Add field_mask rules const/in/not_in (#429)

This implements #428.
I might require some help regarding the test suites. Let me know what
you think.

Signed-off-by: Christoph Hoopmann <[email protected]>

Author: choopm

proto/protovalidate-testing/buf/validate/conformance/cases/BUILD.bazel

@@ -44,6 +44,7 @@ proto_library(
         "strings.proto",
         "wkt_any.proto",
         "wkt_duration.proto",
+        "wkt_field_mask.proto",
         "wkt_nested.proto",
         "wkt_timestamp.proto",
         "wkt_wrappers.proto",
@@ -56,6 +57,7 @@ proto_library(
         "//proto/protovalidate/buf/validate:validate_proto",
         "@com_google_protobuf//:any_proto",
         "@com_google_protobuf//:duration_proto",
+        "@com_google_protobuf//:field_mask_proto",
         "@com_google_protobuf//:timestamp_proto",
         "@com_google_protobuf//:wrappers_proto",
     ],

proto/protovalidate-testing/buf/validate/conformance/cases/wkt_field_mask.proto

@@ -0,0 +1,56 @@
+// Copyright 2023-2025 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package buf.validate.conformance.cases;
+
+import "buf/validate/validate.proto";
+import "google/protobuf/field_mask.proto";
+
+message FieldMaskNone {
+  google.protobuf.FieldMask val = 1;
+}
+message FieldMaskRequired {
+  google.protobuf.FieldMask val = 1 [(buf.validate.field).required = true];
+}
+
+message FieldMaskConst {
+  google.protobuf.FieldMask val = 1 [(buf.validate.field).field_mask.const = {
+    paths: ["a"]
+  }];
+}
+
+message FieldMaskIn {
+  google.protobuf.FieldMask val = 1 [(buf.validate.field).field_mask = {
+    in: [
+      "a",
+      "b"
+    ]
+  }];
+}
+message FieldMaskNotIn {
+  google.protobuf.FieldMask val = 1 [(buf.validate.field).field_mask = {
+    not_in: [
+      "c",
+      "d"
+    ]
+  }];
+}
+
+message FieldMaskExample {
+  google.protobuf.FieldMask val = 1 [(buf.validate.field).field_mask.example = {
+    paths: ["a"]
+  }];
+}

proto/protovalidate/buf/validate/BUILD.bazel

@@ -25,6 +25,7 @@ proto_library(
     deps = [
         "@com_google_protobuf//:descriptor_proto",
         "@com_google_protobuf//:duration_proto",
+        "@com_google_protobuf//:field_mask_proto",
         "@com_google_protobuf//:timestamp_proto",
     ],
 )

proto/protovalidate/buf/validate/validate.proto

@@ -18,6 +18,7 @@ package buf.validate;
 
 import "google/protobuf/descriptor.proto";
 import "google/protobuf/duration.proto";
+import "google/protobuf/field_mask.proto";
 import "google/protobuf/timestamp.proto";
 
 option go_package = "buf.build/gen/go/bufbuild/protovalidate/protocolbuffers/go/buf/validate";
@@ -313,6 +314,7 @@ message FieldRules {
     // Well-Known Field Types
     AnyRules any = 20;
     DurationRules duration = 21;
+    FieldMaskRules field_mask = 28;
     TimestampRules timestamp = 22;
   }
 
