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Full implementation of rust.workspace() #15223

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@bonzini bonzini commented Nov 8, 2025 •
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For the spec see #14639.

This adds a Cargo package object that can provide rustc arguments and dependencies&mdashbut also nice shortcuts pkg.executable(), pkg.library(), pkg.proc_macro(), pkg.shared_module() that can basically reduce a Rust crate to just:

project('something', 'rust')
cargo = import('rust').workspace()
cargo.package().executable(install: true)

Based on #15158.
Fixes: #14639

@bonzini bonzini marked this pull request as draft November 8, 2025 10:31
@bonzini bonzini mentioned this pull request Nov 8, 2025
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@bonzini bonzini force-pushed the cargo-object-full branch 4 times, most recently from 5689c94 to 5427fdf Compare November 12, 2025 16:11
@bonzini bonzini mentioned this pull request Nov 12, 2025
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jpakkane commented Nov 13, 2025

Merge branch 'master' into cargo-object-full

Hmmm?

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bonzini commented Nov 13, 2025

Hmmm?

It's a draft. :) it will go away when I rebase before making it non-draft. I often have merge commits locally when something builds on top of other PRs.

@bonzini bonzini force-pushed the cargo-object-full branch 3 times, most recently from 8d09d29 to 0056c4c Compare November 19, 2025 18:01
@bonzini
cargo: add --check-cfg cfg(test) unconditionally
a90592a 
It should be added even if unexpected_cfgs is not part of Cargo.toml.

Signed-off-by: Paolo Bonzini <[email protected]>
bonzini added 12 commits November 28, 2025 19:45
@bonzini
cargo: include the implicit feature for dependencies in the manifest
6096481 
Make the implicit `xyz = ["dep:xyz"]` declaration explicit in the Manifest.
This also makes it possible to implement correctly the part of the spec where
"If you specify the optional dependency with the dep: prefix anywhere in
the [features] table, that disables the implicit feature."

Unfortunately, this can only be done after target-specific configurations
are resolved, which makes it hard to write a unit test for this.  Rustix
requires it, though; without this patch, something like

        [package]
        name = "rustix"
        edition = "2021"
        rust-version = "1.63"
        version = "0.38.34"

        [dependencies]
        alloc = { version = "1.0.0", optional = true, package = "rustc-std-workspace-alloc" }
        libc = { version = "0.2.0", optional = true, package = "libc" }
        libc_errno = { version = "0.3.8", optional = true, package = "errno" }

        [features]
        alloc = []
        default = ["std"]
        rustc-dep-of-std = ["dep:alloc"]
        std = ["alloc"]
        use-libc = ["libc_errno", "libc"]

would incorrectly request the rustc-std-workspace-alloc crate via the
chain default->std->alloc.  The patch blocks it because it finds the
"dep:alloc" dependency of feature rustc-dep-of-std.

Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
cargo: allow overriding Meson's Cargo interpreter
7438e4e 
Some projects may want to override Meson's AST generation for Cargo
projects.  This was not really doable before without hard coding the
results of feature resolution; however, now it will be possible by
accessing the results of the global feature resolution from the Rust
module's workspace object.

At the same time, the subproject must keep using the Cargo method,
which is forced by the workspace object's subproject() method,
because otherwise the interpreter is not propagated.  So just
skip the interpretation phase if a Meson.build is present.

Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
cargo: show nice exception if Cargo.toml missing
cb61d06 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
rust: add rust.workspace() skeleton implementation
adc2b0c 
rust.workspace() is the entry point for global feature resolution.
It loads a Cargo.toml file and ensures that all dependencies will be
built with the correct set of features.

Fixes: mesonbuild#13404
@bonzini
cargo: add configurable features to Interpreter
9b5e71a 
Add features property to cargo.Interpreter to make default features configurable;
customization of which features are enabled by default is triggered by
rust.workspace().

Fixes: mesonbuild#14290
@bonzini
modules: rust: implement workspace.subproject() and package.dependency()
7c86833 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
docs: add release notes for rust.workspace()
01f8789 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
ast: printer: give a precedence to all kinds of functions
e8c4eb7 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
cargo: use cargo.subproject().dependency()
3596367 
This is up to 2x faster because it avoids checks for pkg-config and cmake.

Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: implement workspace.packages()
a17100f 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: implement more package accessors
653574a 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: implement workspace.package()
8f7e196 
Note that, as shown in the testcase, package() works in the subproject
as well.  This means that in the future the Cargo code generator can be
changed to reduce the amount of generated code and instead rely on the
package object.

Signed-off-by: Paolo Bonzini <[email protected]>
bonzini added 15 commits November 28, 2025 19:48
@bonzini
test: rust.workspace: add another member to the workspace
e04e56c 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: add workspace methods returning arguments for build ta…
cdf1042 
…rgets

Add rustc_args(), env(), and rust_dependency_map() methods to the
RustPackage class.  They simply delegate to PackageState and
PackageConfiguration.
@bonzini
dependencies: make arguments to InternalDependency.__init__ optional
92b63b9 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
rust: add to_system_dependency
97e8a2b 
Move the logic for system dependencies outside Cargo.interpreter and
into the rust module, so that it can be reused by the workspace object.

Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
cargo: use rust.to_system_dependency
904e9e3 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
cargo: use rust.workspace() to build the arguments
f89b799 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: allow passing an array for dependency versions
83348fa 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: add dependencies() method to package object
65c6685 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: invoke subprojects automatically from dependencies()
9239a7e 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
cargo: use dependencies() method to get dependencies
686c50c 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: add package.library/package.proc_macro methods
f410831
@bonzini
cargo: populate bin table from src/bin/
6a4a24b 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: add package.executable
b91d68e 
Signed-off-by: Paolo Bonzini <[email protected]>
@bonzini
modules: rust: add package.shared_module method
2df2a48
@bonzini
docs: update info on Cargo workspace object
6444de9
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@mensinda mensinda Awaiting requested review from mensinda mensinda is a code owner

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Proposal: rust.workspace() Cargo integration

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@bonzini @jpakkane