model: prevent deletion of specific model instances

2 files changed, 18 insertions, 1 deletions

diff --git a/acf2/model/model.lua b/acf2/model/model.lua
index 4140087..fdb7c96 100644
--- a/acf2/model/model.lua
+++ b/acf2/model/model.lua
@@ -168,12 +168,19 @@ function M.Model:init(context)
       return v
    end
 
+   if self.is_removable then
+      function mt.removable() return self:is_removable() end
+   end
+
    if not mt.txn then return end
 
 
    function mt.mmeta(name) return mt.member(name):meta() end
 
-   function mt.save(k, v) return mt.member(k, false, Field):save(v) end
+   function mt.save(k, v)
+      mt.check_removable(k, v)
+      return mt.member(k, false, Field):save(v)
+   end
 
    local function tmeta(tpe)
       return map(function(m) return m:meta() end, _members(tpe))
diff --git a/acf2/model/node.lua b/acf2/model/node.lua
index 86722f2..02eb12f 100644
--- a/acf2/model/node.lua
+++ b/acf2/model/node.lua
@@ -62,6 +62,15 @@ function M.TreeNode:init(context)
    mt.__eq = equal_tns
    mt._meta = {}
    function mt.get(k, options) return mt.load(k, options) end
+   function mt.removable() return true end
+
+   function mt.check_removable(k, v)
+      if v ~= nil then return end
+      local old = mt.load(k, {dereference=false})
+      if isinstance(old, M.TreeNode) and not getmetatable(old).removable() then
+	 raise(pth.join(mt.path, k), 'Cannot be deleted')
+      end
+   end
 
    if not mt.txn then return end
 
@@ -209,6 +218,7 @@ function M.Collection:init(context, params)
       if not params.editable then
 	 raise(mt.path, 'Collection is not editable')
       end
+      mt.check_removable(k, v)
       mt.member(k):save(v)
    end
 end