Add more examples (#93)

`option_*` cover most features from [the standard
options](https://buf.build/bufbuild/protovalidate/docs/main:buf.validate).

`cel_*` cover most features from [CEL's feature
list](https://github.com/google/cel-spec/blob/master/doc/langdef.md#list-of-standard-definitions).
Exception:
- From timestamp's `getFooFromBar` family, including `getDate`,
`getDayOfMonth`, `getDayOfYear`, `getFullYear`, `getHours`,
`getMilliseconds`, `getMinutes`, `getMonth` and `getSeconds`, only
`getDayOrWeek` is covered, but there is a comment mentioning all the
rest and a link to this feature list.

`cel_*` also cover [custom CEL functions and
overloads](https://github.com/bufbuild/protovalidate/blob/main/docs/cel.md#custom-variables-functions-and-overloads)

Author: oliversun9

examples/BUILD.bazel

@@ -18,39 +18,91 @@ load("@rules_buf//buf:defs.bzl", "buf_lint_test")
 proto_library(
     name = "examples_proto",
     srcs = [
+        "cel_assert_value_is_in_a_list.proto",
+        "cel_bytes_concatentation.proto",
+        "cel_bytes_contains.proto",
+        "cel_bytes_starts_with_ends_with.proto",
         "cel_conditional_operator.proto",
+        "cel_duration_arithmetic.proto",
         "cel_duration_from_string.proto",
         "cel_enum_comparision.proto",
         "cel_field_access.proto",
+        "cel_field_mask.proto",
         "cel_field_presence.proto",
+        "cel_field_presence_nested.proto",
         "cel_field_selection.proto",
-        "cel_map_key.proto",
+        "cel_infinity.proto",
+        "cel_list_concatenation.proto",
+        "cel_map_all.proto",
+        "cel_map_exists.proto",
+        "cel_map_exists_one.proto",
+        "cel_map_size.proto",
+        "cel_number_arithmetic.proto",
         "cel_repeated_field_all.proto",
         "cel_repeated_field_exists_one.proto",
-        "cel_repeated_field_filter_and_size.proto",
+        "cel_repeated_field_filter_and_count.proto",
+        "cel_repeated_field_unique.proto",
+        "cel_string_concatentation.proto",
         "cel_string_contains.proto",
+        "cel_string_is_email.proto",
+        "cel_string_is_hostname.proto",
+        "cel_string_is_ip.proto",
+        "cel_string_is_uri.proto",
         "cel_string_match_pattern.proto",
         "cel_string_starts_with_ends_with.proto",
+        "cel_timestamp_comparsion.proto",
+        "cel_timestamp_get_attribute.proto",
         "cel_timestamp_plus_duration.proto",
         "cel_timestamp_subtraction.proto",
-        "cel_timestamp_to_day_of_week.proto",
+        "cel_type_conversion.proto",
+        "cel_value.proto",
+        "cel_wrapper_type.proto",
+        "option_any_type_allow_list.proto",
+        "option_any_type_ban_list.proto",
         "option_bool.proto",
-        "option_bytes.proto",
+        "option_bytes_ban_values.proto",
+        "option_bytes_contains.proto",
+        "option_bytes_equal.proto",
+        "option_bytes_len.proto",
+        "option_bytes_pattern.proto",
+        "option_bytes_prefix_suffix.proto",
+        "option_duration_allow_values.proto",
+        "option_duration_disallow_values.proto",
+        "option_duration_equal.proto",
+        "option_duration_range.proto",
+        "option_enum_allow_values.proto",
+        "option_enum_disallow_values.proto",
+        "option_field_ignore_empty.proto",
+        "option_field_presence.proto",
+        "option_field_skip_validation.proto",
         "option_map.proto",
-        "option_number.proto",
+        "option_message_disable_validation.proto",
+        "option_number_allow_values.proto",
+        "option_number_disallow_values.proto",
+        "option_number_equal.proto",
+        "option_number_finite_and_infinite.proto",
+        "option_number_range.proto",
         "option_oneof.proto",
         "option_repeated.proto",
-        "option_require_field_presence.proto",
-        "option_string.proto",
-        "option_wkt_any.proto",
-        "option_wkt_duration.proto",
+        "option_string_allow_values.proto",
+        "option_string_ban_values.proto",
+        "option_string_contains.proto",
+        "option_string_equal.proto",
+        "option_string_is_http_header.proto",
+        "option_string_len.proto",
+        "option_string_match_pattern.proto",
+        "option_string_prefix_suffix.proto",
+        "option_timestamp_range.proto",
+        "option_timestamp_relative_to_now.proto",
     ],
     strip_import_prefix = "/examples",
     visibility = ["//visibility:public"],
     deps = [
         "//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//:struct_proto",
         "@com_google_protobuf//:timestamp_proto",
         "@com_google_protobuf//:wrappers_proto",
         "@go_googleapis//google/type:postaladdress_proto",

