[jhbuild/desrt/master: 20/22] packagedb: use info/ files as authoritative source

[Ryan Lortie <desrt src gnome org>]

commit a9ee3b8b26f379f8e8dd5a292b47276b770e914a
Author: Ryan Lortie <desrt desrt ca>
Date:   Sun Jan 18 10:29:36 2015 -0500

    packagedb: use info/ files as authoritative source
    
    Move over to using the individual files in info/ as an authoritative
    source for package information, falling back to the packagedb.xml file
    only in the case that we can't find such a file.
    
    We no longer update the packagedb.xml file.
    
    In order to ensure that we don't detect stale packagedb.xml entries as
    installed packages, ensure that we only fall back to reading an entry
    from that file if we are missing an info/ file but have a manifests/
    file.
    
    This commits removes caching of the packages in the _entries variable
    and therefore also removes the code for statting in order to see if the
    cache needs to be updated.  Since we no longer write to the file, we
    also remove the need for locking.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=743127

 jhbuild/utils/packagedb.py |  145 +++++++++++++++-----------------------------
 1 files changed, 49 insertions(+), 96 deletions(-)
---
diff --git a/jhbuild/utils/packagedb.py b/jhbuild/utils/packagedb.py
index d3688cf..467e1a2 100644
--- a/jhbuild/utils/packagedb.py
+++ b/jhbuild/utils/packagedb.py
@@ -18,18 +18,16 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 import os
-import sys 
-import stat
+import sys
 import time
 import logging
+import errno
 import xml.dom.minidom as DOM
 try:
     import hashlib
 except ImportError:
     import md5 as hashlib
 
-from jhbuild.utils import lockfile
-
 try:
     import xml.etree.ElementTree as ET
 except ImportError:
@@ -125,96 +123,53 @@ class PackageEntry:
 
         return dbentry
 
+    @classmethod
+    def open(cls, dirname, package):
+        try:
+            info = open (os.path.join (dirname, 'info', package))
+            doc = ET.parse(info)
+            node = doc.getroot()
+
+            if node.tag == 'entry':
+                return PackageEntry.from_xml(node, dirname)
+
+        except EnvironmentError as e:
+            if e.errno != errno.ENOENT:
+                raise
+
+        # That didn't work: try the old packagedb.xml file instead.  We
+        # use the manifest file to check if the package 'really exists'
+        # because otherwise we may see the old packagedb.xml entry for
+        # an uninstalled package (since we no longer update that file)
+        #
+        # please delete this code in 2016
+        try:
+            if os.path.exists(os.path.join(dirname, 'manifests', package)):
+                info = open (os.path.join (dirname, 'packagedb.xml'))
+                doc = ET.parse(info)
+                root = doc.getroot()
+
+                if root.tag == 'packagedb':
+                    for node in root:
+                        if node.tag == 'entry' and node.attrib['package'] == package:
+                            return PackageEntry.from_xml(node, dirname)
+
+        except EnvironmentError as e:
+            if e.errno != errno.ENOENT:
+                raise
+
+        # it seems not to exist...
+        return None
 
