The Manifest Format
The Cargo.toml
file for each package is called its manifest. Every manifest
file consists of one or more sections.
The [package]
section
The first section in a Cargo.toml
is [package]
.
[package]
name = "hello_world" # the name of the package
version = "0.1.0" # the current version, obeying semver
authors = ["Alice <a@example.com>", "Bob <b@example.com>"]
The name
field
The package name is an identifier used to refer to the package. It is used when listed as a dependency in another package, and as the default name of inferred lib and bin targets.
The name must not be empty, use only alphanumeric characters or -
or _
.
Note that cargo new
and cargo init
impose some additional restrictions on
the package name, such as enforcing that it is a valid Rust identifier and not
a keyword. crates.io imposes even more restrictions, such as
enforcing only ASCII characters, not a reserved name, not a special Windows
name such as "nul", is not too long, etc.
The version
field
Cargo bakes in the concept of Semantic Versioning, so make sure you follow some basic rules:
- Before you reach 1.0.0, anything goes, but if you make breaking changes, increment the minor version. In Rust, breaking changes include adding fields to structs or variants to enums.
- After 1.0.0, only make breaking changes when you increment the major version. Don’t break the build.
- After 1.0.0, don’t add any new public API (no new
pub
anything) in patch-level versions. Always increment the minor version if you add any newpub
structs, traits, fields, types, functions, methods or anything else. - Use version numbers with three numeric parts such as 1.0.0 rather than 1.0.
The authors
field (optional)
The authors
field lists people or organizations that are considered the
"authors" of the package. The exact meaning is open to interpretation — it may
list the original or primary authors, current maintainers, or owners of the
package. These names will be listed on the crate's page on
crates.io. An optional email address may be included within angled
brackets at the end of each author.
The edition
field (optional)
You can opt in to a specific Rust Edition for your package with the
edition
key in Cargo.toml
. If you don't specify the edition, it will
default to 2015.
[package]
# ...
edition = '2018'
The edition
key affects which edition your package is compiled with. Cargo
will always generate packages via cargo new
with the edition
key set to the
latest edition. Setting the edition
key in [package]
will affect all
targets/crates in the package, including test suites, benchmarks, binaries,
examples, etc.
The build
field (optional)
This field specifies a file in the package root which is a build script for building native code. More information can be found in the build script guide.
[package]
# ...
build = "build.rs"
The links
field (optional)
This field specifies the name of a native library that is being linked to.
More information can be found in the links
section of the build
script guide.
[package]
# ...
links = "foo"
build = "build.rs"
The documentation
field (optional)
This field specifies a URL to a website hosting the crate's documentation. If no URL is specified in the manifest file, crates.io will automatically link your crate to the corresponding docs.rs page.
Documentation links from specific hosts are blacklisted. Hosts are added to the blacklist if they are known to not be hosting documentation and are possibly of malicious intent e.g., ad tracking networks. URLs from the following hosts are blacklisted:
- rust-ci.org
Documentation URLs from blacklisted hosts will not appear on crates.io, and may be replaced by docs.rs links.
The exclude
and include
fields (optional)
You can explicitly specify that a set of file patterns should be ignored or
included for the purposes of packaging. The patterns specified in the
exclude
field identify a set of files that are not included, and the
patterns in include
specify files that are explicitly included.
The patterns should be gitignore-style patterns. Briefly:
foo
matches any file or directory with the namefoo
anywhere in the package. This is equivalent to the pattern**/foo
./foo
matches any file or directory with the namefoo
only in the root of the package.foo/
matches any directory with the namefoo
anywhere in the package.- Common glob patterns like
*
,?
, and[]
are supported:*
matches zero or more characters except/
. For example,*.html
matches any file or directory with the.html
extension anywhere in the package.?
matches any character except/
. For example,foo?
matchesfood
, but notfoo
.[]
allows for matching a range of characters. For example,[ab]
matches eithera
orb
.[a-z]
matches letters a through z.
