Copperlace

Getting Started

A Copperlace configuration names the pieces of text you want to reuse. Render a rule to turn those pieces into one result. The examples below work with the released copperlace CLI or with cargo run --bin copperlace -- from rust-core/ (adjust file paths when running there).

Render your first rule

Save this as hello.conf:

name = ["Mia"]
pet = ["owl"]
origin = "{name} travels with {pet | article}."
copperlace check -c hello.conf
copperlace render -c hello.conf

check prints OK when the configuration parses and compiles. render uses origin by default and prints Mia travels with an owl.. The braces in {name} and {pet | article} are template expressions. article adds the English indefinite article.

You can also skip the file for a quick experiment:

printf 'name = "Mia"\norigin = "Hello {name}"\n' | copperlace render -c -

Add variation without losing consistency

Replace hello.conf with:

name = ["Mia", "Lina"]
pet = ["owl", "raven"]
origin = "{% hero:name %}{hero} travels with {pet | article}. {hero} smiles."

Each array chooses one entry when referenced. The binding statement {% hero:name %} chooses a name once, stores it as hero, and prints nothing. Both {hero} expressions reuse that value. Run copperlace render -c hello.conf -n 3 to get three independently rendered lines. Results can differ between runs; Copperlace does not expose a random seed.

{% hero:name %} keeps an existing hero value. This lets a caller supply one:

copperlace render -c hello.conf --set hero=Darcy

The --set value applies to that render only. The next render starts fresh. To replace an existing value inside a template, use {% hero:=name %} instead.

Choose the output shape

A string rule produces text. A top-level array rule chooses one text value. A top-level object rule produces structured JSON in the CLI:

name = ["Mia"]
context {
  hero = "{name}"
}
origin {
  title = "Welcome {hero}"
  tags = ["welcome", "{hero | slug}"]
  count = 2
}
copperlace render -c hello.conf
copperlace render -c hello.conf --compact-json

The tags array stays an array because it is inside a structured object. Use context.hero when multiple fields need the same generated value: object field order is not a way to share a binding. For JSON that an application will parse, --compact-json -n 3 emits one complete JSON object per line.

Where to go next