gdb/testsuite/dap: make dap_wait_for_event_and_check return preceding messages

In the following patch, I change gdb.dap/basic-dap.exp such that after
waiting for some event, it checks if it received another event
meanwhile.  To help with this, make dap_wait_for_event_and_check and
_dap_dap_wait_for_event return a list with everything received before
the event of interest.  This is similar to what
dap_check_request_and_response returns.

Change-Id: I85c8980203a2dec833937e7552c2196bc137935d

1 files changed, 22 insertions, 6 deletions

diff --git a/gdb/testsuite/lib/dap-support.exp b/gdb/testsuite/lib/dap-support.exp
index 179f675..527e7db 100644
--- a/gdb/testsuite/lib/dap-support.exp
+++ b/gdb/testsuite/lib/dap-support.exp
@@ -282,17 +282,27 @@ proc dap_match_values {name d args} {
     pass $name
 }
 
-# A helper for dap_read_event that reads events, looking for one
+# A helper for dap_wait_for_event_and_check that reads events, looking for one
 # matching TYPE.
-proc _dap_wait_for_event {type} {
+#
+# Return a list of two items:
+#
+#  - the matched event
+#  - a list of any JSON objects (events or others) seen before the matched
+#    event.
+proc _dap_wait_for_event { {type ""} } {
+    set preceding [list]
+
     while 1 {
 	# We don't do any extra error checking here for the time
 	# being; we'll just get a timeout thrown instead.
 	set d [_dap_read_json]
 	if {[dict get $d type] == "event"
-	    && [dict get $d event] == $type} {
-	    return $d
+	    && ($type == "" || [dict get $d event] == $type)} {
+	    return [list $d $preceding]
 	}
+
+	lappend preceding $d
     }
 }
 
@@ -302,14 +312,20 @@ proc _dap_wait_for_event {type} {
 # are used to check fields of the event; the arguments alternate
 # between a field name (in "dict get" form) and its expected value.
 #
-# Returns the dict for the chosen event, or empty string on error.
+# Return a list of two items:
+#
+#  - the matched event (regardless of whether it passed the field validation or
+#    not)
+#  - a list of any JSON objects (events or others) seen before the matched
+#    event.
 proc dap_wait_for_event_and_check {name type args} {
     if {$name == ""} {
 	set name $type
     }
 
     set result [_dap_wait_for_event $type]
-    eval dap_match_values [list $name $result] $args
+    set event [lindex $result 0]
+    eval dap_match_values [list $name $event] $args
 
     return $result
 }