vendor/handlebars-0.32.4/src/directives/mod.rs

use render::{Directive, RenderContext};
use registry::Registry;
use error::RenderError;

pub use self::inline::INLINE_DIRECTIVE;

/// Decorator Definition
///
/// Implement this trait to define your own decorators or directives. Currently
/// decorator shares same definition with helper.
///
/// In handlebars, it is recommanded to use decorator to change context data and update helper
/// definition.
/// ## Updating context data
///
/// In decorator, you can change some context data your are about to render.
///
/// ```
/// use handlebars::*;
///
/// fn update_data(_: &Decorator, _: &Handlebars, rc: &mut RenderContext)
///         -> Result<(), RenderError> {
///     // modify json object
///     let mut data = rc.context_mut().data_mut();
///     if let Some(ref mut m) = data.as_object_mut() {
///         m.insert("hello".to_string(), to_json(&"world".to_owned()));
///     }
///     Ok(())
/// }
///
/// ```
///
/// ## Define local helper
///
/// You can override behavior of a helper from position of decorator to the end of template.
///
/// ```
/// use handlebars::*;
///
/// fn override_helper(_: &Decorator, _: &Handlebars, rc: &mut RenderContext)
///         -> Result<(), RenderError> {
///     let new_helper = |h: &Helper, _: &Handlebars, rc: &mut RenderContext|
///             -> Result<(), RenderError> {
///         // your helper logic
///         Ok(())
///     };
///     rc.register_local_helper("distance", Box::new(new_helper));
///     Ok(())
/// }
/// ```
///
pub trait DirectiveDef: Send + Sync {
    fn call(&self, d: &Directive, r: &Registry, rc: &mut RenderContext) -> Result<(), RenderError>;
}

/// implement DirectiveDef for bare function so we can use function as directive
impl<
    F: Send
        + Sync
        + for<'b, 'c, 'd, 'e> Fn(&'b Directive, &'c Registry, &'d mut RenderContext)
        -> Result<(), RenderError>,
> DirectiveDef for F
{
    fn call(&self, d: &Directive, r: &Registry, rc: &mut RenderContext) -> Result<(), RenderError> {
        (*self)(d, r, rc)
    }
}

mod inline;

#[cfg(test)]
mod test {
    use registry::Registry;
    use context::{self, as_string, Context};
    use render::{Directive, Helper, RenderContext};
    use error::RenderError;

    #[test]
    fn test_register_decorator() {
        let mut handlebars = Registry::new();
        handlebars
            .register_template_string("t0", "{{*foo}}".to_string())
            .unwrap();

        let data = btreemap! {
            "hello".to_string() => "world".to_string()
        };

        assert!(handlebars.render("t0", &data).is_err());

        handlebars.register_decorator(
            "foo",
            Box::new(
                |_: &Directive, _: &Registry, _: &mut RenderContext| -> Result<(), RenderError> {
                    Ok(())
                },
            ),
        );
        assert_eq!(handlebars.render("t0", &data).ok().unwrap(), "".to_string());
    }

    #[test]
    fn test_update_data_with_decorator() {
        let mut handlebars = Registry::new();
        handlebars
            .register_template_string("t0", "{{hello}}{{*foo}}{{hello}}".to_string())
            .unwrap();

        let data = btreemap! {
            "hello".to_string() => "world".to_string()
        };

        handlebars.register_decorator(
            "foo",
            Box::new(
                |_: &Directive, _: &Registry, rc: &mut RenderContext| -> Result<(), RenderError> {
                    // modify json object
                    let ctx_ref = rc.context_mut();
                    let data = ctx_ref.data_mut();

                    if let Some(ref mut m) = data.as_object_mut().as_mut() {
                        m.insert("hello".to_string(), context::to_json(&"war".to_owned()));
                    }

                    Ok(())
                },
            ),
        );

        assert_eq!(
            handlebars.render("t0", &data).ok().unwrap(),
            "worldwar".to_string()
        );

        let data2 = 0;
        handlebars.register_decorator(
            "bar",
            Box::new(
                |d: &Directive, _: &Registry, rc: &mut RenderContext| -> Result<(), RenderError> {
                    // modify value
                    let v = d.param(0)
                        .and_then(|v| Context::wraps(v.value()).ok())
                        .unwrap_or(Context::null());
                    *rc.context_mut() = v;
                    Ok(())
                },
            ),
        );
        handlebars
            .register_template_string("t1", "{{this}}{{*bar 1}}{{this}}".to_string())
            .unwrap();
        assert_eq!(
            handlebars.render("t1", &data2).ok().unwrap(),
            "01".to_string()
        );

        handlebars
            .register_template_string(
                "t2",
                "{{this}}{{*bar \"string_literal\"}}{{this}}".to_string(),
            )
            .unwrap();
        assert_eq!(
            handlebars.render("t2", &data2).ok().unwrap(),
            "0string_literal".to_string()
        );

        handlebars
            .register_template_string("t3", "{{this}}{{*bar}}{{this}}".to_string())
            .unwrap();
        assert_eq!(
            handlebars.render("t3", &data2).ok().unwrap(),
            "0".to_string()
        );
    }

    #[test]
    fn test_local_helper_with_decorator() {
        let mut handlebars = Registry::new();
        handlebars
            .register_template_string(
                "t0",
                "{{distance 4.5}},{{*foo \"miles\"}}{{distance 10.1}},{{*bar}}{{distance 3.4}}"
                    .to_string(),
            )
            .unwrap();

        handlebars.register_helper(
            "distance",
            Box::new(
                |h: &Helper, _: &Registry, rc: &mut RenderContext| -> Result<(), RenderError> {
                    let s = format!(
                        "{}m",
                        h.param(0,)
                            .map(|v| v.value(),)
                            .unwrap_or(&context::to_json(&0),)
                    );
                    try!(rc.writer().write(s.into_bytes().as_ref()));
                    Ok(())
                },
            ),
        );
        handlebars.register_decorator(
            "foo",
            Box::new(
                |d: &Directive, _: &Registry, rc: &mut RenderContext| -> Result<(), RenderError> {
                    let new_unit = d.param(0)
                        .and_then(|v| as_string(v.value()))
                        .unwrap_or("")
                        .to_owned();
                    let new_helper = move |h: &Helper,
                                           _: &Registry,
                                           rc: &mut RenderContext|
                          -> Result<(), RenderError> {
                        let s = format!(
                            "{}{}",
                            h.param(0,)
                                .map(|v| v.value(),)
                                .unwrap_or(&context::to_json(&0),),
                            new_unit
                        );
                        try!(rc.writer().write(s.into_bytes().as_ref()));
                        Ok(())
                    };

                    rc.register_local_helper("distance", Box::new(new_helper));
                    Ok(())
                },
            ),
        );
        handlebars.register_decorator(
            "bar",
            Box::new(
                |_: &Directive, _: &Registry, rc: &mut RenderContext| -> Result<(), RenderError> {
                    rc.unregister_local_helper("distance");
                    Ok(())
                },
            ),
        );
        assert_eq!(
            handlebars.render("t0", &0).ok().unwrap(),
            "4.5m,10.1miles,3.4m".to_owned()
        );
    }
}