examples/cel_assert_value_is_in_a_list.proto

@@ -0,0 +1,42 @@
+// 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 = "proto3";
+
+import "buf/validate/validate.proto";
+
+service DivisionService {
+  // IsDivisible solves whether one number is divisible by another.
+  rpc IsDivisible(IsDivisibleRequest) returns (IsDivisibleResponse);
+}
+
+message IsDivisibleRequest {
+  // dividend is the dividend in the division.
+  int32 dividend = 1;
+  // divisor is the divisor in the division.
+  int32 divisor = 2 [(buf.validate.field).cel = {
+    id: "divisor_must_be_a_small_prime",
+    message: "the divisor must be one of 2, 3 and 5",
+    // `in` evaluates list membership. The expression evaluates to
+    // true when the value is in the list.
+    // Validates that divisor must be one of 2, 3 and 5.
+    expression: "this in [2, 3, 5]",
+    // Similarly, you can assert that it's not in a list with `!(this in [2, 3, 5])`.
+  }];
+}
+
+message IsDivisibleResponse {
+  // is_divisible is the result.
+  bool is_divisible = 1;
+}

examples/cel_bytes_concatentation.proto

@@ -0,0 +1,30 @@
+// 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 = "proto3";
+
+import "buf/validate/validate.proto";
+
+message CompactDocument {
+  option (buf.validate.message).cel = {
+    id: "header_footer_size_limit",
+    message: "header and footer should be less than 500 bytes in total",
+    // the `+` operator concatenates two `bytes` together and `size` returns
+    // the length of a `bytes`.
+    // This validates that the combined size of header and footer should be < 500.
+    expression: "size(this.header + this.footer) < 500"
+  };
+  bytes header = 1;
+  bytes footer = 2;
+}

examples/cel_bytes_contains.proto

@@ -0,0 +1,32 @@
+// 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 = "proto3";
+
+import "buf/validate/validate.proto";
+
+// Application is an application.
+message Application {
+  // binary is the application's binary
+  bytes binary = 1 [(buf.validate.field).cel = {
+    id: "without_malicious_code",
+    message: "binary should not contain malicious code",
+    // `contains` returns if the receiver `bytes` contains the argument `bytes`.
+    // This validates that the application binary should not contain bytes for
+    // `'malicious code'`.
+    // Note that when checking whether bytes for a string is contained, `bytes()`
+    // must be called to convert the string into bytes.
+    expression: "!this.contains(bytes('malicious code'))"
+  }];
+}

