shenlu89/pandoc-wasm repository overview

⁠Pandoc WebAssembly (WASM)

This Docker image, part of the pandoc-wasm⁠ project, provides a self-contained toolchain for building the WebAssembly (WASM) version of Pandoc, the universal document converter.

The image is based on Ubuntu 22.04 and comes with:

• GHC and Cabal
• The GHC WebAssembly toolchain
• Binaryen (wasm-opt)
• Wasmtime

⁠Overview

The image compiles the wasm branch of the haskell-wasm/pandoc repository into a pandoc.wasm binary, and then optimizes the output with wasm-opt to reduce size.

Use this image if you want a reproducible, ready-to-run environment for producing a WASM build of Pandoc without setting up the full toolchain on your host.

⁠Dockerfile

This image is built from the Dockerfile⁠ in the pandoc-wasm repository. This provides details on how the toolchain is set up and how Pandoc is built.

⁠Usage: Extract the compiled binary

The primary use case is to build and copy out the optimized pandoc.wasm artifact.

1. Build the Docker image from this directory:

   docker build -t pandoc-wasm .
   

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2. Run the container (it exits when the build finishes):

   docker run --name pandoc-container pandoc-wasm
   

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3. Copy the pandoc.wasm file from the container to your host:

   docker cp pandoc-container:/pandoc.wasm .
   

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4. (Optional) Clean up the stopped container:

   docker rm pandoc-container
   

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You now have pandoc.wasm available on your machine for use with any WASM runtime.

⁠Run pandoc.wasm locally with Wasmtime

If Wasmtime is installed on your host and you have copied pandoc.wasm, you can run it directly:

1. Create a sample file:

   echo '# Local Hello' > local.md
   

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2. Run Pandoc (WASI):

   wasmtime run --dir .::/ ./pandoc.wasm local.md -o local.html
   

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The --dir .::/ flag grants the module access to the current directory.

⁠Usage: Interactive test inside the container

You can also start an interactive session in the build image to test pandoc.wasm without copying it out:

1. Start a shell:

   docker run -it --rm pandoc-wasm bash
   

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2. Create a sample Markdown file:

   echo '# Test Markdown' > test.md
   

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3. Convert using wasmtime and the built pandoc.wasm:

   wasmtime run --dir /::/ /pandoc.wasm /test.md -o /test.html
   

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4. Verify the output:

   ls -l /test.html
   

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