Rename and rework File::Stat as File::Info #5584

RX14 · 2018-01-13T22:39:30Z

I've aimed to make File::Info easier to use, more portable, and nicer than File::Stat.

straight-shoota · 2018-01-13T22:48:30Z

src/crystal/system/unix/file.cr

+    flags |= ::File::Flags::SetGroup if (stat.st_mode & LibC::S_ISGID) != 0
+    flags |= ::File::Flags::Sticky if (stat.st_mode & LibC::S_ISVTX) != 0
+
+    modification_time = ::Time.new(stat.st_mtim, ::Time::Kind::Utc)


you should better use ::Time.utc

st_mtim is a LibC::Timespec. You can't use Time.utc.

lbguilherme · 2018-01-13T23:23:03Z

src/file.cr

@@ -16,7 +16,7 @@ class File < IO::FileDescriptor
  {% end %}

  # :nodoc:
-  DEFAULT_CREATE_MODE = LibC::S_IRUSR | LibC::S_IWUSR | LibC::S_IRGRP | LibC::S_IROTH
+  DEFAULT_CREATE_PERMISSIONS = 0o644


Maybe it is better to use File::Permissions.flags(OwnerRead, OwnerWrite, GroupRead, OtherRead) here?

I don't think so, the shorter octal syntax is far easier to read. "everyone" knows unix octal permission syntax.

Then why bother with a File::Permissions enum?

asterite · 2018-01-13T23:31:29Z

src/file/info.cr

+  # The binary representation of this enum is defined to be same representation
+  # as the permission bits of a unix `st_mode` field. `File::Permissions`
+  # can also be compared to it's underlying bitset, for example
+  # `File::Permissions::All == 0o777` will always be `true`.


What about the opposite? Does 0o777 == File::Permissions::All work?

Also, maybe always isn't necessary here.

Ah, yeah. Perhaps this equality was a bad idea. Or should I just reopen struct Int? It's a bit ugly how these equalities are defined in two places.

asterite

Looks awesome! And much cleaner than before. Plus the inspect of permissions is really nice. Thank you!

RX14 · 2018-01-14T00:21:00Z

@asterite yeah, while debugging I found that I really wanted to be able to see the permissions better so I just implemented it!

ysbaddaden

Instead of always evaluating and copying to populate a generic struct with lots of data —which misses information btw, such as the creation time for the most obvious one— we could keep the simple wrapper over C structs.

If all I need is accessing the mtime for thousands of files, I'd like to avoid copying data for each and every file, or just checking over and over if it's a file, symlink or something else (pointless).

ysbaddaden · 2018-01-14T01:46:34Z

src/file/info.cr

+
+    # :nodoc:
+    def initialize(@size, @permissions, @type, @flags, @modification_time, @owner, @group)
+    end


It lost query methods, such as symlink?, file?, ... which is an unwelcomed change.

It's just type.file? now. The functionality is still there.

We could think about forwarding these methods to type similar to the weekday names in Time. Allthough this would effectively be aliases. But the API would be simpler that way. You shouldn't have to write type in between to ask a File::Info if it describes a symlink.

Why not? It's really just some extra typing and it means you have a clear separation between permissions, types, and flags on files. Which I think is really nice.

I see your argument. But I think that's too bulky.

Why not use delegate here?

RX14 · 2018-01-14T11:37:09Z

@ysbaddaden Information has been intentionally left out to make it portable. atime is disabled on most modern distros, either with relatime or noatime mount options (and nobody uses it) and ctime is usually not what people want or think it is (they want btime which basically no filesystems support). mtime is really the only widely supported and actually useful time. Go only provides modification time too.

I'll benchmark old stat vs new stat but i'm not sure that a bit of bit twiddling is going to make much difference when put next to the price of a syscall, and making it wrap LibC::Stat would move platform-specifics into the definition of File::Info instead of just the construction. Keep in mind that on windows I'm not going to be using LibC::Stat at all, but recostructing the same information from GetFileInformationByHandle.

