[Mikola Lysenko (mikolalysenko)]

Stacked on #2011 (fix/go-discovery-workspace).

Problem

The hosted engine hands the golang rewriter the Go workspace it read (HostedGoWorkspace). In memory (ProjectView::Memory) its paths are root-relative with an empty root. The rewriter still judged them with the disk checks: replace_host, rooted_at, selection and host_conflict resolved paths against the process's working directory and probed <cwd>/go.mod. The in-memory engine's answer therefore depended on where the server process was started.

Example: an in-memory project with a root go.mod and a go.work that only has use ./b. If the cwd had no go.mod, the rewriter refused with "nowhere to go: … holds neither go.work nor a go.mod". If the cwd had one, it gave the correct "does not use this module" answer.

Fix

• The workspace knows where its paths live. GoWorkspace now has files: Option<BTreeSet<PathBuf>>. In memory it lists the root-relative files that exist; on disk it is None. Every method goes through GoWorkspace::paths() (PathSpace::from_files). The _in(PathSpace, ..) variants from Read the governing go.work in Go discovery #2011 and their Disk-default wrappers are removed, so no caller can judge an in-memory workspace against the disk. The rewriter's code is unchanged from the base.
• One in-memory builder. go_workspace::read_memory builds the in-memory workspace for both the hosted engine and discovery, through a small MemoryFiles reader trait. The engine reads through read_advisory; discovery uses its guarded reads, which diagnose an unparseable member go.mod. A file is in files when it exists, whether readable, a link, an entry without content, or a go.mod go cannot parse. Existence is checked without reading the file.
• GoWorkspace::selection no longer shows a main-module member through the disk display_path.

I checked the rest of the in-memory engine's Go path: the memory branch of read_go_workspace reads only through the view, and go_build_list::select_in is pure. No other disk, cwd or env probes remain on that path.

Review findings

1. files counted readable, not existing, files; engine and discovery built it differently. Confirmed, fixed. The engine skipped a symlinked or content-less root go.mod. Discovery skipped an unparseable one. Both now go through read_memory, which uses existence. The new tests hosted::engine::tests::memory_go_workspace_never_probes_the_cwd and vex::discover::golang::tests::in_memory_workspace_files_are_the_files_that_exist use the same three projects: a valid, an unparseable and a symlinked root go.mod, with use ./b. Both expect the same files and the "not a member" verdict. Under the old engine rule the symlinked case loses go.mod and fails. Note: in discovery the root go.mod's presence is only consulted for a parsed go.mod, so its old rule never changed a verdict; it is aligned anyway.
2. members_within counted ../out as in-root in memory. Confirmed, fixed. Only all-Normal relative paths count as within the root, so absolute members are excluded too. memory_members_within_excludes_members_outside_the_root fails without the fix (["a", "../out", "/abs", ""]) and also checks the NoModule member hint.
3. Test helper memory_go_files ignored a root go.mod outside the members. Fixed. go_workspace_key and memory_go_files now take root_go_mod. with_root_go_work passes whether the fixture has one.
4. Store the PathSpace on the workspace. Done. See Fix above.
5. Shared in-memory reader. Done. read_memory returns the workspace and its in-root members. Discovery derives its sum files from those members.
6. PathSpace::from_files. Added, used by GoWorkspace::paths. Discovery's Workspace::paths and HostedGoWorkspace::paths are gone.
7. Root go.mod read only for .is_some(). Fixed. It is now an existence check. The engine's check also counts unreadable entries.
8. read_go_workspace pub(crate) only for a test. Fixed. The test moved into hosted::engine's tests and the function is private again.

Tests

• cargo test -p socket-patch-core --lib -- hosted:: vex::discover:: vendor::go golang: 912 passed.
• CLI --test hosted_memory_engine: 49 passed. --test hosted_memory_parity: 42 passed.
• cargo clippy --locked --workspace --all-features -- -D warnings and cargo fmt --all -- --check are clean.

---

Generated by Claude Code