Rust plugin prevents from building a single package in workspace

Metadata

Project: craft-parts
Number: #934
Type: issue
State: open
Author: artivis
Labels: —
Created: 2024-12-12 04:06 PM UTC
Updated: 2025-03-11 02:28 PM UTC
Closed: —

Current evaluation

Rust plugin hardcodes `cargo build --workspace` in the virtual-workspace branch, so users cannot build a single/selected package; the `rust_cargo_parameters` workaround fails. Still present at HEAD, untriaged and unacknowledged.

Suggested action: needs triage

Reason: The defect is confirmed still present at HEAD: rust_plugin.py:441 emits `cargo build --workspace --release {config_cmd_string}`, with `rust_cargo_parameters` (line 412-413) appended after the flag so cargo's `--workspace` precedence defeats the suggested workaround. The issue has zero labels, zero comments, and no assignee, and git history of rust_plugin.py shows only refactors (#530, #560, #626, #1424, #1706, #1745) with no fix commit, so it has never been assessed by a maintainer. Impact is moderate (blocks a legitimate, commonly needed use case in large workspaces) but not app-breaking, and the fix is small and well-understood since the reporter correctly notes cargo falls back to `default-members`/all-members when neither flag is given.

Evaluated by: mr-cal-bot

Impact: 35 Quick Win: 21 Complexity: 20 Confidence: 85 Actionability: 75

Issue body

### What needs to get done The rust plugin should support building a single (or several) package(s) in a virtual workspace. The `cargo build` command offers the `--package` flag to only build a specific package (the flag can be repeated). However it is superseeded by the `--workspace` flag which effectively instruct to build all packages (not sure if this precedence is a general rule or a positional thing). ### Why it needs to get done While the plugin doesn't explicitely support specifying a package(s), one could abuse the [`rust_cargo_parameters`](https://github.com/canonical/craft-parts/blob/11be8c7a300b28885f9ddcd71f072fae31c440ab/craft_parts/plugins/rust_plugin.py#L50C5-L50C26) to stuff e.g. `['--package', 'foo']`. However, the plugin [hardcode the `--workspace`](https://github.com/canonical/craft-parts/blob/11be8c7a300b28885f9ddcd71f072fae31c440ab/craft_parts/plugins/rust_plugin.py#L316) flag and all packages are built regardless of the workaround. Edit: Similarly, a workspace definition may contain the `default-members` entry. It defines the members of a virtual workspace that should be built in case neither `--workspace` nor `--package` are specified. If `default-members` isn't specified either, the fallback is to build all (`--workspace`). So the hardcoded flag could probably be removed altogether from the plugin. Source: [The cargo book](https://doc.rust-lang.org/cargo/reference/workspaces.html?highlight=workspace#workspaces).

Evaluation history

Date	Model	Scores	Action	Summary
2026-10-02 06:17 PM UTC	stealth/space-bunny-alpha	Impact: 35 Quick Win: 21 Complexity: 20 Confidence: 85 Actionability: 75	needs triage	Rust plugin hardcodes `cargo build --workspace` in the virtual-workspace branch, so users cannot build a single/selected package; the `rust_cargo_parameters` workaround fails. Still present at HEAD, untriaged and unacknowledged.
2026-09-22 06:36 AM UTC	qwen/qwen3.6-35b-a3b	Impact: 30 Quick Win: 17 Complexity: 30 Confidence: 80 Actionability: 80	needs triage	Rust plugin hardcodes --workspace flag preventing single package builds in virtual workspaces. Issue is open with no labels or maintainer response.
2026-09-01 06:10 AM UTC	qwen/qwen3.8-27b	Impact: 45 Quick Win: 25 Staleness: 75 Complexity: 45 Confidence: 80 Support Request: 10	needs triage	Rust plugin hardcodes --workspace in cargo build for virtual workspaces, blocking single-package builds via --package. Open ~18 months with no maintainer interaction; the hardcoded flag still exists in current code.
2026-07-22 01:23 PM UTC	qwen/qwen3.6-35b-a3b	Staleness: 92 Complexity: 20 Confidence: 85 Support Request: 10	needs triage	Rust plugin hardcodes --workspace in cargo build, blocking single-package builds. Untriaged, no maintainer comments, inactive for over a year.
2026-07-09 09:45 AM UTC	qwen3.6-35b-a3b-mtp-q6	Staleness: 90 Complexity: 30 Confidence: 75 Support Request: 10	needs triage	Rust plugin hardcodes --workspace flag, blocking single-package builds. Unlabelled, zero maintainer comments, inactive for over a year.

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