**/
prefix matches in any directory. For example,**/foo/bar
matches the file or directorybar
anywhere that is directly under directoryfoo
./**
suffix matches everything inside. For example,foo/**
matches all files inside directoryfoo
, including all files in subdirectories belowfoo
./**/
matches zero or more directories. For example,a/**/b
matchesa/b
,a/x/b
,a/x/y/b
, and so on.!
prefix negates a pattern. For example, a pattern ofsrc/**.rs
and!foo.rs
would match all files with the.rs
extension inside thesrc
directory, except for any file namedfoo.rs
.
If git is being used for a package, the exclude
field will be seeded with
the gitignore
settings from the repository.
[package]
# ...
exclude = ["build/**/*.o", "doc/**/*.html"]
[package]
# ...
include = ["src/**/*", "Cargo.toml"]
The options are mutually exclusive: setting include
will override an
exclude
. Note that include
must be an exhaustive list of files as otherwise
necessary source files may not be included. The package's Cargo.toml
is
automatically included.
The include/exclude list is also used for change tracking in some situations.
For targets built with rustdoc
, it is used to determine the list of files to
track to determine if the target should be rebuilt. If the package has a
build script that does not emit any rerun-if-*
directives, then the
include/exclude list is used for tracking if the build script should be re-run
if any of those files change.
The publish
field (optional)
The publish
field can be used to prevent a package from being published to a
package registry (like crates.io) by mistake, for instance to keep a package
private in a company.
[package]
# ...
publish = false
The value many also be an array of strings which are registry names that are allowed to be published to.
[package]
# ...
publish = ["some-registry-name"]
The workspace
field (optional)
The workspace
field can be used to configure the workspace that this package
will be a member of. If not specified this will be inferred as the first
Cargo.toml with [workspace]
upwards in the filesystem.
[package]
# ...
workspace = "path/to/workspace/root"
For more information, see the documentation for the workspace table below.
Package metadata
There are a number of optional metadata fields also accepted under the
[package]
section:
[package]
# ...
# A short blurb about the package. This is not rendered in any format when
# uploaded to crates.io (aka this is not markdown).
description = "..."
# These URLs point to more information about the package. These are
# intended to be webviews of the relevant data, not necessarily compatible
# with VCS tools and the like.
documentation = "..."
homepage = "..."
repository = "..."
# This points to a file under the package root (relative to this `Cargo.toml`).
# The contents of this file are stored and indexed in the registry.
# crates.io will render this file and place the result on the crate's page.
readme = "..."
# This is a list of up to five keywords that describe this crate. Keywords
# are searchable on crates.io, and you may choose any words that would
# help someone find this crate.
keywords = ["...", "..."]
# This is a list of up to five categories where this crate would fit.
# Categories are a fixed list available at crates.io/category_slugs, and
# they must match exactly.
categories = ["...", "..."]
# This is an SPDX 2.1 license expression for this package. Currently
# crates.io will validate the license provided against a whitelist of
# known license and exception identifiers from the SPDX license list
# 2.4. Parentheses are not currently supported.
#
# Multiple licenses can be separated with a `/`, although that usage
# is deprecated. Instead, use a license expression with AND and OR
# operators to get more explicit semantics.
license = "..."
# If a package is using a nonstandard license, then this key may be specified in
# lieu of the above key and must point to a file relative to this manifest
# (similar to the readme key).
license-file = "..."
# Optional specification of badges to be displayed on crates.io.
#
# - The badges pertaining to build status that are currently available are
# Appveyor, CircleCI, GitLab, Azure DevOps and TravisCI.
# - Available badges pertaining to code test coverage are Codecov and
# Coveralls.
# - There are also maintenance-related badges based on isitmaintained.com
# which state the issue resolution time, percent of open issues, and future
# maintenance intentions.
#
# If a `repository` key is required, this refers to a repository in
# `user/repo` format.
[badges]
