Crate `mongodb` cannot be compiled using bazel

[YaxinCheng]

Crate mongodb cannot be compiled with the following error message, while cargo compiles it fine:

ERROR: /private/var/tmp/_bazel_cheng/3300dddb442501c4c0a49ee86c897909/external/crate__bson-2.6.1/BUILD.bazel:20:13: Compiling Rust rlib bson v2.6.1 (39 files) failed: (Exit 1): process_wrapper failed: error executing command (from target @crate__bson-2.6.1//:bson) bazel-out/darwin_arm64-opt-exec-2B5CBBC6/bin/external/rules_rust/util/process_wrapper/process_wrapper --arg-file ... (remaining 73 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
error[E0433]: failed to resolve: use of undeclared crate or module `uuid`
   --> external/crate__bson-2.6.1/src/uuid/mod.rs:174:11
    |
174 |     uuid: uuid::Uuid,
    |           ^^^^ use of undeclared crate or module `uuid`

...

Bazel version: bazel 6.1.1-homebrew
OS version: macOS 13.3.1 (a) (22E772610a)
Rustc version: rustc 1.68.0 (2c8cc3432 2023-03-06)
Chip: Apple Silicon M2
Mongodb crate version: 2

How to reproduce

1. Download the package: bazel_test.zip, unzip, and cd into the project directory
2. Run CARGO_BAZEL_REPIN=1 bazel sync --only=crate
3. Run bazel build //src:main

[UebelAndre]

The issue doesn’t seem to be mongo but bson. Can you share the rendered BUILD file for the bson crate?

cat $(bazel info output_base)/external/crate__bson-2.6.1/BUILD.bazel

[UebelAndre]

And what version of rules_rust are you using?

[YaxinCheng]

The issue doesn’t seem to be mongo but bson. Can you share the rendered BUILD file for the bson crate?

cat $(bazel info output_base)/external/crate__bson-2.6.1/BUILD.bazel

###############################################################################
# @generated
# DO NOT MODIFY: This file is auto-generated by a crate_universe tool. To 
# regenerate this file, run the following:
#
#     bazel sync --only=crate
###############################################################################

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

# buildifier: disable=bzl-visibility
load("@rules_rust//crate_universe/private:selects.bzl", "selects")

package(default_visibility = ["//visibility:public"])

# licenses([
#     "TODO",  # MIT
# ])

rust_library(
    name = "bson",
    deps = [
        "@crate__ahash-0.7.6//:ahash",
        "@crate__base64-0.13.1//:base64",
        "@crate__bitvec-1.0.1//:bitvec",
        "@crate__hex-0.4.3//:hex",
        "@crate__indexmap-1.9.3//:indexmap",
        "@crate__lazy_static-1.4.0//:lazy_static",
        "@crate__rand-0.8.5//:rand",
        "@crate__serde-1.0.162//:serde",
        "@crate__serde_bytes-0.11.9//:serde_bytes",
        "@crate__serde_json-1.0.96//:serde_json",
        "@crate__time-0.3.21//:time",
    ] + select({
        "@rules_rust//rust/platform:wasm32-unknown-unknown": [
            "@crate__js-sys-0.3.61//:js_sys",  # cfg(target_arch = "wasm32")
        ],
        "@rules_rust//rust/platform:wasm32-wasi": [
            "@crate__js-sys-0.3.61//:js_sys",  # cfg(target_arch = "wasm32")
        ],
        "//conditions:default": [],
    }),
    compile_data = glob(
        include = ["**"],
        exclude = [
            "**/* *",
            "BUILD",
            "BUILD.bazel",
            "WORKSPACE",
            "WORKSPACE.bazel",
        ],
    ),
    crate_features = [
        "default",
    ],
    crate_root = "src/lib.rs",
    edition = "2018",
    rustc_flags = ["--cap-lints=allow"],
    srcs = glob(["**/*.rs"]),
    tags = [
        "cargo-bazel",
        "crate-name=bson",
        "manual",
        "noclippy",
        "norustfmt",
    ],
    version = "2.6.1",
)

[YaxinCheng]

And what version of rules_rust are you using?

http_archive(
    name = "rules_rust",
    sha256 = "25209daff2ba21e818801c7b2dab0274c43808982d6aea9f796d899db6319146",
    urls = ["https://github.com/bazelbuild/rules_rust/releases/download/0.21.1/rules_rust-v0.21.1.tar.gz"],
)

[YaxinCheng]

If you download the bazel_test.zip I attached, you can find out more details. This zip is a minimal reproducible instance for this bug. The only crate it uses is the mongodb:

crates_repository(
    name = "crate",
    cargo_lockfile = "//:Cargo.lock",
    lockfile = "//:Cargo.Blaze.lock",
    packages = {
        "mongodb": crate.spec( 
            version = "2"
        ),
    },
    render_config = render_config(
        default_package_name = ""
    ),
)

The BUILD rule is pretty simple

rust_binary(
    name = "main",
    srcs = ["main.rs"],
    deps = [
        "@crate//:mongodb",
    ]
)

The main.rs is just some random irrelevant things.

