Build-script helpers for binary skills.

These functions are designed to be called from build.rs to prepare the SKILL.md and set up build-time environment variables.

Plain SKILL.md

If your SKILL.md is a static file with no templating:

// build.rs
fn main() {
    ionem::build::emit_target();
    ionem::build::copy_skill_md();
}

Template with variable substitution

If your SKILL.md uses {version}, {name}, {description} placeholders (auto-populated from Cargo metadata) and/or custom variables:

// build.rs
fn main() {
    ionem::build::emit_target();
    ionem::build::render_skill_md_vars(&[("example_output", &generated_json)]);
}

Custom template engine

For full control (e.g. using minijinja, tera, handlebars):

// build.rs
fn main() {
    ionem::build::emit_target();
    ionem::build::render_skill_md(|template| {
        my_engine::render(template, &context)
    });
}

In main.rs

All approaches produce the same output. In your binary, use:

const SKILL_MD: &str = include_str!(concat!(env!("OUT_DIR"), "/SKILL.md"));

emit_target

pub fn emit_target()

Emit the TARGET environment variable for the build.

This makes env!("TARGET") available in your binary, which is needed by SelfManager to report the build target.

Call this from build.rs.

copy_skill_md

pub fn copy_skill_md()

Copy SKILL.md from the crate root to OUT_DIR/SKILL.md unchanged.

Sets up cargo:rerun-if-changed so the file is re-copied when modified.

Panics

Panics if SKILL.md does not exist in the crate root or cannot be copied.

copy_skill_md_from

pub fn copy_skill_md_from(path: &str)

Copy a SKILL.md from a custom path (relative to crate root) to OUT_DIR/SKILL.md.

Sets up cargo:rerun-if-changed so the file is re-copied when modified.

render_skill_md

pub fn render_skill_md(render: impl FnOnce(&str) -> String)

Render SKILL.md from the crate root using a custom render function.

The function receives the raw template content and should return the rendered output. Sets up cargo:rerun-if-changed.

Example

ionem::build::render_skill_md(|content| {
    content.replace("{custom}", "value")
});

render_skill_md_from

pub fn render_skill_md_from(path: &str, render: impl FnOnce(&str) -> String)

Render a SKILL.md template from a custom path using a custom render function.

Like [render_skill_md] but reads from an arbitrary path relative to the crate root.

render_skill_md_vars

pub fn render_skill_md_vars(extra_vars: &[(&str, &str)])

Render SKILL.md with automatic variable substitution.

Automatically replaces these placeholders from Cargo package metadata:

• {version} — CARGO_PKG_VERSION
• {name} — CARGO_PKG_NAME
• {description} — CARGO_PKG_DESCRIPTION

Additional custom variables can be provided as (key, value) pairs. Keys should not include braces — ("author", "Alice") replaces {author}.

Example

// SKILL.md contains: "Version: {version}, Author: {author}"
ionem::build::render_skill_md_vars(&[("author", "Alice")]);
// Produces: "Version: 0.1.0, Author: Alice"

render_skill_md_vars_from

pub fn render_skill_md_vars_from(path: &str, extra_vars: &[(&str, &str)])

Render a SKILL.md template from a custom path with variable substitution.

Like [render_skill_md_vars] but reads from an arbitrary path.

read_file

pub fn read_file(path: &str) -> String

Helper to read a file relative to the crate root.

Useful in build.rs when you need to read additional files for template context (e.g. JSON examples).