# Appveyor: `repository` is required. `branch` is optional; default is `master`
# `service` is optional; valid values are `github` (default), `bitbucket`, and
# `gitlab`; `id` is optional; you can specify the appveyor project id if you
# want to use that instead. `project_name` is optional; use when the repository
# name differs from the appveyor project name.
appveyor = { repository = "...", branch = "master", service = "github" }
# Circle CI: `repository` is required. `branch` is optional; default is `master`
circle-ci = { repository = "...", branch = "master" }
# GitLab: `repository` is required. `branch` is optional; default is `master`
gitlab = { repository = "...", branch = "master" }
# Azure DevOps: `project` is required. `pipeline` is required. `build` is optional; default is `1`
# Note: project = `organization/project`, pipeline = `name_of_pipeline`, build = `definitionId`
azure-devops = { project = "...", pipeline = "...", build="2" }
# Travis CI: `repository` in format "<user>/<project>" is required.
# `branch` is optional; default is `master`
travis-ci = { repository = "...", branch = "master" }
# Codecov: `repository` is required. `branch` is optional; default is `master`
# `service` is optional; valid values are `github` (default), `bitbucket`, and
# `gitlab`.
codecov = { repository = "...", branch = "master", service = "github" }
# Coveralls: `repository` is required. `branch` is optional; default is `master`
# `service` is optional; valid values are `github` (default) and `bitbucket`.
coveralls = { repository = "...", branch = "master", service = "github" }
# Is it maintained resolution time: `repository` is required.
is-it-maintained-issue-resolution = { repository = "..." }
# Is it maintained percentage of open issues: `repository` is required.
is-it-maintained-open-issues = { repository = "..." }
# Maintenance: `status` is required. Available options are:
# - `actively-developed`: New features are being added and bugs are being fixed.
# - `passively-maintained`: There are no plans for new features, but the maintainer intends to
# respond to issues that get filed.
# - `as-is`: The crate is feature complete, the maintainer does not intend to continue working on
# it or providing support, but it works for the purposes it was designed for.
# - `experimental`: The author wants to share it with the community but is not intending to meet
# anyone's particular use case.
# - `looking-for-maintainer`: The current maintainer would like to transfer the crate to someone
# else.
# - `deprecated`: The maintainer does not recommend using this crate (the description of the crate
# can describe why, there could be a better solution available or there could be problems with
# the crate that the author does not want to fix).
# - `none`: Displays no badge on crates.io, since the maintainer has not chosen to specify
# their intentions, potential crate users will need to investigate on their own.
maintenance = { status = "..." }
The crates.io registry will render the description, display the license, link to the three URLs and categorize by the keywords. These keys provide useful information to users of the registry and also influence the search ranking of a crate. It is highly discouraged to omit everything in a published crate.
SPDX 2.1 license expressions are documented here. The current version of the license list is available here, and version 2.4 is available here.
The metadata
table (optional)
Cargo by default will warn about unused keys in Cargo.toml
to assist in
detecting typos and such. The package.metadata
table, however, is completely
ignored by Cargo and will not be warned about. This section can be used for
tools which would like to store package configuration in Cargo.toml
. For
example:
[package]
name = "..."
# ...
# Metadata used when generating an Android APK, for example.
[package.metadata.android]
package-name = "my-awesome-android-app"
assets = "path/to/static"
Dependency sections
See the specifying dependencies page for
information on the [dependencies]
, [dev-dependencies]
,
[build-dependencies]
, and target-specific [target.*.dependencies]
sections.
The [profile.*]
sections
Cargo supports custom configuration of how rustc is invoked through profiles at the top level. Any manifest may declare a profile, but only the top level package’s profiles are actually read. All dependencies’ profiles will be overridden. This is done so the top-level package has control over how its dependencies are compiled.
There are four currently supported profile names, all of which have the same configuration available to them. Listed below is the configuration available, along with the defaults for each profile.
# The development profile, used for `cargo build`.
[profile.dev]
opt-level = 0 # controls the `--opt-level` the compiler builds with.
# 0-1 is good for debugging. 2 is well-optimized. Max is 3.
# 's' attempts to reduce size, 'z' reduces size even more.
debug = true # (u32 or bool) Include debug information (debug symbols).
# Equivalent to `-C debuginfo=2` compiler flag.
rpath = false # controls whether compiler should set loader paths.
