Fixed bad lzma tar ball detection

src/cygapt/cygapt.py

@@ -790,7 +790,7 @@ def _doInstallExternal(self, ball):
 
     def _doInstall(self):
         ball = self.getBall();
-        if cautils.is_tarfile(ball):
+        if cautils.is_tarfile(ball, self.__dosXz):
             if not self.__cygwinPlatform:
                 self._doInstallExternal(ball);
             tf = cautils.open_tarfile(ball, self.__dosXz);
@@ -1199,7 +1199,7 @@ def _doUnpack(self):
             ));
             return 1;
         os.mkdir(self.__pkgName);
-        if cautils.is_tarfile(ball):
+        if cautils.is_tarfile(ball, self.__dosXz):
             tf = cautils.open_tarfile(ball, self.__dosXz);
             tf.extractall(self.__pkgName);
             tf.close();

src/cygapt/test/fixtures/utils/README

@@ -9,3 +9,9 @@ cyglsa-bad1.dll : MZ header changed to ZM
 cyglsa-bad2.dll : PE\0\0 header changed to EP\0\0
 cyglsa-bad3.dll : machine value changed from 0x014C to 0xDEAD
 cyglsa-bad4.dll : truncated before PE header
+
+empty.tar.xz    : empty file
+emptytar.tar.xz : empty file with lzma compression
+valid.tar.xz    : empty file in a tarball with lzma compression 
+badtar.tar.xz   : corrupted tarball with lzma compression 
+badlzma.tar.xz  : corrupted lzma compression 

src/cygapt/test/test_utils.py

@@ -430,6 +430,35 @@ def _successOpenTarfile(self, pkgname, xzPath="xz"):
 
         self.assertEqual(sorted(filelist), sorted(self._var_setupIni.__dict__[pkgname].filelist));
 
+    @dataProvider('getIsTarfileData')
+    def testIsTarfile(self, filename, expected):
+        fn = os.path.join(__DIR__, 'fixtures', 'utils', filename);
+        self.assertTrue(utils.is_tarfile(fn) is expected);
+        self.assertFalse(os.path.exists(os.path.splitext(fn)[0]));
+
+    def getIsTarfileData(self):
+        return [
+            ['badtar.tar.xz', False],
+            ['empty.tar.xz', False],
+            ['valid.tar.xz', True],
+            ['emptytar.tar.xz', True],
+        ];
+
+    @dataProvider('getIsTarfileData')
+    def testIsTarfileWithoutPATH(self, filename, expected):
+        if not sys.platform.startswith("cygwin") and not sys.platform.startswith("linux") :
+            self.skipTest("requires cygwin or linux");
+
+        fn = os.path.join(__DIR__, 'fixtures', 'utils', filename);
+        old_path = os.environ['PATH'];
+
+        try:
+            os.environ['PATH'] = "";
+            self.assertTrue(utils.is_tarfile(fn, '/usr/bin/xz') is expected);
+            self.assertFalse(os.path.exists(os.path.splitext(fn)[0]));
+        finally:
+            os.environ['PATH'] = old_path;
+
     @dataProvider('getPEArchitectureData')
     def testPEArchitecture(self, filename, expected):
         fn = os.path.join(__DIR__, 'fixtures', 'utils', filename);

src/cygapt/utils.py

@@ -30,6 +30,7 @@
 from cygapt.url_opener import CygAptURLopener;
 from cygapt.structure import ConfigStructure;
 from cygapt.process import Process;
+from cygapt.process.exception import ProcessFailedException;
 
 def cygpath(path):
     p = Process(["cygpath", path]);
@@ -97,7 +98,18 @@ def open_tarfile(ball, xzPath='xz'):
         ball = ball[:-3]; # remove .xz extension
         remove_if_exists(ball);
         Process([xzPath, '-k', '-d', ball_orig]).mustRun();
-    tf = tarfile.open(ball);
+        # an empty tarball is valid
+        if 0 == os.path.getsize(ball) :
+            with tarfile.open(ball, 'w'):
+                pass;
+    try:
+        tf = tarfile.open(ball);
+    except tarfile.TarError:
+        if ball_orig != ball:
+            remove_if_exists(ball);
+
+        raise;
+
     if ball_orig != ball:
         tf_close_orig = tf.close;
         def tf_close():
@@ -107,8 +119,14 @@ def tf_close():
         tf.close = tf_close;
     return tf;
 
-def is_tarfile(ball):
-    return ball.lower().endswith('.tar.xz') or tarfile.is_tarfile(ball);
+def is_tarfile(ball, xzPath='xz'):
+    try:
+        open_tarfile(ball, xzPath).close();
+        return True;
+    except tarfile.TarError:
+        return False;
+    except ProcessFailedException:
+        return False;
 
 def prsort(lst):
     lst.sort();