08-pkg-compose

08-pkg-compose

Package composition via pkg.render — an outer Package calls a reusable inner Package twice with different inputs and concatenates the results. Renders end-to-end today (pure KCL; no helm needed).

What's here

file	purpose
package.k	Outer Package; calls pkg.render(pkg.Render { package = "shared", ... }) twice with distinct inputs.
shared/package.k	Inner Package; emits one ConfigMap parameterized by name + payload.
shared/akua.toml	Inner manifest — marks shared/ as an Akua package.
akua.toml	Outer manifest — declares shared as a workspace-local path dep.
inputs.example.yaml	Per-component inputs, auto-discovered by akua render.

Render

cargo run -q -p akua-cli -- render --package examples/08-pkg-compose/package.k --out ./rendered

Or, from the example directory:

akua render --out ./rendered

Two ConfigMaps land in ./rendered/ (checked in as reference output):

rendered/
├── 000-configmap-frontend.yaml
└── 001-configmap-backend.yaml

How pkg.render works

pkg.render is a synchronous KCL host plugin: the handler resolves the package alias against the calling Package's akua.toml [dependencies] (no filesystem paths in user code), calls PackageK::load(...).render(inputs) inline, and returns the inner resources list directly to the caller. Because the return is a real list, list-comprehension patches and filter expressions on the result work natively — no post-eval rewrite step.

Reentrancy works because akua's KCL fork copies the plugin handler fn pointer out of its mutex before invoking the callback (see cnap-tech/kcl#akua-wasm32); upstream KCL holds the mutex across the call and would deadlock here.

Cycle detection uses akua-core's thread-local render-stack: a Package referring to itself, directly or transitively (A → B → A), is rejected before infinite recursion. Nested pkg.render calls (A → B → C) recurse through the same handler, with each inner Package's render pushing/popping the stack.