Implement a nullable annotation for fields and messages (#26)

* Implement a nullable annotation for fields and messages

* Add back deleted tests

firebase_rules_generator/generator.cc

@@ -457,7 +457,15 @@ bool RulesGenerator::GenerateField(const protobuf::FieldDescriptor *field,
   if (options.has_validate()) {
     printer.Print(" && ($validate$)", "validate", options.validate());
   }
-  printer.Print("))");
+  printer.Print(")");
+  const auto &msg_options =
+      field->containing_type()->options().GetExtension(firebase_rules_message);
+  bool nullable =
+      (!options.has_nullable() && msg_options.nullable()) || options.nullable();
+  if (nullable) {
+    printer.Print(" || resource.$name$ is null", "name", field->json_name());
+  }
+  printer.Print(")");
   return true;
 }
 

proto/firebase_rules_options.proto

@@ -7,11 +7,13 @@ import "google/protobuf/descriptor.proto";
 message RulesMessageOptions {
   optional string validate = 1;
   optional bool extra_properties = 2 [default = false];
+  optional bool nullable = 3 [default = false];
 }
 
 message RulesFieldOptions {
   optional string validate = 1;
   optional bool reference_type = 2 [default = false];
+  optional bool nullable = 3 [default = false];
 }
 
 message RulesFileOptions {

testdata/testA.proto

@@ -0,0 +1,17 @@
+syntax = "proto3";
+
+package example;
+
+import "firebase_rules_options.proto";
+
+message NullableExample {
+  string foo = 1;
+  string bar = 2
+      [(google.firebase.rules.firebase_rules_field).nullable = false];
+  option (google.firebase.rules.firebase_rules_message).nullable = true;
+}
+
+message Example {
+  string foo = 1;
+  string bar = 2 [(google.firebase.rules.firebase_rules_field).nullable = true];
+}

testdata/testA.rules

@@ -0,0 +1,14 @@
+// @@START_GENERATED_FUNCTIONS@@
+function isNullableExampleMessage(resource) {
+  return resource.keys().hasAll([]) &&
+          (resource.keys().hasOnly(['bar','foo'])) &&
+          ((!resource.keys().hasAny(['foo'])) || (resource.foo is string) || resource.foo is null) &&
+          ((!resource.keys().hasAny(['bar'])) || (resource.bar is string));
+}
+function isExampleMessage(resource) {
+  return resource.keys().hasAll([]) &&
+          (resource.keys().hasOnly(['bar','foo'])) &&
+          ((!resource.keys().hasAny(['foo'])) || (resource.foo is string)) &&
+          ((!resource.keys().hasAny(['bar'])) || (resource.bar is string) || resource.bar is null);
+}
+// @@END_GENERATED_FUNCTIONS@@