# If true, passes `-C rpath` flag to the compiler.
lto = false # Link Time Optimization usually reduces size of binaries
# and static libraries. Increases compilation time.
# If true, passes `-C lto` flag to the compiler, and if a
# string is specified like 'thin' then `-C lto=thin` will
# be passed.
debug-assertions = true # controls whether debug assertions are enabled
# (e.g., debug_assert!() and arithmetic overflow checks)
codegen-units = 16 # if > 1 enables parallel code generation which improves
# compile times, but prevents some optimizations.
# Passes `-C codegen-units`.
panic = 'unwind' # panic strategy (`-C panic=...`), can also be 'abort'
incremental = true # whether or not incremental compilation is enabled
# This can be overridden globally with the CARGO_INCREMENTAL
# environment variable or `build.incremental` config
# variable. Incremental is only used for path sources.
overflow-checks = true # use overflow checks for integer arithmetic.
# Passes the `-C overflow-checks=...` flag to the compiler.
# The release profile, used for `cargo build --release` (and the dependencies
# for `cargo test --release`, including the local library or binary).
[profile.release]
opt-level = 3
debug = false
rpath = false
lto = false
debug-assertions = false
codegen-units = 16
panic = 'unwind'
incremental = false
overflow-checks = false
# The testing profile, used for `cargo test` (for `cargo test --release` see
# the `release` and `bench` profiles).
[profile.test]
opt-level = 0
debug = 2
rpath = false
lto = false
debug-assertions = true
codegen-units = 16
panic = 'unwind'
incremental = true
overflow-checks = true
# The benchmarking profile, used for `cargo bench` (and the test targets and
# unit tests for `cargo test --release`).
[profile.bench]
opt-level = 3
debug = false
rpath = false
lto = false
debug-assertions = false
codegen-units = 16
panic = 'unwind'
incremental = false
overflow-checks = false
The [features]
section
Cargo supports features to allow expression of:
- conditional compilation options (usable through
cfg
attributes); - optional dependencies, which enhance a package, but are not required; and
- clusters of optional dependencies, such as
postgres
, that would include thepostgres
package, thepostgres-macros
package, and possibly other packages (such as development-time mocking libraries, debugging tools, etc.).
A feature of a package is either an optional dependency, or a set of other features. The format for specifying features is:
[package]
name = "awesome"
[features]
# The default set of optional packages. Most people will want to use these
# packages, but they are strictly optional. Note that `session` is not a package
# but rather another feature listed in this manifest.
default = ["jquery", "uglifier", "session"]
# A feature with no dependencies is used mainly for conditional compilation,
# like `#[cfg(feature = "go-faster")]`.
go-faster = []
# The `secure-password` feature depends on the bcrypt package. This aliasing
# will allow people to talk about the feature in a higher-level way and allow
# this package to add more requirements to the feature in the future.
secure-password = ["bcrypt"]
# Features can be used to reexport features of other packages. The `session`
# feature of package `awesome` will ensure that the `session` feature of the
# package `cookie` is also enabled.
session = ["cookie/session"]
[dependencies]
# These packages are mandatory and form the core of this package’s distribution.
cookie = "1.2.0"
oauth = "1.1.0"
route-recognizer = "=2.1.0"
# A list of all of the optional dependencies, some of which are included in the
# above `features`. They can be opted into by apps.
jquery = { version = "1.0.2", optional = true }
uglifier = { version = "1.5.3", optional = true }
bcrypt = { version = "*", optional = true }
civet = { version = "*", optional = true }
To use the package awesome
:
[dependencies.awesome]
version = "1.3.5"
default-features = false # do not include the default features, and optionally
# cherry-pick individual features
features = ["secure-password", "civet"]
Rules
The usage of features is subject to a few rules:
- Feature names must not conflict with other package names in the manifest. This
is because they are opted into via
features = [...]
, which only has a single namespace. - With the exception of the
default
feature, all features are opt-in. To opt out of the default feature, usedefault-features = false
and cherry-pick individual features. - Feature groups are not allowed to cyclically depend on one another.
- Dev-dependencies cannot be optional.
- Features groups can only reference optional dependencies.
- When a feature is selected, Cargo will call
rustc
with--cfg feature="${feature_name}"
. If a feature group is included, it and all of its individual features will be included. This can be tested in code via#[cfg(feature = "foo")]
.
Note that it is explicitly allowed for features to not actually activate any optional dependencies. This allows packages to internally enable/disable features without requiring a new dependency.
