qmp-test: Cover syntax and lexical errors

qmp-test neglects to cover QMP input that isn't valid JSON.  libqtest
doesn't let us send such input.  Add qtest_qmp_send_raw() for this
purpose, and put it to use in qmp-test.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180823164025.12553-7-armbru@redhat.com>
[Commit message typo fixed]

tests/libqtest.c

@@ -604,6 +604,23 @@ void qtest_qmp_send(QTestState *s, const char *fmt, ...)
     va_end(ap);
 }
 
+void qtest_qmp_send_raw(QTestState *s, const char *fmt, ...)
+{
+    bool log = getenv("QTEST_LOG") != NULL;
+    va_list ap;
+    char *str;
+
+    va_start(ap, fmt);
+    str = g_strdup_vprintf(fmt, ap);
+    va_end(ap);
+
+    if (log) {
+        fprintf(stderr, "%s", str);
+    }
+    socket_send(s->qmp_fd, str, strlen(str));
+    g_free(str);
+}
+
 QDict *qtest_qmp_eventwait_ref(QTestState *s, const char *event)
 {
     QDict *response;

tests/libqtest.h

@@ -96,6 +96,17 @@ QDict *qtest_qmp(QTestState *s, const char *fmt, ...)
 void qtest_qmp_send(QTestState *s, const char *fmt, ...)
     GCC_FMT_ATTR(2, 3);
 
+/**
+ * qtest_qmp_send_raw:
+ * @s: #QTestState instance to operate on.
+ * @fmt...: text to send, formatted like sprintf()
+ *
+ * Sends text to the QMP monitor verbatim.  Need not be valid JSON;
+ * this is useful for negative tests.
+ */
+void qtest_qmp_send_raw(QTestState *s, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
+
 /**
  * qtest_qmpv:
  * @s: #QTestState instance to operate on.

tests/qmp-test.c

@@ -1,7 +1,7 @@
 /*
  * QMP protocol test cases
  *
- * Copyright (c) 2017 Red Hat Inc.
+ * Copyright (c) 2017-2018 Red Hat Inc.
  *
  * Authors:
  *  Markus Armbruster <armbru@redhat.com>
@@ -42,10 +42,49 @@ static void test_version(QObject *version)
     visit_free(v);
 }
 
+static bool recovered(QTestState *qts)
+{
+    QDict *resp;
+    bool ret;
+
+    resp = qtest_qmp(qts, "{ 'execute': 'no-such-cmd' }");
+    ret = !strcmp(get_error_class(resp), "CommandNotFound");
+    qobject_unref(resp);
+    return ret;
+}
+
 static void test_malformed(QTestState *qts)
 {
     QDict *resp;
 
+    /* syntax error */
+    qtest_qmp_send_raw(qts, "{]\n");
+    resp = qtest_qmp_receive(qts);
+    g_assert_cmpstr(get_error_class(resp), ==, "GenericError");
+    qobject_unref(resp);
+    g_assert(recovered(qts));
+
+    /* lexical error: impossible byte outside string */
+    qtest_qmp_send_raw(qts, "{\xFF");
+    resp = qtest_qmp_receive(qts);
+    g_assert_cmpstr(get_error_class(resp), ==, "GenericError");
+    qobject_unref(resp);
+    g_assert(recovered(qts));
+
+    /* lexical error: impossible byte in string */
+    qtest_qmp_send_raw(qts, "{'bad \xFF");
+    resp = qtest_qmp_receive(qts);
+    g_assert_cmpstr(get_error_class(resp), ==, "GenericError");
+    qobject_unref(resp);
+    g_assert(recovered(qts));
+
+    /* lexical error: interpolation */
+    qtest_qmp_send_raw(qts, "%%p\n");
+    resp = qtest_qmp_receive(qts);
+    g_assert_cmpstr(get_error_class(resp), ==, "GenericError");
+    qobject_unref(resp);
+    g_assert(recovered(qts));
+
     /* Not even a dictionary */
     resp = qtest_qmp(qts, "null");
     g_assert_cmpstr(get_error_class(resp), ==, "GenericError");