I am excited to announce my new project “OpenXML Package Explorer” extension for Visual Studio Code.
It allows to explore content of Office Open XML packages (*.pptx, *.docx, *.xlsx) inside Visual Studio Code. You can open any valid OpenXML package in Tree View, explore parts inside package, their relationships and content of xml parts (pre-formatted xml with highlighting).
Extension is inspired by windows-only PackageExplorer (lost in CodePlex archive) and Open XML Package Editor for Modern Visual Studios (Visual Studio for Windows) but implemented on top of .NET 5 using F#, Fable, Fable.Remoting, and re-using some pieces from Ionide.

How it works
I believe that source code of this extension can be used as one more sample of Fable-powered VSCode extension. Here is how it currently works:

- F# source code compiled to JS using Fable 3 and bundled with webpack.
- Code that interacts with OpenXML packages is written in .NET and uses the latest version of System.IO.Packaging
- When extension is activated it starts .NET 5 process with API exposed using Fable.Remoting.
- Extension assumes that .NET 5 runtime is installed on user machine but it depends on .NET Install Tool for Extension Authors that should help to install runtime to users that do not have it yet.
- JS bundle runs inside Node.js VS Code Extension Host process.
- Fable.Remoting.Client cannot be used, because it is built on top of XMLHttpRequest that does not exist in Node.js world. Here is feature request for Fable.Remoting.NodeClient that may become a thing one day.
- Current client-server communication is built on top of axios library and Fable.Axios bindings with manually written client.
- Extension is created using LambdaFactory/fable-vscode-demo sample that uses ionide/ionide-vscode-helpers with bindings for VS Code Extension API.
P.S. Many thanks for Krzysztof Cieślak and Ionide team for ionide-vscode-fsharp, ionide-vscode-helpers and fable-vscode-demo and Stef Levesque for vscode-zipexplorer used as reference implementation and inspiration.