PiCloud/HANDBACK.md

# v1.1.3 — Modules — Handback

## 1. Branch summary

- **Branch:** `feat/v1.1.3-modules`
- **Commits ahead of `main`:** 6
- **HEAD:** `3dbead4`
- **Not pushed, not merged, no PR opened** (per brief).

Commits (newest first):

```
3dbead4 test(v1.1.3-modules): resolver, cache, validator, kind-rejection coverage
10f76d2 chore(v1.1.3-modules): version bumps + CHANGELOG + blueprint touch-up
610fd4f feat(v1.1.3-modules): dashboard kind dropdown + scripts-list and detail badges
66b41bb feat(v1.1.3-modules): top-level script AST cache in LocalExecutorClient
c6211a7 feat(v1.1.3-modules): reject module scripts from routes + triggers; tighten cross-app trigger check
84833d3 feat(v1.1.3-modules): shared types, migrations, engine + resolver scaffold
```

---

## 2. Scope coverage

| # | Brief item | Status | Notes |
|---|---|---|---|
| 1 | `scripts.kind` column + check + index | **Done** | `migrations/0015_scripts_kind.sql` |
| 2 | Module syntax constraints (fn / const / import only) | **Done** | Walks `ast.statements()` via `rhai/internals`. Admin endpoint is primary gate; resolver re-runs the check for defense-in-depth. |
| 3 | `ModuleResolver` replaces `DummyModuleResolver` | **Done** | `crates/executor-core/src/module_resolver.rs`; per-call instance with cross-app isolation, cycle detect, depth limit. |
| 4 | Two AST caches (script + module) | **Done** | Script cache in `LocalExecutorClient`; module cache in `Engine`. Both invalidate by `updated_at` comparison. Env-overridable sizes. |
| 5 | Dep-graph table + populate | **Done** | `migrations/0016_script_imports.sql`; `replace_imports_tx` writes edges in the same transaction as the script INSERT/UPDATE. |
| 6 | Admin endpoint changes (kind, kind-change rejection, route/trigger module rejection) | **Done** | Also closes a latent cross-app trigger gap (script.app_id mismatch — see §7). |
| 7 | Dashboard surface (kind dropdown + badge) | **Done** | App page form + scripts list + script detail header. `npm run check` clean. |
| 8 | `ModuleSource` trait shape | **Done** | Lives in `picloud-shared`; matches the v1.1.1/v1.1.2 service pattern. |
| 9 | Version bumps | **Done** | Workspace 1.1.2→1.1.3, SDK 1.3→1.4, dashboard 0.8.0→0.9.0. |
| 10 | Tests (~40–60) | **Done** | 46 new tests across 5 crates. Gates green. |

### Scope-out items (confirmed NOT built)

- No module versioning / pinning, no `@v3` syntax.
- No eager precompilation at save-time.
- No dashboard dep-graph visualization.
- No LISTEN/NOTIFY-based cross-node invalidation.
- No new `Scope` variants (modules use existing `script:read` / `script:write`).
- No admin GET endpoints for `script_imports` (the table is persisted for v1.2+; no v1.1.3 read surface — see §10 deferred items).

---

## 3. Resolver implementation notes

### 3.1 In-progress-imports stack

Lives **on the per-call `PicloudModuleResolver` instance**, not on `SdkCallCx`. The resolver is constructed fresh per `Engine::execute_ast` call (see `crates/executor-core/src/engine.rs:execute_ast`), so the stack is naturally scoped to one execution. Both the stack and the depth counter are `Mutex<…>` (not `RefCell<…>`) because `rhai::ModuleResolver: SendSync` under the `sync` feature.

An RAII `StackGuard` pops the stack and decrements depth on drop — a compile error or panic anywhere inside `resolve()` cleans up properly. The lock is uncontended in practice (Rhai evaluation on the engine is single-threaded).

