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extern crate env_logger;
extern crate handlebars;
#[macro_use]
extern crate serde_json;
use std::error::Error as StdError;
use handlebars::{
Context, Handlebars, Helper, Output, RenderContext, RenderError, RenderErrorReason,
};
use thiserror::Error;
#[derive(Debug, Error)]
pub enum HelperError {
#[error("db error")]
DbError,
#[error("api error")]
ApiError,
}
/// A helper that raise error according to parameters
pub fn error_helper(
h: &Helper,
_: &Handlebars,
_: &Context,
_: &mut RenderContext,
_: &mut dyn Output,
) -> Result<(), RenderError> {
let param = h
.param(0)
.ok_or(RenderErrorReason::ParamNotFoundForIndex("error", 0))?;
match param.value().as_str() {
Some("db") => Err(RenderErrorReason::NestedError(Box::new(HelperError::DbError)).into()),
Some("api") => Err(RenderErrorReason::NestedError(Box::new(HelperError::ApiError)).into()),
_ => Ok(()),
}
}
fn main() -> Result<(), Box<dyn StdError>> {
env_logger::init();
let mut handlebars = Handlebars::new();
// template not found
println!(
"{}",
handlebars
.register_template_file("notfound", "./examples/error/notfound.hbs")
.unwrap_err()
);
// an invalid templat
println!(
"{}",
handlebars
.register_template_file("error", "./examples/error/error.hbs")
.unwrap_err()
);
// render error
let e1 = handlebars
.render_template("{{#if}}", &json!({}))
.unwrap_err();
let be1 = Box::new(e1);
println!("{}", be1);
println!("{}", be1.source().unwrap());
println!("{:?}", be1.source().unwrap().source());
// process error generated in helper
handlebars.register_helper("err", Box::new(error_helper));
let e2 = handlebars
.render_template("{{err \"db\"}}", &json!({}))
.unwrap_err();
// get nested error to from `RenderError`
match e2.source().and_then(|e| e.downcast_ref::<HelperError>()) {
Some(HelperError::DbError) => {
println!("Detected error from helper: db error",)
}
_ => {}
}
Ok(())
}
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