Usage in end products
One major use-case for this feature is specifying optional features in end-products. For example, the Servo package may want to include optional features that people can enable or disable when they build it.
In that case, Servo will describe features in its Cargo.toml
and they can be
enabled using command-line flags:
$ cargo build --release --features "shumway pdf"
Default features could be excluded using --no-default-features
.
Usage in packages
In most cases, the concept of optional dependency in a library is best expressed as a separate package that the top-level application depends on.
However, high-level packages, like Iron or Piston, may want the ability to curate a number of packages for easy installation. The current Cargo system allows them to curate a number of mandatory dependencies into a single package for easy installation.
In some cases, packages may want to provide additional curation for optional dependencies:
- grouping a number of low-level optional dependencies together into a single high-level feature;
- specifying packages that are recommended (or suggested) to be included by users of the package; and
- including a feature (like
secure-password
in the motivating example) that will only work if an optional dependency is available, and would be difficult to implement as a separate package (for example, it may be overly difficult to design an IO package to be completely decoupled from OpenSSL, with opt-in via the inclusion of a separate package).
In almost all cases, it is an antipattern to use these features outside of high-level packages that are designed for curation. If a feature is optional, it can almost certainly be expressed as a separate package.
The [workspace]
section
Packages can define a workspace which is a set of crates that will all share the
same Cargo.lock
and output directory. The [workspace]
table can be defined
as:
[workspace]
# Optional key, inferred from path dependencies if not present.
# Additional non-path dependencies that should be included must be given here.
# In particular, for a virtual manifest, all members have to be listed.
members = ["path/to/member1", "path/to/member2", "path/to/member3/*"]
# Optional key, empty if not present.
exclude = ["path1", "path/to/dir2"]
Workspaces were added to Cargo as part of RFC 1525 and have a number of properties:
- A workspace can contain multiple crates where one of them is the root crate.
- The root crate's
Cargo.toml
contains the[workspace]
table, but is not required to have other configuration. - Whenever any crate in the workspace is compiled, output is placed in the
workspace root (i.e., next to the root crate's
Cargo.toml
). - The lock file for all crates in the workspace resides in the workspace root.
- The
[patch]
,[replace]
and[profile.*]
sections inCargo.toml
are only recognized in the root crate's manifest, and ignored in member crates' manifests.
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. Sometimes a package may have a lot of
workspace members and it can be onerous to keep up to date. The path dependency
can also use globs to match multiple paths. Finally, the exclude
key can be used to blacklist 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.
The package.workspace
manifest key (described above) is used in member crates
to point at a workspace's root crate. If this key is omitted then it is inferred
to be the first crate whose manifest contains [workspace]
upwards in the
filesystem.
A crate may either specify package.workspace
or specify [workspace]
. That
is, a crate cannot both be a root crate in a workspace (contain [workspace]
)
and also be a member crate of another workspace (contain package.workspace
).
Most of the time workspaces will not need to be dealt with as cargo new
and
cargo init
will handle workspace configuration automatically.
Virtual Manifest
In workspace manifests, if the package
table is present, the workspace root
crate will be treated as a normal package, as well as a workspace. If the
package
table is not present in a workspace manifest, it is called a virtual
manifest.
Package selection
In a workspace, package-related cargo commands like cargo build
apply to
packages selected by -p
/ --package
or --all
command-line parameters.
When neither is specified, the optional default-members
configuration is 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
.
When default-members
is not specified, the default is the root manifest
if it is a package, or every member manifest (as if --all
were specified
on the command-line) for virtual workspaces.
The project layout
If your package is an executable, name the main source file src/main.rs
. If it
is a library, name the main source file src/lib.rs
.
Cargo will also treat any files located in src/bin/*.rs
as executables. If your
executable consists of more than just one source file, you might also use a directory
inside src/bin
containing a main.rs
file which will be treated as an executable
with a name of the parent directory.
Your package can optionally contain folders named examples
, tests
, and
benches
, which Cargo will treat as containing examples,
integration tests, and benchmarks respectively. Analogous to bin
targets, they
may be composed of single files or directories with a main.rs
file.
