fix(deps): make toon_format an optional extra so uv can install current releases

[Nynir]

Closes #324.

Problem

limacharlie 5.3.1+ declare a hard dependency on toon_format>=0.9.0b1,<1.0. On PyPI, toon-format has published exactly two versions — 0.1.0 and 0.9.0b1 — so no stable release satisfies that range.

pip honours the pre-release specifier and installs 5.5.4 without complaint. uv does not: it accepts pre-releases only for requirements named directly, never for transitive ones. Faced with a limacharlie that needs a pre-release it will not take, uv backtracks to the newest release that does not — 5.3.0.

The failure is silent. No error, no warning:

$ uv pip install --no-cache limacharlie
Resolved 21 packages in 424ms
 + limacharlie==5.3.0

uv tool install limacharlie and uvx limacharlie land on the same 5.3.0, and uv tool upgrade limacharlie reports "Nothing to upgrade" — so uv users have been pinned to a release predating the dependency, with no signal that anything is wrong. (The docs list uv tool install limacharlie as a supported installation method, so this is a documented path: https://docs.limacharlie.io/6-developer-guide/mcp-server/#installation.) Asking for the version explicitly is the only way to surface the real error:

$ uv pip install --no-cache limacharlie==5.5.4
  × No solution found when resolving dependencies:
  ╰─▶ Because only toon-format<0.9.0b1 is available and limacharlie>=5.5.4
      depends on toon-format>=0.9.0b1, we can conclude that limacharlie>=5.5.4
      cannot be used.

Pinning the requirement to the exact pre-release (toon_format==0.9.0b1) would not fix this — uv's rule is about direct vs. transitive requirements, not about the shape of the specifier.

Fix

Move toon_format out of [project.dependencies] into a toon extra. The code already treats it as optional at runtime — limacharlie/output.py imports it in a try/except ImportError with a _toon_format = None fallback, the same pattern used for jmespath and tabulate — and TOON is one of six opt-in --output formats, not a default. Nothing but --output toon touches it.

With the dependency optional, uv installs the current release normally, no flags (shown here resolving a wheel built from this branch):

$ uv pip install --no-cache limacharlie
Resolved 21 packages in 305ms
 + limacharlie==5.5.5

Behavior change

A default install loses --output toon. The other five formats (json, yaml, csv, table, jsonl) are unaffected, and toon stays in the --output choice list so it still validates and tab-completes.

Requesting TOON without the encoder exits 1 with a message naming both install forms — no traceback, matching how --filter reports a missing jmespath:

$ limacharlie --output toon sensor list
Error: toon_format is required for --output toon. Install with: pip install 'limacharlie[toon]'
With uv: uv tool install limacharlie --with 'toon-format>=0.9.0b1'

The uv-specific form is deliberate. uv pip install 'limacharlie[toon]' does not work either — the extra's requirement is still transitive, so uv applies the same rule and quietly falls back to 5.3.0, which does not even have a toon extra (it warns, then installs the old version anyway). Naming toon-format directly makes it a direct requirement, and uv then honours the pre-release specifier. If toon_format ever ships a stable release in range, both forms collapse into the obvious one and the extra keeps working unchanged.

Tests

CI installs [dev], and [dev] now pulls in toon_format, so all existing TOON coverage runs unchanged. Added:

• tests/unit/test_packaging.py — toon_format absent from [project.dependencies], present in the toon extra, and present in dev so CI keeps exercising the path.
• tests/unit/test_output.py::TestFormatToonMissingExtra — with _toon_format patched to None: format_toon() and format_output(fmt="toon") both name the extra, the message carries the uv form, the CLI exits 1 without a traceback, and the other formats keep working.
• TOON tests needing a real encoder are marked skipif, so pip install -e . + pytest no longer fails at collection without the extra.

Full suite, both ways:

# pip install ".[dev]" (CI's install)
3772 passed, 4 skipped

# without the toon extra
3759 passed, 17 skipped

Also verified against a built wheel: fresh venv, uv pip install <wheel> with no pre-release flags succeeds and does not pull toon-format; limacharlie --version works; --output toon gives the friendly error; adding the encoder restores TOON output.

Related

refractionPOINT/lc-ai#112 works around this same resolution failure in the lc-essentials plugin's CLI auto-installer (--prerelease=allow + a 5.4.0 floor). With toon_format optional, that workaround becomes unnecessary for future releases — and its noted trade-off (that --prerelease=allow could also admit a pre-release of limacharlie itself) goes away.