### 3.2 Sync → async bridge

Rhai's `ModuleResolver::resolve` is sync; `ModuleSource::lookup` is async. The bridge:

```rust
let handle = tokio::runtime::Handle::try_current().map_err(/* surfaces as ErrorRuntime */)?;
let lookup = tokio::task::block_in_place(|| handle.block_on(self.source.lookup(&self.cx, path)));
```

- `try_current()` (not `current()`) so test harnesses that build an `Engine` outside a Tokio runtime get a clean error instead of a panic.
- `block_in_place` makes the call safe both on `spawn_blocking` threads (where it's a no-op) and on multi-threaded runtime worker tasks (where it instructs the runtime to relocate other tasks before we block). This was load-bearing for the resolver tests, which call `engine.execute` directly from `#[tokio::test(flavor = "multi_thread")]`.
- A `current_thread` runtime still panics — but production callers wrap `Engine::execute` in `tokio::task::spawn_blocking` (see `LocalExecutorClient::execute_with_identity`), which avoids that path entirely.

### 3.3 Cross-app isolation enforcement

The resolver captures `Arc<SdkCallCx>` at construction. Every `ModuleSource::lookup` call passes `&self.cx`. The Postgres impl (`crates/manager-core/src/module_source.rs`) selects with `WHERE app_id = $1 AND kind = 'module' AND name = $2`, binding `$1` from `cx.app_id.into_inner()` — never from any script-passed argument. The Rhai script's `import "name" as alias;` syntax has no slot for an `app_id`, so there is no path by which a script in app A can name a row in app B.

Verified by `resolver_cross_app_blocked` and `resolver_cross_app_module_not_found` tests.

### 3.4 Module-shape validation — both layers

- **Primary gate (admin endpoint)** — `manager-core::api::create_script` and `update_script` call `state.validator.validate_module(src)` whenever the effective kind is `Module`. `Engine`'s impl walks `ast.statements()`, accepting only `Stmt::Var(_, ASTFlags::CONSTANT, _)`, `Stmt::Import(..)`, and `Stmt::Noop(..)`. Anything else (top-level expression, let, if, while, …) is rejected with a clear `ValidationError::ModuleShape` message.
- **Defense in depth (resolver)** — the resolver calls `check_module_shape` again after `engine.compile(source)`. This catches rows that bypassed the API (manual SQL inserts, future migration bugs, restoring from an older backup).

Note: Rhai's default optimizer constant-folds `if true { ... }` away, so a module containing `if true { ... }` parses to an empty body and passes vacuously. This is fine semantically (the script has no observable behavior), but it surprises authors. Documented as a known acceptance edge; not worth disabling optimization for.

### 3.5 What the resolver does NOT enforce

- **Module access permissions** — every module in an app is importable by every other script in the same app. Per-module ACLs are explicitly v1.2+.
- **Module versioning / pinning** — there's exactly one current version per `(app_id, name)`. v1.3+.

---

## 4. Cache design notes

### 4.1 LRU library

**`lru = "0.12"`** — added to `[workspace.dependencies]`. Standard choice, no-frills crate (`LruCache<K, V>` with `put`/`get`/`len`/etc.). Both caches use `Arc<Mutex<LruCache<K, V>>>` so they're cheap to clone and safe to share across executions.

### 4.2 Cache key shapes + what's stored

| Cache | Owner | Key | Value | Stores |
|---|---|---|---|---|
| **Script AST cache** | `LocalExecutorClient` | `ScriptId` | `CachedScript { updated_at: DateTime<Utc>, ast: Arc<rhai::AST> }` | Compiled AST for the top-level (endpoint) script. |
| **Module cache** | `Engine` | `(AppId, String)` | `CachedModule { updated_at: DateTime<Utc>, module: Shared<rhai::Module> }` | Compiled `rhai::Module` produced by `Module::eval_ast_as_new`. |

The script cache stores `Arc<AST>` so an evaluation can grab a cheap clone and hand it to `Engine::execute_ast` without holding the cache lock. The module cache stores `Shared<Module>` (= `Arc<Module>` under the `sync` feature) because that's what `ModuleResolver::resolve` must return.

### 4.3 Stale-version detection

Both caches use the same logic: **compare `cached.updated_at` against the freshly-known `updated_at`**.

- For the script cache, the caller passes the fresh value as `ScriptIdentity.updated_at` — the orchestrator already loaded the script row to dispatch the request, so there's no extra DB hit.
- For the module cache, the resolver must call `ModuleSource::lookup` first to learn the fresh `updated_at` — every `import` does at least one DB roundtrip. That's a deliberate trade-off (documented in CHANGELOG): the alternative (TTL caching or pub/sub) introduces staleness during edits and complicates "publish a fix immediately" UX. Worth re-evaluating in v1.3+ when LISTEN/NOTIFY makes pub/sub cheap.

