FastBlocks htmy

Type-safe htmy components and a FastBlocks adapter built on top of the fastblocks-ui design system.

fastblocks-htmy is the FastBlocks-native layer: where fastblocks-ui ships the CSS and zero-dependency string helpers, this package wraps them in typed, composable htmy components and provides the adapter that registers assets and template globals with a FastBlocks app (ACB [[ ]] delimiters).

Design principle: this is a thin wrapper. It never reimplements styling — every component renders the corresponding fastblocks-ui helper output wrapped in htmy's SafeStr. A parity test enforces that the two layers can't diverge.

Status

All 27 fastblocks-ui manifest components (including validation_summary) now have a typed htmy wrapper, plus the FastBlocks adapter (asset_paths, asset_urls, template_globals, trusted_components). Button, Container, Table, and Field were hand-written first (Phase 1); the rest were added by WS-16's manifest-driven codegen (scripts/generate_components.py) — see fastblocks_htmy/ui/_generated.py and fastblocks_htmy/layout/_generated.py, and each carve-out module's docstring (Columns, Select, Tabs, Dropdown, Navbar, Breadcrumb, NavList, NavGroups, ValidationSummary) for which components are hand-written instead and why.

Install

pip install fastblocks-htmy   # pulls fastblocks-ui (>=0.8,<0.9) and htmy

Usage

import asyncio
from htmy import Renderer
from fastblocks_htmy import Button

html = asyncio.run(Renderer().render(Button("Save", variant="primary")))
# -> '<button class="ui-button is-primary" type="button">Save</button>'

FastBlocks integration

Status note (unverified against a live FastBlocks app as of this writing — see the integration test in tests/test_fastblocks_integration.py for what's actually confirmed). Two integration paths exist with different maturity:

1. String helpers as plain Jinja globals — the path most likely to already work. ui_button/ui_card/ui_field/ui_alert (and the rest of fastblocks_ui's exports) are ordinary functions returning strings. Registered via templates.env.globals.update(template_globals()) on FastBlocks' plain Jinja2 adapter, calling them from a template is no different from calling any other Jinja global function:

   from fastblocks_htmy.fastblocks import asset_paths, asset_urls, template_globals
   
   # Mount the shipped fastblocks-ui assets (resolved from the installed wheel):
   app.mount("/static/fastblocks-ui", StaticFiles(directory=asset_paths()["root"]))
   
   # Register components + helpers as template globals (cache-busted asset URLs included):
   templates.env.globals.update(template_globals())
   

   <link rel="stylesheet" href="[[ fastblocks_ui_css ]]">
   [[ ui_button(text="Save", variant="primary") ]]
   

2. Typed htmy components used directly as [[ Button(...) ]] template expressions — do not rely on this yet. Two independent issues mean this is not known to work as a bare template expression today:

   • FastBlocks' real htmy component-loading path discovers components from .py source files under a templates/<app>/components/ search path, validated by a sandboxed AST loader that only allows dataclasses/typing as top-level imports. Every component in fastblocks_htmy/ui/ and fastblocks_htmy/layout/ imports fastblocks_ui, htmy, and ..base — all of which that loader would reject if these files were dropped into a discovered-components directory as-is.
   • Independently of the above, a bare instantiated component handed to a template engine's normal output mechanism only renders correctly if something actually calls .htmy(context) on it (which is what FastBlocks' render_component() template global does). FastBlocksComponent now provides a best-effort __str__/__html__ fallback so accidental bare stringification doesn't print a dataclass repr, but this has not been proven against FastBlocks' real render_component()-mediated rendering path with a passing integration test yet.

   Until that's resolved (tracked in fastblocks-ui's roadmap under the cross-repo remediation plan), prefer path 1 above for anything rendered through an actual FastBlocks template. The typed components remain fully usable via direct Renderer().render(...) calls, as this package's own tests do.

Relationship to fastblocks-ui

See the architecture decision record in fastblocks-ui/docs/roadmap.md.

License

BSD-3-Clause