Implement predefined field constraints

docs/README.md

@@ -27,6 +27,11 @@ library.
       This guide will help you understand when and how to use these standard
       constraints effectively.
 
+    - [Shared Constraints](shared-constraints.md): This section discusses how to
+      extend `protovalidate` with custom reusable rules that behave similarly
+      to the pre-defined standard constraints. This can be useful in order to
+      share similar custom validation logic across multiple fields or messages.
+
 - [Errors](errors.md): This section explains the error system in `protovalidate`
   and provides guidance on how to handle them effectively.
 
@@ -38,7 +43,7 @@ designed to help you implement new language support and assist in migrating your
 existing projects to `protovalidate`.
 
 - [Conformance](conformance.md): This document is dedicated to explaining the
-  Conformance tool. Learn how to use this tool to ensure all implementations 
+  Conformance tool. Learn how to use this tool to ensure all implementations
   align with `protovalidate`'s rules and constraints effectively.
 
 - [Migrate](migrate.md): If you're planning to migrate your existing project to

docs/shared-constraints.md

@@ -0,0 +1,69 @@
+# Shared Constraints
+
+Custom constraints in `protovalidate` afford a lot of power, but can become
+cumbersome and repetitive when the same kind of custom constraints are needed
+across multiple fields or messages. To this end, `protovalidate` provides a
+mechanism for creating reusable constraints that can be applied on multiple
+fields.
+
+Shared constraints require Protobuf extensions, which are not available in
+proto3. Either proto2 or at least Protobuf 2023 Edition must be used to define
+shared constraints. Shared constraints defined in proto2 or Protobuf 2023
+Edition or later can be imported and utilized in proto3 files.
+
+## Shared Field Constraints
+
+To define a shared field rule, extend one of the standard rules messages. For
+example, to define a new rule for `float` fields, extend
+`buf.validate.FloatRules`, as follows:
+
+```proto
+import "buf/validate/shared/constraints.proto";
+import "buf/validate/validate.proto";
+
+extend buf.validate.FloatRules {
+  float abs_range = 80048952 [(buf.validate.shared.field).cel = {
+    id: "float.abs_range"
+    expression: "this >= -rule && this <= rule"
+    message: "float value is out of range"
+  }];
+}
+```
+
+> [!TIP]
+> Rules can refer to their own value with the `rule` constant.
+
+> [!WARNING]
+> Be mindful that extension numbers must not conflict with any other extension
+> to the same message across _all_ Protobuf files in a given process. This
+> restriction also applies to users that consume Protobuf files indirectly as
+> dependencies. The same extension number may be re-used across different kinds
+> of rules.
+>
+> Extension numbers may be from 1000 to 536870911, inclusive. Values from 1000
+> to 50000 are reserved for [Protobuf Global Extension Registry][1] entries, and
+> values from 50000 to 536870911 are reserved for randomly-generated integers.
+> If using a randomly-generated integer as a tag number, please use an
+> appropriate source of randomness. [This link to random.org][2] can be used to
+> generate such an appropriate number.
+
+[1]: https://github.com/protocolbuffers/protobuf/blob/main/docs/options.md "Protobuf Global Extension Registry"
+[2]: https://www.random.org/integers/?num=1&min=50000&max=536870911&format=html&col=1&base=10 "RANDOM.ORG - Integer Generator"
+
+Similarly to the standard constraints, a rule will take effect when it is set on
+the options of a field. Here is how one might use a shared rule:
+
+```proto
+message MyMessage {
+  float normal_value = 1 [(buf.validate.field).float.(abs_range) = 1.0];
+}
+```
+
+> [!TIP]
+> Extensions are qualified by the context they are declared in. Therefore, the
+> name in the parenthesis may need to be more specific if the extension appears
+> in a different package or under a message. Like other type identifiers, parts
+> of the path that are common with the current context can be omitted, e.g. in
+> the same package the extension was defined in, the package may be entirely
+> omitted. In this example, we are assuming the extension is declared in the
+> same package.

