feat(router/atc): add new field http.path.segments.len (#12398)

This field represents how much segments the request path contains.

For example, "/a/b/c/" contains 3 segments, "/a" contains 1 and "/" contains 0 segment.

It is useful for implementing segment based routing logic such as these used in OpenAPI spec.

KAG-3604

kong/db/schema/entities/routes.lua

@@ -27,10 +27,11 @@ do
 
     for _, f in ipairs(fields) do
       if f:find(HTTP_PATH_SEGMENTS_PREFIX, 1, true) then
-        local m = re_match(f:sub(#HTTP_PATH_SEGMENTS_PREFIX + 1),
-                           HTTP_PATH_SEGMENTS_SUFFIX_REG, "jo")
+        local suffix = f:sub(#HTTP_PATH_SEGMENTS_PREFIX + 1)
+        local m = re_match(suffix, HTTP_PATH_SEGMENTS_SUFFIX_REG, "jo")
 
-        if not m or (m[2] and tonumber(m[1]) >= tonumber(m[3])) then
+        if (suffix ~= "len") and
+           (not m or (m[2] and tonumber(m[1]) >= tonumber(m[3]))) then
           return nil, "Router Expression failed validation: " ..
                       "illformed http.path.segments.* field"
         end

kong/router/fields.lua

@@ -34,6 +34,7 @@ local HTTP_FIELDS = {
                },
 
   ["Int"]    = {"net.src.port", "net.dst.port",
+                "http.path.segments.len",
                },
 
   ["IpAddr"] = {"net.src.ip", "net.dst.ip",
@@ -209,10 +210,32 @@ if is_http then
 
   local HTTP_SEGMENTS_PREFIX = "http.path.segments."
   local HTTP_SEGMENTS_PREFIX_LEN = #HTTP_SEGMENTS_PREFIX
-  local HTTP_SEGMENTS_REG_CTX = { pos = 2, }  -- skip first '/'
   local HTTP_SEGMENTS_OFFSET = 1
 
 
+  local get_http_segments
+  do
+    local HTTP_SEGMENTS_REG_CTX = { pos = 2, }  -- skip first '/'
+
+    get_http_segments = function(params)
+      if not params.segments then
+        HTTP_SEGMENTS_REG_CTX.pos = 2 -- reset ctx, skip first '/'
+        params.segments = re_split(params.uri, "/", "jo", HTTP_SEGMENTS_REG_CTX)
+      end
+
+      return params.segments
+    end
+  end
+
+
+  FIELDS_FUNCS["http.path.segments.len"] =
+  function(params)
+    local segments = get_http_segments(params)
+
+    return #segments
+  end
+
+
   -- func => get_headers or get_uri_args
   -- name => "headers" or "queries"
   -- max_config_option => "lua_max_req_headers" or "lua_max_uri_args"
@@ -281,12 +304,7 @@ if is_http then
       local range = field:sub(HTTP_SEGMENTS_PREFIX_LEN + 1)
 
       f = function(params)
-        if not params.segments then
-          HTTP_SEGMENTS_REG_CTX.pos = 2 -- reset ctx, skip first '/'
-          params.segments = re_split(params.uri, "/", "jo", HTTP_SEGMENTS_REG_CTX)
-        end
-
-        local segments = params.segments
+        local segments = get_http_segments(params)
 
         local value = segments[range]
 

spec/01-unit/01-db/01-schema/06-routes_spec.lua

@@ -1563,16 +1563,28 @@ describe("routes schema (flavor = expressions)", function()
   end)
 
   it("http route supports http.path.segments.* fields", function()
-    local route = {
+    local r = {
       id             = a_valid_uuid,
       name           = "my_route",
       protocols      = { "grpcs" },
-      expression     = [[http.path.segments.0 == "foo" && http.path.segments.1 ^= "bar" && http.path.segments.20_30 ~ r#"x/y"#]],
       priority       = 100,
       service        = { id = another_uuid },
     }
-    route = Routes:process_auto_fields(route, "insert")
-    assert.truthy(Routes:validate(route))
+
+    local expressions = {
+      [[http.path.segments.0 == "foo"]],
+      [[http.path.segments.1 ^= "bar"]],
+      [[http.path.segments.20_30 ~ r#"x/y"#]],
+      [[http.path.segments.len == 10]],
+    }
+
+    for _, exp in ipairs(expressions) do
+      r.expression = exp
+
+      local route = Routes:process_auto_fields(r, "insert")
+      assert.truthy(Routes:validate(route))
+    end
+
   end)
 
   it("fails if http route has invalid http.path.segments.* fields", function()
@@ -1585,6 +1597,10 @@ describe("routes schema (flavor = expressions)", function()
     }
 
     local wrong_expressions = {
+      [[http.path.segments.len0   == 10]],
+      [[http.path.segments.len_a  == 10]],
+      [[http.path.segments.len    == "10"]],
+
       [[http.path.segments.       == "foo"]],
       [[http.path.segments.abc    == "foo"]],
       [[http.path.segments.a_c    == "foo"]],

spec/01-unit/08-router_spec.lua

@@ -5441,6 +5441,32 @@ do
       assert.falsy(match_t)
     end)
 
+    it("select() should match http.segments.* with len", function()
+      local use_case = {
+        {
+          service = service,
+          route   = {
+            id = "e8fb37f1-102d-461e-9c51-6608a6bb8101",
+            expression = [[http.path.segments.0 == "foo" && http.path.segments.len == 1]],
+            priority = 100,
+          },
+        },
+      }
+
+      local router = assert(new_router(use_case))
+
+      local match_t = router:select("GET", "/foo")
+      assert.truthy(match_t)
+      assert.same(use_case[1].route, match_t.route)
+
+      local match_t = router:select("GET", "/foo/")
+      assert.truthy(match_t)
+      assert.same(use_case[1].route, match_t.route)
+
+      local match_t = router:select("GET", "/foo/xxx")
+      assert.falsy(match_t)
+    end)
+
     it("select() should match range http.segments.*", function()
       local use_case = {
         {
@@ -5459,6 +5485,14 @@ do
             priority = 100,
           },
         },
+        {
+          service = service,
+          route   = {
+            id = "e8fb37f1-102d-461e-9c51-6608a6bb8103",
+            expression = [[http.path.segments.1_2 == r#"xxx/yyy"# && http.path.segments.len == 3]],
+            priority = 100,
+          },
+        },
       }
 
       local router = assert(new_router(use_case))
@@ -5474,6 +5508,14 @@ do
       local match_t = router:select("GET", "/foo/xxx/yyy/zzz/bar")
       assert.truthy(match_t)
       assert.same(use_case[2].route, match_t.route)
+
+      local match_t = router:select("GET", "/foo/xxx/yyy")
+      assert.truthy(match_t)
+      assert.same(use_case[3].route, match_t.route)
+
+      local match_t = router:select("GET", "/foo/xxx/yyy/")
+      assert.truthy(match_t)
+      assert.same(use_case[3].route, match_t.route)
     end)
 
     it("select() accepts but does not match wrong http.segments.*", function()