Third time lucky with metatable logic. We now ensure our header fields are unique

Author: pintsized

lib/resty/http.lua

@@ -66,7 +66,7 @@ end
 
 
 local _M = {
-    _VERSION = '0.04',
+    _VERSION = '0.05',
 }
 
 local mt = { __index = _M }

lib/resty/http_headers.lua

@@ -29,16 +29,30 @@ function _M.new(self)
             return matched
         else
             local k_normalised = str_lower(k_hyphened)
-            return rawget(mt.normalised, k_normalised)
+            return rawget(t, mt.normalised[k_normalised])
         end
     end
 
 
+    -- First check the normalised table. If there's no match (first time) add an entry for 
+    -- our current case in the normalised table. This is to preserve the human (prettier) case
+    -- instead of outputting lowercased header names.
+    --
+    -- If there's a match, we're being updated, just with a different case for the key. We use
+    -- the normalised table to give us the original key, and perorm a rawset().
     mt.__newindex = function(t, k, v)
-        local k_hyphened = str_gsub(k, "_", "-")
-        local k_normalised = str_lower(k_hyphened)
-        rawset(mt.normalised, k_normalised, v)
-        rawset(t, k_hyphened, v)
+        -- we support underscore syntax, so always hyphenate.
+        local k_hyphened = str_gsub(k, "_", "-") 
+
+        -- lowercase hyphenated is "normalised"
+        local k_normalised = str_lower(k_hyphened) 
+
+        if not mt.normalised[k_normalised] then
+            mt.normalised[k_normalised] = k_hyphened
+            rawset(t, k_hyphened, v)
+        else
+            rawset(t, mt.normalised[k_normalised], v)
+        end
     end
 
     return setmetatable({}, mt)

t/12-case_insensitive_headers.t

@@ -130,4 +130,31 @@ test_user_agent
 bar
 --- no_error_log
 [error]
+
+
+=== TEST 4: Test that headers remain unique
+--- http_config eval: $::HttpConfig
+--- config
+    location = /a {
+        content_by_lua '
+            local http_headers = require "resty.http_headers"
+
+            local headers = http_headers.new()
+
+            headers["x-a-header"] = "a"
+            headers["X-A-HEAder"] = "b"
+
+            for k,v in pairs(headers) do
+            ngx.log(ngx.DEBUG, k, ": ", v)
+                ngx.header[k] = v
+            end
+        ';
+    }
+--- request
+GET /a
+--- response_headers
+x-a-header: b
+--- no_error_log
+[error]
+[warn]
 [warn]