fix repeated listing of same Store with different flags

multiple Channels can call driver_t::list_store() with different LIST_*
flags. assuming the flags are actually taken into consideration, using a
single boolean 'listed' flag to track whether the Store still needs to
be listed obviously wouldn't cut it - if INBOX does not live right under
Path and the Channels used entirely disjoint Patterns (say, * and
INBOX*), the second Channel in a single run (probably a Group) would
fail to match anything.

to fix this, make store_t::listed more granular. this also requires
moving its handling back into the drivers (thus reverting c66afdc0),
because the actually performed queries and their possible implicit
results are driver-specific.

note that this slightly pessimizes some cases - e.g., an IMAP Store with
Path "" will now list the entire namespace even if there is only one
Channel with Pattern "INBOX*" (because a hypothetical Pattern "*" would
also include INBOX*, and the queries are kept disjoint to avoid the need
for de-duplication). this isn't expected to be a problem, as listing
mailboxes is generally cheap.

src/drv_imap.c

@@ -2759,23 +2759,35 @@ imap_list_store( store_t *gctx, int flags,
 	imap_cmd_refcounted_state_t *sts = imap_refcounted_new_state( cb, aux );
 
 	// ctx->prefix may be empty, "INBOX.", or something else.
-	// 'flags' may be LIST_INBOX, LIST_PATH (or LIST_PATH_MAYBE), or both.
-	// This matrix determines what to query, and what comes out as a side effect:
+	// 'flags' may be LIST_INBOX, LIST_PATH (or LIST_PATH_MAYBE), or both. 'listed'
+	// already containing a particular value effectively removes it from 'flags'.
+	// This matrix determines what to query, and what comes out as a side effect.
+	// The lowercase letters indicate unnecessary results; the queries are done
+	// this way to have non-overlapping result sets, so subsequent calls create
+	// no duplicates:
 	//
 	// qry \ pfx | empty | inbox | other
 	// ----------+-------+-------+-------
-	// inbox     | i     | i [p] | i
-	// both      | p [i] | i [p] | i + p
-	// path      | p [i] | p {i} | p
+	// inbox     | p [I] | I [p] | I
+	// both      | P [I] | I [P] | I + P
+	// path      | P [i] | i [P] | P
 	//
-	// {i} => This doesn't actually contain INBOX itself, only its subfolders.
-	//
-	if ((flags & (LIST_PATH | LIST_PATH_MAYBE)) && (!(flags & LIST_INBOX) || !is_inbox( ctx, ctx->prefix, -1 )))
+	int pfx_is_empty = !*ctx->prefix;
+	int pfx_is_inbox = !pfx_is_empty && is_inbox( ctx, ctx->prefix, -1 );
+	if (((flags & (LIST_PATH | LIST_PATH_MAYBE)) || pfx_is_empty) && !pfx_is_inbox && !(ctx->gen.listed & LIST_PATH)) {
+		ctx->gen.listed |= LIST_PATH;
+		if (pfx_is_empty)
+			ctx->gen.listed |= LIST_INBOX;
 		imap_exec( ctx, imap_refcounted_new_cmd( sts ), imap_refcounted_done_box,
 		           "LIST \"\" \"%\\s*\"", ctx->prefix );
-	if ((flags & LIST_INBOX) && (!(flags & (LIST_PATH | LIST_PATH_MAYBE)) || *ctx->prefix))
+	}
+	if (((flags & LIST_INBOX) || pfx_is_inbox) && !pfx_is_empty && !(ctx->gen.listed & LIST_INBOX)) {
+		ctx->gen.listed |= LIST_INBOX;
+		if (pfx_is_inbox)
+			ctx->gen.listed |= LIST_PATH;
 		imap_exec( ctx, imap_refcounted_new_cmd( sts ), imap_refcounted_done_box,
 		           "LIST \"\" INBOX*" );
+	}
 	imap_refcounted_done( sts );
 }
 

src/drv_maildir.c

@@ -300,7 +300,11 @@ maildir_list_maildirpp( store_t *gctx, int flags, const char *inbox )
 	int warned = 0;
 	struct stat st;
 
