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gh integration: retire the current symlink #179

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Merged
JPDuchesne merged 1 commit into from
Sep 23, 2026
Merged

gh integration: retire the current symlink #179

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37 changes: 5 additions & 32 deletions lib/dev/deps/gh_integration.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,6 @@
require "digest"
require "fileutils"
require "pathname"
require "securerandom"
require "shellwords"
require_relative "../data_root"
require_relative "integration"
Expand Down Expand Up @@ -39,6 +38,11 @@ module Deps
# multi-gigabyte (the UE engine is ~8GB compressed; a built tree far more), so
# parking a second copy in ~/.dev/cache would double disk usage for no benefit.
# The version-keyed install dir plus its marker file is the cache.
#
# Nothing else is written under install_dir: consumers locate the version
# dir through `dev deps path gh <name>` (Accessor), so an install is a pure
# read once the marker matches — a read-only shared tree (the agent identity
# on the human-owned engine tree, plans#26) needs no write to stay usable.
class GhIntegration < Integration
extend T::Sig

Expand Down Expand Up @@ -100,7 +104,6 @@ def install_prebuilt(dep)
target_dir = versioned_dir(base_dir, dep.version)
if version_published?(target_dir, MARKER_FILE, dep.version)
puts ">>> #{dep.name}@#{dep.version} already installed at #{target_dir}"
publish_current(base_dir, target_dir)
return
end

Expand All @@ -127,7 +130,6 @@ def install_prebuilt(dep)
else
puts ">>> #{dep.name}@#{dep.version} published concurrently at #{target_dir}"
end
publish_current(base_dir, target_dir)
ensure
FileUtils.rm_rf(staging_dir) if staging_dir
end
Expand All @@ -139,7 +141,6 @@ def install_from_source(dep)
target_dir = versioned_dir(base_dir, dep.version)
if version_published?(target_dir, MARKER_FILE, dep.version)
puts ">>> #{dep.name}@#{dep.version} already installed at #{target_dir}"
publish_current(base_dir, target_dir)
return
end

Expand All @@ -164,38 +165,10 @@ def install_from_source(dep)
else
puts ">>> #{dep.name}@#{dep.version} published concurrently at #{target_dir}"
end
publish_current(base_dir, target_dir)
ensure
FileUtils.rm_rf(staging_dir) if staging_dir
end

# Point <install_dir>/current at the just-installed version via a relative
# symlink, swapped in atomically. Host consumers (e.g. cellbound's
# build-game.sh via UE_ROOT) reference this stable path without knowing the
# locked tag; the versioned dirs themselves stay immutable — only this
# pointer moves, to the most recently installed version.
#
# @param base_dir [Pathname] declared install_dir
# @param target_dir [Pathname] the published version dir
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(desired, tmp.to_s)
File.rename(tmp.to_s, link.to_s)
rescue StandardError
FileUtils.rm_f(tmp.to_s) if tmp
raise
end

# Fetch the tag's source tarball into archive_path. Uses `gh api .../tarball`
# rather than a bare codeload URL so the request carries gh's auth token and
# follows the redirect — required for private/Epic-gated repos. Isolated so
Expand Down
17 changes: 8 additions & 9 deletions test/dev/deps/gh_integration_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -141,7 +141,7 @@ def build_integration(fixture_files, cache_dir)
File.read(File.join(version_dir, "Engine", "engine.txt")) == "engine payload"
File.read(File.join(version_dir, "README.md")) == "readme payload"
File.read(File.join(version_dir, ".dev-gh-release")) == "5.6.1-css-83"
File.readlink(File.join(install_dir, "current")) == "5.6.1-css-83"
!File.exist?(File.join(install_dir, "current"))
Dir.glob(File.join(install_dir, ".staging-*")).empty?
integration.download_count == 1

Expand Down Expand Up @@ -170,26 +170,25 @@ 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)"
test "install_all on an already-published version writes nothing — a read-only shared tree stays usable" do
Given "a published version 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"
Then "the marker was recognized and no write was attempted (the retired current-pointer " \
"rewrite crashed dev install-deps here with EACCES at the plans#36 ceremony)"
!File.exist?(File.join(install_dir, "current"))
integration.download_count == 0

Cleanup
Expand Down Expand Up @@ -351,7 +350,7 @@ def build_source_integration(tarball, project_root, cache_dir)
File.read(File.join(version_dir, "built.txt")) == "engine source"
File.read(File.join(version_dir, "version.txt")).strip == "5.6.1-release"
File.read(File.join(version_dir, ".dev-gh-release")) == "5.6.1-release"
File.readlink(File.join(install_dir, "current")) == "5.6.1-release"
!File.exist?(File.join(install_dir, "current"))
Dir.glob(File.join(install_dir, ".staging-*")).empty?
integration.download_count == 1

Expand Down
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