roto/tests/build_generated_code.rs

use std::fs;
use std::process::Command;
use roto::google::protobuf::descriptor::{
    FileDescriptorSet
};
use roto::google::protobuf::compiler::plugin::{
    CodeGeneratorRequest,
};

#[test]
fn test_generated_code_builds() {
    // 1. Generate Rust code from data/request.bin
    let request_path = "data/request.bin";
    let data = fs::read(request_path).expect("Failed to read request.bin");
    let request = CodeGeneratorRequest::new(&data)
        .expect("Failed to parse CodeGeneratorRequest");

    // Mimic the logic from protoc-gen-roto to build a FileDescriptorSet
    let mut set_buf = Vec::new();
    for file_res in request.proto_file() {
        let (file_data, _) = file_res.expect("Failed to iterate proto_file");

        // Tag 1, Length-delimited: (1 << 3) | 2 = 10
        set_buf.push(10);

        // Write length as varint
        let len = file_data.len() as u64;
        let mut len_buf = [0u8; 10];
        let len_size = roto::write_varint(len, &mut len_buf).expect("Failed to write varint length");
        set_buf.extend_from_slice(&len_buf[..len_size]);

        // Write data
        set_buf.extend_from_slice(file_data);
    }
    let set = FileDescriptorSet::new(&set_buf)
        .expect("Failed to create FileDescriptorSet");

    let generated_files = roto::generator::generate_rust_code(&set, None, false);
    assert!(!generated_files.is_empty(), "Generated code should not be empty");

    // 2. Setup a temporary Cargo project to verify the code builds
    let root = std::env::current_dir().expect("Failed to get current directory");
    let temp_project_dir = root.join("test_gen_project");

    // Clean up previous runs
    if temp_project_dir.exists() {
        fs::remove_dir_all(&temp_project_dir).expect("Failed to clean up temp project directory");
    }

    // Create new library project
    let status = Command::new("cargo")
        .args(["new", "--lib", "test_gen_project"])
        .current_dir(&root)
        .status()
        .expect("Failed to run cargo new");
    assert!(status.success(), "cargo new failed");

    // 3. Configure the project to depend on the current roto crate
    let cargo_toml_path = temp_project_dir.join("Cargo.toml");
    let cargo_toml_content = fs::read_to_string(&cargo_toml_path).expect("Failed to read Cargo.toml");
    let updated_cargo_toml = format!(
        "{}\n\nroto = {{ path = \"..\" }}",
        cargo_toml_content
    );
    fs::write(cargo_toml_path, updated_cargo_toml).expect("Failed to write Cargo.toml");

    // 4. Write the generated code to src/lib.rs
    // The generated code uses `use crate::{...}`, but it's now in a separate crate.
    // Replace `crate` with `roto` to reference the types in the dependency.
    let mut all_code = String::new();
    for (_, content) in generated_files {
        all_code.push_str(&content);
        all_code.push_str("\n");
    }
    let final_code = all_code.replace("use crate::", "use roto::");
    let lib_path = temp_project_dir.join("src/lib.rs");
    fs::write(lib_path, final_code).expect("Failed to write generated code to src/lib.rs");

    // 5. Attempt to build the project
    let build_status = Command::new("cargo")
        .args(["build"])
        .current_dir(&temp_project_dir)
        .status()
        .expect("Failed to run cargo build");

    assert!(build_status.success(), "The generated Rust code failed to build in a standalone project!");
}