vis-lua: introduce pre-save hook

The first argument is the file object while the second argument denotes
the full path to which it will be written. Path might be `nil` if the
file is going to be written to stdout.

The Lua function is expected to return a boolean value indicating whether
the write operation should proceed or be aborted.

1 files changed, 5 insertions, 0 deletions

diff --git a/sam.c b/sam.c
index 4bd10d5..1b30258 100644
--- a/sam.c
+++ b/sam.c
@@ -1295,6 +1295,11 @@ static bool cmd_write(Vis *vis, Win *win, Command *cmd, const char *argv[], Curs
 			return false;
 		}
 
+		if (!vis_event_emit(vis, VIS_EVENT_FILE_SAVE_PRE, file, *name) && cmd->flags != '!') {
+			vis_info_show(vis, "Rejected write to `%s' by pre-save hook", *name);
+			return false;
+		}
+
 		TextSave *ctx = text_save_begin(text, *name);
 		if (!ctx) {
 			vis_info_show(vis, "Can't write `%s': %s", *name, strerror(errno));