VSCode - Evolution

1. History and Evolution

• Visual studio code was originaly intended to be an online code editor. Where developers can code and run their codes online. The final decision was to create a desktop application which could be usefull to code in TypeScript and C# only. Also, the developer team created a debugger for coding purposes. All this was made during the beta version of Visual Studio Code which was not open source. Some months later, Visual Studio Code was launched in a more official way, with new functionalities that lasts until today and make Visual Studio Code what it is: The most used code editor. Some of these functionalities are Extension support, the new architecture and the launched it as an open source software. The current repository does not have the complete history of vscode, but it has information since 2016, where all the main functionalities were established.

• Chart describing the evolution of the number of lines of code (in red on the chart) in the Github repository, from the first commit to the current commit. For more details, you can see the image in https://raw.githubusercontent.com/softwaredesign-uandes/architecture-reviews/a87e21224feb88f0297065fb6c388cb08196d464/vscode/assets/vscode_graph.svg and hover the lines.

2. Architecture Decision Records

ADR 1: Electron as main framework (at the beginning)

Context

• The application needed to be a desktop application
• Microsoft wanted to make a cross-platform application

Decision

• Use electron as main framework

Status: Implemented

Consequences

• Had to use NodeJS as backend for vscode
• Maintain further updates of the framework

ADR 2: Core architecture layered (at the beginning)

Context

• Needed an architecture that allow extensibility and order in the code

Decision

• Separate the application in 5 layers: base, platform, editor, languages and workbench

Status: Implemented

Consequences

• Comunication between all the blocks should be implemented for being monitored
• Adapt this layer structure to electron

ADR 3: Monaco editor for workbench layer (at the beginning)

Context

• Needed a base editor for the application
• The editor should be able to use in a JS environment
• The editor should be basic and open source

Decision

• Use Monaco as editor in the workbench layer

Status: Implemented

Consequences

• Make the workbench layer able to provide framework viewlets (explorer, status bar, menu, etc.)
• Integrate the debugging function in the editor

ADR 4: Architecture for extensions (during the evolution)

Context

• The editor only have the base functionalities (in beta version)
• The editor should be extensible with more functionalities

Decision

• Implement an extension archicture, where extensions run isolated in a different proccess
• Create an Extension API

Status: Implemented

Consequences

• The editor have more functionalities
• Since the extensions run in a separate process, vscode performance is improved

ADR 5: Removal of languages layer (during the evolution)

Context

• The laguages supported by vscode are implemented by the language layer and by extensions
• The unification of the languages support is needed

Decision

• Migrate all the language support to extensions
• Remove the language layer

Status: In progress

Consequences

• Regardless of the language, its support for vscode is handled the same way
• A lot of effort dedicated to the migration of languages supported by the language layer to be supported by extensions
• Since the extensions run in a separate process, the performance of language support is improved