[tarantool-patches] [PATCH 2/6] 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.

We keep the eos values in table because we will need to
fetch eos from active format in later patches, thus it
is easier to use dictionary here. Moreover in future
we might need to extend this eos table for other
serializers.

Part-of #3834
---
 src/box/lua/console.lua | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/box/lua/console.lua b/src/box/lua/console.lua
index 22bafab3a..5430e6787 100644
--- a/src/box/lua/console.lua
+++ b/src/box/lua/console.lua
@@ -11,7 +11,6 @@ local urilib = require('uri')
 local yaml = require('yaml')
 local net_box = require('net.box')
 
-local YAML_TERM = '\n...\n'
 local PUSH_TAG_HANDLE = '!push!'
 
 --
@@ -20,6 +19,11 @@ local PUSH_TAG_HANDLE = '!push!'
 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"] = '\n...\n', ["lua"] = ';' }
+
 output_handlers["yaml"] = function(status, opts, ...)
     local err
     if status then
@@ -42,9 +46,11 @@ 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 in case if they are
     -- not inside tables and serpent won't handle
@@ -54,7 +60,7 @@ output_handlers["lua"] = function(status, opts, ...)
     }
     for k,v in pairs(map_direct_symbols) do
         if k == ... then
-            return v
+            return v .. output_eos["lua"]
         end
     end
     --
@@ -75,9 +81,9 @@ 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)
@@ -309,7 +315,7 @@ local text_connection_mt = {
         -- @retval     nil Error.
         --
         read = function(self)
-            local ret = self._socket:read(YAML_TERM)
+            local ret = self._socket:read(output_eos["yaml"])
             if ret and ret ~= '' then
                 return ret
             end
-- 
2.20.1