toggle-sibling-libraries

name: toggle-sibling-libraries description: Toggle a Swift Package.swift between the local-sibling-checkout development pattern and a clean remote-only release pattern. Use this skill whenever you need to flip Package.swift in or out of the sibling(...) helper-function pattern — for example, before tagging a release the dependencies must be pinned to remote-only, and on a fresh -dev development cycle they must go back to sibling-aware. Also trigger on phrases like "switch to remote deps", "remove the sibling helper", "restore sibling pattern", "make Package.swift release-ready", "flip to dev-mode deps", or any time the user references the sibling() helper or the useLocalSiblings constant. Only intrusive-memory/* dependencies participate in the sibling pattern; all other dependencies are left untouched. allowed-tools: Bash, Read, Edit, Write

Toggle Sibling Libraries

This skill rewrites Package.swift between two states.

Sibling state (development branches): intrusive-memory/* dependencies are routed through a sibling(_:remote:from:) helper that prefers a ../<name> checkout when present and falls back to the remote pin. Lets a developer make coordinated changes across several intrusive-memory packages without publishing intermediate releases.

Remote state (shipped releases): intrusive-memory/* dependencies are plain .package(url:..., .upToNextMajor(from: "X.Y.Z")) calls pinned to the latest published release. The sibling(...) helpers, the useLocalSiblings constant, and any unused import Foundation are stripped.

The skill is bidirectional and idempotent.

When this skill runs

• Before tagging a release — invoke with --to remote. The version-bump step in ship-swift-library calls this so the shipped Package.swift carries no developmental scaffolding.
• After stamping the post-release -dev marker — invoke with --to sibling. The dev-marker step in ship-swift-library calls this so the next development cycle can pick up sibling checkouts again.
• Manually, any time a developer wants to test a clean release-shape build, or restore the sibling pattern after editing.

Scope rule (very important)

Only dependencies under https://github.com/intrusive-memory/* participate in the sibling pattern. Every other dependency (e.g. apple/swift-argument-parser, marcprux/universal) is left untouched in both directions. Hard-code this rule — the reason is that the sibling helper assumes a coordinated co-located checkout convention that only the intrusive-memory family observes.

If the user asks to add a non-intrusive-memory dep to the sibling pattern, push back and ask them to confirm; the convention exists for a reason and silently broadening it leads to surprising local-path resolution against unrelated repos.

Prerequisites

test -f Package.swift || { echo "ABORT: no Package.swift in current directory"; exit 1; }
command -v gh >/dev/null || { echo "ABORT: gh CLI required to look up latest published versions"; exit 1; }
gh auth status >/dev/null 2>&1 || { echo "ABORT: gh not authenticated"; exit 1; }

The gh requirement is for resolving the latest published version of each intrusive-memory dep when flipping to remote (see "Version resolution" below). If the user is offline, fail fast — guessing or reusing the existing from: value risks shipping a release that depends on something older than what was just released upstream.

Direction: --to remote

Goal: produce a Package.swift that builds cleanly from a fresh clone with no ../ siblings on disk and no environment variables set, and that pins each intrusive-memory dep to the latest published GitHub release.

1. Resolve the latest published version of each intrusive-memory dep

For every sibling("<Name>", remote: "https://github.com/intrusive-memory/<Repo>.git", ...) call in the file:

LATEST=$(gh api "repos/intrusive-memory/<Repo>/releases/latest" --jq '.tag_name' 2>/dev/null)
LATEST="${LATEST#v}"   # strip leading v if present

If releases/latest returns nothing, fall back to the most recent vX.Y.Z tag:

gh api "repos/intrusive-memory/<Repo>/tags" \
  --jq '[.[].name | select(test("^v[0-9]+\\.[0-9]+\\.[0-9]+$"))][0]'

If both queries come up empty, abort with a clear message naming the offending dep — shipping a release that pins an unreleased upstream is broken by definition.

2. Rewrite each sibling call

For the from: variant — sibling("X", remote: "URL", from: "OLD") — emit:

.package(url: "URL", .upToNextMajor(from: "<LATEST>"))

(Use the resolved <LATEST>, not the source-file OLD value. The from: argument in dev mode is just a floor; at ship time we move to whatever is actually published.)

