feat: vendor pbjson-types descriptor set (#62)

pbjson-types/build.rs

@@ -8,22 +8,26 @@ type Error = Box<dyn std::error::Error>;
 type Result<T, E = Error> = std::result::Result<T, E>;
 
 fn main() -> Result<()> {
-    let root = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("protos");
+    let root = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+    let protos = root.join("protos");
+    let descriptor_path = root.join("descriptors.bin");
+    println!("cargo:rerun-if-changed={}", descriptor_path.display());
 
-    let proto_files = vec![root.join("google/protobuf/types.proto")];
-
-    // Tell cargo to recompile if any of these proto files are changed
-    for proto_file in &proto_files {
-        println!("cargo:rerun-if-changed={}", proto_file.display());
-    }
-
-    let descriptor_path = PathBuf::from(env::var("OUT_DIR").unwrap()).join("proto_descriptor.bin");
-    prost_build::Config::new()
+    let mut config = prost_build::Config::new();
+    config
         .file_descriptor_set_path(&descriptor_path)
         .compile_well_known_types()
         .disable_comments(&["."])
-        .bytes(&[".google"])
-        .compile_protos(&proto_files, &[root])?;
+        .bytes(&[".google"]);
+
+    // Don't regenerate descriptors if already exists, this avoids needing protoc
+    // in order to compile this crate
+    if descriptor_path.exists() {
+        config.skip_protoc_run();
+    }
+
+    let proto_files = vec![protos.join("google/protobuf/types.proto")];
+    config.compile_protos(&proto_files, &[protos])?;
 
     let descriptor_set = std::fs::read(descriptor_path)?;
     pbjson_build::Builder::new()