▾ src/ # directory containing source files
lib.rs # the main entry point for libraries and packages
main.rs # the main entry point for packages producing executables
▾ bin/ # (optional) directory containing additional executables
*.rs
▾ */ # (optional) directories containing multi-file executables
main.rs
▾ examples/ # (optional) examples
*.rs
▾ */ # (optional) directories containing multi-file examples
main.rs
▾ tests/ # (optional) integration tests
*.rs
▾ */ # (optional) directories containing multi-file tests
main.rs
▾ benches/ # (optional) benchmarks
*.rs
▾ */ # (optional) directories containing multi-file benchmarks
main.rs
To structure your code after you've created the files and folders for your package, you should remember to use Rust's module system, which you can read about in the book.
See Configuring a target below for more details on manually configuring target settings. See Target auto-discovery below for more information on controlling how Cargo automatically infers targets.
Examples
Files located under examples
are example uses of the functionality provided by
the library. When compiled, they are placed in the target/examples
directory.
They can compile either as executables (with a main()
function) or libraries
and pull in the library by using extern crate <library-name>
. They are
compiled when you run your tests to protect them from bitrotting.
You can run individual executable examples with the command cargo run --example <example-name>
.
Specify crate-type
to make an example be compiled as a library (additional
information about crate types is available in
The Rust Reference):
[[example]]
name = "foo"
crate-type = ["staticlib"]
You can build individual library examples with the command cargo build --example <example-name>
.
Tests
When you run cargo test
, Cargo will:
- compile and run your library’s unit tests, which are in the files reachable
from
lib.rs
(naturally, any sections marked with#[cfg(test)]
will be considered at this stage); - compile and run your library’s documentation tests, which are embedded inside of documentation blocks;
- compile and run your library’s integration tests; and
- compile your library’s examples.
Integration tests
Each file in tests/*.rs
is an integration test. When you run cargo test
,
Cargo will compile each of these files as a separate crate. The crate can link
to your library by using extern crate <library-name>
, like any other code that
depends on it.
Cargo will not automatically compile files inside subdirectories of tests
, but
an integration test can import modules from these directories as usual. For
example, if you want several integration tests to share some code, you can put
the shared code in tests/common/mod.rs
and then put mod common;
in each of
the test files.
Configuring a target
All of the [[bin]]
, [lib]
, [[bench]]
, [[test]]
, and [[example]]
sections support similar configuration for specifying how a target should be
built. The double-bracket sections like [[bin]]
are array-of-table of
TOML, which means you can
write more than one [[bin]]
section to make several executables in your crate.
The example below uses [lib]
, but it also applies to all other sections
as well. All values listed are the defaults for that option unless otherwise
specified.
[package]
# ...
[lib]
# The name of a target is the name of the library that will be generated. This
# is defaulted to the name of the package, with any dashes replaced
# with underscores. (Rust `extern crate` declarations reference this name;
# therefore the value must be a valid Rust identifier to be usable.)
name = "foo"
# This field points at where the crate is located, relative to the `Cargo.toml`.
path = "src/lib.rs"
# A flag for enabling unit tests for this target. This is used by `cargo test`.
test = true
# A flag for enabling documentation tests for this target. This is only relevant
# for libraries, it has no effect on other sections. This is used by
# `cargo test`.
doctest = true
# A flag for enabling benchmarks for this target. This is used by `cargo bench`.
bench = true
# A flag for enabling documentation of this target. This is used by `cargo doc`.
doc = true
# If the target is meant to be a compiler plugin, this field must be set to true
# for Cargo to correctly compile it and make it available for all dependencies.
plugin = false
# If the target is meant to be a "macros 1.1" procedural macro, this field must
# be set to true.
proc-macro = false
# If set to false, `cargo test` will omit the `--test` flag to rustc, which
# stops it from generating a test harness. This is useful when the binary being
# built manages the test runner itself.
harness = true
# If set then a target can be configured to use a different edition than the
# `[package]` is configured to use, perhaps only compiling a library with the
# 2018 edition or only compiling one unit test with the 2015 edition. By default
# all targets are compiled with the edition specified in `[package]`.
edition = '2015'
# Here's an example of a TOML "array of tables" section, in this case specifying
# a binary target name and path.
[[bin]]
name = "my-cool-binary"
path = "src/my-cool-binary.rs"
Target auto-discovery
By default, Cargo automatically determines the targets to build based on the
layout of the files on the filesystem. The target
configuration tables, such as [lib]
, [[bin]]
, [[test]]
, [[bench]]
, or
[[example]]
, can be used to add additional targets that don't follow the
standard directory layout.
