WARPO Configuration File (asconfig.json)

The WARPO compiler uses a configuration file named asconfig.json to control the build process, specify entry points, and customize output options. This file must be a valid JSON object matching the schema below.

Top-Level Structure

{
  "$schema": "https://raw.githubusercontent.com/wasm-ecosystem/warpo/refs/tags/2.3.0-alpha-1/asconfig.schema.json",
  "entries": [ ... ],
  "options": { ... },
  "targets": { ... }
}

• schema: Pre-defined schema for asconfig.json. It locates in warpo project root.

  INFO

  Specifies the JSON Schema URI that describes the structure and validation rules for the configuration file. This helps tools and editors provide validation, auto-completion, and error checking based on the defined schema.

• entries: Array of entry AssemblyScript source files to compile. Each item is a file path (string).
• options: Global compiler options (see below).
• targets: Object mapping target names to their own compiler options (see below).

Options

Options control the build process and output. They can be specified globally (under options) or per target (under targets). Detail description for each items see schema.

use

use corresponds to AssemblyScript's --use <name>=<value> option.

It supports two forms:

{
  "use": { "NAME": "VALUE" }
}

{
  "use": ["NAME=VALUE"]
}

host

Selects which host API surface the compiler targets for imports. The default is none.

Supported values:

• none: do not assume any host APIs.
• wasi_snapshot_preview1: use WASI Snapshot Preview 1 host imports.

See also: WASI Snapshot Preview 1 Host

You can set it in the config file:

{
  "options": {
    "host": "wasi_snapshot_preview1"
  }
}

Or via CLI:

warpo assembly/index.ts -o build/app.wasm --host wasi_snapshot_preview1

Targets

Targets allow you to define multiple build configurations (e.g., debug, release). Each target is an object with its own options, overriding the global options.

Example:

"targets": {
  "release": {
    "debug": false,
    "optimizeLevel": 3,
    "shrinkLevel": 2
  },
  "debug": {
    "debug": true,
    "sourceMap": true
  }
}

Example Configuration

{
  "entries": ["src/main.ts", "src/module.ts"],
  "options": {
    "exportStart": "main",
    "debug": true,
    "optimizeLevel": 0
  },
  "targets": {
    "release": {
      "debug": false,
      "optimizeLevel": 3,
      "shrinkLevel": 2
    },
    "debug": {
      "debug": true,
      "sourceMap": true
    }
  }
}

How It Works

The compiler loads asconfig.json specified by the --config command line option. It first applies options from the options field. If a target is specified via the --target command line option, the corresponding options from the targets field override the global options. Finally, any additional command line options are applied, taking precedence over previous settings.

Tips

• Use the options section to define the common configurations.
• Use the targets section to easily switch between different build configurations.