Workspaces
A workspace is a collection of one or more packages that share common
dependency resolution (with a shared Cargo.lock), output directory, and
various settings such as profiles. Packages that are part of a workspaces are
called workspace members. There are two flavours of workspaces: as root
package or as virtual manifest.
Root package
A workspace can be created by adding a [workspace]
section to Cargo.toml. This can be added to a
Cargo.toml that already defines a [package], in which case the package is
the root package of the workspace. The workspace root is the directory
where the workspace's Cargo.toml is located.
Virtual manifest
Alternatively, a Cargo.toml file can be created with a [workspace] section
but without a [package] section. This is called a virtual
manifest. This is typically useful when there isn't a "primary" package, or
you want to keep all the packages organized in separate directories.
Key features
The key points of workspaces are:
- All packages share a common
Cargo.lockfile which resides in the workspace root. - All packages share a common output directory, which defaults to a
directory named
targetin the workspace root. - The
[patch],[replace]and[profile.*]sections inCargo.tomlare only recognized in the root manifest, and ignored in member crates' manifests.
The [workspace] section
The [workspace] table in Cargo.toml defines which packages are members of
the workspace:
[workspace]
members = ["member1", "path/to/member2", "crates/*"]
exclude = ["crates/foo", "path/to/other"]
All path dependencies residing in the workspace directory automatically
become members. Additional members can be listed with the members key, which
should be an array of strings containing directories with Cargo.toml files.
The members list also supports globs to match multiple paths, using
typical filename glob patterns like * and ?.
The exclude key can be used to prevent paths from being included in a
workspace. This can be useful if some path dependencies aren't desired to be
in the workspace at all, or using a glob pattern and you want to remove a
directory.
An empty [workspace] table can be used with a [package] to conveniently
create a workspace with the package and all of its path dependencies.
Workspace selection
When inside a subdirectory within the workspace, Cargo will automatically
search the parent directories for a Cargo.toml file with a [workspace]
definition to determine which workspace to use. The package.workspace
manifest key can be used in member crates to point at a workspace's root to
override this automatic search. The manual setting can be useful if the member
is not inside a subdirectory of the workspace root.
Package selection
In a workspace, package-related cargo commands like cargo build can use
the -p / --package or --workspace command-line flags to determine which
packages to operate on. If neither of those flags are specified, Cargo will
use the package in the current working directory. If the current directory is
a virtual workspace, it will apply to all members (as if --workspace were
specified on the command-line).
The optional default-members key can be specified to set the members to
operate on when in the workspace root and the package selection flags are not
used:
[workspace]
members = ["path/to/member1", "path/to/member2", "path/to/member3/*"]
default-members = ["path/to/member2", "path/to/member3/foo"]
When specified, default-members must expand to a subset of members.
The workspace.metadata table
The workspace.metadata table is ignored by Cargo and will not be warned
about. This section can be used for tools that would like to store workspace
configuration in Cargo.toml. For example:
[workspace]
members = ["member1", "member2"]
[workspace.metadata.webcontents]
root = "path/to/webproject"
tool = ["npm", "run", "build"]
# ...
There is a similar set of tables at the package level at
package.metadata. While cargo does not specify a
format for the content of either of these tables, it is suggested that
external tools may wish to use them in a consistent fashion, such as referring
to the data in workspace.metadata if data is missing from package.metadata,
if that makes sense for the tool in question.