Blocks and scopes

Configuration is rarely flat. Aura has two forms of nesting, and they differ not in what they output but in what you are allowed to write inside.

An object literal: just data

security:
  tls:         true
  min_version: "1.3"
end

{ "security": { "tls": true, "min_version": "1.3" } }

Only properties are allowed inside. If you need computations, use domain.

On one line

A short object fits on one line: the same block, with commas where the newlines were (D38).

resources:
  requests: cpu: "250m", memory: "512Mi" end
  limits:   cpu: "500m", memory: "1Gi" end
end

A comma separates two fields and nothing else - one missing, or one before end, is E0205, and the message says which. aura fmt keeps whichever form you wrote. Two ends on a line (a: b: 1 end end) are legal and hard to read: write the outer level as a block.

Inside a list the one-line form needs a schema, new Port name: "http", port: 80 end - there the comma also separates the elements, and the schema checks the fields besides.

Bound with =

= binds an object exactly as : outputs one (D10): the block is the same, and it stays out of the result.

defaults =
  port:    8080
  timeout: "30s"
end

limits = cpu: "500m", memory: "1Gi" end

server:
  port:    defaults.port
  timeout: defaults.timeout
end

{ "server": { "port": 8080, "timeout": "30s" } }

Change defaults = to defaults: and the object is output as well; nothing else about it changes. If an = block is left without its end, the error points at the line with =.

domain — a section with its own scope

The label becomes the key, and the body is a full scope: =, shadow and assert all work.

domain "prod"
  replicas: 3
  region:   "eu-central"
end

{ "prod": { "replicas": 3, "region": "eu-central" } }

The label can be any expression, not only a string literal.

Scope and shadow

Outer variables are visible, but overriding one requires an explicit shadow (D7):

port = 80

domain "prod"
  shadow port = 443 # without `shadow` this is E0302
  listen: port      # 443
end

fallback: port # 80 — nothing outside changed

This is the direct answer to “why is the port different in production”: the override is visible in the code.

Lists of objects: map, with no extra keywords

A lambda body is a scope too (D17), so list elements are described directly, private computations included:

services: ["api", "web"].map (n, i) ->
  base = 8000 # private: never reaches the JSON
  name: n
  port: base + i
end

{
  "services": [
    { "name": "api", "port": 8000 },
    { "name": "web", "port": 8001 }
  ]
}

The name field here is an ordinary property that you write yourself. A component keyword used to insert that line implicitly; D17 removed it, because the language should not add fields behind your back.

Which to use

• Data only → key: … end.
• Data plus computation → domain.
• A list of objects → map with a lambda body; no block needed.

The general rule: code bodies (def, a lambda, domain) are scopes; an object literal is data.