Check binary existence in gclient: 2nd try.

The first approach crrev.com/132446 was reverted due to
Windows build breaks. This approach is more robust because
it actually tests the binary by running the command actually.

BUG=114483
TEST=succeeded on Linux

Review URL: http://codereview.chromium.org/10103024

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@132783 0039d316-1c4b-4281-b951-d872f2087c98

gclient_scm.py

@@ -85,7 +85,10 @@ def CreateSCM(url, root_dir=None, relpath=None):
   scm_name = GetScmName(url)
   if not scm_name in SCM_MAP:
     raise gclient_utils.Error('No SCM found for url %s' % url)
-  return SCM_MAP[scm_name](url, root_dir, relpath)
+  scm_class = SCM_MAP[scm_name]
+  if not scm_class.BinaryExists():
+    raise gclient_utils.Error('%s command not found' % scm_name)
+  return scm_class(url, root_dir, relpath)
 
 
 # SCMWrapper base class
@@ -133,6 +136,18 @@ class GitWrapper(SCMWrapper):
       url = url[4:]
     SCMWrapper.__init__(self, url, root_dir, relpath)
 
+  @staticmethod
+  def BinaryExists():
+    """Returns true if the command exists."""
+    try:
+      # We assume git is newer than 1.7.  See: crbug.com/114483
+      result, version = scm.GIT.AssertVersion('1.7')
+      if not result:
+        raise gclient_utils.Error('Git version is older than 1.7: %s' % version)
+      return result
+    except OSError:
+      return False
+
   def GetRevisionDate(self, revision):
     """Returns the given revision's date in ISO-8601 format (which contains the
     time zone)."""
@@ -775,6 +790,17 @@ class GitWrapper(SCMWrapper):
 class SVNWrapper(SCMWrapper):
   """ Wrapper for SVN """
 
+  @staticmethod
+  def BinaryExists():
+    """Returns true if the command exists."""
+    try:
+      result, version = scm.SVN.AssertVersion('1.4')
+      if not result:
+        raise gclient_utils.Error('SVN version is older than 1.4: %s' % version)
+      return result
+    except OSError:
+      return False
+
   def GetRevisionDate(self, revision):
     """Returns the given revision's date in ISO-8601 format (which contains the
     time zone)."""

tests/gclient_scm_test.py

@@ -64,11 +64,17 @@ class BaseTestCase(GCBaseTestCase, SuperMoxTestBase):
     self.mox.StubOutWithMock(subprocess2, 'Popen')
     self._scm_wrapper = gclient_scm.CreateSCM
     gclient_scm.scm.SVN.current_version = None
+    self._original_SVNBinaryExists = gclient_scm.SVNWrapper.BinaryExists
+    self._original_GitBinaryExists = gclient_scm.GitWrapper.BinaryExists
+    gclient_scm.SVNWrapper.BinaryExists = staticmethod(lambda : True)
+    gclient_scm.GitWrapper.BinaryExists = staticmethod(lambda : True)
     # Absolute path of the fake checkout directory.
     self.base_path = join(self.root_dir, self.relpath)
 
   def tearDown(self):
     SuperMoxTestBase.tearDown(self)
+    gclient_scm.SVNWrapper.BinaryExists = self._original_SVNBinaryExists
+    gclient_scm.GitWrapper.BinaryExists = self._original_GitBinaryExists
 
 
 class SVNWrapperTestCase(BaseTestCase):
@@ -94,6 +100,7 @@ class SVNWrapperTestCase(BaseTestCase):
 
   def testDir(self):
     members = [
+        'BinaryExists',
         'FullUrlForRelativeUrl',
         'GetRevisionDate',
         'GetUsableRev',
@@ -750,16 +757,23 @@ from :3
     self.base_path = join(self.root_dir, self.relpath)
     self.enabled = self.CreateGitRepo(self.sample_git_import, self.base_path)
     StdoutCheck.setUp(self)
+    self._original_GitBinaryExists = gclient_scm.GitWrapper.BinaryExists
+    self._original_SVNBinaryExists = gclient_scm.SVNWrapper.BinaryExists
+    gclient_scm.GitWrapper.BinaryExists = staticmethod(lambda : True)
+    gclient_scm.SVNWrapper.BinaryExists = staticmethod(lambda : True)
 
   def tearDown(self):
     StdoutCheck.tearDown(self)
     TestCaseUtils.tearDown(self)
     unittest.TestCase.tearDown(self)
     rmtree(self.root_dir)
+    gclient_scm.GitWrapper.BinaryExists = self._original_GitBinaryExists
+    gclient_scm.SVNWrapper.BinaryExists = self._original_SVNBinaryExists
 
 class ManagedGitWrapperTestCase(BaseGitWrapperTestCase):
   def testDir(self):
     members = [
+        'BinaryExists',
         'FullUrlForRelativeUrl',
         'GetRevisionDate',
         'GetUsableRev',