failed to parse manifest - no targets specified

Question

I am new to Rust and attempting to build a test project with Cargo. My Cargo.toml looks like:

[package]
name = "rust-play"
version = "0.0.1"
authors = [ "Bradley Wogsland <omitted>" ]

(but the actual TOML file doesn't omit my email). When I cargo build I am getting the following error:

error: failed to parse manifest at /Users/wogsland/Projects/rust-play/Cargo.toml

Caused by: no targets specified in the manifest either src/lib.rs, src/main.rs, a [lib] section, or [[bin]] section must be present

My main function is in a src/test.rs file. Do I need to specify that in the TOML file? If so, how? I tried adding

target = "src/test.rs"

to no avail.

Answer 1

As the error says:

either src/lib.rs, src/main.rs, a [lib] section, or [[bin]] section must be present

So the direct answer is to add a [[bin]] section:

[[bin]]
name = "test"
path = "src/test.rs"

However, it's far more usual to just place the file in the expected location: src/main.rs. You could also place it in src/bin/test.rs if you plan on having multiple binaries.

If it's actually for testing your code, then unit tests go in the same file as the code they are testing and integration tests go in tests/foo.rs.

Answer 2

Alternative issue and solution: You can also be faced with this error if you have copied Cargo.toml file to a parent folder of the crate.

Answer 3

I ran into this issue on Ubuntu 20.04 after having inadvertently copied Cargo.toml to my home folder. Even though my working directory had a properly defined Cargo.toml, the copy in $HOME was taking precedence and causing builds to fail.