tests: add expect_protocol_error function

This function checks if a particular protocol error came in wire.
It's usefull in the cases where we hitherto used FAIL_TEST.
The problem with FAIL_TEST is that *any* assert will pass the test,
but we want only some asserts to pass the test (i. e. we don't
want the test to pass when it, for example, can't connect to display).
FAIL_TESTs are good only for sanity testing.

The expect_protocol_error allows us to turn all FAIL_TESTs to TESTs
as will be introduced in following patches.

v2: fixed white-space error and a mistake in comment

Reviewed-by: Bryce Harrington <b.harrington@samsung.com>
Reviewed-by: Pekka Paalanen <ppaalanen@gmail.com>

tests/weston-test-client-helper.c

@@ -26,6 +26,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#include <errno.h>
 #include <sys/mman.h>
 
 #include "../shared/os-compatibility.h"
@@ -512,6 +513,53 @@ skip(const char *fmt, ...)
 	exit(77);
 }
 
+void
+expect_protocol_error(struct client *client,
+		      const struct wl_interface *intf,
+		      uint32_t code)
+{
+	int err;
+	uint32_t errcode, failed = 0;
+	const struct wl_interface *interface;
+	unsigned int id;
+
+	/* if the error has not come yet, make it happen */
+	wl_display_roundtrip(client->wl_display);
+
+	err = wl_display_get_error(client->wl_display);
+
+	assert(err && "Expected protocol error but nothing came");
+	assert(err == EPROTO && "Expected protocol error but got local error");
+
+	errcode = wl_display_get_protocol_error(client->wl_display,
+						&interface, &id);
+
+	/* check error */
+	if (errcode != code) {
+		fprintf(stderr, "Should get error code %d but got %d\n",
+			code, errcode);
+		failed = 1;
+	}
+
+	/* this should be definitely set */
+	assert(interface);
+
+	if (strcmp(intf->name, interface->name) != 0) {
+		fprintf(stderr, "Should get interface '%s' but got '%s'\n",
+			intf->name, interface->name);
+		failed = 1;
+	}
+
+	if (failed) {
+		fprintf(stderr, "Expected other protocol error\n");
+		abort();
+	}
+
+	/* all OK */
+	fprintf(stderr, "Got expected protocol error on '%s' (object id: %d) "
+			"with code %d\n", interface->name, id, errcode);
+}
+
 static void
 log_handler(const char *fmt, va_list args)
 {

tests/weston-test-client-helper.h

@@ -129,4 +129,8 @@ get_n_egl_buffers(struct client *client);
 void
 skip(const char *fmt, ...);
 
+void
+expect_protocol_error(struct client *client,
+		      const struct wl_interface *intf, uint32_t code);
+
 #endif