ADR: Having a single, customised dev container environment

[lucyb]

Write an ADR in this format to record why we have a single, customised dev container environment and what the consequences of this decision are.

[!NOTE] Please read Michael Nygard's blog post about how to document an architecture decision first.

Rough outline of decision

We will have a single dev container environment, with a single custom Docker image, available for researchers to use within Codespaces.

We believe having a single setup better matches the researcher’s mental model of how the system works and is how they expect to work. It provides a less steep learning curve.

Rough context

We originally had a single dev container environment with a generic Docker image. However, we wanted to improve this to provide a more "habitable" environment for researchers in which to write code. This included providing RStudio, as the majority of researchers write R code.

An alternative option was to have separate python and R configurations and Docker images. However:

• This was too confusing for users as the UI for choosing Codespaces configs is not intuitive.
• Having to maintain and develop two or more different configurations would have added significant complexity.

Multiple setups would add a larger burden on to researchers for both copying and maintaining the dev container config in their local repo and then keeping their code in sync with the correct dev container env later.

[iaindillingham]

I think we should document why we chose to use rocker/rstudio:4.0.5 as the base image. I asked a couple of questions about this choice on Slack.^1 They might be useful when writing this ADR.