Per-command configuration#

Just as you can override configuration per target triple, you can override it per cargo subcommand:

[package.metadata.cargo-fc.subcommands.<command>]

A subcommand override accepts the same feature-matrix keys as a target override — exclude_features, include_features, only_features, the *_feature_sets keys, skip_optional_dependencies, no_empty_feature_set, and matrix — with identical patch semantics.

Example: build it, but don’t test it#

Enable a heavy gpu feature when building, but skip those combinations when testing:

[package.metadata.cargo-fc]
# `gpu` is part of the matrix by default (e.g. for `cargo fc build`).

[package.metadata.cargo-fc.subcommands.test]
# ...but never test the gpu combinations.
exclude_features = { add = ["gpu"] }

Or restrict cargo fc test to a single focused set:

[package.metadata.cargo-fc.subcommands.test]
only_features = ["core"]

The override applies to that command only.

Aliases inherit command overrides#

Built-in short aliases (t → test, b → build, …) and your own .cargo/config.toml aliases that resolve to a built-in inherit the override automatically, the same way configured targets and flag defaults resolve aliases.

Composing target and command#

A target.'cfg(...)'.subcommands.<command> section applies only when both conditions hold — the target matches and the command is selected:

[package.metadata.cargo-fc.target.'cfg(target_os = "linux")'.subcommands.test]
exclude_features = { add = ["cuda"] }

The feature-matrix layers then resolve broad-to-narrow (later wins):

1. package base
2. matching subcommands.<command>
3. matching target.'cfg(...)'
4. matching target.'cfg(...)'.subcommands.<command>

expand_targets: giving a custom command target capability#

Built-in commands (check, clippy, build, doc, test, run, and matrix) already know how to expand configured targets. A custom subcommand that doesn’t resolve to a built-in needs an explicit opt-in:

[workspace.metadata.cargo-fc.subcommands.my-custom-cmd]
expand_targets = true

You can also override a built-in’s default. For example, lint every configured target but keep build on the single effective target:

[workspace.metadata.cargo-fc.subcommands.build]
expand_targets = false

expand_targets is a per-subcommand capability — it only appears in subcommands.<cmd> tables.

Scope note. Feature sets are per package, so the feature-matrix keys are only accepted in package-scope subcommand tables. Workspace-scope subcommand tables ([workspace.metadata.cargo-fc.subcommands.<command>]) accept only the targets capability, expand_targets, driver, and cargo fc flags.