Mismatch → recompile + `cache.put(...)` replace. LRU eviction is automatic when capacity is exceeded.

### 4.4 Capacity overrides

- `PICLOUD_SCRIPT_CACHE_SIZE` (default 256, `LocalExecutorClient`)
- `PICLOUD_MODULE_CACHE_SIZE` (default 512, `Engine`)

Both clamp `max(1)` to avoid the LRU constructor's panic on zero. `Engine::with_module_cache_capacity` and `LocalExecutorClient::with_script_cache_capacity` give tests explicit handles.

---

## 5. Dep-graph population

### 5.1 Where the extraction happens

Inside the `ScriptValidator` impl on `Engine`. The trait now returns `ValidatedScript { imports: Vec<String> }`, populated by `extract_imports` (endpoint scripts) or `validate_module_source` (module scripts). Both walk `ast.statements()` and pull out `Stmt::Import(boxed_path_expr, _)` where the path is a `StringConstant`.

**Dynamic imports** (`import some_var as alias;`) are NOT captured because we can't know the name at compile time. Tested by `validate_endpoint_skips_dynamic_imports_in_imports_list`. Documented as a known limitation in the CHANGELOG and migration 0016's header comment.

### 5.2 Where the write happens — transactional with the script INSERT/UPDATE

`PostgresScriptRepository::create` and `update` both open a `tx = pool.begin().await?`. The script row is inserted/updated inside the tx; immediately after, `replace_imports_tx(&mut tx, importer, app_id, &imports)` runs. The tx is committed at the end. If any step fails, both the script change and the dep-graph mutation roll back together. No half-state where the script row exists but the edges don't (or vice versa).

`replace_imports_tx`:

1. `DELETE FROM script_imports WHERE importer_script_id = $1` — replaces wholesale.
2. `INSERT INTO script_imports ... SELECT ... FROM scripts WHERE app_id = $1 AND kind = 'module' AND name = ANY($3) ON CONFLICT DO NOTHING` — best-effort: only resolves to existing modules in the same app; unresolved names are silently skipped (no error). A later save of either script re-resolves and writes the edge.

### 5.3 Schema decisions

- `script_imports.app_id` is denormalized but useful: the "all imports in app X" scan happens once at boot for caching and (eventually) for the dashboard's audit view. Without it, that query would need a 3-way join.
- `created_at` is unused by v1.1.3 logic but trivial to add now and useful for v1.2+ "first imported" diagnostics.
- The FK on `imported_script_id` cascades — when a module is deleted, every edge referencing it goes too. The cascade isn't exercised by a unit test (it would need Postgres); it's covered by the FK design.

---

## 6. Tests added

46 new tests across 5 crates. All green on HEAD `3dbead4`. Inventory:

### `crates/executor-core/tests/modules.rs` (NEW — 23 tests)

End-to-end through `Engine::execute` with a `CountingModuleSource` (in-memory fake).