The automatic target discovery can be disabled so that only manually
configured targets will be built. Setting the keys autobins
, autoexamples
,
autotests
, or autobenches
to false
in the [package]
section will
disable auto-discovery of the corresponding target type.
Disabling automatic discovery should only be needed for specialized
situations. For example, if you have a library where you want a module named
bin
, this would present a problem because Cargo would usually attempt to
compile anything in the bin
directory as an executable. Here is a sample
layout of this scenario:
├── Cargo.toml
└── src
├── lib.rs
└── bin
└── mod.rs
To prevent Cargo from inferring src/bin/mod.rs
as an executable, set
autobins = false
in Cargo.toml
to disable auto-discovery:
[package]
# …
autobins = false
Note: For packages with the 2015 edition, the default for auto-discovery is
false
if at least one target is manually defined inCargo.toml
. Beginning with the 2018 edition, the default is alwaystrue
.
The required-features
field (optional)
The required-features
field specifies which features the target needs in order
to be built. If any of the required features are not selected, the target will
be skipped. This is only relevant for the [[bin]]
, [[bench]]
, [[test]]
,
and [[example]]
sections, it has no effect on [lib]
.
[features]
# ...
postgres = []
sqlite = []
tools = []
[[bin]]
# ...
required-features = ["postgres", "tools"]
Building dynamic or static libraries
If your package produces a library, you can specify which kind of library to
build by explicitly listing the library in your Cargo.toml
:
# ...
[lib]
name = "..."
crate-type = ["dylib"] # could be `staticlib` as well
The available options are dylib
, rlib
, staticlib
, cdylib
, and
proc-macro
.
You can read more about the different crate types in the Rust Reference Manual
The [patch]
Section
This section of Cargo.toml can be used to override dependencies with
other copies. The syntax is similar to the [dependencies]
section:
[patch.crates-io]
foo = { git = 'https://github.com/example/foo' }
bar = { path = 'my/local/bar' }
[dependencies.baz]
git = 'https://github.com/example/baz'
[patch.'https://github.com/example/baz']
baz = { git = 'https://github.com/example/patched-baz', branch = 'my-branch' }
The [patch]
table is made of dependency-like sub-tables. Each key after
[patch]
is a URL of the source that is being patched, or the name of a
registry. The name crates-io
may be used to override the default registry
crates.io. The first [patch]
in the example above demonstrates overriding
crates.io, and the second [patch]
demonstrates overriding a git source.
Each entry in these tables is a normal dependency specification, the same as
found in the [dependencies]
section of the manifest. The dependencies listed
in the [patch]
section are resolved and used to patch the source at the
URL specified. The above manifest snippet patches the crates-io
source (e.g.
crates.io itself) with the foo
crate and bar
crate. It also
patches the https://github.com/example/baz
source with a my-branch
that
comes from elsewhere.
Sources can be patched with versions of crates that do not exist, and they can also be patched with versions of crates that already exist. If a source is patched with a crate version that already exists in the source, then the source's original crate is replaced.
More information about overriding dependencies can be found in the overriding dependencies section of the documentation and RFC 1969 for the technical specification of this feature.
The [replace]
Section
This section of Cargo.toml can be used to override dependencies with
other copies. The syntax is similar to the [dependencies]
section:
[replace]
"foo:0.1.0" = { git = 'https://github.com/example/foo' }
"bar:1.0.2" = { path = 'my/local/bar' }
Each key in the [replace]
table is a package ID
specification, which allows arbitrarily choosing a node in the
dependency graph to override. The value of each key is the same as the
[dependencies]
syntax for specifying dependencies, except that you can't
specify features. Note that when a crate is overridden the copy it's overridden
with must have both the same name and version, but it can come from a different
source (e.g., git or a local path).
More information about overriding dependencies can be found in the overriding dependencies section of the documentation.