T-ZAZO-intersect-fs-layer

Status: closed/done · Impact: medium · Complexity: medium

Goal

Implement intersect/fs — filesInScope and resolveIntersection — wrapping a filesystem globber and filtering with the pure path API, as a subpath entry so the core stays dependency-free.

Today

The fs surface and its fixtures exist as stubs from T-FGMJ; the path API used to filter enumerated files is implemented by T-IRYT.

Location	Role today
plugin/lib/intersect/fs.ts	fs surface — throwing stubs.
plugin/lib/intersect/index.ts	The path API used to filter enumerated files.
plugin/lib/intersect/fixtures/fs.cases.json	fs spec, all pending.
package.json	Root manifest; new runtime deps for the workspace land here.

Proposed

intersect/fs is implemented over a chosen globber; filesInScope(patterns, {cwd,…}) enumerates on-disk files matching the scope, resolveIntersection(a, b, …) returns the files matching both; the core entries (intersect, intersect/segments) still pull zero runtime deps. fs fixtures run as integration tests over a temp tree.

Approach

1. Choose the globber (fast-glob or tinyglobby) and add it as a dependency used only by fs.ts.
2. filesInScope(patterns, opts): glob the tree under cwd honoring ignore/onlyFiles/absolute; post-filter the results through the path API’s matches so fs semantics are identical to the pure layer.
3. resolveIntersection(a, b, opts): filesInScope(a, opts) then keep those that also matches(_, b).
4. Convert the fs fixtures to an integration harness: each case declares a file list to materialize under a temp dir, the op + args, and the expected relative paths; the harness builds the tree, runs the op, asserts, and cleans up.
5. Assert the core entries do not transitively load the globber.

Files to touch

Location	Kind	Change
plugin/lib/intersect/fs.ts	modify	Implement filesInScope / resolveIntersection.
plugin/lib/intersect/tests/fs.test.ts	new	Temp-tree integration harness for the fs cases.
plugin/lib/intersect/fixtures/fs.cases.json	modify	Activate as integration cases (temp-dir file lists).
package.json	modify	Add the chosen globber to dependencies.

Acceptance criteria

• AC-1: The fs.cases.json integration cases pass against materialized temp trees.
• AC-2: filesInScope(["a/**"], { cwd }) returns exactly the files under a/ in the fixture tree; resolveIntersection returns their intersection with the second scope.
• AC-3: A test asserts that importing intersect or intersect/segments does not load the globber (dependency-isolation check).
• AC-4: bunx tsc --noEmit passes.

Out of scope

• Package exports finalization and extraction — T-9XXD.
• Watch mode / streaming enumeration.

Dependencies

• Requires the implemented path API from T-IRYT.

Discovery context

• The L2 section of D-4FRD-intersect-api layered-api.md; serves DR-0011 (context assembly).

Depends on

T-IRYT

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