Could not find `Cargo.toml` when building a dependent crate from GitHub

Question

I'm trying to use the rust-mosquitto library. My current Cargo.toml is:

[package]
name = "HomeDaemon"
version = "0.1.0"
authors = ["RTR <[email protected]>"]

[dependencies.mosquitto]
git = "https://github.com/kteza1/rust-mosquitto"

When I run cargo build, following error is reported:

Could not find `Cargo.toml` in `/Users/ravitejareddy/.cargo/git/checkouts/rust-mosquitto-8203e77dcf072bf7/rust-mosquitto`

The actual download in ~/.cargo/git/checkouts/rust-mosquitto-8203e77dcf072bf7/master shows that Cargo.toml is present.

There is an extra rust-mosquitto in the path above, is that a problem?

Solution 1

The problem comes from your Cargo.toml in examples/ticktock:

[dependencies.mosquitto]
version = "*"
path = "../../../rust-mosquitto" 

When downloading your project from git, all the subdirectories are scanned for more Cargo.toml files. If you run RUST_LOG=trace cargo build -v, you see what's happening:

TRACE:cargo::ops::cargo_read_manifest: looking for root package: /Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master, source_id=https://github.com/kteza1/rust-mosquitto#7e08a291
TRACE:cargo::ops::cargo_read_manifest: looking for child package: /Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master
TRACE:cargo::ops::cargo_read_manifest: read_package; path=/Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master/Cargo.toml; source-id=https://github.com/kteza1/rust-mosquitto#7e08a291
TRACE:cargo::ops::cargo_read_manifest: looking for child package: /Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master/.git
TRACE:cargo::ops::cargo_read_manifest: not processing /Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master/.git
TRACE:cargo::ops::cargo_read_manifest: looking for child package: /Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master/examples
TRACE:cargo::ops::cargo_read_manifest: looking for child package: /Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master/examples/c-mosquitto
TRACE:cargo::ops::cargo_read_manifest: looking for child package: /Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master/examples/ticktock
TRACE:cargo::ops::cargo_read_manifest: read_package; path=/Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/master/examples/ticktock/Cargo.toml; source-id=https://github.com/kteza1/rust-mosquitto#7e08a291
DEBUG:cargo: handle_error; err=CliError { error: ChainedError { error: Unable to update https://github.com/kteza1/rust-mosquitto, cause: Could not find `Cargo.toml` in `/Users/shep/.cargo/git/checkouts/rust-mosquitto-77eb7033f32b19c9/rust-mosquitto` }, unknown: false, exit_code: 101 }

Cargo then tries to ensure that the nested Cargo.toml can have all of the dependencies satisfied.

Solution 2

This does not specifically answer the question that @tez asked, but I encountered the same error with a slightly different root culprit. I was writing some simple code in vim, so I created a simple main.rs file. When I cargo run it, it was spitting out the same error:

error: could not find Cargo.toml in /Users/yvonmanzi/Documents/Rust or any parent directory

The surprising thing, without the hindsight, of course, was that rustc main.rs was creating a binary executable as expected while cargo run wasn't. It turns out I had created all my rust packages(aka projects) up to that point using cargo new project-name --bin as shown here, thus by default including Cargo.lock, Cargo.toml, and src folder. Hopefully, it is clear by now that mine was just a simple rookie mistake; I simply, quite literally, didn't have Cargo.toml in my project folder. So, dear fellow rooky league Rustacean, if you get the same error, create your project with cargo new project-name --bin command.

Comments

[DK.]

@tez: Because you go up three directories, when there are only two in the repository. You're effectively requiring that your repository always be checked out with the name rust-mosquitto and nothing else.

[tez]

Ok. The folder structure is different while downloading from git where Cargo.toml resides inside branch name. 'master' in this case.

[Jason Aller]

If this contains a separate question and answer you can post it as a separate question and then self answer it. If very relevant when you have enough reputation to post comments you could even leave a comment on this question referencing the related question.

[George]

I think a correction is needed; both your "mistake" and "recommendations" presently show to use, cargo new project-name --bin to create a project.