Props

Props are input values passed from parent components (or bootstrap initial_props) into a component.

In moon-spa, props defaults are declared in setup(self, props).

Passing props

From parent template:

<Card title="Hello" count="42" active="true" />

From spa.config.json:

{
  "initial_props": { "user": "admin", "debug": false }
}

Declaring props in setup()

class Card(Component):
  def setup(self, props):
    return {
      "props": {
        "title": "Default Title",
        "count": 0,
        "active": False,
        **props,
      },
      "state": {},
      "data": {},
      "actions": {},
      "lifecycle": {},
    }

You can also omit return entirely. In that case, moon-spa infers props from the local props variable created in setup(self, props):

class Card(Component):
  def setup(self, props):
    props = {
      "title": "Default Title",
      "count": 0,
      "active": False,
      **props,
    }

    state = {}
    data = {}

The runtime merges defaults with incoming values and coerces scalar types (int/float/bool/str) safely.

Reading props in setup and template

setup(self, props) receives props as a Python dict:

def setup(self, props):
  title = props.get("title", "Default Title")
  return {
    "props": {"title": title, **props},
    "state": {},
    "data": {},
    "actions": {},
    "lifecycle": {},
  }

Template:

<template>
  <p>{{ props.title }}</p>
  <p l-if="props.active">Active!</p>
</template>

Rules

• Define props defaults in setup(self, props).
• setup may return a mapping or omit return and rely on server inference.
• Use props for input values and state for reactive mutations.
• Server callables may return explicit prop patches, but mutating data is also enough because moon-spa patches those keys automatically.