We should also figure out if there are other parts of the build and test process that run up against this limit that we can also check for. Adding a few people who might know of them ...

In bug 609853, kojii noted that web-platform-tests has a check for max path length of 150. Specifically, the check is here: https://github.com/w3c/wpt-tools/blob/master/lint/lint.py#L46

I wonder whether folks would be OK with decreasing that limit, just based on the rationale that we're running into Windows path length issues here.

Anyway, that can be separate from adding a check to our importer to skip long path lengths and give warnings, for now.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e651182c099f9d0f3c8b106f762736051f15e3be

commit e651182c099f9d0f3c8b106f762736051f15e3be
Author: qyearsley <qyearsley@chromium.org>
Date: Fri May 13 23:11:24 2016

Check for and skip long paths when importing w3c tests.

BUG= 609871 

Review-Url: https://codereview.chromium.org/1970963002
Cr-Commit-Position: refs/heads/master@{#393679}

[modify] https://crrev.com/e651182c099f9d0f3c8b106f762736051f15e3be/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_importer.py
[modify] https://crrev.com/e651182c099f9d0f3c8b106f762736051f15e3be/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_importer_unittest.py

I think the whole Chromium repository should probably have a presubmit which prevents overly long paths ending up in the repository as a whole? (IE This problem isn't unique to w3c importing?)

See also  bug 612667  that tansell@ just filed that addresses my comment #1.

With ToT, I found update-w3c-deps skipped a reference file though it imported the corresponding test HTML.  

imported/wpt/html/dom/elements/requirements-relating-to-bidirectional-algorithm-formatting-characters/dir-isolation-002b-expected.html was skipped due to the long path length.
imported/wpt/html/dom/elements/requirements-relating-to-bidirectional-algorithm-formatting-characters/dir-isolation-002b.html was imported.

Dropping only -expected.html causes a test failure, of course.

I didn't think of that -- sounds like if we skip a reference, we should skip the corresponding test. Will make a follow-up CL.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2014d9ba913adaeae35027b2bed27a6f38fb278f

commit 2014d9ba913adaeae35027b2bed27a6f38fb278f
Author: qyearsley <qyearsley@chromium.org>
Date: Fri May 20 23:34:54 2016

W3C test importer: Skip importing files whose ref files would be too long.

BUG= 609871 

Review-Url: https://codereview.chromium.org/1997113002
Cr-Commit-Position: refs/heads/master@{#395202}

[modify] https://crrev.com/2014d9ba913adaeae35027b2bed27a6f38fb278f/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_importer.py

As it stands, skipping these tests by importer script is a silent act. This leads to head scratch moments for anyone trying to figure out why a wpt test in missing in Blink. Normally any test that is skipped has an entry in LayoutTests/W3CImportExpectations which is where one looks to find tests that are not imported. 

Base on my check, currently there are only 12 tests that hit this file name limit.

Couple of suggested ways to help (in my order of preference):

 1. Add a separate auto-generated expectations file that list these skipped files. Import script can generate this file and add it.

 2. Print these in the output of Tools/Scripts/update-w3c-deps. Right now you can see these sprinkled in the --verbose output but I think they should be printed out more prominently e.g., in normal output.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/706a4e2dceb1e19d8b74cff5a9cd8b04dc781b1d

commit 706a4e2dceb1e19d8b74cff5a9cd8b04dc781b1d
Author: majidvp <majidvp@chromium.org>
Date: Mon Jan 23 23:45:10 2017

Increase file path length limit for w3c test importer

Since the original limit was added the base path has been reduced by 15 chars.*
Increasing the limit by this amount allows us to import more tests without
breaking any existing windows bots.

* from 'imported/web-platform-tests' to 'external/wpt'

BUG= 609871 

Review-Url: https://codereview.chromium.org/2645323003
Cr-Commit-Position: refs/heads/master@{#445546}

[modify] https://crrev.com/706a4e2dceb1e19d8b74cff5a9cd8b04dc781b1d/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_importer.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/26d54578790fb151be4c68ff3a8fd7843695e624

commit 26d54578790fb151be4c68ff3a8fd7843695e624
Author: qyearsley <qyearsley@chromium.org>
Date: Wed Mar 01 04:55:17 2017

Remove long path check in test import process.

In this CL:
 - Remove code in test_copier.py related to long paths
 - Unskip tests that are skipped due to long paths

Context: https://codereview.chromium.org/2708883004/.

BUG= 609871 

Review-Url: https://codereview.chromium.org/2722843002
Cr-Commit-Position: refs/heads/master@{#453845}

[modify] https://crrev.com/26d54578790fb151be4c68ff3a8fd7843695e624/third_party/WebKit/LayoutTests/W3CImportExpectations
[modify] https://crrev.com/26d54578790fb151be4c68ff3a8fd7843695e624/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_copier.py
[modify] https://crrev.com/26d54578790fb151be4c68ff3a8fd7843695e624/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_copier_unittest.py