[PATCH 3/2] lei: auto-refresh watches in config, cancel missing

[Eric Wong <e@80x24.org>]

This makes behavior less surprising on restarts as we no longer
lose state on restarts, so there's no need to manually run "lei
add-watch" to re-enable watches.  This also allows us to
transparently handle changes if somebody edits the lei config
file directly or via git-config(1).
---
 lib/PublicInbox/DirIdle.pm      |  5 +++-
 lib/PublicInbox/LEI.pm          | 50 +++++++++++++++++++++++++--------
 lib/PublicInbox/LeiNoteEvent.pm |  2 +-
 t/lei-watch.t                   | 39 +++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 13 deletions(-)

diff --git a/lib/PublicInbox/DirIdle.pm b/lib/PublicInbox/DirIdle.pm
index 7031e5fd..65896f95 100644
--- a/lib/PublicInbox/DirIdle.pm
+++ b/lib/PublicInbox/DirIdle.pm
@@ -56,10 +56,13 @@ sub new {
 sub add_watches {
 	my ($self, $dirs, $gone) = @_;
 	my $fl = $MAIL_IN | ($gone ? $MAIL_GONE : 0);
+	my @ret;
 	for my $d (@$dirs) {
-		$self->{inot}->watch($d, $fl);
+		my $w = $self->{inot}->watch($d, $fl) or next;
+		push @ret, $w;
 	}
 	PublicInbox::FakeInotify::poll_once($self) if !$ino_cls;
+	@ret
 }
 
 sub rm_watches {
diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index b92d7512..52c551cf 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -36,7 +36,7 @@ my $GLP_PASS = Getopt::Long::Parser->new;
 $GLP_PASS->configure(qw(gnu_getopt no_ignore_case auto_abbrev pass_through));
 
 our %PATH2CFG; # persistent for socket daemon
-our $MDIR2CFGPATH; # /path/to/maildir => { /path/to/config => undef }
+our $MDIR2CFGPATH; # /path/to/maildir => { /path/to/config => [ ino watches ] }
 
 # TBD: this is a documentation mechanism to show a subcommand
 # (may) pass options through to another command:
@@ -820,6 +820,8 @@ sub _lei_cfg ($;$) {
 		}
 	}
 	$self->{cfg} = $PATH2CFG{$f} = $cfg;
+	refresh_watches($self);
+	$cfg;
 }
 
 sub _lei_store ($;$) {
@@ -1353,36 +1355,62 @@ sub watch_state_ok ($) {
 	$state =~ /\Apause|(?:import|index|tag)-(?:ro|rw)\z/;
 }
 
+sub cancel_maildir_watch ($$) {
+	my ($d, $cfg_f) = @_;
+	my $w = delete $MDIR2CFGPATH->{$d}->{$cfg_f};
+	scalar(keys %{$MDIR2CFGPATH->{$d}}) or
+		delete $MDIR2CFGPATH->{$d};
+	for my $x (@{$w // []}) { $x->cancel }
+}
+
 sub refresh_watches {
 	my ($lei) = @_;
 	my $cfg = _lei_cfg($lei) or return;
-	$cfg->{-env} //= { %{$lei->{env}}, PWD => '/' }; # for cfg2lei
+	my $old = $cfg->{-watches};
 	my $watches = $cfg->{-watches} //= {};
-	require PublicInbox::LeiWatch;
+	my %seen;
+	my $cfg_f = $cfg->{'-f'};
 	for my $w (grep(/\Awatch\..+\.state\z/, keys %$cfg)) {
 		my $url = substr($w, length('watch.'), -length('.state'));
-		my $lw = $watches->{$w} //= PublicInbox::LeiWatch->new($url);
+		require PublicInbox::LeiWatch;
+		my $lw = $watches->{$url} //= PublicInbox::LeiWatch->new($url);
+		$seen{$url} = undef;
 		my $state = $cfg->get_1("watch.$url", 'state');
 		if (!watch_state_ok($state)) {
 			$lei->err("watch.$url.state=$state not supported");
 			next;
 		}
-		my $f = $cfg->{'-f'};
 		if ($url =~ /\Amaildir:(.+)/i) {
 			my $d = File::Spec->canonpath($1);
 			if ($state eq 'pause') {
-				delete $MDIR2CFGPATH->{$d}->{$f};
-				scalar(keys %{$MDIR2CFGPATH->{$d}}) or
-					delete $MDIR2CFGPATH->{$d};
-			} elsif (!exists($MDIR2CFGPATH->{$d}->{$f})) {
-				$dir_idle->add_watches(["$d/cur", "$d/new"], 1);
-				$MDIR2CFGPATH->{$d}->{$f} = undef;
+				cancel_maildir_watch($d, $cfg_f);
+			} elsif (!exists($MDIR2CFGPATH->{$d}->{$cfg_f})) {
+				my @w = $dir_idle->add_watches(
+						["$d/cur", "$d/new"], 1);
+				push @{$MDIR2CFGPATH->{$d}->{$cfg_f}}, @w if @w;
 			}
 		} else { # TODO: imap/nntp/jmap
 			$lei->child_error(1,
 				"E: watch $url not supported, yet");
 		}
 	}
+	if ($old) { # cull old non-existent entries
+		for my $url (keys %$old) {
+			next if exists $seen{$url};
+			delete $old->{$url};
+			if ($url =~ /\Amaildir:(.+)/i) {
+				my $d = File::Spec->canonpath($1);
+				cancel_maildir_watch($d, $cfg_f);
+			} else { # TODO: imap/nntp/jmap
+				$lei->child_error(1, "E: watch $url TODO");
+			}
+		}
+	}
+	if (scalar keys %$watches) {
+		$cfg->{-env} //= { %{$lei->{env}}, PWD => '/' }; # for cfg2lei
+	} else {
+		delete $cfg->{-watches};
+	}
 }
 
