Why does Tera say TemplateNotFound when rendering a template?

Question

I am experimenting with building a web app in Rust using Tera and there is a panic every time on the render() call below. Example of the chunk of code:

async fn login(tera: web::Data<Tera>) -> impl Responder {
    let mut data = Context::new();
    data.insert("title", "Login");

    let rendered = tera.render("login.html", &data).unwrap();
    HttpResponse::Ok().body(rendered)
}

Link to my repo to review: https://github.com/ClusterberrySquirrels/oasis/blob/oasis_db/src/main.rs

I get the following panic call:

thread 'actix-rt:worker:0' panicked at 'called `Result::unwrap()` on an `Err` value: Error { kind: TemplateNotFound("login.html"), source: None }', src/main.rs:101:53

Something fixed this panic when I was having the same problem at the beginning of this project on the index.html page. At first I thought it was Tera causing the issue but I didn't find any steps to fix it. Eventually something I did made it behave as intended and everything was fine until now. I would appreciate any advice on how to fix this and avoid it happening in the future.

File structure:

Project Folder\
  templates\
    login.html
    index.html
  src\
    main.rs

Trouble shooting on my side not necessarily in order:

1. Switch toolchain default from stable -> cargo build/run, to nightly -> cargo build/run and back.
2. rustup update
3. sudo apt update
4. sudo apt upgrade
5. wsl --set-default-version 2
6. cargo clean
7. Delete target folder then cargo clean, cargo build, cargo run
8. cargo update

Update to question: Minimum reproducible example.

use actix_web::{HttpServer, App, web, HttpResponse, Responder};
use tera::{Tera, Context};

async fn index(tera: web::Data<Tera>) -> impl Responder {
    let mut data = Context::new();

    let posts = [
        Post {
            title: String::from("This is the first link"),
            link: String::from("https://example.com"),
            author: String::from("Nutrition-Tracker"),
        },
        Post {
            title: String::from("This is the second Link"),
            link: String::from("https://example.com"),
            author: String::from("Other cool app"),
        },
    ];

    data.insert("title", "index");
    data.insert("posts", &posts);

    let rendered = tera.render("index.html", &data).unwrap(); // TemplateNotFound??
    HttpResponse::Ok().body(rendered)
}

async fn login(tera: web::Data<Tera>) -> impl Responder {
    let mut data = Context::new();
    data.insert("title", "Login");

    let rendered = tera.render("login.html", &data).unwrap(); // TemplateNotFound??
    HttpResponse::Ok().body(rendered)
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| {
        let tera = Tera::new("templates/**/*").unwrap(); 
        App::new()
            .data(tera)
            .route("/", web::get().to(index))
            .route("/login", web::get().to(login))
    })
        .bind("127.0.0.1:8000")?
        .run()
        .await
}

Answer 1

I figured out the issue. I am also running kubernetes for this application and the ports I was selecting were being occupied by kubernetes at random times. I killed all of the processes however, the problem still remains which is an issue for another thread.

Answer 2

To render a template on Tera you need to:

async fn index(req: HttpRequest) -> Result<HttpResponse> {

    // Create new tera instance with sample template
    let mut tera = Tera::default();
    tera.add_template_file("templates/default.html", Some("TEMPLATE_NAME")).unwrap();

    // Create new context
    let mut context = tera::Context::new();
    context.insert("key1", "value2");
    context.insert("key2", "value2");

    // Render template using the context
    let rendered = tera.render("TEMPLATE_NAME", &context).unwrap();

    Ok(HttpResponse::Ok().content_type("text/html").body(rendered))
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| {
        App::new()
            .route("/", web::get().to(index))
    })
    .bind("127.0.0.1:8080")?
    .run()
    .await
}

This is the file structure:

Cargo.toml
src
 - main.rs
templates
 - default.html

It works for me, let me know if anything needs clarification.

Answer 3

For your debugging, I had a similar issue, and now solved so sharing this.

TemplateNotFound is the correct error message, in other words, Rust runtime might not recognize the template. Let me advise for debugging.

You declare reading tera template directory like this:

let tera = Tera::new(concat!(env!("CARGO_MANIFEST_DIR"), "/templates/**/*")).unwrap();

// Let's check this
println!("tera root {:?}", concat!(env!("CARGO_MANIFEST_DIR"), "/templates/**/*"));

My problem was that the place where the runtime recognize is different between dev-env and prod-env. This is caused by my deployment flow (I was building on dev-env and deploying to prod env).