use UID EXPUNGE also when trashing remotely

amends 2f0fbcd3.

src/driver.h

@@ -97,6 +97,9 @@ BIT_ENUM(
 	OPEN_APPEND,
 	OPEN_SETFLAGS,
 	OPEN_EXPUNGE,
+	// Expunge only deleted messages we know about. Relies on OPEN_{OLD,NEW,FLAGS}
+	// being set externally. The driver may unset it if it can't handle it.
+	OPEN_UID_EXPUNGE,
 )
 
 #define UIDVAL_BAD ((uint)-1)

src/drv_imap.c

@@ -2812,6 +2812,8 @@ imap_prepare_load_box( store_t *gctx, uint opts )
 {
 	imap_store_t *ctx = (imap_store_t *)gctx;
 
+	if (!CAP(UIDPLUS))
+		opts &= ~OPEN_UID_EXPUNGE;
 	ctx->opts = opts;
 	return opts;
 }
@@ -3129,7 +3131,7 @@ imap_close_box( store_t *gctx,
 
 	assert( !ctx->num_wait_check );
 
-	if (ctx->conf->trash && CAP(UIDPLUS)) {
+	if (ctx->opts & OPEN_UID_EXPUNGE) {
 		INIT_REFCOUNTED_STATE(imap_expunge_state_t, sts, cb, aux)
 		imap_message_t *msg, *fmsg, *nmsg;
 		int bl;

src/drv_maildir.c

@@ -1406,7 +1406,7 @@ maildir_prepare_load_box( store_t *gctx, uint opts )
 	if (opts & OPEN_SETFLAGS)
 		opts |= OPEN_PAIRED;
 	if (opts & OPEN_EXPUNGE)
-		opts |= OPEN_PAIRED | OPEN_OLD | OPEN_NEW | OPEN_FLAGS;
+		opts |= OPEN_PAIRED | OPEN_OLD | OPEN_NEW | OPEN_FLAGS | OPEN_UID_EXPUNGE;
 	ctx->opts = opts;
 	return opts;
 }

src/sync.c

@@ -793,9 +793,9 @@ box_opened2( sync_vars_t *svars, int t )
 			if (chan->stores[t]->trash) {
 				if (!chan->stores[t]->trash_only_new)
 					opts[t] |= OPEN_OLD;
-				opts[t] |= OPEN_NEW|OPEN_FLAGS;
+				opts[t] |= OPEN_NEW | OPEN_FLAGS | OPEN_UID_EXPUNGE;
 			} else if (chan->stores[t^1]->trash && chan->stores[t^1]->trash_remote_new) {
-				opts[t] |= OPEN_NEW|OPEN_FLAGS;
+				opts[t] |= OPEN_NEW | OPEN_FLAGS | OPEN_UID_EXPUNGE;
 			}
 		}
 	}