json: Fix search result with no matches to be a valid json object.

In the original json code, search matching nothing would return a
valid, empty json array (that is, "[]"). I broke this in commit
6dcb7592e32ed5140ea0c0357ce78d6a37af6066 when adding support for
--output=threads|messages|tags. This time, while fixing the bug also
add a test to the test suite to help avoid future regressions.

1 files changed, 4 insertions, 0 deletions

diff --git a/test/json b/test/json
index 7fe2a27..307cd1e 100755
--- a/test/json
+++ b/test/json
@@ -39,4 +39,8 @@ test_expect_equal "$output" "[{\"thread\": \"XXX\",
 \"subject\": \"json-search-utf8-body-sübjéct\",
 \"tags\": [\"inbox\", \"unread\"]}]"
 
+test_begin_subtest "Search returning no messages"
+output=$(notmuch search --format=json "this string had better not match any messages" | notmuch_search_sanitize)
+test_expect_equal "$output" "[]"
+
 test_done