[gentoo-portage-dev] [PATCH] emerge: check for writable PKGDIR (490732)

[Zac Medico]

If there are packages to be merged and "buildpkg" or "buildsyspkg" is
enabled, then bail out early if PKGDIR is not writable (in order to
avoid a fatal EROFS error which would otherwise occur later on).
Behavior remains unchanged for --pretend, --fetchonly and
--fetch-all-uri. For --ask, it will bail out just after the last
relevant --ask prompt.

X-Gentoo-Bug: 490732
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=490732
---
 pym/_emerge/actions.py       | 28 ++++++++++++++++++++++++++--
 pym/portage/dbapi/bintree.py | 12 ++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/pym/_emerge/actions.py b/pym/_emerge/actions.py
index 6f7dfe0..dec5b04 100644
--- a/pym/_emerge/actions.py
+++ b/pym/_emerge/actions.py
@@ -428,7 +428,18 @@ def action_build(settings, trees, mtimedb,
 			# least show warnings about missed updates and such.
 			mydepgraph.display_problems()
 
-		if not Scheduler._opts_no_self_update.intersection(myopts):
+
+		need_write_vardb = not Scheduler. \
+			_opts_no_self_update.intersection(myopts)
+
+		need_write_bindb = not any(x in myopts for x in
+			("--fetchonly", "--fetch-all-uri", "--pretend")) and \
+			(any("buildpkg" in trees[eroot]["root_config"].
+				settings.features for eroot in trees) or
+			any("buildsyspkg" in trees[eroot]["root_config"].
+				settings.features for eroot in trees))
+
+		if need_write_bindb or need_write_vardb:
 
 			eroots = set()
 			for x in mydepgraph.altlist():
@@ -436,13 +447,26 @@ def action_build(settings, trees, mtimedb,
 					eroots.add(x.root)
 
 			for eroot in eroots:
-				if not trees[eroot]["vartree"].dbapi.writable:
+				if need_write_vardb and \
+					not trees[eroot]["vartree"].dbapi.writable:
 					writemsg_level("!!! %s\n" %
 						_("Read-only file system: %s") %
 						trees[eroot]["vartree"].dbapi._dbroot,
 						level=logging.ERROR, noiselevel=-1)
 					return 1
 
+				if need_write_bindb and \
+					("buildpkg" in trees[eroot]["root_config"].
+					settings.features or
+					"buildsyspkg" in trees[eroot]["root_config"].
+					settings.features) and \
+					not trees[eroot]["bintree"].dbapi.writable:
+					writemsg_level("!!! %s\n" %
+						_("Read-only file system: %s") %
+						trees[eroot]["bintree"].pkgdir,
+						level=logging.ERROR, noiselevel=-1)
+					return 1
+
 		if ("--resume" in myopts):
 			favorites=mtimedb["resume"]["favorites"]
 
diff --git a/pym/portage/dbapi/bintree.py b/pym/portage/dbapi/bintree.py
index a5d7ac9..b56c8c1 100644
--- a/pym/portage/dbapi/bintree.py
+++ b/pym/portage/dbapi/bintree.py
@@ -18,6 +18,7 @@ portage.proxy.lazyimport.lazyimport(globals(),
 	'portage.util:atomic_ofstream,ensure_dirs,normalize_path,' + \
 		'writemsg,writemsg_stdout',
 	'portage.util.listdir:listdir',
+	'portage.util.path:first_existing',
 	'portage.util._urlopen:urlopen@_urlopen',
 	'portage.versions:best,catpkgsplit,catsplit,_pkg_str',
 )
@@ -85,6 +86,17 @@ class bindbapi(fakedbapi):
 		self._aux_cache_slot_dict = slot_dict_class(self._aux_cache_keys)
 		self._aux_cache = {}
 
+	@property
+	def writable(self):
+		"""
+		Check if PKGDIR is writable, or permissions are sufficient
+		to create it if it does not exist yet.
+		@rtype: bool
+		@return: True if PKGDIR is writable or can be created,
+			False otherwise
+		"""
+		return os.access(first_existing(self.bintree.pkgdir), os.W_OK)
+
 	def match(self, *pargs, **kwargs):
 		if self.bintree and not self.bintree.populated:
 			self.bintree.populate()
-- 
2.0.4