Protobuf is awesome but what if we need to quickly debug or test a client?
This is especially helpful if you work with Twirp and code in Python since the code generator does not yield a JSON Protobuf client.
Solution
You can use the protoc command to generate binary data and then pass them to curl (see 1 and 2).
Switch to the location in the Gopath which contains your api.proto file:
cd $GOPATH/src/git.example.com/my-project/
Assuming a message type with fully qualified name example.Example
package example;
message Example {
string data = 1;
}
we can generate a protobuf serialization by running
echo 'data: "bla"' \
| protoc --proto-path $GOPATH/src/git.example.com/my-project --encode example.Example api.proto
Piping this into curl call which expects binary data on STDIN lets us send protobuf serialized binary data to the target URL; e.g. for localhost:8000/twirp/example.MyRPCService/MyEndpoint
echo 'data: "bla"' \
| protoc --proto-path $GOPATH/src/git.example.com/my-project --encode example.Example api.proto
| curl -H "Content-Type: application/protobuf" --data-binary @- localhost:8000/twirp/example.MyRPCService/MyEndpoint
The input string for the encoder has a unique notation which is similar but not identical to JSON in that
- double quotes around object keys are omitted,
- object key-value pairs are separated with semicolons (”;”), and
- curly braces for the top-level object are omitted.
Otherwise, the serialization rules are the same as given in the Protobuf language guide (e.g. messages map to objects, …).