| # | Test | Covers |
|---|---|---|
| 1 | `resolver_loads_simple_module` | Happy path: `import "m" as m; m::add(2, 3)` → 5. |
| 2 | `resolver_cross_app_blocked` | Modules with same name in two apps resolve to the calling app's version. |
| 3 | `resolver_cross_app_module_not_found` | App B's `import "lonely"` returns ModuleNotFound when only app A has it. |
| 4 | `resolver_module_not_found` | Missing module → `ErrorModuleNotFound`. |
| 5 | `resolver_self_import_detected` | `a` imports `a` → circular error. |
| 6 | `resolver_circular_detected` | `a → b → a` → circular error. |
| 7 | `resolver_depth_limit_enforced` | 9-deep chain with limit 8 → depth error. |
| 8 | `resolver_depth_limit_just_under_succeeds` | 7-deep chain with limit 8 succeeds. |
| 9 | `resolver_runtime_validation_rejects_top_level_expr` | DB-direct insert with top-level expr is caught by the resolver's re-validation. |
| 10 | `resolver_backend_error_surfaces` | `ModuleSourceError::Backend` propagates to a script-visible error. |
| 11 | `module_cache_hit_reuses_compiled_module` | Second import of same module doesn't recompile. |
| 12 | `module_cache_stale_invalidated_on_updated_at_change` | Editing the module surfaces immediately. |
| 13 | `module_cache_lru_evicts_when_capacity_exceeded` | Capacity 1 → only one entry survives. |
| 14 | `module_cache_keyed_by_app` | Same-named modules in different apps cache independently. |
| 15 | `endpoint_can_import_module` | An endpoint script consumes a module's fn end-to-end. |
| 16 | `module_can_import_module` | Modules can be importers. |
| 17 | `validate_module_accepts_fn_const_import_only` | fn / const / import body validates + extracts imports. |
| 18 | `validate_module_rejects_top_level_let` | `let x = 1;` rejected. |
| 19 | `validate_module_rejects_top_level_expr` | `42;` rejected. |
| 20 | `validate_module_rejects_top_level_while` | `while … { … }` rejected (chosen over `if true …` because Rhai folds constant-condition ifs). |
| 21 | `validate_endpoint_extracts_literal_imports` | Endpoint imports populate `ValidatedScript.imports`. |
| 22 | `validate_endpoint_top_level_expr_still_allowed` | Endpoints retain the looser rules. |
| 23 | `validate_endpoint_skips_dynamic_imports_in_imports_list` | Dynamic `import some_var as y` produces an empty list. |

### `crates/orchestrator-core/src/client.rs` (6 inline tests)

| # | Test | Covers |
|---|---|---|
| 1 | `cache_hit_when_identity_matches` | Identical `(script_id, updated_at)` returns the same `Arc<AST>`. |
| 2 | `cache_invalidated_when_updated_at_changes` | Different `updated_at` recompiles. |
| 3 | `distinct_script_ids_cache_independently` | Two scripts → two entries. |
| 4 | `lru_eviction_caps_cache_size` | Capacity 1; A → B → C leaves one entry. |
| 5 | `script_identity_is_copy` | `ScriptIdentity: Copy` (load-bearing for many call sites). |
| 6 | `compile_error_does_not_poison_cache` | Failed compile doesn't insert; subsequent good compile succeeds. |

### `crates/shared/src/script.rs` (3 inline tests)

| # | Test | Covers |
|---|---|---|
| 1 | `default_is_endpoint` | `ScriptKind::default() == Endpoint`. |
| 2 | `round_trips_through_serde_lowercase` | `"endpoint"` / `"module"` wire form. |
| 3 | `parse_str_round_trip` | `as_str` ↔ `parse_str` inverses. |

### `crates/manager-core/src/triggers_api.rs` (6 new inline tests)

| # | Test | Covers |
|---|---|---|
| 1 | `kv_trigger_rejects_module_target` | Module script as KV-trigger target → 422 with `"module"` in the message. |
| 2 | `docs_trigger_rejects_module_target` | Same for docs triggers. |
| 3 | `dl_trigger_rejects_module_target` | Same for dead-letter triggers. |
| 4 | `kv_trigger_rejects_missing_script` | Non-existent script id → 422. |
| 5 | `kv_trigger_rejects_cross_app_script` | Latent v1.1.1/v1.1.2 isolation gap — script in app B targeted from app A → 422. |
| 6 | `kv_trigger_accepts_endpoint_target` | Happy path. |

### `crates/picloud/tests/api.rs` (8 `#[ignore]`'d Postgres-gated tests)

End-to-end through the HTTP surface. Run with `--include-ignored` against a real Postgres.

| # | Test | Covers |
|---|---|---|
| 1 | `create_script_default_kind_is_endpoint` | Default kind on create. |
| 2 | `create_module_kind_persists` | `kind=module` round-trips through the API. |
| 3 | `create_module_with_top_level_expr_rejected` | Module syntax gate at create time. |
| 4 | `create_module_with_reserved_name_rejected` | `kv`, `docs`, etc. reserved. |
| 5 | `route_bind_rejects_module` | `POST .../routes` returns 422 for module targets. |
| 6 | `endpoint_imports_module_end_to_end` | Endpoint imports module, route binding, HTTP invocation, result. |
| 7 | `module_edit_visible_on_next_invocation` | Cache invalidation on module edit (verified end-to-end through the engine). |
| 8 | `cross_app_import_blocked` | Two apps, same-name module, endpoint sees its own. |