[YaxinCheng]

I have taken a look at the line where the error message indicates

    |
174 |     uuid: uuid::Uuid,
    |           ^^^^ use of undeclared crate or module `uuid`

The "undeclared crate or module uuid" is actually pointing to the module itself. So it is equivalent to

uuid: Uuid

That makes this like a bug to me. It is equivalent to

mod foo {
  struct Bar;
  fn test(value: foo::Bar) { // this foo::Bar is the same as the uuid::Uuid above
    // ... 
  }
}

[hobofan]

The "undeclared crate or module uuid" is actually pointing to the module itself. So it is equivalent to

uuid: Uuid

No, it's not. The equivalent would be crate::uuid::Uuid. uuid::Uuid does state that it's looking for type Uuid from the uuid package (= crate).

I think the cause may lie here:
https://github.com/mongodb/bson-rust/blob/70b49c5ca52f9909e3ce71742ac7d33ee5d1c125/Cargo.toml#LL65-L66

The uuid crate is defined twice as a dependency. Once in an older optional version that is renamed, and once in a current non-optional version. It seems that somewhere in the process crate_universe mixes them up/loses the information that they are distinct dependencies and makes both of them optional.

I am pretty sure that there has been a reported issue not that long ago that was related to a renamed crate dependency, but I can't seem to find it. EDIT: I think it was this one: #1809

As a temporary workaround I suspect that you could from your top-level crate depend on bson with the uuid-0_8 feature, which might add both versions of uuid as a dependency.

[UebelAndre]

Thanks for the details @YaxinCheng and great find @hobofan! I'd be happy to review a pull-request that corrected how crate_universe handled substations like this 😄

[YaxinCheng]

No, it's not. The equivalent would be crate::uuid::Uuid. uuid::Uuid does state that it's looking for type Uuid from the uuid package (= crate).

I think the cause may lie here: https://github.com/mongodb/bson-rust/blob/70b49c5ca52f9909e3ce71742ac7d33ee5d1c125/Cargo.toml#LL65-L66

You are right. I missed that. Thanks for pointing it out

[YaxinCheng]

From the generated Cargo.Blaze.lock, neither of the two uuids appears in the dependency list of bson crate:

    "bson 2.6.1": {
      "name": "bson",
      "version": "2.6.1",
      "repository": {
        "Http": {
          "url": "https://crates.io/api/v1/crates/bson/2.6.1/download",
          "sha256": "9aeb8bae494e49dbc330dd23cf78f6f7accee22f640ce3ab17841badaa4ce232"
        }
      },
      "targets": [
        {
          "Library": {
            "crate_name": "bson",
            "crate_root": "src/lib.rs",
            "srcs": [
              "**/*.rs"
            ]
          }
        }
      ],
      "library_target_name": "bson",
      "common_attrs": {
        "compile_data_glob": [
          "**"
        ],
        "crate_features": {
          "common": [
            "default"
          ],
          "selects": {}
        },
        "deps": {
          "common": [
            {
              "id": "ahash 0.7.6",
              "target": "ahash"
            },
            {
              "id": "base64 0.13.1",
              "target": "base64"
            },
            {
              "id": "bitvec 1.0.1",
              "target": "bitvec"
            },
            {
              "id": "hex 0.4.3",
              "target": "hex"
            },
            {
              "id": "indexmap 1.9.3",
              "target": "indexmap"
            },
            {
              "id": "lazy_static 1.4.0",
              "target": "lazy_static"
            },
            {
              "id": "rand 0.8.5",
              "target": "rand"
            },
            {
              "id": "serde 1.0.162",
              "target": "serde"
            },
            {
              "id": "serde_bytes 0.11.9",
              "target": "serde_bytes"
            },
            {
              "id": "serde_json 1.0.96",
              "target": "serde_json"
            },
            {
              "id": "time 0.3.21",
              "target": "time"
            }
          ],
          "selects": {
            "cfg(target_arch = \"wasm32\")": [
              {
                "id": "js-sys 0.3.61",
                "target": "js_sys"
              }
            ]
          }
        },
        "edition": "2018",
        "version": "2.6.1"
      },
      "license": "MIT"
    }

Given this, I think the error has already happened when I ran CARGO_BAZEL_REPIN=1 bazel sync --only=crate

[YaxinCheng]

Cargo.lock has one of the uuid. I think this is correct, since by default, the uuid-0.8 is disabled (as it's optional).

[[package]]
name = "bson"
version = "2.6.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "9aeb8bae494e49dbc330dd23cf78f6f7accee22f640ce3ab17841badaa4ce232"
dependencies = [
 "ahash",
 "base64 0.13.1",
 "bitvec",
 "hex",
 "indexmap",
 "js-sys",
 "lazy_static",
 "rand",
 "serde",
 "serde_bytes",
 "serde_json",
 "time",
 "uuid",
]

[YaxinCheng]

I am still looking into the issue, but here is the deps that is generated with the bazel sync command.

The Cargo.Blaze.lock file is just an instance of Context. Tracing down how the Context is generated can potentially find out the culprit.