pongo2 stays host-side and is never compiled into a guest; plugins render
templates by handing the host a {template, data} pair, and the host calls
back into the free guest instance for plugin-declared tags/filters.
ABI (additive, buf-breaking clean):
- RenderBlockResponse gains a `powered` PoweredBlock{template, data_json};
a block returns EITHER html OR powered.
- New hooks HOOK_RENDER_TAG (10) / HOOK_APPLY_FILTER (11) with
RenderTag{Request,Response} and ApplyFilter{Request,Response}.
- PluginManifest gains repeated declared_tags / declared_filters (31/32).
Guest SDK (core/blocks, core/plugin/wasmguest):
- blocks.PoweredBlock(template, data) / DecodePoweredBlock: NUL-sentinel
marker so BlockFunc's string signature is unchanged (smallest additive
change — no ripple to existing blocks or the host guest-side).
- blocks.RegisterTag / RegisterFilter (+ RenderContext = context.Context)
write a package-level registry; runRegister resets it per registration
for deterministic DESCRIBE + dispatch.
- DESCRIBE emits declared_tags/filters; dispatch handles RENDER_TAG /
APPLY_FILTER (fn errors → response.error; panics → AbiError INTERNAL,
instance stays callable).
Docs: core/docs/wasm-abi.md gains the render-as-a-host-capability model,
the powered-block flow (re-entrancy-free), the plugin API, and the
HOST-SIDE CONTRACT the cms phase implements.
Tests: unit round-trips for powered/RENDER_TAG/APPLY_FILTER (dispatch +
error + unknown + panic + per-guest registry isolation) plus a real
wazero round-trip through the compiled fixture module. Verified no
guest-reachable package imports pongo2 (go list -deps on the wasip1
fixture build is clean).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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