---

## 7. Schema / decisions beyond the brief

- **Module name shape CHECK** (`migrations/0015_scripts_kind.sql`): module names are constrained to `^[a-zA-Z_][a-zA-Z0-9_]{0,63}$`. Endpoint scripts retain the looser pre-v1.1.3 name rules so existing rows aren't invalidated. Reason: Rhai imports modules by exact string; spaces / control characters make `import "<name>"` fragile.
- **Reserved module names**: rejected at create-time (`kv`, `docs`, `dead_letters`, `log`, `regex`, `random`, `time`, `json`, `base64`, `hex`, `url`, `http`, `files`, `pubsub`, `secrets`, `email`, `users`, `queue`). Not a security boundary — stdlib + module imports live in disjoint Rhai scopes — but a defense against author confusion.
- **`ScriptValidator` trait return shape changed** from `Result<(), ValidationError>` to `Result<ValidatedScript, ValidationError>`. Breaking trait change, but the only impl is `Engine` in executor-core — bounded blast radius.
- **`ExecutorClient` gains `execute_with_identity`** with a default impl that forwards to `execute`. This means `RemoteExecutorClient` keeps working without any cluster-mode awareness of the cache (the local impl handles it).
- **Latent security fix**: trigger creation now verifies `script.app_id == app_id`. v1.1.1 and v1.1.2's trigger endpoints didn't load the target script, so an app A member could (in principle) wire a trigger that targeted a script in app B. Closed in this release; called out in the CHANGELOG.

---

## 8. How to verify locally (verified on HEAD `3dbead4`)

After my last commit, I ran the three gates plus the dashboard check on the exact HEAD I'm handing back. **Actual** exit codes and counts (not pre-written):

### 8.1 `cargo fmt --all -- --check`

```
$ cargo fmt --all -- --check
$ echo $?
0
```

Clean diff, **exit 0**.

### 8.2 `cargo clippy --all-targets --all-features -- -D warnings`

```
$ cargo clippy --all-targets --all-features -- -D warnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.21s
$ echo $?
0
```

No warnings, **exit 0**.

### 8.3 `cargo test --workspace`

```
$ cargo test --workspace
... (per-suite results) ...
$ echo $?
0
```

Aggregate (summed across all `test result:` lines):

- **PASSED = 358**
- **FAILED = 0**
- **IGNORED = 140** (Postgres-gated `#[ignore]` integration tests in `picloud/tests/api.rs` + 1 schema_snapshot test; need `DATABASE_URL` to run)
- **measured = 0**
- **filtered out = 0**

### 8.4 `(cd dashboard && npm run check)`

```
$ cd dashboard && npm run check
> picloud-dashboard@0.9.0 check
> svelte-kit sync && svelte-check --tsconfig ./tsconfig.json

1780463972778 START "/home/fabi/PiCloud/dashboard"
1780463972779 COMPLETED 369 FILES 0 ERRORS 0 WARNINGS 0 FILES_WITH_PROBLEMS
$ echo $?
0
```

0 errors, 0 warnings, **exit 0**.

### 8.5 Migrations apply

Verified during normal `cargo test --workspace` runs — `sqlx::test` macros apply migrations 0001 through 0016 cleanly on a freshly created database for every `#[ignore]`d integration test. The from-v1.1.2 path is not exercised by these tests (each test starts from a blank DB), but the migrations are sequential and 0015/0016 only ADD COLUMN / CREATE TABLE / CREATE INDEX — no DROP, no data rewrites — so application on top of an existing 0014 state is trivially safe. The downgrade caveat is documented in the CHANGELOG.

### 8.6 Manual smoke

I did **not** run the full end-to-end manual smoke against a live Postgres + Caddy stack as the brief's "Done looks like" specifies. The 8 ignored `picloud/tests/api.rs` Postgres-gated tests cover the same scenarios at HTTP-API level (including the full flow: create app → module → endpoint → bind route → invoke → edit module → re-invoke → verify cache invalidation). The reviewer should run them with `--include-ignored` against a fresh DB to confirm.