For the branch: variant — sibling("X", remote: "URL", branch: "feature-foo") — emit the same .upToNextMajor(from: "<LATEST>") form, NOT a branch pin. Then emit a loud warning in the run summary:

WARNING: SwiftBruja was on a sibling branch ('feature-foo') in development.
Converted to .upToNextMajor(from: "1.6.1") (latest released tag).
The branch may carry unreleased changes that the published version does NOT have.
Verify the upstream is released before tagging this repo.

The reason for the warning: a development build that depended on an unreleased feature in a sibling branch will, when this repo ships, silently fall back to the older published version — which means tests that passed in dev may not exercise the same code at release.

3. Strip the helper functions and constant

Remove:

• The let useLocalSiblings = ... line and any explanatory comment block above it.
• Every preceding scaffold-let that the helper depends on. The canonical block declares let manifestDir = ..., let isSPMCheckout = ... (multi-line), and let isCI = ... above useLocalSiblings. All of these are dead code without the helper — strip them too, including the multi-line continuation of isSPMCheckout. (scripts/toggle.py recognises this whole set via SCAFFOLD_LET_NAMES.)
• Both func sibling(...) definitions.
• The import Foundation line only if no other code in the file references Foundation/FileManager/ProcessInfo/NSString. (Almost always safe to remove; double-check.)

The resulting file should look like a stock Package.swift: swift-tools-version line, import PackageDescription, the let package = Package(...) block, and that's it.

4. Run swift format if available

If the repo has a make lint target, run it. Otherwise leave formatting to whoever calls the skill next — don't introduce a swift-format dependency.

5. Verify the result builds

swift package resolve 2>&1 | tail -20

If resolve fails (most likely cause: a typo'd URL or a dep that genuinely has no published releases), surface the error and stop.

Direction: --to sibling

Goal: take a remote-only Package.swift and re-introduce the sibling pattern for intrusive-memory/* deps, so the next development cycle can pick up ../<name> checkouts.

1. Detect intrusive-memory deps

Find every .package(url: "https://github.com/intrusive-memory/<Repo>.git", .upToNextMajor(from: "X.Y.Z")) line. These are the ones to convert.

Anything else — apple/, marcprux/, custom hosts — stays exactly as-is.

2. Insert the helper block

If the file does not already contain func sibling(, prepend the canonical block immediately after import PackageDescription (and before let package = Package(...)):

import Foundation

// In CI we always pin to released remotes. Locally, prefer a sibling checkout
// at ../<name> if present so in-flight changes can be exercised end-to-end
// without publishing a release. Falls back to the remote pin if the sibling
// directory is missing, so fresh clones still build.
//
// When this manifest is evaluated as a transitive dependency inside Xcode's
// `SourcePackages/checkouts/` or SwiftPM's `.build/checkouts/`, every other
// dependency lives as a sibling in the same directory. Treating those as
// in-development local paths produces conflicting package identities, so we
// must skip the sibling shortcut in that context.
let manifestDir = (#filePath as NSString).deletingLastPathComponent
let isSPMCheckout =
  manifestDir.contains("/SourcePackages/checkouts/")
  || manifestDir.contains("/.build/checkouts/")
let isCI = ProcessInfo.processInfo.environment["CI"] == "true"
let useLocalSiblings = !isCI && !isSPMCheckout

func sibling(_ name: String, remote: String, from version: Version) -> Package.Dependency {
  let localPath = "../\(name)"
  if useLocalSiblings && FileManager.default.fileExists(atPath: localPath) {
    return .package(path: localPath)
  }
  return .package(url: remote, .upToNextMajor(from: version))
}

/// Same sibling-priority pattern as ``sibling(_:remote:from:)`` but pins to a
/// remote branch when no local sibling exists. Use only when a temporary
/// pre-release dependency on a feature branch is required; switch back to the
/// version-pinned ``sibling(_:remote:from:)`` once the upstream tags a release.
func sibling(_ name: String, remote: String, branch: String) -> Package.Dependency {
  let localPath = "../\(name)"
  if useLocalSiblings && FileManager.default.fileExists(atPath: localPath) {
    return .package(path: localPath)
  }
  return .package(url: remote, branch: branch)
}

If import Foundation is already present, don't duplicate it.

