Allow running cargo add foo when a foo.workspace = true already exists

[Muscraft]

Tracking issue: #8415
RFC: rust-lang/rfcs#2906

PRs in this RFC:

• Base Implementation
  • Part 1 of RFC2906 - Packages can inherit fields from their root workspace #10497
  • Part 2 of RFC2906 -- allow inheriting from a different Cargo.toml #10517
  • Part 3 of RFC2906 - Add support for inheriting license-path, and depednency.path #10538
  • Part 4 of RFC2906 - Add support for inheriting readme #10548
• New Fields
  • Part 5 of RFC2906 - Add support for inheriting rust-version #10563
  • Part 7 of RFC2906 - Add support for inheriting exclude and include #10565
• Update inheritance source
  • Part 6 of RFC2906 - Switch the inheritance source from workspace to… #10564
• Optimizations
  • Part 8 of RFC2906 - Keep InheritableFields in a LazyCell inside `… #10568
• Documentation changes
  • Prefer key.workspace = true to key = { workspace = true } #10584

This is currently a draft

This PR focuses on adding initial support to allow running cargo add foo when a foo.workspace = true already exists.

Changes:

• Added WorkspaceSource to allow for foo.workspace = true
• Added MaybeWorkspace to allow returning a WorkspaceSource when trying to query for a dependency or trying to get a SourceId for that query.

Remaining implementation work for the RFC

• cargo-add support, see epage's comment
• Optimizations as needed

r? @epage

[Muscraft]

I accidentally had my commits from an earlier branch that hadn't been merged under this one. It should be fixed now.

[epage]

This is unrelated to the source

[Muscraft]

Features and optional are unrelated to the source?

[epage]

See

pub struct Dependency {
    /// The name of the dependency (as it is set in its `Cargo.toml` and known to crates.io)
    pub name: String,
    /// Whether the dependency is opted-in with a feature flag
    pub optional: Option<bool>,

    /// List of features to add (or None to keep features unchanged).
    pub features: Option<IndexSet<String>>,
    /// Whether default features are enabled
    pub default_features: Option<bool>,

    /// Where the dependency comes from
    pub source: Option<Source>,
    /// Non-default registry
    pub registry: Option<String>,

    /// If the dependency is renamed, this is the new name for the dependency
    /// as a string.  None if it is not renamed.
    pub rename: Option<String>,

    /// Features that are exposed by the dependency
    pub available_features: BTreeMap<String, Vec<String>>,
}

[Muscraft]

Ah so we should make it so features from foo = { workspace = true, features = ["test"]} get put into the Dependency

[epage]

Correct

[epage]

This will just print a bool. We should probably just print workspace

[epage]

Can this ever be false? Should we just have the presence of this assume true?

[Muscraft]

That is up to you. I don't think it should be false ever since we check if it's false before we create it.

[epage]

Let's just have this be a unit struct for now. We can always add fields later

[epage]

We should delete all of the keys incompatible with workspace = true.

[epage]

The other branches should remove "workspace"

[epage]

Would it be more clear to say "{key}.workspace = false is unsupported"

[epage]

I might go as far as an unreachable!("registry depedencies required, found a workspace dependency")

[epage]

ditto

unreachable!("path or git dependency expected, found workspace dependency");

[epage]

Don't we need to be looking up the workspace's dependency and getting its query?

[Muscraft]

Possibly, this was one area that I wasn't sure how we should be going about this. I know that this makes it so foo = { workspace = true, features = ["test"]} works.

[epage]

We have two feature lists

• What the user specified
• What the crate defines

This code is putting the user-specified features into the list of what the crate defines so anything the user enters will always be valid.

[epage]

#10581 will add a masquerade_as_nightly_cargo() function to Command.

[Muscraft]

I saw that and put this in until that PR is merged or we plan to merge this one and then have a cleanup PR that fixes it

[Muscraft]

Closing as #10606 includes this commit