 1;
diff --git a/lib/PublicInbox/LeiNoteEvent.pm b/lib/PublicInbox/LeiNoteEvent.pm
index bf15cd26..d6511cf6 100644
--- a/lib/PublicInbox/LeiNoteEvent.pm
+++ b/lib/PublicInbox/LeiNoteEvent.pm
@@ -14,7 +14,7 @@ sub flush_lei ($) {
 	my ($lei) = @_;
 	if (my $lne = delete $lei->{cfg}->{-lei_note_event}) {
 		$lne->wq_close(1, undef, $lei); # runs _lei_wq_eof;
-	} else { # lms_clear_src calls only:
+	} elsif ($lei->{sto}) { # lms_clear_src calls only:
 		my $wait = $lei->{sto}->ipc_do('done');
 	}
 }
diff --git a/t/lei-watch.t b/t/lei-watch.t
index 3a2f9e64..492f6c1d 100644
--- a/t/lei-watch.t
+++ b/t/lei-watch.t
@@ -13,9 +13,27 @@ $have_fast_inotify or
 my ($ro_home, $cfg_path) = setup_public_inboxes;
 test_lei(sub {
 	my $md = "$ENV{HOME}/md";
+	my $cfg_f = "$ENV{HOME}/.config/lei/config";
 	my $md2 = $md.'2';
 	lei_ok 'ls-watch';
 	is($lei_out, '', 'nothing in ls-watch, yet');
+
+	my ($ino_fdinfo, $ino_contents);
+	SKIP: {
+		$have_fast_inotify && $^O eq 'linux' or
+			skip 'Linux/inotify-only internals check', 1;
+		lei_ok 'daemon-pid'; chomp(my $pid = $lei_out);
+		skip 'missing /proc/$PID/fd', 1 if !-d "/proc/$pid/fd";
+		my @ino = grep {
+			readlink($_) =~ /\binotify\b/
+		} glob("/proc/$pid/fd/*");
+		is(scalar(@ino), 1, 'only one inotify FD');
+		my $ino_fd = (split('/', $ino[0]))[-1];
+		$ino_fdinfo = "/proc/$pid/fdinfo/$ino_fd";
+		open my $fh, '<', $ino_fdinfo or xbail "open $ino_fdinfo: $!";
+		$ino_contents = [ <$fh> ];
+	}
+
 	if (0) { # TODO
 		my $url = 'imaps://example.com/foo.bar.0';
 		lei_ok([qw(add-watch --state=pause), $url], undef, {});
@@ -44,6 +62,27 @@ test_lei(sub {
 	my $e2 = eml_load($f2[0]);
 	my $e1 = eml_load("$f[0]S");
 	is_deeply($e2, $e1, 'results match');
+
+	SKIP: {
+		$ino_fdinfo or skip 'Linux/inotify-only watch check', 1;
+		open my $fh, '<', $ino_fdinfo or xbail "open $ino_fdinfo: $!";
+		my $cmp = [ <$fh> ];
+		ok(scalar(@$cmp) > scalar(@$ino_contents),
+			'inotify has Maildir watches');
+	}
+
+	is(xsys(qw(git config -f), $cfg_f,
+			'--remove-section', "watch.maildir:$md"),
+		0, 'unset config state');
+	lei_ok 'ls-watch', \'refresh watches';
+	is($lei_out, '', 'no watches left');
+
+	SKIP: {
+		$ino_fdinfo or skip 'Linux/inotify-only removal removal', 1;
+		open my $fh, '<', $ino_fdinfo or xbail "open $ino_fdinfo: $!";
+		my $cmp = [ <$fh> ];
+		is_deeply($cmp, $ino_contents, 'inotify Maildir watches gone');
+	};
 });
 
 done_testing;