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

@@ -37,6 +37,9 @@ proto_library(
         "required_field_proto2.proto",
         "required_field_proto3.proto",
         "required_field_proto_editions.proto",
+        "shared_rules_proto2.proto",
+        "shared_rules_proto3.proto",
+        "shared_rules_proto_editions.proto",
         "strings.proto",
         "wkt_any.proto",
         "wkt_duration.proto",
@@ -50,6 +53,7 @@ proto_library(
         "//proto/protovalidate-testing/buf/validate/conformance/cases/other_package:buf_validate_conformance_cases_other_package_proto",
         "//proto/protovalidate-testing/buf/validate/conformance/cases/yet_another_package:buf_validate_conformance_cases_yet_another_package_proto",
         "//proto/protovalidate/buf/validate:validate_proto",
+        "//proto/protovalidate/buf/validate/shared:shared_proto",
         "@com_google_protobuf//:any_proto",
         "@com_google_protobuf//:duration_proto",
         "@com_google_protobuf//:timestamp_proto",

proto/protovalidate-testing/buf/validate/conformance/cases/shared_rules_proto2.proto

@@ -0,0 +1,252 @@
+// Copyright 2023 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 = "proto2";
+
+package buf.validate.conformance.cases;
+
+import "buf/validate/shared/constraints.proto";
+import "buf/validate/validate.proto";
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+
+extend buf.validate.FloatRules {
+  optional float float_abs_range_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "float.abs_range.proto2"
+    expression: "this >= -rule && this <= rule"
+    message: "float value is out of range"
+  }];
+}
+
+extend buf.validate.DoubleRules {
+  optional double double_abs_range_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "double.abs_range.proto2"
+    expression: "this >= -rule && this <= rule"
+    message: "double value is out of range"
+  }];
+}
+
+extend buf.validate.Int32Rules {
+  optional bool int32_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "int32.even.proto2"
+    expression: "this % 2 == 0"
+    message: "int32 value is not even"
+  }];
+}
+
+extend buf.validate.Int64Rules {
+  optional bool int64_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "int64.even.proto2"
+    expression: "this % 2 == 0"
+    message: "int64 value is not even"
+  }];
+}
+
+extend buf.validate.UInt32Rules {
+  optional bool uint32_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "uint32.even.proto2"
+    expression: "this % 2u == 0u"
+    message: "uint32 value is not even"
+  }];
+}
+
+extend buf.validate.UInt64Rules {
+  optional bool uint64_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "uint64.even.proto2"
+    expression: "this % 2u == 0u"
+    message: "uint64 value is not even"
+  }];
+}
+
+extend buf.validate.SInt32Rules {
+  optional bool sint32_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "sint32.even.proto2"
+    expression: "this % 2 == 0"
+    message: "sint32 value is not even"
+  }];
+}
+
+extend buf.validate.SInt64Rules {
+  optional bool sint64_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "sint64.even.proto2"
+    expression: "this % 2 == 0"
+    message: "sint64 value is not even"
+  }];
+}
+
+extend buf.validate.Fixed32Rules {
+  optional bool fixed32_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "fixed32.even.proto2"
+    expression: "this % 2u == 0u"
+    message: "fixed32 value is not even"
+  }];
+}
+
+extend buf.validate.Fixed64Rules {
+  optional bool fixed64_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "fixed64.even.proto2"
+    expression: "this % 2u == 0u"
+    message: "fixed64 value is not even"
+  }];
+}
+
+extend buf.validate.SFixed32Rules {
+  optional bool sfixed32_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "sfixed32.even.proto2"
+    expression: "this % 2 == 0"
+    message: "sfixed32 value is not even"
+  }];
+}
+
+extend buf.validate.SFixed64Rules {
+  optional bool sfixed64_even_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "sfixed64.even.proto2"
+    expression: "this % 2 == 0"
+    message: "sfixed64 value is not even"
+  }];
+}
+
+extend buf.validate.BoolRules {
+  optional bool bool_false_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "bool.false.proto2"
+    expression: "this == false"
