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publish_current: skip the rewrite when the pointer already resolves #168

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Merged
JPDuchesne merged 1 commit into from
Sep 13, 2026
Merged

publish_current: skip the rewrite when the pointer already resolves #168

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10 changes: 9 additions & 1 deletion lib/dev/deps/gh_integration.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -178,8 +178,16 @@ def install_from_source(dep)
sig { params(base_dir: Pathname, target_dir: Pathname).void }
def publish_current(base_dir, target_dir)
link = base_dir / "current"
desired = target_dir.basename.to_s
# A pointer that already resolves to the target is converged — skip
# the rewrite. The swap is not free idempotence but a write, and
# identities that can only read the shared tree (the ai-agent user
# on the human-owned engine tree, plans#26) crash on it (caught
# live at the plans#36 ceremony via dev install-deps).
return if File.symlink?(link.to_s) && File.readlink(link.to_s) == desired

tmp = base_dir / ".current-#{Process.pid}-#{SecureRandom.hex(4)}"
File.symlink(target_dir.basename.to_s, tmp.to_s)
File.symlink(desired, tmp.to_s)
File.rename(tmp.to_s, link.to_s)
rescue StandardError
FileUtils.rm_f(tmp.to_s) if tmp
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27 changes: 27 additions & 0 deletions test/dev/deps/gh_integration_test.rb
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Expand Up @@ -150,6 +150,33 @@ def build_integration(fixture_files, cache_dir)
FileUtils.rm_rf(dir)
end

test "install_all leaves an already-correct current pointer untouched — a read-only shared tree stays usable" do
Given "a published version whose current pointer already resolves to it, in a base dir the " \
"caller cannot write (the agent identity on the human-owned shared engine tree, plans#26)"
dir = Dir.mktmpdir("dev-gh-int-test-")
parts = build_split_archive(dir, "engine.tar.zst", part_size: 64)
install_dir = File.join(dir, "engines", "unreal-engine-css")
version_dir = File.join(install_dir, "5.6.1-css-83")
FileUtils.mkdir_p(version_dir)
File.write(File.join(version_dir, ".dev-gh-release"), "5.6.1-css-83")
File.symlink("5.6.1-css-83", File.join(install_dir, "current"))
FileUtils.chmod(0o555, install_dir)
dep = build_dependency(parts, install_dir)
integration = build_integration(parts, File.join(dir, "cache"))

When "installing again"
integration.install_all([dep])

Then "the converged pointer was recognized, not rewritten (caught live at the plans#36 " \
"ceremony: the unconditional rewrite crashed dev install-deps with EACCES)"
File.readlink(File.join(install_dir, "current")) == "5.6.1-css-83"
integration.download_count == 0

Cleanup
FileUtils.chmod(0o755, install_dir)
FileUtils.rm_rf(dir)
end

test "install_all installs a new version alongside the existing one when the locked tag changes" do
Given "an existing version dir for an older tag"
dir = Dir.mktmpdir("dev-gh-int-test-")
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