examples/cel_bytes_starts_with_ends_with.proto

@@ -0,0 +1,37 @@
+// 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 = "proto3";
+
+import "buf/validate/validate.proto";
+
+message ScriptFile {
+  bytes content = 1 [(buf.validate.field).cel = {
+    id: "script_start_with_shabang_end_with_line_feed",
+    expression:
+      // this is a ternary expression in the form of a ? b : c, if the the
+      // script file doesn't start with '#!', the expression evaluates to the
+      // first error message, which fails the validation. Otherwise it
+      // evaluates to the next expression.
+      "!this.startsWith(bytes('#!')) ? 'must start with #!'"
+      // If this file does not end with the new line character, it evaluates
+      // to the second error message.
+      // Note: the `'\x0A'` is byte string for the new line character, but
+      // we have two backslashes below. This is because we need to escape the
+      // backslash.
+      ": !this.endsWith(bytes('\\x0A')) ? 'must end with a new line'"
+      // If the file passes the two checks above, there is no error.
+      ": ''"
+  }];
+}

examples/cel_duration_arithmetic.proto

@@ -0,0 +1,37 @@
+// 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 = "proto3";
+
+import "buf/validate/validate.proto";
+import "google/protobuf/duration.proto";
+
+message IndirectFlight {
+  option (buf.validate.message).cel = {
+    id: "totol_lenght_limit",
+    message: "the entire trip should be less than 48 hours",
+    expression:
+      // This validates that the total duration of an indirect flight should be
+      // less than 48 hours.
+      // Adding two duration yields a duration.
+      // Note that if the CEL expression is too long, you can break it down into
+      // multiple lines like so:
+      "this.first_flight_duration + this.second_flight_duration"
+      // Durations can be compared with `<`, `<=`, `>=`, `>`, `==` and `!=`.
+      "+ this.layover_duration < duration('48h')"
+  };
+  google.protobuf.Duration first_flight_duration = 1;
+  google.protobuf.Duration layover_duration = 2;
+  google.protobuf.Duration second_flight_duration = 3;
+}

examples/cel_field_mask.proto

@@ -0,0 +1,54 @@
+// 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 = "proto3";
+
+import "buf/validate/validate.proto";
+import "google/protobuf/duration.proto";
+import "google/protobuf/field_mask.proto";
+import "google/protobuf/timestamp.proto";
+
+service SongService {
+  rpc UpdateSong(UpdateSongRequest) returns (UpdateSongResponse);
+}
+
+message UpdateSongRequest {
+  // song is the updated song.
+  Song song = 1;
+  // field_mask masks the fields to update.
+  google.protobuf.FieldMask field_mask = 2 [(buf.validate.field).cel = {
+    id: "valid_field_mask",
+    message: "a field mask path must be one of name, duration and artist.name",
+    // `some_list.all()` validates that a predicate is true for all elements
+    // from that list.
+    // In this case, `this.paths` is the field paths from.
+    expression: "this.paths.all(path, path in ['name', 'duration', 'artist.name'])",
+  }];
+}
+
+message Song {
+  string name = 1;
+  fixed64 id = 2;
+  google.protobuf.Timestamp create_time = 3;
+  google.protobuf.Duration duration = 4;
+  Artist artist = 5;
+}
+
+message Artist {
+  string name = 1;
+  // other fields:
+  // ...
+}
+
+message UpdateSongResponse {}

examples/cel_field_presence_nested.proto

@@ -0,0 +1,45 @@
+// 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 = "proto3";
+
+import "buf/validate/validate.proto";
+
+service ContactService {
+  // CreateContact creates a contact.
+  rpc CreateContact(CreateContactRequest) returns (CreateContactResponse);
+}
+
+message CreateContactRequest {
+  option (buf.validate.message).cel = {
+    id: "create_contact_with_first_name",
+    message: "the contact must have first name",
+    // This expression validates that all of `this.contact`, `this.contact.full_name`
+    // and `this.contact.full_name.first_name` are set.
+    expression: "has(this.contact.full_name.first_name)"
+  };
+  // contact is the contact to create.
+  Contact contact = 1;
+}
+
+message Contact {
+  FullName full_name = 1;
+}
+
+message FullName {
+  string first_name = 1;
+  string last_name = 2;
+}
+
+message CreateContactResponse {}