Add createDirectory() to MemoryFileSystemEntity.

Add createDirectory() to MemoryFileSystemEntity.

We need this API to create a mock SDK in a way that makes
ProcessedOptions.validateOptions() to accept it - the SDK root
must exist.

Alternatively (or in addition to) we could make writeXYZ create parent
directories implicitly. So, to "create" a directory, you would need
to create a file in this directory.

R=ahe@google.com, paulberry@google.com, sigmund@google.com
BUG=

Committed: https://github.com/dart-lang/sdk/commit/41bcfaa4a46aa1b90849fdc97950f2f53dd4e72b

[Paul Berry, 2017-08-04 17:27:23]

A counterintuitive behavior of this CL is that you can successfully write a
"file" to the memory file system even if its parent "directory" doesn't exist,
and the parent directory continues to not exist.  That could confuse people.

So I might personally favor the alternative you mentioned, where writing a file
implicitly creates parent directories.

But since the memory file system is basically only used for testing, I don't
think it matters that much.  lgtm either way.

[scheglov, 2017-08-04 18:45:31]

Description was changed from

==========
Add createDirectory() to MemoryFileSystemEntity.

We need this API to create a mock SDK in a way that makes
ProcessedOptions.validateOptions() to accept it - the SDK root
must exist.

Alternatively (or in addition to) we could make writeXYZ create parent
directories implicitly. So, to "create" a directory, you would need
to create a file in this directory.

R=ahe@google.com, paulberry@google.com, sigmund@google.com
BUG=
==========

to

==========
Add createDirectory() to MemoryFileSystemEntity.

We need this API to create a mock SDK in a way that makes
ProcessedOptions.validateOptions() to accept it - the SDK root
must exist.

Alternatively (or in addition to) we could make writeXYZ create parent
directories implicitly. So, to "create" a directory, you would need
to create a file in this directory.

R=ahe@google.com, paulberry@google.com, sigmund@google.com
BUG=

Committed:
https://github.com/dart-lang/sdk/commit/41bcfaa4a46aa1b90849fdc97950f2f53dd4e72b
==========

[scheglov, 2017-08-04 18:45:33]

Committed patchset #1 (id:1) manually as
41bcfaa4a46aa1b90849fdc97950f2f53dd4e72b (presubmit successful).

[Siggi Cherem (dart-lang), 2017-08-05 03:08:41]

lgtm - btw we have some unit tests in processed_options_test that were working
around this by writing the directories as if they were empty files. I should go
back and fix those to use createDirectory instead.

[scheglov, 2017-08-06 18:16:39]

On 2017/08/05 03:08:41, Siggi Cherem (dart-lang) wrote:
> lgtm - btw we have some unit tests in processed_options_test that were working
> around this by writing the directories as if they were empty files. I should
go
> back and fix those to use createDirectory instead.

OK, see https://codereview.chromium.org/2994683002 for this change.