I am currently trying to implement a protobuf parser but it's a bit unclear
to me how I should interpret some parts of the specification.
Lets start with RPC option. Options for normal fields and enum fields are
pretty clear.
Here's the specification for normal fields:
field = [ "repeated" ] type fieldName "=" fieldNumber [ "[" fieldOptions
"]" ] ";" fieldOptions = fieldOption { "," fieldOption } fieldOption =
optionName "=" constant
Here's the specification for enum fields:
enum = "enum" enumName enumBody enumBody = "{" { option | enumField |
emptyStatement | reserved } "}" enumField = ident "=" [ "-" ] intLit [ "["
enumValueOption { "," enumValueOption } "]" ]";" enumValueOption =
optionName "=" constant
Both fields boils down to optionName which is specified as:
optionName = ( ident | "(" ["."] fullIdent ")" )
Here's the specification for RPC:
service = "service" serviceName "{" { option | rpc | emptyStatement } "}" rpc
= "rpc" rpcName "(" [ "stream" ] messageType ")" "returns" "(" [ "stream" ]
messageType
")" (( "{" {option | emptyStatement } "}" ) | ";")
RPC refers to plain option. Does this mean that the following is valid and
intended syntax?
rpc Foo (Req) returns (Res);
rpc Foo (Req) returns (Res) {option opt1 = "opt1"; option opt2 = true; };
rpc Foo (Req) returns (Res) {option opt1 = "opt1"; ;;; option opt2 = true;
;;;};
I added number 3, because it seems like repetition is allowed together with
emptyStatement. As a side note, I could not find any examples with RPC
options as inspiration or to clear things up.
Further, I also find the specification for optionName a bit unclear.
Here's the specification for option and optionName:
option = "option" optionName "=" constant ";" optionName = ( ident | "("
["."] fullIdent ")" )
optionName does not seem to allow for repetition and fullIdent is only
allowed within parenthesis(custom option). However multiple examples on
https://protobuf.dev/programming-guides/proto3/#option-targets
use custom-like options on the format:
option (bar).baz = "value";
For me it's pretty clear that the following optionNames are allowed:
foo
(foo)
(foo.bar)
(.foo)
(.foo.bar)
I don't really get which part of the specification that states that "baz",
in the example above, is allowed outside of the parenthesis.
Thanks in advance,
/Mattias
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