What should be in the Cargo.toml file at the root of the workspace so that Visual Studio Code supports all features? - visual-studio-code

Question

Visual Studio Code says:
A Cargo.toml file must be at the root of the workspace in order to
support all features
However I did not find what should be in Cargo.toml file located in the workspace root. Is it common for all project subdirectories?
I have read the chapter Hello, Cargo! of the documentation, but it only speaks about the Cargo.toml files within the project directory.
By experimenting, I have found out that the file with only one line [workspace] makes the VS Code note go away, but now every time I set up a new project it nags me about the fact that this project is not mentioned in the members array within this "workspace" Cargo.toml
Visual Studio Code directory structure is as follows
workspace
|
---> project1
|
---> project2
the cargo new project3 generates Cargo.toml within newly created project3 directory, but Visual Studio Code expects another Cargo.toml within the workspace directory itself.

Answer 1

This is covered in chapter 14 of the book, section 3. The Cargo.toml at the root of a Cargo workspace should explicitly contain its member projects in the members property. Note that this is exactly what the IDE was advising you to do.
[workspace]
members = [
"project1",
"project2",
]
Quoting:
Next, in the add directory, we create the Cargo.toml file that will configure the entire workspace. This file won’t have a [package] section or the metadata we’ve seen in other Cargo.toml files. Instead, it will start with a [workspace] section that will allow us to add members to the workspace by specifying the path to our binary crate; in this case, that path is adder:
Filename: Cargo.toml
[workspace]
members = [
"adder",
]
Next, we’ll create the adder binary crate by running cargo new within the add directory:
$ cargo new --bin adder
Created binary (application) adder project
At this point, we can build the workspace by running cargo build. The files in your add directory should look like this:
├── Cargo.lock
├── Cargo.toml
├── adder
│ ├── Cargo.toml
│ └── src
│ └── main.rs
└── target
Another example of this in the wild is serde (Cargo.toml).
The Cargo documentation provides additional details on the members field, including that path dependencies are included automatically.
The root crate of a workspace, indicated by the presence of [workspace] in its manifest, is responsible for defining the entire workspace. All path dependencies residing in the workspace directory become members. You can add additional packages to the workspace by listing them in the members key. Note that members of the workspaces listed explicitly will also have their path dependencies included in the workspace. [...]
In this case, no path dependencies nor members were stated in the root Cargo project, leading to the sub-directories not being regarded as workspace members.

Answer 2

As a workaround, I was able to create a top-level Cargo.toml with the following content:
[workspace]
members = [
"./*/src/..",
]
With this, I can create new projects under the workspace without explicitly updating the top-level Cargo.html.
As a note, the more obvious globs like "*", "./*" and "*/" do not work because the resulting matches must be directories with Cargo.toml files, and these globs match more than that (including "./target/", for example). The path I came up with results in the right subset (at least in the basic, typical case).