Plug.Conn helpers. Requires the optional :plug dependency.
These are not a pipeline plug. They read and write headers only; they do
not send 304, 412, or 400. Load the resource, mint a tag with
HttpEtag.new!/1 (for example user.lock_version), then call if_match/2
or if_none_match/2. Repeated If-Match / If-None-Match field lines are
combined with ", " (RFC 9110 §5.3).
if_match/2 and if_none_match/2 return the same RFC tuples as
HttpEtag. This is not Plug.Static: that plug compares If-None-Match as
raw field-line membership.
Examples
etag = HttpEtag.new!(user.lock_version)
case HttpEtag.Conn.if_none_match(conn, etag) do
:ok ->
conn |> HttpEtag.Conn.put_etag(etag) |> json(user)
{:error, %{reason: :precondition_failed}} ->
conn
|> HttpEtag.Conn.put_etag(etag)
|> Plug.Conn.send_resp(304, "")
{:error, %{reason: :invalid_header}} ->
Plug.Conn.send_resp(conn, 400, "")
endSummary
Functions
Returns the combined If-Match request field, or nil if it is absent.
Returns the combined If-None-Match request field, or nil if it is absent.
Evaluates If-Match on conn against current.
Evaluates If-None-Match on conn against current.
Sets the ETag response header from a parsed tag.
Functions
@spec get_if_match(Plug.Conn.t()) :: String.t() | nil
Returns the combined If-Match request field, or nil if it is absent.
Repeated field lines are joined with ", " (RFC 9110 §5.3).
@spec get_if_none_match(Plug.Conn.t()) :: String.t() | nil
Returns the combined If-None-Match request field, or nil if it is absent.
Repeated field lines are joined with ", " (RFC 9110 §5.3).
@spec if_match(Plug.Conn.t(), HttpEtag.t() | nil) :: :ok | {:error, HttpEtag.Error.t()}
Evaluates If-Match on conn against current.
See HttpEtag.if_match/2.
@spec if_none_match(Plug.Conn.t(), HttpEtag.t() | nil) :: :ok | {:error, HttpEtag.Error.t()}
Evaluates If-None-Match on conn against current.
@spec put_etag(Plug.Conn.t(), HttpEtag.t()) :: Plug.Conn.t()
Sets the ETag response header from a parsed tag.