unprivileged mode: generate PORTAGE_DEPCACHEDIR

For unprivileged mode, if PORTAGE_DEPCACHEDIR is unset and the default
PORTAGE_DEPCACHEDIR setting does not refer to a writable directory
(or there are not sufficient permissions to create it), then
automatically make PORTAGE_DEPCACHEDIR relative to the current target
root (which should always be writable for unprivileged mode). Also, in
create_trees, propagate the automatically generated PORTAGE_DEPCACHEDIR
setting to the config instance that is instantiated for ROOT = "/".

The result is that unprivileged mode will get a writable
PORTAGE_DEPCACHEDIR by default, and the default can be overridden by
setting the PORTAGE_DEPCACHEDIR variable.

Fixes: 1364fcd ("Support unprivileged mode for bug #433453.")
X-Gentoo-Bug: 433453
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=433453
Acked-by: Alexander Berntsen <bernalex@gentoo.org>

pym/portage/__init__.py

@@ -570,6 +570,7 @@ def create_trees(config_root=None, target_root=None, trees=None, env=None,
 		env=env, eprefix=eprefix)
 	settings.lock()
 
+	depcachedir = settings.get('PORTAGE_DEPCACHEDIR')
 	trees._target_eroot = settings['EROOT']
 	myroots = [(settings['EROOT'], settings)]
 	if settings["ROOT"] == "/" and settings["EPREFIX"] == const.EPREFIX:
@@ -587,6 +588,8 @@ def create_trees(config_root=None, target_root=None, trees=None, env=None,
 			v = settings.get(k)
 			if v is not None:
 				clean_env[k] = v
+		if depcachedir is not None:
+			clean_env['PORTAGE_DEPCACHEDIR'] = depcachedir
 		settings = config(config_root=None, target_root="/",
 			env=clean_env, eprefix=None)
 		settings.lock()

pym/portage/package/ebuild/config.py

@@ -8,6 +8,7 @@
 ]
 
 import copy
+import errno
 from itertools import chain
 import grp
 import logging
@@ -826,16 +827,6 @@ def __init__(self, clone=None, mycpv=None, config_profile_path=None,
 			if "USE_ORDER" not in self:
 				self.backupenv["USE_ORDER"] = "env:pkg:conf:defaults:pkginternal:repo:env.d"
 
-			self.depcachedir = DEPCACHE_PATH
-			if portage.const.EPREFIX:
-				self.depcachedir = os.path.join(portage.const.EPREFIX,
-					DEPCACHE_PATH.lstrip(os.sep))
-
-			if self.get("PORTAGE_DEPCACHEDIR", None):
-				self.depcachedir = self["PORTAGE_DEPCACHEDIR"]
-			self["PORTAGE_DEPCACHEDIR"] = self.depcachedir
-			self.backup_changes("PORTAGE_DEPCACHEDIR")
-
 			if "CBUILD" not in self and "CHOST" in self:
 				self["CBUILD"] = self["CHOST"]
 				self.backup_changes("CBUILD")
@@ -898,6 +889,34 @@ def __init__(self, clone=None, mycpv=None, config_profile_path=None,
 					self[var] = default_val
 				self.backup_changes(var)
 
+			self.depcachedir = self.get("PORTAGE_DEPCACHEDIR")
+			if self.depcachedir is None:
+				self.depcachedir = os.path.join(os.sep,
+					portage.const.EPREFIX, DEPCACHE_PATH.lstrip(os.sep))
+				if unprivileged and target_root != os.sep:
+					# In unprivileged mode, automatically make
+					# depcachedir relative to target_root if the
+					# default depcachedir is not writable.
+					current_dir = self.depcachedir
+					found_dir = False
+					while current_dir != os.sep and not found_dir:
+						try:
+							os.stat(current_dir)
+							found_dir = True
+						except OSError as e:
+							if e.errno == errno.ENOENT:
+								current_dir = os.path.dirname(
+									current_dir)
+							else:
+								found_dir = True
+
+					if not os.access(current_dir, os.W_OK):
+						self.depcachedir = os.path.join(eroot,
+							DEPCACHE_PATH.lstrip(os.sep))
+
+			self["PORTAGE_DEPCACHEDIR"] = self.depcachedir
+			self.backup_changes("PORTAGE_DEPCACHEDIR")
+
 			if portage._internal_caller:
 				self["PORTAGE_INTERNAL_CALLER"] = "1"
 				self.backup_changes("PORTAGE_INTERNAL_CALLER")