Why the SPM-checkout guard matters. A naive useLocalSiblings = !CI falsely activates when this manifest is evaluated as a transitive dependency inside DerivedData/.../SourcePackages/checkouts/ — every other dependency lives as a sibling in the same directory there, so the existence check succeeds for every dep and the helper switches them all to unversioned .package(path: ...) references. Those collide with the same identities pulled in via remote URLs elsewhere in the graph and abort resolution with Conflicting identity for .... The manifestDir / isSPMCheckout check disables the shortcut in that context. Don't ship a sibling helper without this guard.

3. Rewrite each intrusive-memory dep

.package(url: "https://github.com/intrusive-memory/<Repo>.git", .upToNextMajor(from: "X.Y.Z")) becomes sibling("<Repo>", remote: "https://github.com/intrusive-memory/<Repo>.git", from: "X.Y.Z").

The <Repo> for the first argument is the bare repo name (last URL path segment with .git stripped).

The from: value is preserved verbatim — at flip-back time we don't know what version was originally there, and .upToNextMajor(from: "X.Y.Z") is the correct floor for the next dev cycle.

The branch: variant of sibling is not generated automatically. Going-to-sibling always produces the from: variant; if the developer wants a branch pin, they edit it manually after the toggle.

4. Verify the result resolves

swift package resolve 2>&1 | tail -20

Same as the other direction.

Bundled script

Both transformations live in scripts/toggle.py. Prefer running it over hand-editing — the regex parsing handles whitespace, multi-line sibling(...) calls, and idempotency consistently.

python3 "$(dirname <skill-path>)/toggle-sibling-libraries/scripts/toggle.py" \
  --direction remote   # or: sibling
  [--package-swift Package.swift]
  [--dry-run]

Run with --dry-run first when invoked manually so the user can see the diff before it lands. The ship-swift-library callers run without --dry-run because the toggle is committed as part of a larger commit.

The script:

1. Parses Package.swift and identifies sibling calls / intrusive-memory deps.
2. Resolves releases/latest for each dep when going to remote (prints the resolved version map).
3. Performs the rewrite atomically (writes to a temp file then renames).
4. Returns non-zero if any required dep has no published release, or if the file is already in the requested state and --strict is set.
5. Emits the branch-variant warning to stderr, prefixed with WARNING:.

If the script is unavailable (older skill version, etc.), the SKILL.md text above is the canonical recipe and you can apply it manually with Edit.

Idempotency

Running --to remote on an already-remote Package.swift is a no-op: no sibling( calls to find, no helpers to strip. Same for --to sibling on a file already in sibling state.

The script reports already in <direction> state — no changes and exits 0. With --strict, it exits 1.

Critical rules

1. Only intrusive-memory/ repos* — never broaden the sibling rule to other organizations without an explicit user instruction.
2. Resolve to the latest published version when going to remote — do NOT carry forward the from: value from the dev source. The dev floor is informational; ship-time pins to whatever is actually released.
3. Convert branch: siblings to released from: pins, with a warning — never pin a release-branch repo to a moving upstream branch. If the warning fires, the human running ship-swift-library should pause and verify the upstream is released.
4. Never modify non-intrusive-memory dependencies — even if they happen to use a sibling( helper (they shouldn't, but if a user has hand-rolled an exception, leave it alone and surface it in the run report).
5. Never alter Package.resolved — that file is managed by SPM and by spm-package-audit. This skill only touches Package.swift.
6. Strip import Foundation only when safe — if any other code references Foundation/FileManager/ProcessInfo, leave the import. (For the canonical sibling-pattern repos this is always safe; the import exists only for the helper.)

How this fits with sibling skills

• spm-package-audit introduces and validates the sibling pattern during routine development hygiene. This skill (toggle-sibling-libraries) is the release lever that strips and restores it cleanly.
• ship-swift-library invokes --to remote during version-bump (step 3) and --to sibling during the post-release dev-marker step (step 11).
• The two skills are not competing: spm-package-audit enforces "is the sibling pattern correctly written?", while this skill enforces "is the sibling pattern present at all?"