im-course-tools

The im command for the Instructing Machines course: a small, pure-Python CLI that students run from their course folder.

im check                 # is my environment working?
im doctor                # why is it not working?
im get iteration         # download a chapter notebook
im get alignmentproject  # download a whole project
im get                   # everything on offer
im update                # refresh the environment from the website

Why it is a package

The course folder students download holds their own work and nothing else. The four commands used to be four Python files copied into that folder, which put code students had no reason to read next to the notebooks they did, and left no way to fix a bug for a hundred people already holding a copy. Here they travel with the environment instead: a fix reaches everyone through a release.

What the commands guarantee

Nothing ever overwrites a student's work.

• A notebook that already exists is left exactly as it is, and the fresh copy lands beside it as iteration-2.ipynb.
• A project that already exists stops the command. A project is a folder worked in for a week, and unpacking over it would put the empty starting file back on top of real code.
• A project zip is checked before it is unpacked: every entry must live inside the project's own folder, so an archive naming ../../somewhere writes nothing.
• im update downloads both pixi.toml and pixi.lock, checks each is what it claims to be, and keeps a .backup of the old one before writing.

Files land in the course folder, found by walking up from wherever the student happens to be, so im get works two subfolders deep.

When something is wrong

im check answers one question: are the packages there. im doctor answers the question a student actually has, which is why they are not, and it is the one command that runs anywhere rather than only in the course folder — because being in the wrong folder is one of the things it is there to notice.

It reads the machine and changes nothing on it, so it is always safe to tell a hundred people to run it. It looks at, in this order:

• This machine — which OS and Python, and on a Mac whether the terminal is the Intel one being emulated, which quietly gets the wrong build of everything.
• The course folder — whether there is one, and where it probably is if not; whether it is inside OneDrive or iCloud, which will fight pixi over tens of thousands of small files; letters in the path that the tools underneath pixi mishandle; the Windows 260-character path limit; a network or removable drive; whether anything can be written there at all; and whether there is room.
• pixi — installed, and whether this terminal can see it, which is a different question and a much shorter fix.
• The environment — built or not, its lock file current, whether it was built for the folder it is now sitting in, because a pixi environment holds that folder's path in hundreds of places and a moved or renamed course folder breaks every one of them; every course package importable in that environment rather than in whichever Python is running im; and whether the im being run is the one inside it.
• Security software — on Windows by asking Windows' own Security Center, on macOS by looking where the dozen products a university laptop carries install themselves.
• Internet access — a TLS connection to every host pixi downloads from, and then the part that matters: who signed each certificate. Antivirus that inspects encrypted traffic substitutes its own, which pixi refuses and a browser accepts, and that gap is the single most common reason an install fails on a laptop that browses the web perfectly well. Also proxy and certificate variables set in the terminal, and a clock wrong enough to make valid certificates look expired.
• VS Code — installed, with the Python and Jupyter extensions.

Every problem is printed twice: once as a line in the scan, and once at the bottom with the command or click-path that fixes it, written out in full, because a student reading it is by definition having trouble reaching the website.

im doctor                # the whole thing
im doctor --offline      # skip the network checks
im doctor --report       # also write im-doctor-report.txt to send to an instructor
im doctor --no-upgrade   # do not offer to upgrade `im` itself first

Warnings do not set the exit code; only failures do.

Keeping itself current

A fix only reaches a hundred students if it arrives, and no student thinks of upgrading a tool that has never asked them to. So im asks on their behalf: at most once a day, on a background thread so no command ever waits for it, with the answer cached in the home folder rather than the course folder, which gets moved and copied and started over.

Which index it asks depends on how this copy was installed, read off the machine rather than guessed — the conda record in the prefix, the shape of the path around it, or the absence of both. That same answer decides what is offered:

Every command prints one line when there is something newer, after its own output rather than before it. im update upgrades im first, since it is the command for putting the environment right and im is part of the environment. im doctor asks before doing it, because it otherwise changes nothing.

Neither of them re-runs the command afterwards. im cannot replace the files it is running out of while it is running out of them — on Windows it plainly cannot — so what follows an upgrade is the command typed back out, to be run again. An upgrade that finishes cleanly is also checked to have actually changed the version, read fresh off disk: one that runs, succeeds and changes nothing would otherwise send a student round the same loop indefinitely.

Set IM_NO_UPDATE_CHECK=1 to switch the whole thing off.

Installing it outside the course environment

im doctor is most useful on a machine where the course environment is exactly what is broken, so it is worth having a copy that does not depend on one:

pixi global install -c conda-forge -c munch-group im-course-tools

A globally installed im notices that it is the global one and says so, since im check can only see the packages in the Python it is itself running on and would otherwise report a working environment as empty.

Development

pixi run install-dev     # editable install into the pixi environment
pixi run test            # the test suite

The tests run against a fake course website on disk, reached through a file:// URL, so they never touch the real site, and a suite-wide fixture sets IM_NO_UPDATE_CHECK so no test asks a package index anything. IM_COURSE_URL and IM_COURSE_FOLDER are the two overrides they use, and they work by hand too:

IM_COURSE_URL=file:///path/to/_book im get iteration

Release

pixi run release         # bump, tag, and push; CI builds the conda and pip packages

License

MIT