feat(pdk): add negative value to support unlimited body size

It is the cherry-pick of #9472.

KAG-4698

kong/pdk/request.lua

@@ -695,13 +695,14 @@ local function new(self)
   -- If the size of the body is greater than the Nginx buffer size (set by
   -- `client_body_buffer_size`), this function fails and returns an error
   -- message explaining this limitation, unless `max_allowed_file_size`
-  -- is set and larger than the body size buffered to disk.
+  -- is set and less than 0 or larger than the body size buffered to disk.
   -- Use of `max_allowed_file_size` requires Kong to read data from filesystem
   -- and has performance implications.
   --
   -- @function kong.request.get_raw_body
   -- @phases rewrite, access, response, admin_api
-  -- @max_allowed_file_size[opt] number the max allowed file size to be read from
+  -- @max_allowed_file_size[opt] number the max allowed file size to be read from,
+  -- less than zero mean no limit.
   -- @treturn string|nil The plain request body or nil if it does not fit into
   -- the NGINX temporary buffer.
   -- @treturn nil|string An error message.
@@ -731,7 +732,7 @@ local function new(self)
       end
 
       local size = file:seek("end") or 0
-      if size > max_allowed_file_size then
+      if max_allowed_file_size >= 0 and size > max_allowed_file_size then
         return nil, ("request body file too big: %d > %d"):format(size, max_allowed_file_size)
       end
 

t/01-pdk/04-request/15-get_raw_body.t

@@ -170,4 +170,30 @@ body length: 20000
 --- response_body
 body err: request body file too big: 20000 > 19999
 --- no_error_log
-[error]
+[error]
+
+
+
+=== TEST 8: request.get_raw_body() returns correctly if max_allowed_file_size is less than 0
+--- http_config eval: $t::Util::HttpConfig
+--- config
+    location = /t {
+        access_by_lua_block {
+            local PDK = require "kong.pdk"
+            local pdk = PDK.new()
+
+            local body, err = pdk.request.get_raw_body(-1)
+            if body then
+              ngx.say("body length: ", #body)
+
+            else
+              ngx.say("body err: ", err)
+            end
+        }
+    }
+--- request eval
+"GET /t\r\n" . ("a" x 20000)
+--- response_body
+body length: 20000
+--- no_error_log
+[error]