[PATCH v4 20/29] t/helper/fsmonitor-client: create IPC client to talk to FSMonitor Daemon

["Jeff Hostetler via GitGitGadget" <gitgitgadget@gmail.com>]

From: Jeff Hostetler <jeffhost@microsoft.com>

Create an IPC client to send query and flush commands to the daemon.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
---
 Makefile                         |   1 +
 t/helper/test-fsmonitor-client.c | 121 +++++++++++++++++++++++++++++++
 t/helper/test-tool.c             |   1 +
 t/helper/test-tool.h             |   1 +
 4 files changed, 124 insertions(+)
 create mode 100644 t/helper/test-fsmonitor-client.c

diff --git a/Makefile b/Makefile
index 8a26696c9ed..5ad0cef69f4 100644
--- a/Makefile
+++ b/Makefile
@@ -710,6 +710,7 @@ TEST_BUILTINS_OBJS += test-dump-split-index.o
 TEST_BUILTINS_OBJS += test-dump-untracked-cache.o
 TEST_BUILTINS_OBJS += test-example-decorate.o
 TEST_BUILTINS_OBJS += test-fast-rebase.o
+TEST_BUILTINS_OBJS += test-fsmonitor-client.o
 TEST_BUILTINS_OBJS += test-genrandom.o
 TEST_BUILTINS_OBJS += test-genzeros.o
 TEST_BUILTINS_OBJS += test-getcwd.o
diff --git a/t/helper/test-fsmonitor-client.c b/t/helper/test-fsmonitor-client.c
new file mode 100644
index 00000000000..f7a5b3a32fa
--- /dev/null
+++ b/t/helper/test-fsmonitor-client.c
@@ -0,0 +1,121 @@
+/*
+ * test-fsmonitor-client.c: client code to send commands/requests to
+ * a `git fsmonitor--daemon` daemon.
+ */
+
+#include "test-tool.h"
+#include "cache.h"
+#include "parse-options.h"
+#include "fsmonitor-ipc.h"
+
+#ifndef HAVE_FSMONITOR_DAEMON_BACKEND
+int cmd__fsmonitor_client(int argc, const char **argv)
+{
+	die("fsmonitor--daemon not available on this platform");
+}
+#else
+
+/*
+ * Read the `.git/index` to get the last token written to the
+ * FSMonitor Index Extension.
+ */
+static const char *get_token_from_index(void)
+{
+	struct index_state *istate = the_repository->index;
+
+	if (do_read_index(istate, the_repository->index_file, 0) < 0)
+		die("unable to read index file");
+	if (!istate->fsmonitor_last_update)
+		die("index file does not have fsmonitor extension");
+
+	return istate->fsmonitor_last_update;
+}
+
+/*
+ * Send an IPC query to a `git-fsmonitor--daemon` daemon and
+ * ask for the changes since the given token or from the last
+ * token in the index extension.
+ *
+ * This will implicitly start a daemon process if necessary.  The
+ * daemon process will persist after we exit.
+ */
+static int do_send_query(const char *token)
+{
+	struct strbuf answer = STRBUF_INIT;
+	int ret;
+
+	if (!token || !*token)
+		token = get_token_from_index();
+
+	ret = fsmonitor_ipc__send_query(token, &answer);
+	if (ret < 0)
+		die(_("could not query fsmonitor--daemon"));
+
+	write_in_full(1, answer.buf, answer.len);
+	strbuf_release(&answer);
+
+	return 0;
+}
+
+/*
+ * Send a "flush" command to the `git-fsmonitor--daemon` (if running)
+ * and tell it to flush its cache.
+ *
+ * This feature is primarily used by the test suite to simulate a loss of
+ * sync with the filesystem where we miss kernel events.
+ */
+static int do_send_flush(void)
+{
+	struct strbuf answer = STRBUF_INIT;
+	int ret;
+
+	ret = fsmonitor_ipc__send_command("flush", &answer);
+	if (ret)
+		return ret;
+
+	write_in_full(1, answer.buf, answer.len);
+	strbuf_release(&answer);
+
+	return 0;
+}
+
+int cmd__fsmonitor_client(int argc, const char **argv)
+{
+	const char *subcmd;
+	const char *token = NULL;
+
+	const char * const fsmonitor_client_usage[] = {
+		N_("test-helper fsmonitor-client query [<token>]"),
+		N_("test-helper fsmonitor-client flush"),
+		NULL,
+	};
+
+	struct option options[] = {
+		OPT_STRING(0, "token", &token, N_("token"),
+			   N_("command token to send to the server")),
+		OPT_END()
+	};
+
+	if (argc < 2)
+		usage_with_options(fsmonitor_client_usage, options);
+
+	if (argc == 2 && !strcmp(argv[1], "-h"))
+		usage_with_options(fsmonitor_client_usage, options);
+
+	subcmd = argv[1];
+	argv--;
+	argc++;
+
+	argc = parse_options(argc, argv, NULL, options, fsmonitor_client_usage, 0);
+
+	setup_git_directory();
+
+	if (!strcmp(subcmd, "query"))
+		return !!do_send_query(token);
+
+	if (!strcmp(subcmd, "flush"))
+		return !!do_send_flush();
+
+	die("Unhandled subcommand: '%s'", subcmd);
+}
+#endif
diff --git a/t/helper/test-tool.c b/t/helper/test-tool.c
index 3ce5585e53a..39119844693 100644
--- a/t/helper/test-tool.c
+++ b/t/helper/test-tool.c
@@ -31,6 +31,7 @@ static struct test_cmd cmds[] = {
 	{ "dump-untracked-cache", cmd__dump_untracked_cache },
 	{ "example-decorate", cmd__example_decorate },
 	{ "fast-rebase", cmd__fast_rebase },
+	{ "fsmonitor-client", cmd__fsmonitor_client },
 	{ "genrandom", cmd__genrandom },
 	{ "genzeros", cmd__genzeros },
 	{ "getcwd", cmd__getcwd },
diff --git a/t/helper/test-tool.h b/t/helper/test-tool.h
index 9f0f5228508..0f1074a32a6 100644
--- a/t/helper/test-tool.h
+++ b/t/helper/test-tool.h
@@ -21,6 +21,7 @@ int cmd__dump_split_index(int argc, const char **argv);
 int cmd__dump_untracked_cache(int argc, const char **argv);
 int cmd__example_decorate(int argc, const char **argv);
 int cmd__fast_rebase(int argc, const char **argv);
+int cmd__fsmonitor_client(int argc, const char **argv);
 int cmd__genrandom(int argc, const char **argv);
 int cmd__genzeros(int argc, const char **argv);
 int cmd__getcwd(int argc, const char **argv);
-- 
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