template_render

Render a string template with context variable interpolation.

Parameters

The template parameter supports the shared context path grammar:

• dotted object access: ${ctx.user.email}
• zero-based array access: ${ctx.items[0].name}
• JSON double-quoted bracket keys: ${ctx["key.with.dots"]}

These forms can be combined. Missing paths, out-of-range indexes, and null values resolve to an empty string. Expressions, function calls, and fallback operators are invalid; compute derived/default values in an explicit workflow step. Non-ctx placeholders such as ${HOME} remain literal. To render ${ctx.user} literally, pass \${ctx.user} at runtime (written as "\\${ctx.user}" in a Lua string). Rendering is one pass, so placeholder text inside a resolved context string is not evaluated again.

Context Output

• {output_key} -- the rendered string, stored under the key specified by the output_key parameter

Example

local flow = Flow.new("order_confirmation")

flow:step("render", nodes.template_render({
    template = "Hello ${ctx.users[0].name}, your order #${ctx.order_id} is confirmed.",
    output_key = "confirmation_message"
}))

flow:step("done", nodes.log({
    message = "Rendered: ${ctx.confirmation_message}"
})):depends_on("render")

return flow

Given a context with users[0].name = "Alice" and order_id = 42, the output key confirmation_message will contain:

Hello Alice, your order #42 is confirmed.