add-fetcher-renderer

---

name: add-fetcher-renderer description: Implement a new fetcher or renderer for splashboard. Use when the user asks to add a fetcher (e.g. system_battery, weather_*, git_*) or a renderer (e.g. gauge_battery, chart_radar). Drives the workflow: pick-candidate → spec-out → code → self-review → user smoke-tests via .splashboard/dashboard.toml → wrap up.

add-fetcher-renderer

Implements one fetcher or one renderer (not the whole Fetcher × Renderer × Layout composition — the layout slot is the user's call). Read AGENTS.md first for the architectural contracts; this skill only covers process.

Phases 0 and 1 are blocking on a user reply. Auto mode does not license you to pick a candidate or finalise a spec on the user's behalf — both decisions ship in user-visible config (render = "..." / fetcher = "...") and are expensive to rename. Always ask a concrete question and stop until the user answers. Only Phase 2 onward proceeds without further prompts.

Phase 0 — Pick the candidate (候補選定)

Skip this phase only if the user named a specific candidate ("add system_battery", "implement gauge_segment"). Otherwise — including any open-ended ask ("add some renderer", "implement a fetcher") — work through this phase before Phase 1.

1. Survey ALL relevant catalog issues in parallel. Don't pick from memory; the boxes churn — yesterday's open box may already be checked.

   • Renderer ask → #61 only.
   • Fetcher ask → all of #62 through #68, dispatched as a single batch of parallel gh issue view calls. No partial surveys "starting with Local/System and seeing what fits". The biggest daily-driver classes (task tools in #66, coding-time in #64, music in #67) sit exactly where a partial survey would stop early.
   • Cross-cutting context (composition model, ReadStore recipes, rejected designs): gh issue view 41 --json body -q .body.

2. Filter to the open boxes in the surveyed issues.

3. Score candidates with these four filters (these supersede #41's looser rubric for ranking — keep #41 for cross-cutting context, do scoring here):

   A. Renderer primitive leverage (renderer asks). Counts only if you can name ≥2 specific consumer fetchers from the current catalog — shipped or in an open box, by name. Vague "could be useful for some Ratio fetcher" doesn't count. text_big_number clears it (github_repo_stars, oss_followers_delta, deploy_error_budget, package downloads). chart_funnel doesn't (no roadmap fetcher emits funnel-shaped Bars yet) — defer until a consumer lands.

   B. Recurring-change × repeated-look-value (the real "daily-driver" test, replacing #41's vague rubric ②). Both sub-tests must pass for a high rank:

   • Recurring-change: does displayed content change ≥1×/day?
   • Repeated-look-value: would the user still want to see it after 100 splash opens? Novelty traps fail here — iss_position (fun once, ignored after), f1_next_race (fan-only then forgotten), random_cat, fortune. todoist_today / linear_assigned / slack_unread pass — people check these on purpose every day.

   C. Persona name test. Name in one phrase the user who'd open splash and benefit every day. "Anyone with a Todoist account" ✅. "Devs at modern startups using Linear" ✅. "Kids learning about space" ❌ (not a regular shell user). "People who like weather data" ❌ (they check phones). If you can't name a concrete recurring user, demote to ambient/novelty tier.

   D. Setup-cost is an amortized tiebreaker, not a gate. Distinguish:

   • Zero-config (drop-in TOML works) → no penalty.
   • One-time setup (token / lat-lon / country code) → amortized over years of daily glances. Negligible penalty when B+C are strong. todoist_today's token is paid back in week 1 of daily use.
   • Per-use friction (OAuth re-auth, custom URL each invocation) → real penalty.

   The old "Network class with required setup loses to a Safe sibling" rule was too coarse. A Safe widget no one looks at loses to a Network widget actively checked daily. Gate on whether the persona will pay the setup cost, not on Safety class itself.

4. Present a 3–5 candidate shortlist, one line each: catalog box being ticked, family, and which of A/B/C/D scored it where — not vague phrases like "fills a gap". Lead with the top pick, note a runner-up. Include candidates from at least 2 different scoring profiles (e.g., one A-strong renderer primitive, one B+C-strong daily-driver fetcher, optionally one ambient for contrast) so the user sees the real trade-off space, not just one cluster.

5. Ask the user which to implement. Stop. Do not start Phase 1 on a guess. Auto mode does not override this — the candidate decision is the user's, not yours.