RX14 · 2018-01-14T11:47:41Z

Benchmarks say it doesn't matter much. I'd definitely say it's not worth optimizing for a while.

old:

 File.stat   1.77M (565.92ns) (± 4.62%)  0 B/op   1.77× slower
File.lstat   1.76M (568.21ns) (± 4.58%)  0 B/op   1.78× slower
 File#stat   3.13M (319.46ns) (± 3.19%)  0 B/op        fastest

new:

 File.stat   1.74M (575.88ns) (± 4.60%)  0 B/op   1.79× slower
File.lstat   1.69M (590.26ns) (±10.11%)  0 B/op   1.84× slower
 File#stat   3.11M (321.26ns) (± 3.22%)  0 B/op        fastest

RX14 · 2018-01-14T13:00:29Z

Also keep in mind that benchmark is a best-case for stat: one file only in a loop. When you add in a typical usage where the stat may not be in cache all the time you're going to see far less than the 2-4% overhead seen here.

bew · 2018-01-14T02:42:22Z

spec/std/file_spec.cr

+    it "can take File::Permissions" do
+      path = "#{__DIR__}/data/chmod.txt"
+      begin
+        File.write(path, "")


You can use File.touch(path) here I think

It's copied from the spec two above it with minor tweaks.

oh ok, probably not worth to change it here then

RX14 · 2018-01-14T19:02:16Z

I do wonder whether we should rename File.stat? as File.info? and have File.info?(follow_symlink: false).

Also I'm probably going to just rename File::Type::SymbolicLink to File::Type::Symlink, almost everyone uses the shortened name these days.

asterite · 2018-01-14T23:43:56Z

I actually learned in this PR that lstat doesn't (or does) follow symlinks, so a named argument to select that behavior is better in my opinion. lstat is too cryptic. So maybe it's better to just use info.

I believe Ruby started with "works only in unix" and eventually had to keep all those cryptic, unix-specific names. Go for example doesn't do this, it provides a clear interface to the computer without using ancient strange names. I think we should do the same, even if it means a bigger barrier to those coming from Ruby.

RX14 · 2018-01-15T12:07:44Z

@asterite its called stat and lstat on go too...

asterite · 2018-01-15T12:25:00Z

Maybe because go isn't that flexible with method names.

RX14 · 2018-01-15T12:35:35Z

@asterite I do agree it should be File.info. (eventually Path#info and File#info for stat/lstat and fstat respectively)

RX14 · 2018-01-21T00:44:23Z

Updated this PR to take into account the above suggestions.

RX14 · 2018-01-21T00:54:17Z

Looks like I accidentally made this PR depend on #5619... I'll fix it tomorrow.

RX14 · 2018-01-21T16:24:16Z

Pushed again to fix this, this can be re-reviewed now.

ysbaddaden

I'm sorry I'll feel grumpy, but I still have goosebumps, and no explanation for many (unwelcomed) changes:

Why change stat naming to info? it's still an abbreviation and doesn't tell any better.

Why decode & copy everything (check each file type, decode/copy permissions, generate Time instances) instead of using a wrapper for on-demand generation? Sure File::Stat would be a mere delegation struct for the underlying POSIX vs Windows implementations, mostly to hold documentation, but the optimizer will inline calls, or we can just flag them with @[AlwaysInline].

Having to type .info.type.directory? over .stat.directory? can feel minor, but that's still an unwelcomed hick; forward calls from the struct to the enum, please.

Also:

ctime & atime are still missing (!)

ysbaddaden · 2018-01-22T10:29:50Z

src/file/info.cr

+end
+
+struct Int
+  def ==(other : File::Permissions)


I'm not sure reopening Int is a good idea.

And the alternative is?

Not support Int==(File::Permissions) nor File::Info#permissions==(Int). You must wrap the octal value. I believe it's better than reopening Int for a corner case —checking exact permissions equality doesn't seem like a usual case.