 class PackageDB:
     def __init__(self, dbfile, config):
         self.dirname = os.path.dirname(dbfile)
-        self.dbfile = dbfile
         self.config = config
-        self._lock = lockfile.LockFile.get(os.path.join(dirname, 'packagedb.xml.lock'))
-        self._entries = None # hash
-        self._entries_stat = None # os.stat structure
-
-    def _ensure_cache(function):
-        def decorate(self, *args, **kwargs):
-            if self._entries is None:
-                self._read_cache()
-            elif self._entries_stat is None:
-                # It didn't exist before, see if it does now
-                self._read_cache()
-            else:
-                try:
-                    stbuf = os.stat(self.dbfile)
-                except OSError, e:
-                    pass
-                if not (self._entries_stat[stat.ST_INO] == stbuf[stat.ST_INO]
-                        and self._entries_stat[stat.ST_MTIME] == stbuf[stat.ST_MTIME]):
-                    logging.info(_('Package DB modified externally, rereading'))
-                    self._read_cache()
-            return function(self, *args, **kwargs)
-        return decorate
-
-    def _read_cache(self):
-        self._entries = {}
-        self._entries_stat = None
-        try:
-            f = open(self.dbfile)
-        except OSError, e:
-            return # treat as empty cache
-        except IOError, e:
-            return
-        doc = ET.parse(f)
-        root = doc.getroot()
-        if root.tag != 'packagedb':
-            return # doesn't look like a cache
-        for node in root:
-            if node.tag != 'entry':
-                continue
-            entry = PackageEntry.from_xml(node, self.dirname)
-            self._entries[entry.package] = entry
-        self._entries_stat = os.fstat(f.fileno())
-
-    def _write_cache(self):
-        pkgdb_node = ET.Element('packagedb')
-        doc = ET.ElementTree(pkgdb_node)
-        for package,entry in self._entries.iteritems():
-            node = entry.to_xml()
-            pkgdb_node.append(node)
-
-        writer = fileutils.SafeWriter(self.dbfile)
-
-        # Because ElementTree can't pretty-print, we convert it to a string
-        # and then read it back with DOM, then write it out again.  Yes, this
-        # is lame.
-        # http://renesd.blogspot.com/2007/05/pretty-print-xml-with-python.html
-        buf = StringIO()
-        doc.write(buf, encoding='UTF-8')
-        dom_doc = DOM.parseString(buf.getvalue())
-        try:
-            dom_doc.writexml(writer.fp, addindent='  ', newl='\n', encoding='UTF-8')
-        except:
-            writer.abandon()
-            raise
-        writer.commit()
-        # Ensure we don't reread what we already have cached
-        self._entries_stat = os.stat(self.dbfile)
-
-    def _locked(function):
-        def decorate(self, *args, **kwargs):
-            self._lock.lock()
-            try:
-                function(self, *args, **kwargs)
-            finally:
-                self._lock.unlock()
-        return decorate
-
-    @_ensure_cache
+
     def get(self, package):
         '''Return entry if package is installed, otherwise return None.'''
-        return self._entries.get(package)
+        return PackageEntry.open(self.dirname, package)
 
-    @_ensure_cache
-    @_locked
     def add(self, package, version, contents, configure_cmd = None):
         '''Add a module to the install cache.'''
         entry = self.get(package)
@@ -225,10 +180,9 @@ class PackageDB:
         metadata['installed-date'] = time.time() # now
         if configure_cmd:
             metadata['configure-hash'] = hashlib.md5(configure_cmd).hexdigest()
-        self._entries[package] = PackageEntry(package, version, metadata, self.dirname)
-        self._entries[package].manifest = contents
-        self._entries[package].write()
-        self._write_cache()
+        pkg = PackageEntry(package, version, metadata, self.dirname)
+        pkg.manifest = contents
+        pkg.write()
 
     def check(self, package, version=None):
         '''Check whether a particular module is installed.'''
@@ -248,11 +202,12 @@ class PackageDB:
             return None
         return entry.metadata['installed-date']
 
-    @_ensure_cache
-    @_locked
     def uninstall(self, package_name):
         '''Remove a module from the install cache.'''
-        entry = self._entries[package_name]
+        entry = self.get(package_name)
+
+        if entry is None:
+            raise KeyError
 
         if entry.manifest is None:
             logging.error(_("no manifest for '%s', can't uninstall.  Try building again, then 
uninstalling.") % (package_name,))
@@ -275,6 +230,4 @@ class PackageDB:
                 logging.warn(_("Failed to delete %(file)r: %(msg)s") % { 'file': path,
                                                                          'msg': error_string})
 
-        self._entries[package_name].remove()
-        del self._entries[package_name]
-        self._write_cache()
+        entry.remove()