lei export-kw: skip read-only IMAP folders

Since we want to store IMAP flags asynchronously and not wait
for results, we can't check for IMAP errors this way and end up
wasting bandwidth on public-inbox-imapd.  Now, we just check
PERMANENTFLAGS up front to ensure a folder can handle IMAP flag
storage before proceeding.

2 files changed, 20 insertions, 1 deletions

diff --git a/lib/PublicInbox/LeiExportKw.pm b/lib/PublicInbox/LeiExportKw.pm
index 756d0e9c..0ecfb782 100644
--- a/lib/PublicInbox/LeiExportKw.pm
+++ b/lib/PublicInbox/LeiExportKw.pm
@@ -67,7 +67,17 @@ sub input_path_url {
                 $self->{lms}->each_src($input, \&export_kw_md, $self, $mdir);
         } elsif ($input =~ m!\Aimaps?://!i) {
                 my $uri = PublicInbox::URIimap->new($input);
-                if (my $mic = $self->{nwr}->mic_for_folder($uri)) {
+                my $mic = $self->{nwr}->mic_for_folder($uri);
+                if ($mic && !$self->{nwr}->can_store_flags($mic)) {
+                        my $m = "$input does not support PERMANENTFLAGS";
+                        if (defined $self->{lei}->{opt}->{all}) {
+                                $self->{lei}->qerr("# $m");
+                        } else { # set error code if user explicitly requested
+                                $self->{lei}->child_error(0, "E: $m");
+                        }
+                        return;
+                }
+                if ($mic) {
                         $self->{lms}->each_src($$uri, \&export_kw_imap,
                                                 $self, $mic);
                         $mic->expunge;
diff --git a/lib/PublicInbox/NetWriter.pm b/lib/PublicInbox/NetWriter.pm
index 629a752a..4a1f34f6 100644
--- a/lib/PublicInbox/NetWriter.pm
+++ b/lib/PublicInbox/NetWriter.pm
@@ -56,4 +56,13 @@ sub imap_set_kw {
         $mic; # caller must ->expunge
 }
 
+sub can_store_flags {
+        my ($self, $mic) = @_;
+        for ($mic->Results) {
+                /^\* OK \[PERMANENTFLAGS \(([^\)]*)\)\].*/ and
+                        return $self->can('perm_fl_ok')->($1);
+        }
+        undef;
+}
+
 1;