f"attachment; filename*=UTF-8''{filename}"
         )
 
+    if canonical is not None:
+        response.setHeader("Link", f'<{canonical}>; rel="canonical"')
 
 def stream_data(file, start=0, end=None):
     """Return the given file as a stream if possible."""