[gentoo-portage-dev] [PATCH v2] install-qa-check: Do not install empty directories

[Michał Górny]

Remove empty directories in install-qa-check phase in order to prevent
Portage from installing them, and therefore from developers relying
on them being installed.

The PMS specifies the behavior upon merging empty directories
as undefined, and specifically prohibits ebuilds from attempting
to install empty directories. However, ebuilds occasionally still fall
into the trap of relying on 'dodir' preserving the directory. Make
the Portage behavior more strict in order to prevent that.

Use 'install-qa-check.d' machinery for this as this provides an easy way
for users to restore the old behavior (by overriding the check) if they
need it for their private ebuilds. It also makes it possible to extend
the check with some QA warnings, if we figure out how to do them.

Currently no QA warnings are emitted as we do not want to pursue
upstream build systems that create empty directories but the packages
themselves do not rely on them being installed, e.g. when some files
are installed into the directory conditionally.
---
 bin/install-qa-check.d/95empty-dirs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 bin/install-qa-check.d/95empty-dirs

diff --git a/bin/install-qa-check.d/95empty-dirs b/bin/install-qa-check.d/95empty-dirs
new file mode 100644
index 000000000..92f3da86d
--- /dev/null
+++ b/bin/install-qa-check.d/95empty-dirs
@@ -0,0 +1,25 @@
+# Remove empty directories installed by ebuild.
+
+# Rationale: PMS prohibits ebuilds from installing empty directories.
+# Cleaning them up from the installation image provides an easy way
+# to make sure that ebuilds are not relying on it while making it easy
+# for users to override this if they need to.
+#
+# The ebuilds that need to preserve empty directories should use keepdir
+# as documented e.g.:
+# https://devmanual.gentoo.org/function-reference/install-functions/index.html
+#
+# Technically, we could emit QA warnings here. However, we do not want
+# to pursue every upstream build system that creates a directory
+# and does not install any file into it (think of files installed
+# conditionally), as long as the package functions correctly without
+# the directory being actually installed.
+
+strip_empty_dirs() {
+	find "${ED}" -mindepth 1 -type d -empty -delete
+}
+
+strip_empty_dirs
+: # guarantee successful exit
+
+# vim:ft=sh
-- 
2.16.0.rc1