Mango match_failures/2 function

rel/overlay/etc/default.ini

@@ -132,6 +132,13 @@ view_index_dir = {{view_index_dir}}
 ; Javascript engine. The choices are: spidermonkey and quickjs
 ;js_engine = spidermonkey
 
+; When set to "true", the `validate_doc_update` field will be validated when
+; design documents are updated. For `javascript` design docs, the field must
+; contain a well-formed JavaScript function, and for `query` design docs it
+; must contain a Mango selector that is correctly structured to validate
+; document updates.
+validate_vdu = true
+
 ; Use cfile. This is a C-based file I/O module that can execute parallel file
 ; read calls. The regular Erlang VM file module, at least as of OTP 28 forces
 ; all file operations to go through a single controlling process which can

share/server/dispatch-quickjs.js

@@ -162,6 +162,9 @@ globalThis.dispatch = function(line) {
     case "reset":
       State.reset.apply(null, cmd);
       break;
+    case "validate_fun":
+      State.validateFun.apply(null, cmd);
+      break;
     case "add_fun":
       State.addFun.apply(null, cmd);
       break;

share/server/loop.js

@@ -126,6 +126,7 @@ var Loop = function() {
     "ddoc"     : DDoc.ddoc,
     // "view"    : Views.handler,
     "reset"    : State.reset,
+    "validate_fun": State.validateFun,
     "add_fun"  : State.addFun,
     "add_lib"  : State.addLib,
     "map_doc"  : Views.mapDoc,

share/server/state.js

@@ -10,6 +10,18 @@
 // License for the specific language governing permissions and limitations under
 // the License.
 
+var makefun = function(newFun, option) {
+  switch (option) {
+    case 'nouveau':
+      var sandbox = create_nouveau_sandbox();
+      break;
+    default:
+      var sandbox = create_dreyfus_sandbox();
+      break;
+  }
+  return Couch.compileFunction(newFun, {views : {lib : State.lib}}, undefined, sandbox);
+}
+
 var State = {
   reset : function(config) {
     // clear the globals and run gc
@@ -19,17 +31,15 @@ var State = {
     gc();
     print("true"); // indicates success
   },
+  validateFun : function(newFun, option) {
+    // Validate a function but do not store it
+    makefun(newFun, option);
+    print("true");
+  },
   addFun : function(newFun, option) {
     // Compile to a function and add it to funs array
-    switch (option) {
-      case 'nouveau':
-        var sandbox = create_nouveau_sandbox();
-        break;
-      default:
-        var sandbox = create_dreyfus_sandbox();
-        break;
-    }
-    State.funs.push(Couch.compileFunction(newFun, {views : {lib : State.lib}}, undefined, sandbox));
+    var fun = makefun(newFun, option);
+    State.funs.push(fun);
     print("true");
   },
   addLib : function(lib) {

src/couch/src/couch_query_servers.erl

@@ -42,7 +42,12 @@
 
 try_compile(Proc, FunctionType, FunctionName, FunctionSource) ->
     try
-        proc_prompt(Proc, [<<"add_fun">>, FunctionSource]),
+        case FunctionType of
+            validate_doc_update ->
+                proc_prompt(Proc, [<<"validate_fun">>, FunctionSource]);
+            _ ->
+                proc_prompt(Proc, [<<"add_fun">>, FunctionSource])
+        end,
         ok
     catch
         {compilation_error, E} ->

src/couch_mrview/src/couch_mrview.erl

@@ -248,12 +248,11 @@ validate(Db, DDoc) ->
             ok
     end,
 
-    try Views =/= [] andalso couch_query_servers:get_os_process(Lang) of
-        false ->
-            ok;
+    try couch_query_servers:get_os_process(Lang) of
         Proc ->
             try
-                lists:foreach(fun(V) -> ValidateView(Proc, V) end, Views)
+                lists:foreach(fun(V) -> ValidateView(Proc, V) end, Views),
+                validate_vdu(Proc, DDoc)
             after
                 couch_query_servers:ret_os_process(Proc)
             end
@@ -263,6 +262,21 @@ validate(Db, DDoc) ->
             ok
     end.
 
+validate_vdu(Proc, #doc{body = {Props}}) ->
+    case config:get_boolean("couchdb", "validate_vdu", false) of
+        true ->
+            case couch_util:get_value(<<"validate_doc_update">>, Props) of
+                undefined ->
+                    ok;
+                VDU ->
+                    couch_query_servers:try_compile(
+                        Proc, validate_doc_update, <<"validate_doc_update">>, VDU
+                    )
+            end;
+        _ ->
+            ok
+    end.
+
 check_rank(<<N/binary>>) ->
     try binary_to_integer(N) of
         Val when Val >= 1 andalso Val =< ?MAX_RANK ->

src/couch_scanner/test/eunit/couch_scanner_test.erl

@@ -95,7 +95,7 @@ setup() ->
             #{from => <<"x">>, to => <<"y">>}
         ],
         updates => #{u1 => <<"function(d,r){return [];}">>},
-        validate_doc_update => <<"function(n,o,u,s){return true;">>
+        validate_doc_update => <<"function(n,o,u,s){return true;}">>
     }),
     ok = add_doc(DbName2, ?DOC3, #{foo3 => bax}),
     ok = add_doc(DbName2, ?DOC4, #{foo4 => baw, <<>> => this_is_ok_apparently}),

src/docs/src/config/couchdb.rst

@@ -258,6 +258,19 @@ Base CouchDB Options
             [couchdb]
             js_engine = spidermonkey
 
+    .. config:option:: validate_vdu :: Enable checking of ``validate_doc_update``
+
+        .. versionadded:: TODO
+
+        When set to ``true``, the ``validate_doc_update`` field will be
+        validated when design documents are updated. For ``javascript`` design
+        docs, the field must contain a well-formed JavaScript function, and for
+        ``query`` design docs it must contain a Mango selector that is correctly
+        structured to validate document updates. ::
+
+            [couchdb]
+            validate_vdu = true
+
     .. config:option:: time_seq_min_time :: Minimum time-seq threshold
 
         .. versionchanged:: 3.6

src/docs/src/ddocs/ddocs.rst

@@ -955,7 +955,8 @@ To use Mango selectors for validation, the design document must have the
 containing the following fields:
 
 * ``newDoc``: New version of document that will be stored.
-* ``oldDoc``: Previous version of document that is already stored.
+* ``oldDoc``: Previous version of document that is already stored; this field is
+  absent if the doc is being created for the first time.
 
 For example, to check that all docs contain a ``title`` which is a string, and a
 ``year`` which is a number:
@@ -1012,3 +1013,72 @@ this design document:
         }
       }
     }
+
+By using the ``oldDoc`` field, we can create rules that say a document can only
+be updated if it is currently in a certain state. For example, this rule would
+enforce that only documents describing actors can be updated:
+
+.. code-block:: json
+
+    {
+      "language": "query",
+
+      "validate_doc_update": {
+        "oldDoc": { "type": "actor" }
+      }
+    }
+
+This also makes it so that no new documents can be created, because a write is
+only accepted if a previous version of the doc already exists. To relax this
+constraint, allow ``oldDoc`` not to exist:
+
+.. code-block:: json
+
+    {
+      "language": "query",
+
+      "validate_doc_update": {
+        "oldDoc": {
+          "$or": [
+            { "$exists": false },
+            { "type": "actor" }
+          ]
+        }
+      }
+    }
+
+This validator will allow any new document creation, and updates to docs where
+the ``type`` field is ``"actor"``. We can also have multiple rules for new
+document states that depend on the current state, by combining ``$or`` with
+several sets of ``{ oldDoc, newDoc }`` rules:
+
+.. code-block:: json
+
+    {
+      "language": "query",
+
+      "validate_doc_update": {
+        "$or": [
+          // allow creation of docs with an acceptable type
+          {
+            "oldDoc": { "$exists": false },
+            "newDoc": {
+              "type": { "$in": ["movie", "actor"] }
+            }
+          },
+          // if a doc currently has "type": "actor", make sure its "movies"
+          // field is a non-empty list of strings
+          {
+            "oldDoc": { "type": "actor" },
+            "newDoc": {
+              "movies": {
+                "$type": "array",
+                "$not": { "$size": 0 },
+                "$allMatch": { "$type": "string" }
+              }
+            }
+          },
+          // etc.
+        ]
+      }
+    }

