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Add a "blacklisted methods" test #7166
Description
The following async file I/O methods should never be called -- they create undue overhead in the async wiring required to accomplish them, and their corresponding sync versions require minimal overhead.
-
File.lastModified() -
FileSystemEntity.isDirectory() -
FileSystemEntity.isFile() -
FileSystemEntity.isLink() -
FileSystemEntity.type() -
FileSystemEntity.exists() -
FileSystemEntity.stat()
We should convert all existing uses of these methods (in flutter_tools - we don't use them in the framework) to use the sync versions, and we should add a test that ensures we don't re-introduce them. Over time, if any other such methods come up, we can just add them to this method blacklist.
Activity
tvolkert commentedon Dec 6, 2016
/cc @danrubel
Hixie commentedon Dec 6, 2016
We should definitely either always use one or always use the other.
Having said that, some people use NFS, and NFS can take a long time to return from these calls...
danrubel commentedon Dec 8, 2016
Landed a new lint to discourage use of specific async i/o methods
johnmccutchan commentedon Dec 8, 2016
@danrubel nice!
Update analysis options (#8203)
Hixie commentedon Jan 8, 2018
I was running the linter over some code recently and ran into this lint.
I'm not convinced this is actually a good idea. Won't these methods risk entirely locking up the app when run on networked file systems or file systems with bad disks?
tvolkert commentedon Jan 8, 2018
They'll lock up the app to the extent that the syscalls hang (whereas with async, we could add a timeout). So bottom-line: yes.
That said, for local disk access, what spawned this issue is that @johnmccutchan and I were seeing real slowdowns in the Flutter tool due to the use of these async ops (in loops, for instance) -- where converting to sync calls saved a few hundred milliseconds.
Hixie commentedon Jan 8, 2018
A difficult trade-off. We definitely have users on NFS, but we also have many users on local disks...
github-actions commentedon Aug 8, 2021
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flutter doctor -vand a minimal reproduction of the issue.