test262 file path limit on Windows

[Tekman]

Hi,

There were a few test files added in test262 that push the total path size beyond the 260 character limit on Windows machines; unfortunately, that makes it very difficult to build v8 because gclient sync fails with a "You have unstaged changes" error in test262, caused by the missing files.

If I try to manually run 'git reset --hard' in test262, this is what I'm seeing:

D:\work\engine\v8\test\test262\data>git reset --hard

error: unable to create file test/built-ins/String/prototype/split/arguments-are-objects-and-instance-is-string-first-object-have-overrided-to-string-function-and-value-of-function-that-throw-exception-second-object-have-overrided-value-of-function-that-throw-exception.js: Filename too long

error: unable to create file test/built-ins/String/prototype/split/arguments-are-objects-and-instance-is-string-first-object-have-overrided-to-string-function-second-object-have-overrided-value-of-function-and-to-string-function-that-throw-exception.js: Filename too long

error: unable to create file test/built-ins/String/prototype/split/arguments-are-objects-and-instance-is-string-first-object-have-overrided-to-string-function-that-throw-exception-second-object-have-overrided-value-of-function-that-throw-exception.js: Filename too long

fatal: Could not reset index file to revision 'HEAD'.

The repro steps are literally just running `fetch v8`, which fails with this error message:

v8\test\test262\data (ERROR)

----------------------------------------

[0:00:00] Started.

[0:00:01] Finished running: git config remote.origin.url

[0:00:01] Finished running: git rev-list -n 1 HEAD

[0:00:01] Finished running: git rev-parse --abbrev-ref=strict HEAD

----------------------------------------

Error: 12>

12> ____ v8\test\test262\data at ad8a5e9940ee60d1ecb6e150b7aecf09b17545dd

12>     You have unstaged changes.

12>     Please commit, stash, or reset.

Subprocess failed with return code 1.

Any tips about how to resolve this? It looks like on Windows 10 there is a registry hack to support filepaths longer than 260 characters, but that won't work on older Windows versions and it'll be a pain to configure in CI environments without administrative control. Can I temporarily hold back test262?

Thank you!

[Tekman]

It looks like this is the change that renamed the files and introduced the issue: https://chromium.googlesource.com/external/github.com/tc39/test262.git/+/834789514d095d8055cdb12e2b4df40fedd5f5e7

FWIW, it looks like this can be worked around locally in Windows 10 by using Group Policy to turn on "Enable Win32 long paths" in Computer Configuration > Administrative Templates > System > Filesystem and running `git config --system core.longpaths true` from an administrative command prompt. I didn't find a solution for CI loops (build agents) though.

[Julio César Rocha]

Out of curiosity, why wouldn't that approach work on CI build agents, if the ones in Azure Pipelines usually allow Administrator privileges?

[Julio César Rocha]

Another alternate approach is to do a partial checkout (omit a repo subtree).

Git supports it, but I'm not sure if this can be done in gclient. Taking a look...

[Tekman]

The repro for this issue is literally running `fetch v8` on a Windows machine; follow the official build instructions and when reaching the fetch v8 step, you'll see this error:

v8\test\test262\data (ERROR)

----------------------------------------

[0:00:00] Started.

[0:00:01] Finished running: git config remote.origin.url

[0:00:01] Finished running: git rev-list -n 1 HEAD

[0:00:01] Finished running: git rev-parse --abbrev-ref=strict HEAD

----------------------------------------

Error: 12>

12> ____ v8\test\test262\data at ad8a5e9940ee60d1ecb6e150b7aecf09b17545dd

12>     You have unstaged changes.

12>     Please commit, stash, or reset.

Am I not looking at the right instructions for building V8?