feat(wasm): combine config and json_config fields

This allows JSON filter configuration to live in the same .config
attribute as raw configuration. Filters must have an associated
JSON schema in order to use this feature.

changelog/unreleased/kong/wasm-filter-json-config.yml

@@ -0,0 +1,3 @@
+message: Support JSON in Wasm filter configuration
+type: feature
+scope: Core

kong/db/schema/entities/filter_chains.lua

@@ -20,37 +20,33 @@ local constants = require "kong.constants"
 ---
 ---@field name        string
 ---@field enabled     boolean
----@field config      string|nil
----@field json_config any|nil
+---@field config      any|nil
 
 
 local filter = {
   type = "record",
   fields = {
     { name       = { type = "string", required = true, one_of = wasm.filter_names,
                      err = "no such filter", }, },
-    { config     = { type = "string", required = false, }, },
     { enabled    = { type = "boolean", default = true, required = true, }, },
 
-    { json_config = {
+    { config = {
         type = "json",
         required = false,
         json_schema = {
           parent_subschema_key = "name",
           namespace = constants.SCHEMA_NAMESPACES.PROXY_WASM_FILTERS,
           optional = true,
+          default = {
+            -- filters with no user-defined JSON schema may accept an optional
+            -- config, but only as a string
+            type = { "string", "null" },
+          },
         },
       },
     },
 
   },
-  entity_checks = {
-    { mutually_exclusive = {
-        "config",
-        "json_config",
-      },
-    },
-  },
 }
 
 return {

kong/db/schema/init.lua

@@ -1135,7 +1135,7 @@ validate_fields = function(self, input)
 
         if json_subschema_key then
           local schema_name = json_schema.namespace .. "/" .. json_subschema_key
-          inline_schema = json.get_schema(schema_name)
+          inline_schema = json.get_schema(schema_name) or json_schema.default
 
           if inline_schema then
             _, errors[k] = json_validate(v, inline_schema)

kong/db/schema/metaschema.lua

@@ -128,13 +128,38 @@ local validators = {
 -- means that input validation will fail. When `optional` is `true`, the input
 -- is always accepted.
 --
+-- Schemas which use this dynamic reference format can also optionally supply
+-- a default inline schema, which will be evaluated when the dynamic schema
+-- does not exist:
+--
+-- ```lua
+-- local record = {
+--   type = "record",
+--   fields = {
+--     { name = { type = "string" } },
+--     { config = {
+--         type = "json",
+--         json_schema = {
+--           namespace = "my-record-type",
+--           parent_subschema_key = "name",
+--           default = {
+--             { type = { "string", "null" } },
+--           },
+--         },
+--       },
+--     },
+--   },
+-- }
+-- ```
+--
 local json_metaschema = {
   type = "record",
   fields = {
     { namespace = { type = "string", one_of = values(constants.SCHEMA_NAMESPACES), }, },
     { parent_subschema_key = { type = "string" }, },
     { optional = { type = "boolean", }, },
     { inline = { type = "any", custom_validator = json_lib.validate_schema, }, },
+    { default = { type = "any", custom_validator = json_lib.validate_schema, }, },
   },
   entity_checks = {
     { at_least_one_of = { "inline", "namespace", "parent_subschema_key" }, },

kong/runloop/wasm.lua

@@ -398,10 +398,18 @@ local function rebuild_state(db, version, old_state)
 
       for _, filter in ipairs(chain.filters) do
         if filter.enabled then
-          -- serialize all JSON configurations up front
-          if not filter.config and filter.json_config ~= nil then
-            filter.config = cjson_encode(filter.json_config)
-            filter.json_config = nil
+          -- Serialize all JSON configurations up front
+          --
+          -- NOTE: there is a subtle difference between a raw, non-JSON filter
+          -- configuration which requires no encoding (e.g. `my config bytes`)
+          -- and a JSON filter configuration of type=string, which should be
+          -- JSON-encoded (e.g. `"my config string"`).
+          --
+          -- Properly disambiguating between the two cases requires an
+          -- inspection of the filter metadata, which is not guaranteed to be
+          -- present on data-plane/proxy nodes.
+          if filter.config ~= nil and type(filter.config) ~= "string" then
+            filter.config = cjson_encode(filter.config)
           end
         end
       end

spec/02-integration/20-wasm/01-admin-api_spec.lua

@@ -4,7 +4,6 @@ local utils = require "kong.tools.utils"
 local fmt = string.format
 
 local FILTER_PATH = assert(helpers.test_conf.wasm_filters_path)
-local NULL = ngx.null
 
 local function json(body)
   return {
@@ -207,9 +206,9 @@ describe("wasm admin API [#" .. strategy .. "]", function()
         assert.same({ "foo", "bar" }, patched.tags)
         assert.is_false(patched.enabled)
         assert.equals(2, #patched.filters)
-        assert.same({ name = "tests", config = "123", enabled = true, json_config = NULL },
+        assert.same({ name = "tests", config = "123", enabled = true },
                     patched.filters[1])
-        assert.same({ name = "tests", config = "456", enabled = false, json_config = NULL },
+        assert.same({ name = "tests", config = "456", enabled = false },
                     patched.filters[2])
       end)
     end)
@@ -366,9 +365,9 @@ describe("wasm admin API [#" .. strategy .. "]", function()
         assert.same({ "foo", "bar" }, patched.tags)
         assert.is_false(patched.enabled)
         assert.equals(2, #patched.filters)
-        assert.same({ name = "tests", config = "123", enabled = true, json_config = NULL },
+        assert.same({ name = "tests", config = "123", enabled = true },
                     patched.filters[1])
-        assert.same({ name = "tests", config = "456", enabled = false, json_config = NULL },
+        assert.same({ name = "tests", config = "456", enabled = false },
                     patched.filters[2])
       end)
     end)
@@ -428,7 +427,7 @@ describe("wasm admin API [#" .. strategy .. "]", function()
       fcs = {
         assert(bp.filter_chains:insert({
           filters = {
-            { name = "tests", config = ngx.null, enabled = true },
+            { name = "tests", config = nil, enabled = true },
             { name = "response_transformer", config = "{}", enabled = false },
           },
           service = { id = service.id },

