[tarantool-patches] [PATCH 1/4] box/console: Add explicit output EOS mapping

[Cyrill Gorcunov <gorcunov@gmail.com>]

This will help us to distinguish end of string/stream
in text protocols (such as remote console connection).

Note that we start printing ";" terminator for every
lua output. Actually current yaml output does the
same but inside console.c module.

And since lua output is yet a new feature in stabilization
phase we're safe to make such changes without breaking api.

Part-of #3834
---
 src/box/lua/console.lua | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/box/lua/console.lua b/src/box/lua/console.lua
index 64086cf5b..be277d610 100644
--- a/src/box/lua/console.lua
+++ b/src/box/lua/console.lua
@@ -11,6 +11,7 @@ local urilib = require('uri')
 local yaml = require('yaml')
 local net_box = require('net.box')
 
+local LUA_TERM = ';'
 local YAML_TERM = '\n...\n'
 local PUSH_TAG_HANDLE = '!push!'
 
@@ -19,6 +20,10 @@ local PUSH_TAG_HANDLE = '!push!'
 -- compatibility reason.
 local default_output_format = { ["fmt"] = "yaml", ["opts"] = nil }
 local output_handlers = { }
+--
+-- End of streams/strings. They will allow to recognize blocks
+-- depending on output format.
+local output_eos = { ["yaml"] = YAML_TERM, ["lua"] = LUA_TERM }
 
 output_handlers["yaml"] = function(status, opts, ...)
     local err
@@ -42,9 +47,11 @@ end
 
 output_handlers["lua"] = function(status, opts, ...)
     --
-    -- Don't print nil if there is no data
+    -- If no data present at least EOS should be put,
+    -- otherwise wire readers won't be able to find
+    -- where end of string is.
     if not ... then
-        return ""
+        return output_eos["lua"]
     end
     --
     -- Map internal symbols which serpent doesn't know
@@ -64,9 +71,9 @@ output_handlers["lua"] = function(status, opts, ...)
         nocode = true,
     }
     if opts == "block" then
-        return serpent.block(..., serpent_opts)
+        return serpent.block(..., serpent_opts) .. output_eos["lua"]
     end
-    return serpent.line(..., serpent_opts)
+    return serpent.line(..., serpent_opts) .. output_eos["lua"]
 end
 
 local function output_verify_opts(fmt, opts)
-- 
2.20.1