EVA Declarative Configuration Language (eva-dcl)

EVA is a declarative, readable, and expressive configuration language designed to make application configuration simple and powerful. With EVA, you can compose data, use utility functions, and resolve values dynamically—all in a straightforward format.

What is EVA?

EVA lets you:

• Define configurations in a clear and organized way
• Use utility functions like env(), format(), merge(), and more
• Compose and reuse values
• Make all your project smart, even also the configuration file

Example EVA configuration:

@project
name: "EVA"
version: "1.0.0"

@dev
name: "Lucas Silveira"
messages: [
    format("Hello, I am {}!", ref(name)),
    "Hello, world"
]

Installation

With Bun:

$ bun install eva-dcl

Usage

import { Eva, EvaMap, EvaList } from "eva-dcl";
import { join } from "path";

const config = new Eva(join(__dirname, "config.eva"));
const project_name = await config.get<string>("project", "name");
console.log(`Running ${project_name} project`);

const dev = await config.get<EvaMap>("dev", "name");
console.log(`created by ${dev}`);

const dev_messages = await config.get<EvaList>("dev", "messages");
const index = 0;
const message = await dev_messages.get(index);
console.log(`${dev} said: ${message}`);

Example config.eva file:

@project
name: "EVA"
version: "1.0.0"

@dev
name: "Lucas Silveira"
messages: [
    format("Hello, I am {}!", ref(name)),
    "Hello, world"
]

Available Functions

You can use utility functions like:

| Function | Description | Example | |---|---|---| | absolute() | Returns the absolute version of a path | absolute("./config") | | basename() | Returns the file name from a path | basename("/home/file.txt") | | clamp() | Restricts a number between a minimum and maximum value | clamp(volume, 0, 100) | | coalesce() | Returns the first non-null value | coalesce(a, b, c) | | contains() | Checks whether a string, array or map contains a value | contains(items, "apple") | | debug() | Prints or exposes internal debug information | debug(config) | | deepmerge() | Recursively merges maps | deepmerge(base, user) | | else() | Returns a fallback value if the first value is null | else(port, 8080) | | endswith() | Checks whether a string ends with a value | endswith(name, ".png") | | entries() | Returns all key-value pairs from a map | entries(user) | | env() | Reads environment variables | env("HOME") | | extname() | Returns the extension of a file | extname("image.png") | | format() | Formats a string using placeholders | format("Hello {}", name) | | if() | Returns one of two values based on a condition | if(debug, "yes", "no") | | important() | Marks a value or section as important | important(token) | | keys() | Returns all keys from a map | keys(config) | | lower() | Converts text to lowercase | lower(name) | | merge() | Merges maps shallowly | merge(a, b) | | ref() | References local values inside the current namespace | ref(home) | | startswith() | Checks whether a string starts with a value | startswith(path, "/home") | | trim() | Removes leading and trailing whitespace | trim(input) | | upper() | Converts text to uppercase | upper(name) | | values() | Returns all values from a map | values(config) |