Repository navigation
feat: writable WASM sources (Phase C2) #216
Description
Context
This is the final item from the progressive complexity plan. WASM sources currently implement Source (read-only). Extending them to implement WritableSource would let users build fully custom CRUD backends in TinyGo.
Progressive complexity tiers:
- Tier 0: Pure markdown (auto-tasks) ✅
- Tier 1: Markdown + YAML (auto-tables) ✅ PR feat: auto-tables — infer interactive UI from markdown tables + YAML sources #207
- Tier 2: HTML + lvt-* attributes ✅ (existed)
- Tier 3: Go templates ✅ (existed)
- Tier 4: Custom sources — WASM read-only ✅, writable WASM ← this issue
Task Description
Extend internal/wasm/source.go (WasmSource) to implement the WritableSource interface:
type WritableSource interface {
Source
WriteItem(ctx context.Context, action string, data map[string]interface{}) error
IsReadonly() bool
}The WASM module would need to export a WriteItem(action, data) function (or similar) that tinkerdown calls for Add/Update/Delete operations. The TinyGo WASM SDK would need a corresponding update.
Implementation notes
WasmSourcealready hasIsReadonly()(returns true) — change to check if the module exports a write function- Add
WriteItemthat calls the WASM module's exported write function - Update the
wasm-sourcetemplate (cmd/tinkerdown/commands/templates/wasm-source/) to show a writable example - Update
docs/sources/wasm.md
Files to modify
internal/wasm/source.go— implementWritableSourcecmd/tinkerdown/commands/templates/wasm-source/— update templatedocs/sources/wasm.md— document writable WASM
From the progressive complexity plan (Phase C2).
Activity
adnaan commentedon Jul 24, 2026
Progress (M5 Phase 3, #310) — CLI parity landed; keeping this open
tinkerdown clinow constructswasmsources (createCLISourcepreviously fell through to "unsupported source type for CLI"), so a WASM source has the same CRUD surface on the CLI as underserve. Also fixed a load-breaking bug found while writing the docs:docs/sources/wasm.mdand thewasm-sourcetemplate used a non-existentmodule:key (the real key ispath:) andconfig:(real:options:), so following the docs failed to load. A Read-only vs. writable section now documents thewrite-export contract + CLI parity.Verified running:
tinkerdown cli … list quotesreturns rows;tinkerdown cli … addagainst a read-only module returnsError: source is read-only; a unit test covers construct +Fetch+IsReadonly+ theWriteItemguard error.Why this stays open: the feature this issue names — a successful write through a
write-exporting module — still has zero verified coverage in any transport (CLI or WebSocket). "Verify, don't infer" found the assumption thatexamples/lvt-source-wasm-test/is a writable path to be wrong:quotes.wasmis read-only (nowriteexport), it's the only.wasmin the repo, and there's no TinyGo in this environment to build a write-exporting fixture (a committed one that can't be rebuilt would be the #295/#297 provenance trap). Tracked as #311 — a reproducible TinyGo fixture wired intomake+ a write-landing test over CLI and WS. This issue closes when that write path is demonstrated end-to-end.🤖 Generated with Claude Code
https://claude.ai/code/session_018M9pJSPmG6i1D8s6rpEV4h
M5: save & share the captured skill — capture completeness + gallery …