spec/02-integration/20-wasm/02-db_spec.lua

@@ -371,7 +371,13 @@ describe("wasm DB entities [#" .. strategy .. "]", function()
       end)
 
       describe(".config", function()
-        it("is an optional string", function()
+        local schema_name = "proxy-wasm-filters/test"
+
+        lazy_teardown(function()
+          schema_lib.remove_schema(schema_name)
+        end)
+
+        it("is an optional string when no json schema exists", function()
           local service = assert(db.services:insert({
             url = "http://example.test",
           }))
@@ -381,7 +387,7 @@ describe("wasm DB entities [#" .. strategy .. "]", function()
             filters = {
               {
                 name = "test",
-                config = "foo",
+                config = nil,
               }
             }
           }))
@@ -395,26 +401,48 @@ describe("wasm DB entities [#" .. strategy .. "]", function()
             filters = {
               {
                 name = "test",
-                config = nil,
+                config = "my config",
               }
             }
           }))
-        end)
-      end)
 
-      describe(".json_config", function()
-        local schema_name = "proxy-wasm-filters/test"
+          assert.falsy(dao:insert({
+            service = { id = service.id },
+            filters = {
+              {
+                name = "test",
+                config = 123,
+              }
+            }
+          }))
 
-        lazy_teardown(function()
-          schema_lib.remove_schema(schema_name)
+          assert.falsy(dao:insert({
+            service = { id = service.id },
+            filters = {
+              {
+                name = "test",
+                config = true,
+              }
+            }
+          }))
+
+          assert.falsy(dao:insert({
+            service = { id = service.id },
+            filters = {
+              {
+                name = "test",
+                config = { a = 1, b = 2 },
+              }
+            }
+          }))
         end)
 
         it("is validated against user schema", function()
           local service = assert(db.services:insert({
             url = "http://example.test",
           }))
 
-          schema_lib.add_schema("proxy-wasm-filters/test", {
+          schema_lib.add_schema(schema_name, {
             type = "object",
             properties = {
               foo = { type = "string" },
@@ -429,7 +457,7 @@ describe("wasm DB entities [#" .. strategy .. "]", function()
             filters = {
               {
                 name = "test",
-                json_config = {
+                config = {
                   foo = "foo string",
                   bar = { a = 1, b = 2 },
                 },
@@ -446,7 +474,7 @@ describe("wasm DB entities [#" .. strategy .. "]", function()
             filters = {
               {
                 name = "test",
-                json_config = {
+                config = {
                   foo = 123,
                   bar = { a = 1, b = 2 },
                 },
@@ -465,7 +493,7 @@ describe("wasm DB entities [#" .. strategy .. "]", function()
             filters = {
               {
                 name = "test",
-                json_config = ngx.null,
+                config = ngx.null,
               }
             }
           })
@@ -481,7 +509,7 @@ describe("wasm DB entities [#" .. strategy .. "]", function()
             filters = {
               {
                 name = "test",
-                json_config = nil,
+                config = nil,
               }
             }
           })

spec/02-integration/20-wasm/09-filter-meta_spec.lua

@@ -158,7 +158,7 @@ describe("filter metadata [#" .. strategy .. "]", function()
         filters = {
           {
             name = "rt_with_validation",
-            json_config = {}, -- empty
+            config = {}, -- empty
           },
         },
       })
@@ -185,7 +185,7 @@ describe("filter metadata [#" .. strategy .. "]", function()
         assert.same({
           filters = {
             {
-              json_config = "property add is required"
+              config = "property add is required"
             }
           }
         }, body.fields)
@@ -197,7 +197,7 @@ describe("filter metadata [#" .. strategy .. "]", function()
         filters = {
           {
             name = "rt_with_validation",
-            json_config = {
+            config = {
               add = {
                 headers = {
                   "x-foo:123",
@@ -217,19 +217,44 @@ describe("filter metadata [#" .. strategy .. "]", function()
       end).has_no_error()
     end)
 
-    it("filters without config schemas are not validated", function()
+    it("filters without config schemas can only accept a string", function()
       local host = random_name() .. ".test"
 
       local res = create_filter_chain(host, {
         name = random_name(),
         filters = {
           {
             name = "rt_no_validation",
-            json_config = {
+            config = {
               add = {
                 headers = 1234,
               },
-            },
+            }
+          },
+        },
+      })
+
+      assert.response(res).has.status(400)
+      local body = assert.response(res).has.jsonbody()
+      assert.same({
+        filters = {
+          { config = "wrong type: expected one of string, null, got object" }
+        }
+      }, body.fields)
+    end)
+
+    it("filters without config schemas are not validated", function()
+      local host = random_name() .. ".test"
+      local res = create_filter_chain(host, {
+        name = random_name(),
+        filters = {
+          {
+            name = "rt_no_validation",
+            config = cjson.encode({
+              add = {
+                headers = 123,
+              },
+            }),
           },
         },
       })
@@ -242,7 +267,6 @@ describe("filter metadata [#" .. strategy .. "]", function()
         assert.logfile().has.line("failed parsing filter config", true, 0)
       end).has_no_error()
     end)
-
   end)
 
 end)