Enable debug log under an environment variable

Author: Totktonada

README.md

@@ -404,6 +404,14 @@ TEST_RUN_TESTS=common/mutation make test
 * For building apidoc (additionally to 'for use'):
   * ldoc.
 
+## Hacking
+
+Enable debug log:
+
+```sh
+export TARANTOOL_GRAPHQL_DEBUG=1
+```
+
 ## License
 
 Consider LICENSE file for details. In brief:

graphql/bfs_executor.lua

@@ -858,7 +858,6 @@ end
 
 -- Debugging {{{
 
---[[
 local function prepared_object_digest(prepared_object)
     local json = require('json')
     local digest = {
@@ -883,29 +882,30 @@ local function prepared_object_digest(prepared_object)
     return json.encode(digest)
 end
 
-local function print_open_set(open_set)
+local function open_set_tostring(open_set, name)
+    local res = ('\n==== %s ====\n'):format(name)
     for _, item in ipairs(open_set) do
         if item.prepared_object ~= nil then
             local digest = prepared_object_digest(item.prepared_object)
-            print('prepared_object: ' .. digest)
+            res = res .. '\nprepared_object: ' .. digest
         elseif item.prepared_object_list ~= nil then
-            print('prepared_object_list:')
+            res = res .. '\nprepared_object_list:'
             for _, prepared_object in ipairs(item.prepared_object_list) do
                 local digest = prepared_object_digest(prepared_object)
-                print('    ' .. digest)
+                res = res .. '\n    ' .. digest
             end
         elseif item.squash_marker ~= nil then
             if item.fetch_id ~= nil then
-                print('squash marker: ' .. tostring(item.fetch_id))
+                res = res .. '\nsquash marker: ' .. tostring(item.fetch_id)
             else
-                print('squash marker')
+                res = res .. '\nsquash marker'
             end
         else
-            print('unknown open_set item')
+            res = res .. '\nunknown open_set item'
         end
     end
+    return res
 end
-]]--
 
 -- }}}
 
@@ -980,14 +980,9 @@ function bfs_executor.execute(schema, query_ast, variables, operation_name, opts
     table.insert(open_set, 1, {squash_marker = true})
 
     while true do
-        --[[
-        print('')
-        print('==== cache only open set ====')
-        print_open_set(cache_only_open_set)
-        print('')
-        print('==== open set ====')
-        print_open_set(open_set)
-        ]]--
+        utils.debug(open_set_tostring, cache_only_open_set,
+            'cache only open set')
+        utils.debug(open_set_tostring, open_set, 'open set')
 
         local item
         local is_item_cache_only = next(cache_only_open_set) ~= nil
@@ -997,11 +992,7 @@ function bfs_executor.execute(schema, query_ast, variables, operation_name, opts
             item = table.remove(open_set, 1)
         end
 
-        --[[
-        print('')
-        print('==== item (before) ====')
-        print_open_set({item})
-        ]]--
+        utils.debug(open_set_tostring, {item}, 'item (before)')
 
         if item == nil then break end
         if item.prepared_object ~= nil then
@@ -1035,11 +1026,7 @@ function bfs_executor.execute(schema, query_ast, variables, operation_name, opts
             assert(false, 'unknown open_set item format')
         end
 
-        --[[
-        print('')
-        print('==== item (after) ====')
-        print_open_set({item})
-        ]]--
+        utils.debug(open_set_tostring, {item}, 'item (after)')
     end
 
     -- XXX: support several parallel graphql instances (use

graphql/utils.lua

@@ -286,4 +286,27 @@ function utils.expand_list(list, tail)
     end
 end
 
+--- Add a debug print to the log enabled by an environment variable.
+---
+--- @param data_or_func (string or function) data to print or a function that
+--- will be return the data to print; the function called only if the
+--- environment variable toogle is enabled
+---
+--- @param ... parameters of the function `data_or_func`
+---
+--- @return nothing
+function utils.debug(data_or_func, ...)
+    if (os.getenv('TARANTOOL_GRAPHQL_DEBUG') or ''):len() > 0 then
+        local data
+        if type(data_or_func) == 'function' then
+            data = data_or_func(...)
+        else
+            data = data_or_func
+            assert(select('#', ...) == 0)
+        end
+        assert(type(data) == 'string')
+        log.info('DEBUG: %s', data)
+    end
+end
+
 return utils