Phase 1 — Spec-out (要件確認)

Don't write code yet. Confirm the shape of the work in conversation:

1. Fetcher or renderer? If both, do them as two passes through this skill, not one.
2. Catalog target. Cross-check #41 and the relevant sub-issue (#61 renderers, #62–#68 fetchers). If the candidate is in a checkbox list, link it. If it isn't, ask whether to add it.
3. For fetchers:
   • Family prefix (clock_*, system_*, git_*, …) — pick the right one or justify a new family.
   • Cached or realtime? Realtime contract is < 1ms, infallible, no I/O. Anything that touches reqwest / disk / process state is cached, not realtime.
   • Safety class. Ask "can config control where the traffic goes?" If yes → Network (rss / calendar / any fetcher with a url option). If no, even an authenticated fixed-host fetcher is Safe. Exec is closed (#5 / #20 — don't reintroduce).
   • Output shape(s). A multi-shape fetcher branches on ctx.shape inside compute / fetch and lists every variant in shapes(). Enumerate every Shape variant from src/render/mod.rs::Shape and accept-or-reject each one — don't just pick the obvious ones from the catalog blurb. The bar for acceptance is "can this data be meaningfully expressed in this form?", not "is this the most natural form?". A list of files renders as Text (comma-joined "main.rs (42), lib.rs (31), …"), TextBlock (one row each), Entries (path→count), Bars (label+value) — all four pass. Look at how the closest sibling fetcher in the same family handled each shape; family precedent is a strong signal. Reject only when no representation exists (Heatmap needs a 2D grid you don't have, Timeline needs chronological order, Calendar needs a year/month). "Feels redundant with another shape" or "the catalog didn't mention it" are not rejection reasons. Present the full 12-row table in the spec so the user can challenge any verdict before code lands.
   • Options. Per-fetcher options struct (#[derive(Deserialize)], serde(deny_unknown_fields)) parsed from ctx.options; surface each field as an OptionSchema entry so the docs generator picks it up.
4. For renderers:
   • Family prefix (text_*, list_*, chart_*, gauge_*, grid_*, status_*, media_*, animated_*). Module name = registered name.
   • Accepted shapes. Exactly one. Primary renderers are single-shape — the only exception is animated post-process wrappers (animated_postfx, animated_boot, animated_scanlines, animated_splitflap, animated_wave) that delegate to an inner renderer via ALL_SHAPES. If two shapes feel like they should share a renderer, register two renderers that share helpers (text_plain vs list_plain is the canonical pair).
   • animates() — return true only if output changes across calls within a single draw cycle.
   • Options. First check whether an existing field on RenderOptions already covers it (align, color, label, marker, bullet, style, …). Add a new field only when none fits, and wire an OptionSchema entry on the renderer.
5. Color semantics warning (renderers). Don't bake a context-specific colour map as the default. The gauge_battery lesson: a battery-coloured fill (low → red) silently mis-coloured every "fraction used" widget. If the colour mapping depends on caller intent, default to theme.text and add an opt-in tone / mode option.
6. Memory check. If the user says 考えたい / 検討したい, propose options and stop — don't branch yet.

State the plan back in 3–5 bullets and ask an explicit yes/no question ("Proceed with this plan?") — don't just narrate the plan and roll into Phase 2. Stop until the user answers. Auto mode does not override this; naming, options, and safety class all leak into user-facing config and are painful to undo.

Phase 2 — Implement (実装)

1. Files.
   • Fetcher: src/fetcher/<family>/<name>.rs (or src/fetcher/<family>.rs if the family is one file).
   • Renderer: src/render/<family>_<variant>.rs.
2. Pattern. Open the closest sibling and mirror its structure (constants → struct → trait impl → helpers → tests).
3. Wire up.
   • Renderer: mod line + r.register(...) in src/render/mod.rs::Registry::with_builtins, add the name to the registry_resolves_all_builtins test list. If it becomes the default for a shape, update default_renderer_for. Override xtask/src/snapshots.rs::renderer_dimensions only when the default (40, 5) doesn't fit the renderer's natural aspect.
   • Fetcher: add to realtime_fetchers() / cached_fetchers() in the family module's registration entry point.
4. New shape? Five-touch-point change per AGENTS.md: Body variant + *Data struct, Shape enum, shape_of(), default_renderer_for(), at least one renderer's accepts().
5. Tests. Inline #[cfg(test)] mod tests.
   • Renderer: use src/render/test_utils.rs (render_to_buffer_with_spec, line_text). Cover each visual mode (compact vs boxed, with/without label, clamp out-of-range, narrow area).
   • Fetcher: cover each shape branch + options parsing. Realtime fetchers test compute directly; cached fetchers test sample_body and the actual fetch path with whatever stand-in is appropriate.
6. House style. English in code/comments/commits. map / filter / for_each over imperative loops. Functions ~10–15 lines, files ~100 lines as a guideline. Minimal comments — only when the why is non-obvious.

