Fix examples

[Tim-Zhang]

Got: cargo run --example server unix:///tmp/1 error[E0425]: cannot find value VERSION_2_8_0 in crate protobuf

The above error is caused by protobuf version checking mechanism in the generated codes in examples.

For more information:

• https://github.com/stepancheg/rust-protobuf/commit/2ab4d50c27c4dd7803b64ce1a43e2c134532c7a6
• https://github.com/stepancheg/rust-protobuf/issues/466

This PR remove generated files in example and add instructions to README to fix the above error and explain how to avoid the error.

[teawater]

I would like we keep these files until this file can be auto generated with build. Do you mind to take a look on build.rs that can do it.

[Tim-Zhang]

@teawater I have tried to generate *.rs file from .proto automatically by build.rs today, it works but I think it is not a good idea because build.rs will run with cargo build, but 'cargo build' is not supposed to generate codes in examples, maybe it's not an action which Rustaceans will do.

[teawater]

@teawater I have tried to generate *.rs file from .proto automatically by build.rs today, it works but I think it is not a good idea because build.rs will run with cargo build, but 'cargo build' is not supposed to generate codes in examples, maybe it's not an action which Rustaceans will do.

@Tim-Zhang Cool! I really like build.rs example. That is a really important example for user. Please keep it. If it cannot be a part of normal example, maybe we can change example to a special directory name or something. What do you think about it? @lifupan

[Tim-Zhang]

@teawater @lifupan I have pushed the commit. In this commit I have renamed examples to example to make it a standalone cargo project, and I have created a file example/build.rs which will generate example/protocols/*.rs when users run cargo run --example server/client in the folder example the first time.

[teawater]

teawater@teawater-HP-ProDesk-680-G1-TWR:~/ttrpc-rust/example$ rm -rf protocols/*_ttrpc.rs
teawater@teawater-HP-ProDesk-680-G1-TWR:~/ttrpc-rust/example$ cargo build --examples
error[E0583]: file not found for module `agent_ttrpc`
 --> protocols/mod.rs:2:9
  |
2 | pub mod agent_ttrpc;
  |         ^^^^^^^^^^^
  |
  = help: name the file either agent_ttrpc.rs or agent_ttrpc/mod.rs inside the directory "protocols"

error: aborting due to previous error

For more information about this error, try `rustc --explain E0583`.
error[E0583]: file not found for module `agent_ttrpc`
 --> protocols/mod.rs:2:9
  |
2 | pub mod agent_ttrpc;
  |         ^^^^^^^^^^^
  |
  = help: name the file either agent_ttrpc.rs or agent_ttrpc/mod.rs inside the directory "protocols"

error: aborting due to previous error

For more information about this error, try `rustc --explain E0583`.
error: could not compile `ttrpc-example`.
warning: build failed, waiting for other jobs to finish...
error: could not compile `ttrpc-example`.

To learn more, run the command again with --verbose.
teawater@teawater-HP-ProDesk-680-G1-TWR:~/ttrpc-rust/example$ cd protocols/
teawater@teawater-HP-ProDesk-680-G1-TWR:~/ttrpc-rust/example/protocols$ hack/update-generated-proto.sh
/usr/local/bin/protoc
/home/teawater/.cargo/bin/protoc-gen-rust
/home/teawater/gopath//bin//ttrpc_rust_plugin
protoc --rust_out=./ --ttrpc_out=./,plugins=ttrpc:./ --plugin=protoc-gen-ttrpc=/home/teawater/gopath//bin//ttrpc_rust_plugin -I ./protos/ ./protos/agent.proto
protoc --rust_out=./ --ttrpc_out=./,plugins=ttrpc:./ --plugin=protoc-gen-ttrpc=/home/teawater/gopath//bin//ttrpc_rust_plugin -I ./protos/ ./protos/health.proto
protoc --rust_out=./ --ttrpc_out=./,plugins=ttrpc:./ --plugin=protoc-gen-ttrpc=/home/teawater/gopath//bin//ttrpc_rust_plugin -I ./protos/ ./protos/github.com/kata-containers/agent/pkg/types/types.proto
protoc --rust_out=./ --ttrpc_out=./,plugins=ttrpc:./ --plugin=protoc-gen-ttrpc=/home/teawater/gopath//bin//ttrpc_rust_plugin -I ./protos/ ./protos/google/protobuf/empty.proto
protoc --rust_out=./ --ttrpc_out=./,plugins=ttrpc:./ --plugin=protoc-gen-ttrpc=/home/teawater/gopath//bin//ttrpc_rust_plugin -I ./protos/ ./protos/oci.proto
oci.proto:12:1: warning: Import google/protobuf/wrappers.proto but not used.
teawater@teawater-HP-ProDesk-680-G1-TWR:~/ttrpc-rust/example/protocols$ cd ..
teawater@teawater-HP-ProDesk-680-G1-TWR:~/ttrpc-rust/example$ cargo build --examples
Finished dev [unoptimized + debuginfo] target(s) in 3.16s

Why "cargo build --examples" cannot generate "protocols/*_ttrpc.rs" but "hack/update-generated-proto.sh" can generate them?

[Tim-Zhang]

@teawater I just updated the pull request: remove *_ttrpc.rs and call ./hack/update-generated-proto.sh to generate codes.