Address review comments and small updates for DNS warnings

This commit addresses review feedback for DH-4155. Furthermore it fixes
test failures, and adds a new test for the is_event_handled bif.

src/analyzer/protocol/dns/events.bif

@@ -498,7 +498,7 @@ event dns_unknown_reply%(c: connection, msg: dns_msg, ans: dns_answer%);
 ##
 ## .. note::
 ##
-##      Note that this event will only be raised if ``dns_skip_all_addl``
+##      Note that this event will only be raised if :zeek:see:`dns_skip_all_addl`
 ##      is set to false.
 ##
 ## .. zeek:see:: dns_AAAA_reply dns_A_reply dns_CNAME_reply dns_HINFO_reply dns_MX_reply
@@ -526,7 +526,7 @@ event dns_EDNS_addl%(c: connection, msg: dns_msg, ans: dns_edns_additional%);
 ##
 ## .. note::
 ##
-##      Note that this event will only be raised if ``dns_skip_all_addl``
+##      Note that this event will only be raised if :zeek:see:`dns_skip_all_addl`
 ##      is set to false.
 ##
 ## .. zeek:see:: dns_AAAA_reply dns_A_reply dns_CNAME_reply dns_HINFO_reply dns_MX_reply
@@ -556,7 +556,7 @@ event dns_EDNS_ecs%(c: connection, msg: dns_msg, opt: dns_edns_ecs%);
 ##
 ## .. note::
 ##
-##      Note that this event will only be raised if ``dns_skip_all_addl``
+##      Note that this event will only be raised if :zeek:see:`dns_skip_all_addl`
 ##      is set to false.
 ##
 ## .. zeek:see:: dns_AAAA_reply dns_A_reply dns_CNAME_reply dns_HINFO_reply dns_MX_reply
@@ -586,7 +586,7 @@ event dns_EDNS_tcp_keepalive%(c: connection, msg: dns_msg, opt: dns_edns_tcp_kee
 ##
 ## .. note::
 ##
-##      Note that this event will only be raised if ``dns_skip_all_addl``
+##      Note that this event will only be raised if :zeek:see:`dns_skip_all_addl`
 ##      is set to false.
 ##
 ## .. zeek:see:: dns_AAAA_reply dns_A_reply dns_CNAME_reply dns_HINFO_reply dns_MX_reply
@@ -614,7 +614,7 @@ event dns_EDNS_cookie%(c: connection, msg: dns_msg, opt: dns_edns_cookie%);
 ##
 ## .. note::
 ##
-##      Note that ``ans`` will only be populated if ``dns_skip_all_addl``
+##      Note that ``ans`` will only be populated if :zeek:see:`dns_skip_all_addl`
 ##      is set to false.
 ##
 ## .. zeek:see:: dns_TSIG_addl
@@ -633,10 +633,10 @@ event dns_TKEY%(c: connection, msg: dns_msg, ans: dns_tkey%);
 ## msg: The parsed DNS message header.
 ##
 ## ans: The parsed TSIG reply.
-#
+##
 ## .. note::
 ##
-##      Note that this event will only be raised if ``dns_skip_all_addl``
+##      Note that this event will only be raised if :zeek:see:`dns_skip_all_addl`
 ##      is set to false.
 ##
 ## .. zeek:see:: dns_AAAA_reply dns_A_reply dns_CNAME_reply dns_EDNS_addl

src/zeek.bif

@@ -5019,13 +5019,21 @@ function generate_all_events%(%) : bool
 ## This currently is mainly used to warn when events are defined that will not be used
 ## in certain conditions.
 ##
+## Raises an error if the named event does not exist.
+##
 ## event_name: event name to check
 ##
 ## returns: true if the named event is handled.
 function is_event_handled%(event_name: string%) : bool
 	%{
 	auto *h = event_registry->Lookup(event_name->ToStdStringView());
-	if ( h && *h )
+	if ( ! h )
+		{
+		zeek::emit_builtin_error(zeek::util::fmt("is_event_handled: '%s' is not an event", event_name->CheckString()));
+		return zeek::val_mgr->False();
+		}
+
+	if ( *h )
 		return zeek::val_mgr->True();
 
 	return zeek::val_mgr->False();

testing/btest/Baseline/bifs.is_event_handled/err

@@ -0,0 +1,3 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+error in <...>/is_event_handled.zeek, line 11: is_event_handled: 'myfunc1' is not an event (is_event_handled(myfunc1))
+error in <...>/is_event_handled.zeek, line 12: is_event_handled: 'conn_id' is not an event (is_event_handled(conn_id))

testing/btest/Baseline/bifs.is_event_handled/out

@@ -0,0 +1,5 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+T
+F
+F
+F

testing/btest/Baseline/coverage.default-load-baseline/canonified_loaded_scripts.log

@@ -385,6 +385,7 @@ scripts/base/init-default.zeek
   scripts/base/protocols/dns/__load__.zeek
     scripts/base/protocols/dns/consts.zeek
     scripts/base/protocols/dns/main.zeek
+    scripts/base/protocols/dns/check-event-handlers.zeek
   scripts/base/protocols/finger/__load__.zeek
     scripts/base/protocols/finger/spicy-events.zeek
     scripts/base/protocols/finger/main.zeek

testing/btest/bifs/is_event_handled.zeek

@@ -0,0 +1,12 @@
+# @TEST-EXEC: zeek -b %INPUT >out 2>err
+# @TEST-EXEC: btest-diff out
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff err
+
+function myfunc1(a: addr, b: addr): int
+	{
+	}
+
+print is_event_handled("zeek_init"); # T
+print is_event_handled("dns_EDNS_cookie"); # F
+print is_event_handled("myfunc1"); # builtin error
+print is_event_handled("conn_id"); # builtin error