+    message: "bool value is not false"
+  }];
+}
+
+extend buf.validate.StringRules {
+  optional bool string_valid_path_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "string.valid_path.proto2"
+    expression: "!this.matches('^([^/.][^/]?|[^/][^/.]|[^/]{3,})(/([^/.][^/]?|[^/][^/.]|[^/]{3,}))*$') ? 'not a valid path: `%s`'.format([this]) : ''"
+  }];
+}
+
+extend buf.validate.BytesRules {
+  optional bool bytes_valid_path_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "bytes.valid_path.proto2"
+    expression: "!string(this).matches('^([^/.][^/]?|[^/][^/.]|[^/]{3,})(/([^/.][^/]?|[^/][^/.]|[^/]{3,}))*$') ? 'not a valid path: `%s`'.format([this]) : ''"
+  }];
+}
+
+extend buf.validate.EnumRules {
+  optional bool enum_non_zero_proto2 = 1161 [(buf.validate.shared.field).cel = {
+    id: "enum.non_zero.proto2"
+    expression: "int(this) != 0"
+    message: "enum value is not non-zero"
+  }];
+}
+
+extend buf.validate.RepeatedRules {
+  optional bool repeated_at_least_five_proto2 = 1161 [(shared.field).cel = {
+    id: "repeated.at_least_five.proto2"
+    expression: "uint(this.size()) >= 5u"
+    message: "repeated field must have at least five values"
+  }];
+}
+
+extend buf.validate.DurationRules {
+  optional bool duration_too_long_proto2 = 1161 [(shared.field).cel = {
+    id: "duration.too_long.proto2"
+    expression: "this <= duration('10s')"
+    message: "duration can't be longer than 10 seconds"
+  }];
+}
+
+extend buf.validate.TimestampRules {
+  optional bool timestamp_in_range_proto2 = 1161 [(shared.field).cel = {
+    id: "timestamp.time_range.proto2"
+    expression: "int(this) >= 1049587200 && int(this) <= 1080432000"
+    message: "timestamp out of range"
+  }];
+}
+
+message SharedFloatRuleProto2 {
+  optional float val = 1 [(buf.validate.field).float.(float_abs_range_proto2) = 1.0];
+}
+
+message SharedDoubleRuleProto2 {
+  optional double val = 1 [(buf.validate.field).double.(double_abs_range_proto2) = 1.0];
+}
+
+message SharedInt32RuleProto2 {
+  optional int32 val = 1 [(buf.validate.field).int32.(int32_even_proto2) = true];
+}
+
+message SharedInt64RuleProto2 {
+  optional int64 val = 1 [(buf.validate.field).int64.(int64_even_proto2) = true];
+}
+
+message SharedUInt32RuleProto2 {
+  optional uint32 val = 1 [(buf.validate.field).uint32.(uint32_even_proto2) = true];
+}
+
+message SharedUInt64RuleProto2 {
+  optional uint64 val = 1 [(buf.validate.field).uint64.(uint64_even_proto2) = true];
+}
+
+message SharedSInt32RuleProto2 {
+  optional sint32 val = 1 [(buf.validate.field).sint32.(sint32_even_proto2) = true];
+}
+
+message SharedSInt64RuleProto2 {
+  optional sint64 val = 1 [(buf.validate.field).sint64.(sint64_even_proto2) = true];
+}
+
+message SharedFixed32RuleProto2 {
+  optional fixed32 val = 1 [(buf.validate.field).fixed32.(fixed32_even_proto2) = true];
+}
+
+message SharedFixed64RuleProto2 {
+  optional fixed64 val = 1 [(buf.validate.field).fixed64.(fixed64_even_proto2) = true];
+}
+
+message SharedSFixed32RuleProto2 {
+  optional sfixed32 val = 1 [(buf.validate.field).sfixed32.(sfixed32_even_proto2) = true];
+}
+
+message SharedSFixed64RuleProto2 {
+  optional sfixed64 val = 1 [(buf.validate.field).sfixed64.(sfixed64_even_proto2) = true];
+}
+
+message SharedBoolRuleProto2 {
+  optional bool val = 1 [(buf.validate.field).bool.(bool_false_proto2) = true];
+}
+
+message SharedStringRuleProto2 {
+  optional string val = 1 [(buf.validate.field).string.(string_valid_path_proto2) = true];
+}
+
+message SharedBytesRuleProto2 {
+  optional bytes val = 1 [(buf.validate.field).bytes.(bytes_valid_path_proto2) = true];
+}
+
+message SharedEnumRuleProto2 {
+  enum EnumProto2 {
+    ENUM_PROTO2_ZERO_UNSPECIFIED = 0;
+    ENUM_PROTO2_ONE = 1;
+  }
+  optional EnumProto2 val = 1 [(buf.validate.field).enum.(enum_non_zero_proto2) = true];
+}
+
+message SharedRepeatedRuleProto2 {
+  repeated uint64 val = 1 [(buf.validate.field).repeated.(repeated_at_least_five_proto2) = true];
+}
+
+message SharedDurationRuleProto2 {
+  optional google.protobuf.Duration val = 1 [(buf.validate.field).duration.(duration_too_long_proto2) = true];
+}
+
+message SharedTimestampRuleProto2 {
+  optional google.protobuf.Timestamp val = 1 [(buf.validate.field).timestamp.(timestamp_in_range_proto2) = true];
+}