Add example options for most types (#239)

This PR adds an example field for many types. Examples are no-op
constraints that allow you to declare what an example value for each
field may look like. These values SHOULD match the other constraints.
It's planned that a `buf lint` rule will check these values to see if
they do, in fact, validate given the other constraints on the field.
Here are the types that this was added to:
- float
- double
- int32
- int64
- uint32
- uint64
- sint32
- sint64
- fixed32
- fixed64
- sfixed32
- sfixed64
- bool
- string
- bytes
- enum
- duration
- timestamp

All fields are `repeatable`, to allow for multiple examples. I'm unsure
if there is a better way to have a no-op constraint other than
`expression: "true"`, so please let me know if I can just exclude
`expression` altogether or if there is another way to do that. This
resolves #237.

---------

Co-authored-by: Chris Roche <[email protected]>

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

@@ -27,3 +27,6 @@ message BoolConstTrue {
 message BoolConstFalse {
   bool val = 1 [(buf.validate.field).bool.const = false];
 }
+message BoolExample {
+  bool val = 1 [(buf.validate.field).bool.example = true];
+}

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

@@ -88,3 +88,6 @@ message BytesIPv6Ignore {
     (buf.validate.field).ignore_empty = true
   ];
 }
+message BytesExample {
+  bytes val = 1 [(buf.validate.field).bytes.example = "\x99"];
+}

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

@@ -121,3 +121,7 @@ message EnumInsideOneof {
     }];
   }
 }
+
+message EnumExample {
+  TestEnum val = 1 [(buf.validate.field).enum.example = 2];
+}

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

@@ -90,6 +90,10 @@ message FloatIncorrectType {
   float val = 1 [(buf.validate.field).double.gt = 0];
 }
 
+message FloatExample {
+  float val = 1 [(buf.validate.field).float.example = 8];
+}
+
 message DoubleNone {
   double val = 1;
 }
@@ -162,6 +166,10 @@ message DoubleIncorrectType {
   double val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message DoubleExample {
+  double val = 1 [(buf.validate.field).double.example = 0];
+}
+
 message Int32None {
   int32 val = 1;
 }
@@ -231,6 +239,10 @@ message Int32IncorrectType {
   int32 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message Int32Example {
+  int32 val = 1 [(buf.validate.field).int32.example = 10];
+}
+
 message Int64None {
   int64 val = 1;
 }
@@ -325,6 +337,10 @@ message Int64IncorrectType {
   int64 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message Int64Example {
+  int64 val = 1 [(buf.validate.field).float.example = 10];
+}
+
 message UInt32None {
   uint32 val = 1;
 }
@@ -394,6 +410,10 @@ message UInt32IncorrectType {
   uint32 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message UInt32Example {
+  uint32 val = 1 [(buf.validate.field).uint32.example = 0];
+}
+
 message UInt64None {
   uint64 val = 1;
 }
@@ -463,6 +483,10 @@ message UInt64IncorrectType {
   uint64 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message UInt64Example {
+  uint64 val = 1 [(buf.validate.field).uint64.example = 0];
+}
+
 message SInt32None {
   sint32 val = 1;
 }
@@ -532,6 +556,10 @@ message SInt32IncorrectType {
   sint32 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message SInt32Example {
+  sint32 val = 1 [(buf.validate.field).int32.example = 0];
+}
+
 message SInt64None {
   sint64 val = 1;
 }
@@ -600,6 +628,10 @@ message SInt64IncorrectType {
   sint64 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message SInt64Example {
+  sint64 val = 1 [(buf.validate.field).sint64.example = 0];
+}
+
 message Fixed32None {
   fixed32 val = 1;
 }
@@ -669,6 +701,10 @@ message Fixed32IncorrectType {
   fixed32 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message Fixed32Example {
+  fixed32 val = 1 [(buf.validate.field).fixed32.example = 0];
+}
+
 message Fixed64None {
   fixed64 val = 1;
 }
@@ -738,6 +774,10 @@ message Fixed64IncorrectType {
   fixed64 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message Fixed64Example {
+  fixed64 val = 1 [(buf.validate.field).fixed64.example = 0];
+}
+
 message SFixed32None {
   sfixed32 val = 1;
 }
@@ -807,6 +847,10 @@ message SFixed32IncorrectType {
   sfixed32 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message SFixed32Example {
+  sfixed32 val = 1 [(buf.validate.field).sfixed32.example = 0];
+}
+
 message SFixed64None {
   sfixed64 val = 1;
 }
@@ -876,6 +920,10 @@ message SFixed64IncorrectType {
   sfixed64 val = 1 [(buf.validate.field).float.gt = 0];
 }
 
+message SFixed64Example {
+  sfixed64 val = 1 [(buf.validate.field).sfixed64.example = 0];
+}
+
 message Int64LTEOptional {
   optional int64 val = 1 [(buf.validate.field).int64.lte = 64];
 }

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

@@ -195,3 +195,7 @@ message StringHostAndOptionalPort {
     expression: "this.isHostAndPort(false)"
   }];
 }
+
+message StringExample {
+  string val = 1 [(buf.validate.field).string.example = "foo"];
+}

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

@@ -89,3 +89,7 @@ message DurationFieldWithOtherFields {
   google.protobuf.Duration duration_val = 1 [(buf.validate.field).duration.lte = {seconds: 1}];
   int32 int_val = 2 [(buf.validate.field).int32.gt = 16];
 }
+
+message DurationExample {
+  google.protobuf.Duration val = 1 [(buf.validate.field).duration.example = {seconds: 3}];
+}

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

@@ -89,3 +89,7 @@ message TimestampGTNowWithin {
     within: {seconds: 3600}
   }];
 }
+
+message TimestampExample {
+  google.protobuf.Timestamp val = 1 [(buf.validate.field).timestamp.example = {seconds: 3}];
+}