@@ -4630,6 +4632,93 @@ message DurationRules {
   extensions 1000 to max;
 }
 
+// FieldMaskRules describe rules applied exclusively to the `google.protobuf.FieldMask` well-known type.
+message FieldMaskRules {
+  // `const` dictates that the field must match the specified value of the `google.protobuf.FieldMask` type exactly.
+  // If the field's value deviates from the specified value, an error message
+  // will be generated.
+  //
+  // ```proto
+  // message MyFieldMask {
+  //   // value must equal ["a"]
+  //   google.protobuf.FieldMask value = 1 [(buf.validate.field).field_mask.const = {
+  //       paths: ["a"]
+  //   }];
+  // }
+  // ```
+  optional google.protobuf.FieldMask const = 1 [(predefined).cel = {
+    id: "field_mask.const"
+    expression: "this != getField(rules, 'const') ? 'value must equal %s'.format([getField(rules, 'const')]) : ''"
+  }];
+
+  // `in` requires the field value to only contain paths matching specified
+  // values or their subpaths.
+  // If any of the field value's paths doesn't match the rule,
+  // an error message is generated.
+  // See: https://protobuf.dev/reference/protobuf/google.protobuf/#field-mask
+  //
+  // ```proto
+  // message MyFieldMask {
+  //   //  The `value` FieldMask must only contain paths listed in `in`.
+  //   google.protobuf.FieldMask value = 1 [(buf.validate.field).field_mask = {
+  //       in: ["a", "b", "c.a"]
+  //   }];
+  // }
+  // ```
+  repeated string in = 2 [(predefined).cel = {
+    id: "field_mask.in"
+    expression: "!this.paths.all(p, p in getField(rules, 'in') || getField(rules, 'in').exists(f, p.startsWith(f+'.'))) ? 'value must only contain paths in %s'.format([getField(rules, 'in')]) : ''"
+  }];
+
+  // `not_in` requires the field value to not contain paths matching specified
+  // values or their subpaths.
+  // If any of the field value's paths matches the rule,
+  // an error message is generated.
+  // See: https://protobuf.dev/reference/protobuf/google.protobuf/#field-mask
+  //
+  // ```proto
+  // message MyFieldMask {
+  //   //  The `value` FieldMask shall not contain paths listed in `not_in`.
+  //   google.protobuf.FieldMask value = 1 [(buf.validate.field).field_mask = {
+  //       not_in: ["forbidden", "immutable", "c.a"]
+  //   }];
+  // }
+  // ```
+  repeated string not_in = 3 [(predefined).cel = {
+    id: "field_mask.not_in"
+    expression: "!this.paths.all(p, !(p in getField(rules, 'not_in') || getField(rules, 'not_in').exists(f, p.startsWith(f+'.')))) ? 'value must not contain any paths in %s'.format([getField(rules, 'not_in')]) : ''"
+  }];
+
+  // `example` specifies values that the field may have. These values SHOULD
+  // conform to other rules. `example` values will not impact validation
+  // but may be used as helpful guidance on how to populate the given field.
+  //
+  // ```proto
+  // message MyFieldMask {
+  //   google.protobuf.FieldMask value = 1 [
+  //     (buf.validate.field).field_mask.example = { paths: ["a", "b"] },
+  //     (buf.validate.field).field_mask.example = { paths: ["c.a", "d"] },
+  //   ];
+  // }
+  // ```
+  repeated google.protobuf.FieldMask example = 4 [(predefined).cel = {
+    id: "field_mask.example"
+    expression: "true"
+  }];
+
+  // Extension fields in this range that have the (buf.validate.predefined)
+  // option set will be treated as predefined field rules that can then be
+  // set on the field options of other fields to apply field rules.
+  // Extension numbers 1000 to 99999 are reserved for extension numbers that are
+  // defined in the [Protobuf Global Extension Registry][1]. Extension numbers
+  // above this range are reserved for extension numbers that are not explicitly
+  // assigned. For rules defined in publicly-consumed schemas, use of extensions
+  // above 99999 is discouraged due to the risk of conflicts.
+  //
+  // [1]: https://github.com/protocolbuffers/protobuf/blob/main/docs/options.md
+  extensions 1000 to max;
+}
+
 // TimestampRules describe the rules applied exclusively to the `google.protobuf.Timestamp` well-known type.
 message TimestampRules {
   // `const` dictates that this field, of the `google.protobuf.Timestamp` type, must exactly match the specified value. If the field value doesn't correspond to the specified timestamp, an error message will be generated.