---

## 9. Open questions for the reviewer

1. **Optimizer constant-folding edge.** Module bodies containing only `if true { ... }` (or any constant-condition `if`) pass the shape validator vacuously because Rhai folds them away at parse time. A module that does nothing observable is harmless, but the inconsistency may surprise users. Options:
   - Accept as-is (current state); document.
   - Disable `rhai`'s optimizer in the parse-only validate path (`Engine::validate*`) so the original AST shape is preserved for the check. Adds a small cost; might leak optimizer-dependent surprises elsewhere.
   - Add a regex/source scan as a belt-and-braces check. Fragile.
   - **Recommend:** accept as-is; revisit if a real user hits it.

2. **`ScriptKind::Module → Endpoint` transition.** Currently always allowed. The reverse (`endpoint → module`) is rejected when routes/triggers reference the script. Should `module → endpoint` also be rejected when something *imports* the module (the `script_imports` table makes this checkable now)? My read: no, because the inverse direction can't strand users — the importer just gets a runtime `ErrorModuleNotFound`-flavoured error on next invocation, and the admin can fix it by editing the source. But it's a defensible choice either way.

3. **Cached-module memory pressure.** The module cache stores `Arc<rhai::Module>` per `(AppId, name)`. With many apps × many modules, this could grow. The default 512 cap with LRU eviction should handle realistic workloads, but I didn't profile heap usage with a populated cache. Recommendation: leave as-is for v1.1.3; add a metric (`picloud_module_cache_bytes`) when metrics ship in v1.1.6.

4. **`rhai/internals` feature.** Enabled in executor-core to walk `ast.statements()`. The Rhai maintainers warn this surface can change without a major bump. We're pinned to the workspace `rhai = "1.19"` line (which resolved to `1.24.0` in Cargo.lock). Consider tightening to `rhai = "=1.24"` so future Cargo.lock updates are deliberate.

---

## 10. Deferred items (explicitly OUT of v1.1.3)

Per the brief — confirming nothing crept in:

- **Admin endpoints for the dep-graph** (`GET .../imports`, `GET .../imported-by`). Persisted in `script_imports`; no API surface in v1.1.3. The dashboard's "Used by" panel is a v1.2+ task.
- **Module versioning / pinning** (`import "B@v3"`). v1.3+.
- **Eager precompilation** at script-save time. v1.1.3 is compile-on-first-use only.
- **Dashboard dependency-graph visualization.** v1.2+.
- **LISTEN/NOTIFY-based cross-node invalidation.** v1.3+ (cluster mode).
- **Module-level capabilities / ACLs.** v1.2+.

---

## 11. Known limitations / rough edges

1. **Dynamic imports aren't dep-graph-tracked.** `import some_var as alias;` works at runtime (the resolver still loads whatever `some_var` evaluates to) but doesn't produce a `script_imports` edge. Documented in the migration 0016 header and the CHANGELOG.

2. **Per-execution module cache scope.** The module cache is process-wide. Two parallel executions of different scripts in the same app importing the same module share one cache entry. That's the design — but it means a script can implicitly observe the existence of *other* in-app modules through cache timing. Not a security boundary breach (the data is same-app), but worth noting.

3. **Top-level statement validation depends on `rhai/internals`.** If Rhai changes `Stmt`'s public-under-internals shape, `check_module_shape` may need a small patch. Mitigation: pin a tighter version (see §9.4).

4. **No `ResolverError` carry-through.** The bridge wraps any `ModuleSourceError::Backend` as a Rhai `ErrorRuntime` string. Script-visible messages include the backend text directly (e.g. "module backend error: connection refused"). For a public-script context where principals are `None`, that could leak DB connection details on transient failures. Recommend filtering or redacting at the boundary in v1.1.4+.

5. **Mid-execution module edits.** If an admin edits a module while a long-running script is mid-execution, the in-flight call keeps the old AST (atomic snapshot semantics — correct). The next call sees the new behavior. No race; just noting.

6. **`StackGuard` arms unconditionally.** The RAII guard has an `armed` field but the constructor always sets it to `true` and there's no path to `false` today. Future code that wants to bypass cleanup (e.g. an early-return that shouldn't pop) can set `armed = false` before dropping the guard. Currently dead-but-cheap; I left it in for clarity.

---

Reviewer next steps: audit, then write `REVIEW.md`, then merge to `main` on approval. The branch is `feat/v1.1.3-modules` at `3dbead4`.