-	add_string_list( &gctx->boxes, "INBOX" );
+	if (gctx->listed & LIST_PATH)  // Implies LIST_INBOX
+		return 0;
+
+	if (!(gctx->listed & LIST_INBOX))
+		add_string_list( &gctx->boxes, "INBOX" );
 
 	char path[_POSIX_PATH_MAX];
 	int pathLen = nfsnprintf( path, _POSIX_PATH_MAX, "%s/", inbox );
@@ -317,6 +321,8 @@ maildir_list_maildirpp( store_t *gctx, int flags, const char *inbox )
 		char name[_POSIX_PATH_MAX];
 		char *effName = name;
 		if (*ent == '.') {
+			if (gctx->listed & LIST_INBOX)
+				continue;
 			if (!*++ent)
 				continue;
 			// The Maildir++ Inbox is technically not under Path (as there is none), so
@@ -346,6 +352,10 @@ maildir_list_maildirpp( store_t *gctx, int flags, const char *inbox )
 		}
 	}
 	closedir (dir);
+
+	if (flags & (LIST_PATH | LIST_PATH_MAYBE))
+		gctx->listed |= LIST_PATH;
+	gctx->listed |= LIST_INBOX;
 	return 0;
 }
 
@@ -384,14 +394,14 @@ maildir_list_recurse( store_t *gctx, int isBox, int flags,
 			continue;
 		pl += pathLen;
 		if (inbox && equals( path, pl, inbox, inboxLen )) {
-			/* Inbox nested into Path. List now if it won't be listed separately anyway. */
-			if (!(flags & LIST_INBOX) && maildir_list_inbox( gctx, flags, 0 ) < 0) {
+			// Inbox nested into Path.
+			if (maildir_list_inbox( gctx, flags, 0 ) < 0) {
 				closedir( dir );
 				return -1;
 			}
 		} else if (basePath && equals( path, pl, basePath, basePathLen )) {
-			/* Path nested into Inbox. List now if it won't be listed separately anyway. */
-			if (!(flags & (LIST_PATH | LIST_PATH_MAYBE)) && maildir_list_path( gctx, flags, 0 ) < 0) {
+			// Path nested into Inbox.
+			if (maildir_list_path( gctx, flags, 0 ) < 0) {
 				closedir( dir );
 				return -1;
 			}
@@ -433,6 +443,10 @@ maildir_list_inbox( store_t *gctx, int flags, const char *basePath )
 {
 	char path[_POSIX_PATH_MAX], name[_POSIX_PATH_MAX];
 
+	if (gctx->listed & LIST_INBOX)
+		return 0;
+	gctx->listed |= LIST_INBOX;
+
 	add_string_list( &gctx->boxes, "INBOX" );
 	return maildir_list_recurse(
 	        gctx, 1, flags, 0, 0, basePath, basePath ? strlen( basePath ) - 1 : 0,
@@ -445,6 +459,10 @@ maildir_list_path( store_t *gctx, int flags, const char *inbox )
 {
 	char path[_POSIX_PATH_MAX], name[_POSIX_PATH_MAX];
 
+	if (gctx->listed & LIST_PATH)
+		return 0;
+	gctx->listed |= LIST_PATH;
+
 	if (maildir_ensure_path( (maildir_store_conf_t *)gctx->conf ) < 0)
 		return -1;
 	return maildir_list_recurse(

src/main.c

@@ -945,7 +945,7 @@ store_connected( int sts, void *aux )
 	case DRV_CANCELED:
 		return;
 	case DRV_OK:
-		if (!mvars->skip && !mvars->chanptr->boxlist && mvars->chan->patterns && !mvars->ctx[t]->listed) {
+		if (!mvars->skip && !mvars->chanptr->boxlist && mvars->chan->patterns) {
 			for (cflags = 0, cpat = mvars->chan->patterns; cpat; cpat = cpat->next) {
 				const char *pat = cpat->string;
 				if (*pat != '!') {
@@ -1004,7 +1004,6 @@ store_listed( int sts, void *aux )
 	case DRV_CANCELED:
 		return;
 	case DRV_OK:
-		mvars->ctx[t]->listed = 1;
 		if (DFlags & DEBUG_MAIN) {
 			debug( "got mailbox list from %s:\n", str_ms[t] );
 			for (bx = mvars->ctx[t]->boxes; bx; bx = bx->next)