Targets

Note: This is a user guide (informative). For normative requirements, see the Targets Specification.

A target is a buildable unit in your Structyl project. Targets can be programming language implementations or auxiliary tools.

Target Types

Language Targets

Language targets represent implementations of your library in different programming languages.

{
  "targets": {
    "rs": {
      "type": "language",
      "title": "Rust",
      "toolchain": "cargo"
    }
  }
}

Language targets:

• Participate in structyl test and structyl demo
• Are expected to pass reference tests
• Get README files generated

Auxiliary Targets

Auxiliary targets are supporting tools that aren't code implementations.

{
  "targets": {
    "img": {
      "type": "auxiliary",
      "title": "Image Generation",
      "commands": {
        "build": "python scripts/generate.py"
      }
    }
  }
}

Use auxiliary targets for:

• Documentation generation
• Image/asset generation
• Code generation
• Website builds

Auxiliary targets only run during structyl build, not test or demo.

Configuring Targets

Minimal Configuration

With auto-detection:

{
  "targets": {
    "rs": {
      "type": "language",
      "title": "Rust"
    }
  }
}

Structyl detects Cargo.toml in rs/ and uses the cargo toolchain.

With Toolchain

Specify the toolchain explicitly:

{
  "targets": {
    "py": {
      "type": "language",
      "title": "Python",
      "toolchain": "uv"
    }
  }
}

With Command Overrides

Customize specific commands:

{
  "targets": {
    "cs": {
      "type": "language",
      "title": "C#",
      "toolchain": "dotnet",
      "commands": {
        "test": "dotnet run --project MyLib.Tests",
        "demo": "dotnet run --project MyLib.Demo"
      }
    }
  }
}

Full Configuration

{
  "targets": {
    "py": {
      "type": "language",
      "title": "Python",
      "toolchain": "uv",
      "directory": "py",
      "cwd": "py",
      "vars": {
        "test_dir": "tests"
      },
      "env": {
        "PYTHONPATH": "."
      },
      "commands": {
        "demo": "uv run python examples/demo.py"
      }
    }
  }
}

Target Dependencies

Targets can depend on other targets:

{
  "targets": {
    "img": {
      "type": "auxiliary",
      "title": "Images"
    },
    "pdf": {
      "type": "auxiliary",
      "title": "PDF Manual",
      "depends_on": ["img"]
    },
    "web": {
      "type": "auxiliary",
      "title": "Website",
      "depends_on": ["img", "pdf"]
    }
  }
}

Execution Order

When running structyl build:

1. Targets with no dependencies build first
2. Targets build when all their dependencies complete
3. Independent targets run in parallel

For the example above:

1. img (no dependencies)
2. pdf (after img completes)
3. web (after img and pdf complete)

Language targets without explicit dependencies build in parallel.

Running Target Commands

Single Target

structyl build rs
structyl test py
structyl clean go

All Targets

structyl build      # Build all targets
structyl test       # Test all language targets
structyl clean      # Clean all targets

Filtered by Type

structyl build --type=language    # Language targets only
structyl build --type=auxiliary   # Auxiliary targets only

Specific Targets

structyl build rs py go           # Build specific targets

Listing Targets

View configured targets:

structyl targets

Output:

Languages:
  rs   Rust       (cargo)
  py   Python     (uv)
  go   Go         (go)

Auxiliary:
  img  Image Generation
  pdf  PDF Manual (depends: img)

Default Language Target Names

These target names are recognized as language targets:

Name	Language	Default Toolchain
c	C	cmake
cpp	C++	cmake
cs	C#	dotnet
go	Go	go
java	Java	gradle
js	JavaScript	npm
kt	Kotlin	gradle
py	Python	python
r	R	—
rb	Ruby	—
rs	Rust	cargo
scala	Scala	gradle
swift	Swift	swift
ts	TypeScript	npm

Unknown slugs default to auxiliary type.

Target Naming

Target names must:

• Start with a lowercase letter
• Contain only lowercase letters, digits, and hyphens
• Be 1-64 characters long

Valid: rs, my-lib, python3 Invalid: MyLib, _internal, 123start

Next Steps

• Commands - Understand the command system
• Toolchains - See all supported toolchains
• Testing - Set up cross-language tests