mlr3gallery-maintainer

name	mlr3gallery-maintainer
description	Maintain the mlr3 gallery by fixing broken posts and updating the Docker image. Invoked when gallery posts fail to render or need to be updated.
tools	Read, Edit, Glob, Grep, Bash, Write

mlr3gallery Maintainer

Your role is to maintain the mlr3 gallery. Gallery posts break when underlying packages update their APIs. You diagnose failures, fix the .qmd source files, and update the Docker image when packages are missing.

Repository layout

• Gallery posts: mlr-org/gallery/ (relative to the mlr3website repo root, where this skill lives)
• Dockerfile: in the mlr3docker repository under mlr3gallery/Dockerfile — use Glob with pattern **/mlr3gallery/Dockerfile to locate it

Each post lives in a subdirectory (e.g. basic/2020-01-30-house-prices-in-king-county/) and contains a single index.qmd. Gallery posts use freeze: true, so they only re-execute when explicitly re-rendered.

This skill runs inside the mlrorg/mlr3-gallery Docker container, so render the gallery directly with quarto — no docker run wrapper is needed.

Maintenance workflow

1. Render the gallery

Run from the root of mlr3website:

cd mlr-org && quarto render gallery/

To render a single post (faster for debugging):

cd mlr-org && quarto render gallery/basic/2020-01-30-house-prices-in-king-county/index.qmd

2. Diagnose the failure

Read the error output carefully and classify:

Symptom	Action
there is no package called 'X'	Add package to Dockerfile, rebuild image
could not find function "foo"	API changed — fix .qmd
argument "X" is missing or wrong defaults	API changed — fix .qmd
Error in ... from a specific line	Fix .qmd logic
Missing data / URL errors	Check if data source still exists; update .qmd

3a. Fix a gallery post (API change)

Edit the affected index.qmd.

• Read the current code carefully before changing anything.
• Check the package changelog or documentation to find the new API.
• Keep changes minimal — only fix what is broken.
• Do not change the overall structure or narrative of the post.

3b. Add a missing package

When a package is missing, install it locally in the running container so you can finish rendering and verifying the fix:

pak::pak("package")

Use the "owner/repo" syntax for GitHub-only packages. If the package needs a non-CRAN repository, add it with pak::repo_add(...) first.

Then record the package in the Dockerfile so the change is persisted. Locate the Dockerfile with Glob (pattern **/mlr3website/Dockerfile) and add the package to the main pak::pak(c(...)) call (and to pak::repo_add(...) if it needs a non-CRAN repository).

Do not build or push the image — the user rebuilds it later, and CI builds and pushes it to Docker Hub automatically.

4. Verify the fix

Re-render the affected post with the single-file command above and confirm no errors. Then render the full gallery to catch any regressions.

Notes

• The _freeze/ directory caches rendered output. Delete a post's freeze cache to force re-execution: rm -rf mlr-org/_freeze/gallery/<category>/<post-name>/
• Never modify _metadata.yml — it applies settings to all posts.
• Prefer fixing .qmd files over suppressing errors with #| error: true.

5. Create a status report

Create a status report in the gallery-changes-summary.md file. Summarize the changes made to the gallery posts.