tests(migrations): add tests to detect not listed migration files (#1…

…4320)

To write a database migration, there are two steps:

1. Writing a migration file inside the `kong/db/migrations/core`.
2. Adding this migration to the `kong/db/migrations/core/init.lua`.

However, we might forget to do the step#2, so I added a test for this case.

KAG-6494

spec/01-unit/01-db/12-missing-migrations_spec.lua

@@ -0,0 +1,112 @@
+local pl_dir  = require("pl.dir")
+local pl_path = require("pl.path")
+local pl_tblx = require("pl.tablex")
+
+
+local MIGRATIONS = {
+  {
+    dir = "kong/db/migrations/core",
+    index = "kong/db/migrations/core/init.lua",
+    skip = {},
+  },
+}
+local PLUGIN_DIRS = {
+  "kong/plugins",
+}
+
+
+--[[
+  This function will fail for the following cases:
+  1. An migration file is exists but not listed in the `init.lua` file.
+  2. An migration file is marked as skipped but still listed in the `init.lua` file.
+--]]
+local function assert_no_missing_migrations(migrations)
+  for _, migration in ipairs(migrations) do
+    --[[
+      {
+        "010_210_to_211" = true,
+        ...
+      }
+    --]]
+    local indexed_migration = pl_tblx.makeset(loadfile(migration.index)())
+    local files = pl_dir.getfiles(migration.dir)
+    for _, file in ipairs(files) do
+      if file == migration.index then
+        goto continue
+      end
+
+      -- @file: kong/db/migrations/core/010_210_to_211.lua
+      -- @basename: 010_210_to_211.lua
+      local basename = pl_path.basename(file)
+
+      if basename:sub(-4) ~= ".lua" then
+        -- skip non-lua files
+        goto continue
+      end
+
+      -- strip the extension
+      -- @migration_name: 010_210_to_211
+      local migration_name = basename:sub(1, -5)
+
+      if migration.skip[file] then
+        assert.Falsy(indexed_migration[migration_name], "do not skip an already indexed file: " .. file)
+        goto continue
+      end
+
+      assert.True(indexed_migration[migration_name], "missing entry for " .. file .. " in " .. migration.index)
+
+      ::continue::
+    end
+  end
+end
+
+
+describe("Checking missing entry for migrations", function()
+  -- same like `@MIGRATIONS`, but for plugins
+  local plugin_migrations = {}
+
+  lazy_setup(function()
+    local migrations = {
+      --[[
+        [plugin_name] = {
+          dir = <plugin_dir>/migrations,
+          index = <plugin_dir>/migrations/init.lua,
+          skip = {
+            <plugin_dir>/migrations/_001_280_to_300.lua = true,
+          },
+        },
+        ...
+      --]]
+    }
+
+    for _, plugins_dir in ipairs(PLUGIN_DIRS) do
+      local plugins = pl_dir.getdirectories(plugins_dir)
+      for _, plugin_dir in ipairs(plugins) do
+        -- is this plugin has `migrations/` directory?
+        -- and is this plugin has `migrations/init.lua` file?
+        if pl_path.exists(pl_path.join(plugin_dir, "migrations")) and
+            pl_path.exists(pl_path.join(plugin_dir, "migrations", "init.lua"))
+        then
+          local plugin_name = pl_path.basename(plugin_dir)
+          plugin_migrations[plugin_name] = {
+            dir = pl_path.join(plugin_dir, "migrations"),
+            index = pl_path.join(plugin_dir, "migrations", "init.lua"),
+            skip = {},
+          }
+        end
+      end
+    end
+
+    plugin_migrations["pre-function"].skip["kong/plugins/pre-function/migrations/_001_280_to_300.lua"] = true
+
+    plugin_migrations = pl_tblx.values(migrations)
+  end)
+
+  it("core migrations", function()
+    assert_no_missing_migrations(MIGRATIONS)
+  end)
+
+  it("plugin migrations", function()
+    assert_no_missing_migrations(plugin_migrations)
+  end)
+end)