Trait BufferScopeSource 

pub trait BufferScopeSource:
    Send
    + Sync
    + Debug {
    // Required method
    fn scope_dir_for_name(&self, buffer_name: &str) -> Option<PathBuf>;
}

A provider’s answer to “which directory is the buffer called this about?”, asked by the host the moment it creates a synthetic buffer.

Why by name, and why a pull rather than a push

A provider that opens its buffer with Effect::OpenSyntheticBuffer never touches the buffer: it returns a name and a mode id, and the host does the rest. So it has no BufferId to attach a BufferScopeDir to, and by the time its mode’s on_activate runs there is no &mut reach into the buffer-local map either.

It does, however, know the directory before the buffer exists — that is the whole reason magit’s RepoScopes is keyed by name rather than by id. So the host asks, at creation, with the one thing both sides have: the name.

The alternative was a scope_dir field on Effect::OpenSyntheticBuffer, which is ABI churn on a widely-constructed effect (and on its WIT peer) to carry data most callers do not have.

Required Methods

fn scope_dir_for_name(&self, buffer_name: &str) -> Option<PathBuf>

The directory a buffer named buffer_name is about, if this source knows. None for a name it does not recognise — every source is asked and most will not know.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors