Add support for PlM (Oodle Mermaid) compressed save files

[jstop01]

Summary

Palworld v0.6+ changed the save file compression format from PlZ (zlib) to PlM (Oodle Mermaid). This broke all file imports on palworld.tf, causing the "Is it really a Palworld Save?" error for every drag-and-drop attempt.

This PR adds full support for the new PlM format while maintaining backward compatibility with older PlZ saves.

Fixes #8, #9, #10

What Changed

PlM (Oodle) Decompression Support (src/libs/save.js)

• Detects the compression format by reading the magic bytes in the file header (PlZ vs PlM)
• PlM files are decompressed using the ooz Oodle decompressor (compiled to WASM)
• PlZ files continue to use the existing zlib (pako) decompression
• On save/export, PlM files are re-compressed as PlZ (double zlib) since Oodle compression is proprietary and not available in ooz-wasm. Palworld can read both formats, so this is fully compatible.

Custom Oodle WASM Loader (src/libs/oozLoader.js)

• The ooz-wasm npm package uses Emscripten, which is incompatible with webpack/CRA's module resolution (new URL('./', import.meta.url) fails)
• This file manually loads the Oodle WASM binary from public/ooz.wasm and exposes the Kraken_Decompress function
• Import mapping derived from the Emscripten glue code: a.a = emscripten_resize_heap, a.b = emscripten_memcpy_js

Updated uesave-rs (rust/Cargo.toml, rust/src/lib.rs)

• Switched dependency from iebb/uesave-rs (pinned at Jan 2024) to upstream trumank/uesave-rs which includes:
  • Fix for PackageVersion::New serialization (the old version panicked on write for v0.6+ saves)
  • Fix for missing property tag array index on serialization
  • Many other serialization improvements
• Rewrote rust/src/lib.rs to use the new SaveReader API with error_to_raw(true) for resilient parsing
• Changed from panic!() to proper Result<T, JsValue> error handling (no more "unreachable" WASM errors)
• deserialize() now accepts &[u8] directly instead of a custom Buffer JS type
• Pre-built WASM artifacts included in src/libs/uesave/ (built with wasm-pack build rust --target web)

Raw JSON Preservation (src/libs/save.js, src/components/RawEditor.js)

• The raw JSON string from deserialize() is now preserved and passed through to writeFile()
• This prevents type coercion issues where the tree editor converts string values like "1234" to integers 1234, which would cause serde deserialization errors on save
• Falls back to LosslessJSON.stringify(gvas) if rawJson is not available

Webpack Configuration (config-overrides.js)

• Added topLevelAwait: true experiment for async WASM initialization
• Added Node.js module fallbacks (module, path, fs, url, crypto) for browser builds
• Wrapped git rev-parse in try/catch so the build works outside of git repos

Binary Files

File	Size	Description
public/ooz.wasm	~90KB	Oodle decompressor (extracted from ooz-wasm npm package)
public/uesave_wasm_bg.wasm	~580KB	uesave GVAS parser/writer
src/libs/uesave/uesave_wasm_bg.wasm	~580KB	Same file, used by wasm-pack JS bindings

How to Rebuild

# Install Rust and wasm-pack (if not installed)
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
cargo install wasm-pack

# Build uesave WASM module
npm run build-rust    # or: wasm-pack build rust --out-dir ../src/libs/uesave --target web

# Copy WASM to public directory
cp src/libs/uesave/uesave_wasm_bg.wasm public/

# Install dependencies and start
npm install
npm start

Test Plan

• Load a PlM format save file (Palworld v0.6+) via drag-and-drop
• Load a PlZ format save file (older Palworld versions) via drag-and-drop
• Edit values in the JSON tree editor
• Export as .sav file (Save button)
• Export as .json file
• Verify exported .sav can be loaded back into the editor
• Verify exported .sav works in Palworld (needs game testing)

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