Use LocalWPT.test_patch when filtering exportable commits

third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
index d7217c0999415007a3f5e9ea49322a3559e2f160..c0e17d4f7d1514a60052283f6a611eee0f65c892 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
@@ -6,6 +6,7 @@
 
 import logging
 
+from webkitpy.common.system.executive import ScriptError
 from webkitpy.w3c.chromium_commit import ChromiumCommit
 
 WPT_REPO_URL = 'https://chromium.googlesource.com/external/w3c/web-platform-tests.git'
@@ -107,6 +108,32 @@ class LocalWPT(object):
 
         return branch_name
 
+    def test_patch(self, patch):
+        """Returns the expected output of a patch agains origin/master.

[qyearsley, 2016/12/22 22:04:54]

Nit: agains -> against

+
+        Args:
+            patch: The patch to test against.
+
+        Returns:
+            A string containing the diff the patch produced.

[qyearsley, 2016/12/22 22:04:54]

Sometimes I'm confused about the words "diff" and "patch".

Sometimes a patch is a diff and a diff is a patch (i.e. the output of `git diff`
or `diff`), but there are different types of diffs and patch can sometimes mean
other things.

Even if this method isn't very testable because it because involves interacting
with external systems (the filesystem and git subprocesses), it might be nice to
see a simple example input and output.

Also: I'm not sure if it's a good idea, but in scm_unittest.py, it actually
creates a real git repo in a temp dir to do testing (see:
https://codereview.chromium.org/2594513003). That kind of test may also be
possible for some methods of LocalWPT?

[jeffcarp, 2016/12/22 23:14:29]

Hm what do you suggest re: diff/patch?

That sounds like a good idea but I'd like to do that after I transfer things to
webkitpy.common.checkout.git.Git. I can make a bug for it.

[qyearsley, 2016/12/22 23:19:53]

I was wondering if you could put an example (very short) input and output that
this might produce, depending on the state of origin/master -- if the files in
WPT at origin/master is the same as Chromium was before the Chromium CL, then
the input and output would be very similar, right?

But then if WPT has been updated since the time when the Chromium CL was made,
then there may or may not be a conflict, and if there's no conflict, the output
diff might be different from the input diff?

+        """
+        self.clean()
+
+        # Remove Chromium WPT directory prefix.
+        # TODO(jeffcarp): dedupe

[qyearsley, 2016/12/22 22:04:54]

Dedupe what?

[jeffcarp, 2016/12/22 23:14:29]

Oops it was already deduped.

+        patch = patch.replace(CHROMIUM_WPT_DIR, '')
+
+        try:
+            self.run(['git', 'apply', '-'], input=patch)
+            self.run(['git', 'add', '.'])
+            output = self.run(['git', 'diff', 'origin/master'])
+        except ScriptError as error:
+            _log.error('Error while applying patch: %s', error)
+            output = ''
+
+        self.clean()
+        return output
+
     def commits_behind_master(self, commit):
         """Returns the number of commits after the given commit on origin/master.