rust-hmr-experiment

Rust Web Dev; Proof of Concept for HMR (Hot Module Replacement) using WASM modules.

Significance

• mod1.wasm has all its dependencies externalized
  • It compiles extremely fast and is extremely lightweight.
    • mod1.wasm imports all dependencies (std libraries, dependency functions, memory, etc.)
• It proves the possibility of dynamic component replacement on browser without page reloading.

File tree

• ./hmr-server
  • It does:
    • compilation & modification of host-wasm
    • compilation & modification of mod1.wasm
    • serves to localhost:3000
• ./wasm-project
  • It is the sample project that will be compiled into wasm
  • contains lib.rs and mod1.rs

Run

cd hmr-server
cargo run

Brief Roadmap

• compile whole cargo project into WASM (main module)
• modify the main wasm so it exports all the library functions
  • e.g. alloc::alloc::handle_alloc_error
• Compile a single rust file into a separate WASM file (component module)
  • Compile mod1.rs into object file with --emit obj flag in rustc
    • mod1.wasm will be minimal and imports all library functions at runtime
    • also imports memory from outside
  • Modify the wasm binary with Walrus
    • add exports
      • parse Custom Linking section of wasm binary and obtain name map of functions
    • demangle import & func names
• Load the component WASM module (mod1.wasm) from main WASM module
  • Import object: __wbindgen_placeholder__, __wbindgen_externref_xform__ fields
  • Use of Proxy in JS to flexibly resolve the importObject for WASM instanciation
  • pass in the host's memory & imports to instanciate mod1.wasm
• Invoking functions in mod1.wasm
  • func with no param
  • func that takes in params of values / references
• Accessing thread_local! value in host from mod1.wasm
• Make a test function in mod1 that appends a Leptos component to body() when invoked
• Modify the source code and pass to the compiling process

  • Idea: Virtual sandboxed filesystem that returns processed file content

    • Similar idea as using Proxy in JS but for filesystems

  • substitute crate::mod with proj_name::mod only in the module compilation

• rust source modifier plugin (for activating HMR thru plugin interface)

Current Status