Allow loading file descriptor sets again

src/protoc.rs

@@ -1,15 +1,37 @@
-use std::path::Path;
+use std::{ffi::OsStr, path::Path};
 
 use anyhow::{bail, Result};
 use prost_reflect::DescriptorPool;
 
 pub fn load_file(path: &Path) -> Result<DescriptorPool> {
+    match compile(path) {
+        Ok(pool) => Ok(pool),
+        Err(err) if err.is_parse() => match load(path) {
+            Ok(pool) => Ok(pool),
+            Err(_) => {
+                if path.extension() == Some(OsStr::new("proto")) {
+                    bail!("{:?}", err)
+                } else {
+                    bail!("failed to parse '{}' as either a protobuf source file or encoded file descriptor set: {}", path.display(), err)
+                }
+            }
+        },
+        Err(err) => bail!("{:?}", err),
+    }
+}
+
+fn compile(path: &Path) -> Result<DescriptorPool, protox::Error> {
     match path.parent() {
         Some(include) => Ok(protox::Compiler::new([include])?
             .include_imports(true)
             .include_source_info(false)
             .open_file(path)?
             .descriptor_pool()),
-        None => bail!("invalid path"),
+        None => Err(protox::Error::new("invalid path")),
     }
 }
+
+fn load(path: &Path) -> Result<DescriptorPool> {
+    let bytes = fs_err::read(path)?;
+    DescriptorPool::decode(bytes.as_slice()).map_err(|err| anyhow::anyhow!("{:?}", err))
+}