policy/routing: add support for liquid templating

gateway/src/apicast/policy/routing/apicast-policy.json

@@ -36,6 +36,21 @@
           },
           "value": {
             "type": "string"
+          },
+          "value_type": {
+            "description": "How to evaluate 'type'",
+            "type": "string",
+            "default": "plain",
+            "oneOf": [
+              {
+                "enum": ["plain"],
+                "title": "Evaluate 'value' as plain text."
+              },
+              {
+                "enum": ["liquid"],
+                "title": "Evaluate 'value' as liquid."
+              }
+            ]
           }
         },
         "required": [

gateway/src/apicast/policy/routing/routing_operation.lua

@@ -12,51 +12,52 @@ local _M = {}
 
 local mt = { __index = _M }
 
-local function new(evaluate_left_side_func, op, value)
+local function new(evaluate_left_side_func, op, value, value_type)
   local self = setmetatable({}, mt)
 
   self.evaluate_left_side_func = evaluate_left_side_func
   self.op = op
   self.value = value
+  self.value_type = value_type
 
   return self
 end
 
-function _M.new_op_with_path(op, value)
+function _M.new_op_with_path(op, value, value_type)
   local eval_left_func = function(request) return request:get_uri() end
-  return new(eval_left_func, op, value)
+  return new(eval_left_func, op, value, value_type)
 end
 
-function _M.new_op_with_header(header_name, op, value)
+function _M.new_op_with_header(header_name, op, value, value_type)
   local eval_left_func = function(request)
     return request:get_header(header_name)
   end
 
-  return new(eval_left_func, op, value)
+  return new(eval_left_func, op, value, value_type)
 end
 
-function _M.new_op_with_query_arg(query_arg_name, op, value)
+function _M.new_op_with_query_arg(query_arg_name, op, value, value_type)
   local eval_left_func = function(request)
     return request:get_uri_arg(query_arg_name)
   end
 
-  return new(eval_left_func, op, value)
+  return new(eval_left_func, op, value, value_type)
 end
 
-function _M.new_op_with_jwt_claim(jwt_claim_name, op, value)
+function _M.new_op_with_jwt_claim(jwt_claim_name, op, value, value_type)
   local eval_left_func = function(request)
     local jwt = request:get_validated_jwt()
     return (jwt and jwt[jwt_claim_name]) or nil
   end
 
-  return new(eval_left_func, op, value)
+  return new(eval_left_func, op, value, value_type)
 end
 
 function _M:evaluate(context)
   local left_operand_val = self.evaluate_left_side_func(context.request)
 
   local op = Operation.new(
-    left_operand_val, 'plain', self.op, self.value, 'plain'
+    left_operand_val, 'plain', self.op, self.value, self.value_type
   )
 
   return op:evaluate(context)

gateway/src/apicast/policy/routing/rule.lua

@@ -24,15 +24,16 @@ local function init_operation(config_operation)
   local thing_to_match_val = value_of_thing_to_match(thing_to_match, config_operation)
   local op = config_operation.op
   local value = config_operation.value
+  local value_type = config_operation.value_type
 
   if thing_to_match == 'path' then
-    return RoutingOperation.new_op_with_path(op, value)
+    return RoutingOperation.new_op_with_path(op, value, value_type)
   elseif thing_to_match == 'header' then
-    return RoutingOperation.new_op_with_header(thing_to_match_val, op, value)
+    return RoutingOperation.new_op_with_header(thing_to_match_val, op, value, value_type)
   elseif thing_to_match == 'query_arg' then
-    return RoutingOperation.new_op_with_query_arg(thing_to_match_val, op, value)
+    return RoutingOperation.new_op_with_query_arg(thing_to_match_val, op, value, value_type)
   elseif thing_to_match == 'jwt_claim' then
-    return RoutingOperation.new_op_with_jwt_claim(thing_to_match_val, op, value)
+    return RoutingOperation.new_op_with_jwt_claim(thing_to_match_val, op, value, value_type)
   else
     error('Thing to be matched not supported: ' .. thing_to_match)
   end

spec/policy/routing/routing_operation_spec.lua

@@ -1,4 +1,5 @@
 local RoutingOperation = require('apicast.policy.routing.routing_operation')
+local ngx_variable = require 'apicast.policy.ngx_variable'
 
 describe('RoutingOperation', function()
   describe('.evaluate', function()
@@ -213,5 +214,27 @@ describe('RoutingOperation', function()
         assert.is_false(operation:evaluate(context))
       end)
     end)
+
+    it('can evaluate the right operand as liquid', function()
+      -- Stub the available context to avoid depending on ngx.var.*
+      stub(ngx_variable, 'available_context', function(context) return context end)
+
+      local path = '/a_path'
+
+      local operation = RoutingOperation.new_op_with_path(
+        '==', '{{ value_in_liquid_ctx }}', 'liquid'
+      )
+
+      local request_with_matching_path = {
+        get_uri = function() return path end
+      }
+
+      local context = {
+        request = request_with_matching_path,
+        value_in_liquid_ctx = path
+      }
+
+      assert.is_true(operation:evaluate(context))
+    end)
   end)
 end)

t/apicast-policy-routing.t

@@ -2028,3 +2028,56 @@ yay, api backend
 --- error_code: 200
 --- no_error_log
 [error]
+
+=== TEST 32: conditions with liquid templating
+--- configuration
+{
+  "services": [
+    {
+      "id": 42,
+      "proxy": {
+        "policy_chain": [
+          {
+            "name": "apicast.policy.routing",
+            "configuration": {
+              "rules": [
+                {
+                  "url": "http://test:$TEST_NGINX_SERVER_PORT",
+                  "condition": {
+                    "operations": [
+                      {
+                        "thing_to_match": "header",
+                        "header_name": "Service-Id",
+                        "op": "==",
+                        "value": "{{ service.id }}",
+                        "value_type": "liquid"
+                      }
+                    ]
+                  }
+                }
+              ]
+            }
+          },
+          {
+            "name": "apicast.policy.echo"
+          }
+        ]
+      }
+    }
+  ]
+}
+--- upstream
+  location / {
+     content_by_lua_block {
+       ngx.say('yay, api backend');
+     }
+  }
+--- request
+GET /
+--- more_headers
+Service-Id: 42
+--- response_body
+yay, api backend
+--- error_code: 200
+--- no_error_log
+[error]