[PATCH 6/6] lib: choose oldest message when breaking reference loops

[Tomi Ollila]

On Fri, Apr 20 2018, David Bremner wrote:

> This preserves a sensible thread order
> ---
>  lib/thread.cc    | 33 ++++++++++++++++++++++++---------
>  test/T050-new.sh |  1 -
>  2 files changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/lib/thread.cc b/lib/thread.cc
> index dbac002f..a6dc4e5a 100644
> --- a/lib/thread.cc
> +++ b/lib/thread.cc
> @@ -390,20 +390,18 @@ _thread_add_matched_message (notmuch_thread_t *thread,
>  static void
>  _resolve_thread_relationships (notmuch_thread_t *thread)
>  {
> -    notmuch_message_node_t *node;
> +    notmuch_message_node_t *node, *first_node;
>      notmuch_message_t *message, *parent;
>      const char *in_reply_to;
>  
> -    for (node = thread->message_list->head; node; node = node->next) {
> +    first_node = thread->message_list->head;
> +    if (!first_node)

Our style *dictates* space after '!'.

> +	return;
> +
> +    for (node = first_node->next; node; node = node->next) {
>  	message = node->message;
>  	in_reply_to = _notmuch_message_get_in_reply_to (message);
> -	/*
> -	 * if we reach the end of the list without finding a top-level
> -	 * message, that means the thread is a cycle (or set of
> -	 * cycles) and any message can be considered top-level
> -	 */
> -	if ((thread->toplevel_list->head || node->next) &&
> -	     in_reply_to && strlen (in_reply_to) &&
> +	if (in_reply_to && strlen (in_reply_to) &&
>  	    g_hash_table_lookup_extended (thread->message_hash,
>  					  in_reply_to, NULL,
>  					  (void **) &parent))
> @@ -412,6 +410,23 @@ _resolve_thread_relationships (notmuch_thread_t *thread)
>  	    _notmuch_message_list_add_message (thread->toplevel_list, message);
>      }
>  
> +    /*
> +     * if we reach the end of the list without finding a top-level
> +     * message, that means the thread is a cycle (or set of cycles)
> +     * and any message can be considered top-level.  Choose the oldest
> +     * message, which happens to be first in our list.
> +     */
> +    message=first_node->message;
> +    in_reply_to = _notmuch_message_get_in_reply_to (message);
> +    if (thread->toplevel_list->head &&
> +	in_reply_to && strlen (in_reply_to) &&

Otherwise the series _looks_ good do me. The thing that disturbs me are
these `strlen (in_reply_to)` contents. Perhaps SomeOne(TM) changes these
to e.g. in_reply_to[0] in the future...

Tomi


> +	g_hash_table_lookup_extended (thread->message_hash,
> +				      in_reply_to, NULL,
> +				      (void **) &parent))
> +	_notmuch_message_add_reply (parent, message);
> +    else
> +	_notmuch_message_list_add_message (thread->toplevel_list, message);
> +
>      /* XXX: After scanning through the entire list looking for parents
>       * via "In-Reply-To", we should do a second pass that looks at the
>       * list of messages IDs in the "References" header instead. (And
> diff --git a/test/T050-new.sh b/test/T050-new.sh
> index 320a7646..9025fa7a 100755
> --- a/test/T050-new.sh
> +++ b/test/T050-new.sh
> @@ -359,7 +359,6 @@ test_begin_subtest "reference loop does not crash"
>  test_expect_code 0 "notmuch show --format=json id:mid-loop-12 at example.org id:mid-loop-21 at example.org > OUTPUT"
>  
>  test_begin_subtest "reference loop ordered by date"
> -test_subtest_known_broken
>  threadid=$(notmuch search --output=threads  id:mid-loop-12 at example.org)
>  notmuch show --format=mbox $threadid | grep '^Date'  > OUTPUT
>  cat <<EOF > EXPECTED
> -- 
> 2.17.0
>
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