Watgo, a WebAssembly Toolkit for Go

watgo is a WebAssembly Toolkit implemented entirely in Go that parses and validates WAT (WebAssembly Text), then encodes it into a WASM binary, and can also decode a WASM binary back.

At its core is wasmir, a semantic representation of a WebAssembly module. Users can directly inspect or manipulate this structure, and it's available both via the CLI and the Go API.

The main features are as follows.

• Parse: converts WAT into wasmir
• Validate: checks the module's well-formedness and safety according to the official WebAssembly validation semantics
• Encode: outputs wasmir as a WASM binary
• Decode: reads a WASM binary into wasmir

The CLI can be installed with go install github.com/eliben/watgo/cmd/watgo@latest, and it aims for compatibility with wasm-tools. The author states that they have already migrated their own wasm-wat-samples project to be based on watgo.

In the API example, a WAT string is parsed, then the module's function signatures and instructions are traversed to perform analysis that tallies the number of i32 parameters, the number of local.get, and the number of i32.add. Function bodies are represented as a flat sequence of wasmir.Instruction.

The syntactic conveniences of WAT are normalized when lowered to wasmir. For example, folded instructions are converted to unfolded form, and function names and type names are resolved into numeric indices. These transformations align with WASM's validation and execution semantics, as well as its binary representation.

Testing is organized very rigorously.

• Using the official test suite from the WebAssembly spec, .wast files are processed, converted with watgo, and then execution-verified with Node.js
• The interp test suite from wabt is also verified with a separate harness
• wasm-wat-samples, a collection of real WAT program samples, is also used in testing

The author particularly emphasizes that it passes all of the official spec tests, and explains that while some wasm-tools features are currently unsupported, a strong testing strategy has been maintained since early in the project.