[Doc] How to use Rust analyzer support?

[bertulli]

Hi, first of all, thank you for your work.

I am trying to set up Bazel to build a Rust project. I followed the instructions in the documentation, and I can successfully build an executable. However, I have trouble in using the Rust analyzer extension. Specifically, I get

~/MWE$ bazel build //rust:executable-rs
Starting local Bazel server and connecting to it...
WARNING: --enable_bzlmod is set, but no MODULE.bazel file was found at the workspace root. Bazel will create an empty MODULE.bazel file. Please consider migrating your external dependencies from WORKSPACE to MODULE.bazel. For more details, please refer to https://github.com/bazelbuild/bazel/issues/18958.
ERROR: Traceback (most recent call last):
        File "/home/abertulli/MWE/rust/BUILD.bazel", line 9, column 27, in <toplevel>
                rust_analyzer_dependencies()
        File "/home/abertulli/.cache/bazel/_bazel_abertulli/b2e37475533f474e11fd385fceaab463/external/rules_rust/tools/rust_analyzer/deps.bzl", line 9, column 30, in rust_analyzer_dependencies
                return crate_repositories()
        File "/home/abertulli/.cache/bazel/_bazel_abertulli/b2e37475533f474e11fd385fceaab463/external/rules_rust/tools/rust_analyzer/3rdparty/crates/defs.bzl", line 413, column 10, in crate_repositories
                maybe(
        File "/home/abertulli/.cache/bazel/_bazel_abertulli/b2e37475533f474e11fd385fceaab463/external/bazel_tools/tools/build_defs/repo/utils.bzl", line 268, column 18, in maybe
                repo_rule(name = name, **kwargs)
Error in repository_rule: 'repository rule http_archive' can only be called during workspace loading
WARNING: Target pattern parsing failed.
ERROR: Skipping '//rust:executable-rs': Error evaluating '//rust:executable-rs': error loading package 'rust': Package 'rust' contains errors
ERROR: Error evaluating '//rust:executable-rs': error loading package 'rust': Package 'rust' contains errors
INFO: Elapsed time: 7.895s
INFO: 0 processes.
ERROR: Build did NOT complete successfully

If I comment the two lines using the Rust analyzer extension I can compile successfully. Also notice how it created an (empty) MODULE.bazel and a MODULE.bazel.lock file. However, I also tried the new approach using MODULE.bazel (see below), but I got the same error. I don't know if I misread the docs, or if they are not mentioning something. What am I doing worng? Thanks!

---

MWE

• my workspace:

~/MWE$ tree
.
├── WORKSPACE.bazel
└── rust
    ├── BUILD.bazel
    └── main.rs

1 directory, 3 files

• WORKSPACE.bazel:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

# To find additional information on this release or newer ones visit:
# https://github.com/bazelbuild/rules_rust/releases
http_archive(
    name = "rules_rust",
    integrity = "sha256-r09Wyq5QqZpov845sUG1Cd1oVIyCBLmKt6HK/JTVuwI=",
    urls = ["https://github.com/bazelbuild/rules_rust/releases/download/0.54.1/rules_rust-v0.54.1.tar.gz"],
)

load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies", "rust_register_toolchains")

rules_rust_dependencies()

rust_register_toolchains(
    edition = "2021",
)

load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")

• rust/BUILD.bazel:

load("@rules_rust//rust:defs.bzl", "rust_binary")

rust_binary(
    name = "executable-rs",
    srcs = ["main.rs"]
)

# try commenting these two lines
load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")
rust_analyzer_dependencies()

• rust/main.rs:

fn main() {
    let a = vec![test(), test()];
    dbg!(a);
}

fn test() -> i32 { 0 }

• Extra: MODULE.bazel that I tried:

bazel_dep(name = "rules_rust", version = "0.54.1")

# Rust toolchain
RUST_EDITION = "2021"

RUST_VERSION = "1.79.0"

rust = use_extension("@rules_rust//rust:extensions.bzl", "rust")
rust.toolchain(
    edition = RUST_EDITION,
    versions = [RUST_VERSION],
)
use_repo(rust, "rust_toolchains")

register_toolchains("@rust_toolchains//:all")

that gave me the same

~/MWE$ bazel build //rust:executable-rs
ERROR: Traceback (most recent call last):
        File "/home/abertulli/MWE/rust/BUILD.bazel", line 9, column 27, in <toplevel>
                rust_analyzer_dependencies()
        File "/home/abertulli/.cache/bazel/_bazel_abertulli/b2e37475533f474e11fd385fceaab463/external/rules_rust~/tools/rust_analyzer/deps.bzl", line 9, column 30, in rust_analyzer_dependencies
                return crate_repositories()
        File "/home/abertulli/.cache/bazel/_bazel_abertulli/b2e37475533f474e11fd385fceaab463/external/rules_rust~/tools/rust_analyzer/3rdparty/crates/defs.bzl", line 413, column 10, in crate_repositories
                maybe(
        File "/home/abertulli/.cache/bazel/_bazel_abertulli/b2e37475533f474e11fd385fceaab463/external/bazel_tools/tools/build_defs/repo/utils.bzl", line 268, column 18, in maybe
                repo_rule(name = name, **kwargs)
Error in repository_rule: 'repository rule http_archive' can only be called during workspace loading
WARNING: Target pattern parsing failed.
ERROR: Skipping '//rust:executable-rs': Error evaluating '//rust:executable-rs': error loading package 'rust': Package 'rust' contains errors
ERROR: Error evaluating '//rust:executable-rs': error loading package 'rust': Package 'rust' contains errors
INFO: Elapsed time: 3.394s
INFO: 0 processes.
ERROR: Build did NOT complete successfully

[UebelAndre]

We have some documentation here: https://bazelbuild.github.io/rules_rust/rust_analyzer.html

Your issue is:

load("@rules_rust//rust:defs.bzl", "rust_binary")

rust_binary(
    name = "executable-rs",
    srcs = ["main.rs"]
)

# try commenting these two lines
load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")
rust_analyzer_dependencies()

Where rust_analyzer_dependencies is incorrectly being called in a BUILD.bazel file. Remove this and you should be good.

We would also happily accept pull-requests to improve docs!

Gonna close this out for now since the issue seems fairly straight forward. Please reopen if I missed something

[bertulli]

Thanks for your answer. I think i found the problem: i needed to manually run

bazel run @rules_rust//tools/rust_analyzer:gen_rust_project

to generate the rust-project.json file.

Also I think the documentation is outdated, as the code reported there IIUC is for the WORKSPACE style of project.

For instance, the rust_analyzer_dependencies() is explicitly listed in the example code, but it causes errors when used with bzlmod, if i got it right? i refernced this in a pull request #3365