error-chain | Error boilerplate for Rust

It's a problem of reqwest's version. Replace your original version with

You need to enable an extra feature in tokio to be able to use tokio::main.

Try adding the full feature to the tokio dependency in your Cargo.toml file:

Reqwest lists OpenSSL as a requirement on Linux due to it using native-tls, which depends on openssl. You need to install the pkg-config and libssl-dev packages:

The reqwest::Response::text will try to parse the body of your request and replace any invalid UTF-8 sequence with REPLACEMENT CHARACTER. For binary files, this will result in a corrupted file.

Instead you need to use reqwest::Response::bytes which returns the content as-is.

Why is this error not handled automatically?

According to error_chain documentation

chain_err can be called on any Result type where the contained error type implements std::error::Error+Send + 'static

The error type in the Result of child.join() is Box because a thread can panic with any value. For example the thread can do

It looks like I missed installing some dependencies.

sudo apt install pkg-config libasound2-dev libssl-dev cmake libfreetype6-dev libexpat1-dev libxcb-composite0-dev

https://github.com/amethyst/amethyst#debianubuntu

First things first, go back and re-read The Rust Programming Language's chapter on "Packages, Crates, and Modules". This discusses several fundamental concepts that are vital for understanding.

Why can I not clone a git project, add a main.rs and import one of the structs?

To me, this feels like the same question as "why can't I reach into another human, grab their lungs, and then use them to breathe"? You simply cannot download some arbitrary Rust library and start pulling random files out of it and expect them to work.

Specifically in your case, all libraries have a lib.rs that is the crate root. The crate root tends to have many common definitions that are needed by the rest of the code and imports all the submodules. When you create a main.rs and declare the modules from the library as your own, your main.rs becomes the crate root, but it doesn't define all the things that the library needs. This causes the code to fail to compile.

Instead, just use the crate as a library, as it's intended.

The easiest thing to do create a new Cargo project and add the crate as a dependency to your Cargo.toml. The gitlab crate is already distributed on crates.io, so you just add the version number:

In the tutorial you were following, all of the examples are in an "examples" directory. You can build these using the --example argument, as shown in the tutorial:

mqttc::Error contains a mqttc::netopt::Error, which in turns contains a Box (which desugars to std::boxed::Box. std::error::Error here is a trait object. Because the Error trait doesn't have Send as a supertrait, implementations of Error are not required to implement Send. Therefore, Box doesn't implement Send because not all types T: std::error::Error implement Send.

This could be fixed by changing the mqttc::netopt::Error type to use Box instead of Box (which would be a breaking change for the library).