Python library support for adding aliases

[simonw]

I'm going to depend on LLM 0.7 or higher and have the download-model ... --alias llama2 option work by writing to the aliases.json file.

Originally posted by @simonw in simonw/llm-mlc#4 (comment)

This would make sense as a Python API method that plugins can use.

Maybe this:

from llm import set_alias

set_alias("llama2", "... model ID ...")

[simonw]

After implementing this I should upgrade the various plugins that have their own alias mechanism to use this instead.

[simonw]

llm aliases --help

llm aliases
Usage: llm aliases [OPTIONS] COMMAND [ARGS]...

  Manage model aliases

Options:
  --help  Show this message and exit.

Commands:
  list    List current aliases
  path    Output the path to the aliases.json file
  remove  Remove an alias
  set     Set an alias for a model

I should add llm.remove_alias(name) too. It can raise KeyError if invalid.

And I'll make llm aliases run llm aliases list by default, refs:

• llm models should default to llm models list #167

[simonw]

Here's the current implementation of the aliases_set() CLI command:

llm/llm/cli.py

Lines 715 to 724 in 0cd9333

	path = user_dir() / "aliases.json"
	path.parent.mkdir(parents=True, exist_ok=True)
	if not path.exists():
	path.write_text("{}\n")
	try:
	current = json.loads(path.read_text())
	except json.decoder.JSONDecodeError as ex:
	raise click.ClickException("aliases.json is invalid: {}".format(ex))
	current[alias] = model_id
	path.write_text(json.dumps(current, indent=4) + "\n")

It catches JSONDecodeError and turns that into ClickException - which makes sense for a CLI tool but isn't the right thing for a Python library method to do.

What SHOULD the Python library do if you call llm.set_alias() but it turns out the aliases.json file is invalid? Which isn't something that should ever happen.

Two options:

1. Raise an error, and hope that the caller is ready for that.
2. Discard the current aliases.json file and write a new, valid one

I'm very tempted to implement 2 - a broken aliases.json file is useless, and we want the set_alias() function to succeed.

[simonw]

I'm going for that - if the JSON is invalid it rewrites it.

[simonw]

Now to refactor some code to use this.

[simonw]

Documentation https://llm.datasette.io/en/latest/python-api.html#other-functions