src/mango/src/mango_native_proc.erl

@@ -46,7 +46,12 @@ set_timeout(Pid, TimeOut) when is_integer(TimeOut), TimeOut > 0 ->
     gen_server:call(Pid, {set_timeout, TimeOut}).
 
 prompt(Pid, Data) ->
-    gen_server:call(Pid, {prompt, Data}).
+    case gen_server:call(Pid, {prompt, Data}) of
+        {error, Error} ->
+            throw(Error);
+        Other ->
+            Other
+    end.
 
 init(_) ->
     {ok, #st{}}.
@@ -95,6 +100,17 @@ handle_call({prompt, [<<"nouveau_index_doc">>, Doc]}, _From, St) ->
                 Else
         end,
     {reply, Vals, St};
+handle_call({prompt, [<<"validate_fun">>, Selector0 | _Rest]}, _From, St) ->
+    try mango_selector:normalize(Selector0) of
+        Selector ->
+            case validate_vdu(Selector) of
+                ok -> {reply, true, St};
+                Error -> {reply, {error, Error}, St}
+            end
+    catch
+        throw:{mango_error, mango_selector, Error} ->
+            {reply, {error, Error}, St}
+    end;
 handle_call({prompt, [<<"ddoc">>, <<"new">>, DDocId, {DDoc}]}, _From, St) ->
     NewSt =
         case couch_util:get_value(<<"validate_doc_update">>, DDoc) of
@@ -112,18 +128,39 @@ handle_call({prompt, [<<"ddoc">>, DDocId, [<<"validate_doc_update">>], Args]}, _
             Msg = [<<"validate_doc_update">>, DDocId],
             {stop, {invalid_call, Msg}, {invalid_call, Msg}, St};
         Selector ->
-            [NewDoc, OldDoc, _Ctx, _SecObj] = Args,
-            Struct = {[{<<"newDoc">>, NewDoc}, {<<"oldDoc">>, OldDoc}]},
-            Reply =
-                case mango_selector:match(Selector, Struct) of
-                    true -> true;
-                    _ -> {[{<<"forbidden">>, <<"document is not valid">>}]}
-                end,
-            {reply, Reply, St}
+            case validate_vdu(Selector) of
+                {_, Error} ->
+                    {stop, {invalid_call, Error}, {invalid_call, Error}, St};
+                ok ->
+                    [NewDoc, OldDoc, _Ctx, _SecObj] = Args,
+                    Struct =
+                        case OldDoc of
+                            null -> {[{<<"newDoc">>, NewDoc}]};
+                            Doc -> {[{<<"newDoc">>, NewDoc}, {<<"oldDoc">>, Doc}]}
+                        end,
+                    Reply =
+                        case mango_selector:match_failures(Selector, Struct) of
+                            [] ->
+                                true;
+                            Failures ->
+                                {[{<<"forbidden">>, {[{<<"failures">>, Failures}]}}]}
+                        end,
+                    {reply, Reply, St}
+            end
     end;
 handle_call(Msg, _From, St) ->
     {stop, {invalid_call, Msg}, {invalid_call, Msg}, St}.
 
+validate_vdu(VDU) ->
+    case mango_selector:has_allowed_fields(VDU, [<<"newDoc">>, <<"oldDoc">>]) of
+        true ->
+            ok;
+        false ->
+            Msg =
+                <<"'validate_doc_update' may only contain 'newDoc' and 'oldDoc' as top-level fields">>,
+            {compilation_error, Msg}
+    end.
+
 handle_cast(garbage_collect, St) ->
     garbage_collect(),
     {noreply, St};