Phase 3 — Self-review (各種レビュー)

Run the gates before asking the user to verify:

cargo fmt --all -- --check
cargo clippy --all-targets -- -D warnings
cargo test

Then read your own code critically. Common findings worth catching yourself:

• Naming: family prefix consistent? module name matches registered name?
• Edge cases: empty body, width == 0, very narrow area, ratio out of [0,1], fetchers handling timezone / locale defaults.
• Color semantics (renderer): does the default mapping make sense for every fetcher listed under Compatible fetchers? Add a tone-style opt-in if not.
• Safety class (fetcher): re-apply the Phase 1 rule — config-controlled destination → Network, otherwise Safe.
• Test coverage: each visual mode / shape branch has a test? clamps_out_of_range, empty_area_does_not_panic, narrow-area degradation if applicable.
• Catalog parity: cargo run --bin splashboard -- catalog renderer <name> (or ... fetcher <name>) prints the option schema and compatible counterparts you intended.

Report findings as a punch list with severity (🔴 / 🟡 / 🟢). Apply 🔴 fixes before Phase 4.

Phase 4 — User smoke-test (動作確認)

The CLI requires a real tty, so you can't visually verify colours yourself. Hand off to the user:

1. Write a temporary ./.splashboard/dashboard.toml exercising the new fetcher / renderer in 2–3 configurations (renderer: default + each opt-in tone / variant + compact size; fetcher: with and without each meaningful option).
2. Tell the user: cargo run --bin splashboard from the repo root.
3. Wait for confirmation. Visual / colour issues that ASCII tests miss show up here.

Phase 5 — Wrap up (完了)

• Delete .splashboard/dashboard.toml after the user signs off — it was a throwaway smoke-test fixture, not a ship artifact. Keep it only when the user explicitly says so. Note: in splashboard's own repo a committed .splashboard/dashboard.toml doubles as the "ship-with-the-clone" project dashboard, so committing one is a separate decision the user has to make deliberately, not a side-effect of the smoke-test.
• Don't commit unprompted. Wait for explicit ask. When you do commit:
  • Conventional commit (feat(render): ..., feat(fetcher): ...).
  • Co-Authored-By: Claude Opus 4.7 (1M context) <[e-mail]> trailer.
  • Tick the relevant #41 sub-issue checkbox in the PR description, not in code.
• PR description mirrors the auto-generated reference page so reviewers see what /reference/... will show after the docs site rebuilds. Run cargo xtask locally; copy the relevant block from docs-site/src/content/docs/reference/{renderers,fetchers}/<family>/<name>.md (untracked — .gitignore'd). Strip the frontmatter, keep Accepts / Animates / Options / Theme tokens / Compatible fetchers (or Compatible renderers for fetchers), and rewrite the relative ../../...md links to absolute https://splashboard.unhappychoice.com/reference/... URLs.
• Merge strategy is --merge (merge commit). Never rebase or squash — captured project preference.
• Tick the catalog checkbox after merge. Once the PR lands, edit the relevant sub-issue (#61 for renderers, #62–#68 for fetchers) and flip the candidate's [ ] to [x]. Replace the planned blurb with a one-line "Shipped in #NNN" note plus any non-obvious behaviour decisions worth recording (auto-fit, opt-in options, threshold quirks). The PR description alone isn't enough — the issue body is the catalog index everyone scans for what's still open. Use gh issue view <N> --json body -q .body to dump it, edit, then gh issue edit <N> --body-file <path> to apply.

Out of scope

• Plugin protocol (#5) and command widget (#20) are closed. If the user's request shape is "run a subprocess and render its output", explain why it's rejected and steer toward basic_read_store (the user writes the file) or a dedicated built-in.
• Screensaver-style persistent loops. Animation lives within the ANIMATION_WINDOW; a dedicated idle-loop sub-mode is a different product.