From 6bfdddd0b53ac4c3d1583bcfbff99cd0d2b91cb1 Mon Sep 17 00:00:00 2001
From: Martin Stein <martin.stein@genode-labs.com>
Date: Thu, 25 Mar 2021 15:15:45 +0100
Subject: [PATCH] fs_query: gracefully deal with missing directories

The fs_query component used to exit with an uncaught exception if a queried
directory didn't exist. Now, fs_query will catch this event and simply skip the
affected query, thereby indicating to the user the inexistence of the
queried directory.

Ref #4032
---
 repos/gems/run/fs_query.run         | 15 +++++++++++++++
 repos/gems/src/app/fs_query/main.cc |  7 ++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/repos/gems/run/fs_query.run b/repos/gems/run/fs_query.run
index 791e3cbc48..c928de15e3 100644
--- a/repos/gems/run/fs_query.run
+++ b/repos/gems/run/fs_query.run
@@ -81,7 +81,9 @@ install_config {
 			<resource name="RAM" quantum="2M"/>
 			<config>
 				<vfs> <dir name="fs"> <fs writeable="yes"/> </dir> </vfs>
+				<query path="/fs/items/non_existent_1"/>
 				<query path="/fs/items" content="yes"/>
+				<query path="/fs/non_existent_2" content="yes"/>
 			</config>
 		</start>
 
@@ -154,6 +156,19 @@ install_config {
 					</config>
 				</start>
 
+				<start name="/bin/bash" caps="500">
+					<config>
+						<libc stdin="/dev/null" stdout="/dev/log" stderr="/dev/log" rtc="/dev/null"/>
+						<vfs>
+							<dir name="fs"> <fs writeable="yes"/> </dir>
+							<dir name="dev"> <log/> <null/> </dir>
+						</vfs>
+						<arg value="/bin/bash"/>
+						<arg value="-c"/>
+						<arg value="echo updated > /fs/items/3"/>
+					</config>
+				</start>
+
 				<start name="/bin/sleep" caps="500">
 					<config>
 						<libc stdin="/dev/null" stdout="/dev/log" stderr="/dev/log"/>
diff --git a/repos/gems/src/app/fs_query/main.cc b/repos/gems/src/app/fs_query/main.cc
index a1a4592668..492933de4e 100644
--- a/repos/gems/src/app/fs_query/main.cc
+++ b/repos/gems/src/app/fs_query/main.cc
@@ -234,7 +234,12 @@ struct Fs_query::Main : Vfs::Watch_response_handler
 
 		config.for_each_sub_node("query", [&] (Xml_node query) {
 			Directory::Path const path = query.attribute_value("path", Directory::Path());
-			new (_heap) Registered<Watched_directory>(_dirs, _heap, _root_dir, path, *this);
+			try {
+				new (_heap)
+					Registered<Watched_directory>(
+						_dirs, _heap, _root_dir, path, *this);
+			}
+			catch (Genode::Directory::Nonexistent_directory) { }
 		});
 
 		_reporter.generate([&] (Xml_generator &xml) {