RX14 · 2018-04-13T11:40:50Z

I've added some shortcuts for file? directory? and symlink?, as they are the common options. I've also fixed DEFAULT_CREATE_PERMISSIONS. Looking forward to finally getting this merged!

straight-shoota · 2018-04-13T12:17:11Z

I don't like delegating only a few type predicates. It should be either all (my preference) or none to provide the least surprise.

sdogruyol · 2018-04-13T12:31:59Z

I prefer having the most common ones than having all / nothing. IMHO this is good to go as it is 👍

RX14 · 2018-05-29T12:30:23Z

@ysbaddaden After looking at crystal-lang/shards#203 I'm wondering if making File::Info#== perform samefile was correct. Perhaps it should have been File.info(foo).same_file? File.info(bar)? File.same_file?(foo, bar)? I'd like other people's input on this API.

ysbaddaden · 2018-05-29T13:07:51Z

Maybe File.same?(foo, bar) or just keep exposing the inode on POSIX systems.

RX14 · 2018-05-29T13:21:42Z

I don't think we should expose inode and device numbers (nicely). I'd much rather just expose samefile.

bcardiff · 2018-05-30T18:41:45Z

File.same?(foo, bar) LGTM, but I would propose something else

Given the following files:

$ touch a.txt
$ ln -s a.txt b.txt
$ touch c.txt

With the stdlib at master we currently have:

a = File.new("./a.txt") 
a_copy = File.new("./a.txt")

How to check if a1 and a1_copy refer to the same file?

a == a_copy # => false
a.info == a_copy.info # => true

Ok, but how that works with b?

b = File.new("./b.txt")
a.info == b.info # => true

How can I know that a and b are different files?

File.info?(a.path, follow_symlinks: false) == File.info?(a_copy.path, follow_symlinks: false) # => true
File.info?(a.path, follow_symlinks: false) == File.info?(b.path, follow_symlinks: false) # => false

Ok, but what about if I use only the path of the File?
File instances initialized with different path indeed have different path

a_diff = File.new("a.txt")
a.path      # => "./a.txt"
a_diff.path # => "a.txt"

You can use File.expand_path, but there are a lot of rules to expand the
path and we had already a File instance

File.expand_path(a.path)      # => /full/path/to/a.txt
File.expand_path(a_diff.path) # => /full/path/to/a.txt

So, what about?

Changing File#info to File#info(follow_symlinks = true)
Add File.same?(file1, file2, follow_symlinks = true)
Remove override of File::Info==

That would make simpler all of the above scenarios with File.same? having follow_symlinks set to one or another value.

RX14 · 2018-05-30T21:06:48Z

Because file.info(follow_symlinks: false) doesn't make sense. file.info != File.info(file.path). file.info is fstat and File.info is stat/lstat.

RX14 · 2018-05-30T21:11:03Z

How can I know that a and b are different files?

They are the same file. The whole premise for that question is wrong on posix. The confusing part here is actually storing File#path in the first place. File#path is never actually guaranteed to mean anything. Not all files even have a (valid) path.

You can unlink a path from the filesystem while it is open in a program just fine. And any open programs will keep the inode around in the filesystem, and the file will continue to use up disk space until the program is closed. Then File#path will continue to report the path of the deleted file where it may well have been replaced by a completely different file. That's part of the reason why fstat exists: because open is atomic and then you can call fstat on the file descriptor to check permissions, then perform operations with the FD while being sure that an attacker hasn't raced you to swap out the file for another malicious one under your nose.

Path equality and file equality are entirely different things, and are pretty much entirely unrelated and unreliable until the moment in time you call open.

bcardiff · 2018-05-31T08:21:43Z

Ok, so @RX14 you say to only

Add File.same?(file1, file2) that will always "follow symlinks" in the comparison
Remove override of File::Info==
Treat path comparison in another way. Later.

I'm fine with that also.

Although the premise for the question might seems wrong, but I think it depends on the use case. If someone wants to deal with lower level of file system some api are not the best. But is not the more common use case and it is still doable.

ysbaddaden · 2018-05-31T09:29:46Z

Mixing symlinks with hard links to detect file identify is IMHO introducing confusing behavior. Furthermore, detecting hard links is quite specific, and not widely used. We don't need a abstraction for this, hence why I'm proposing to keep exposing inodes on POSIX systems and be done with it.

So:

detecting hard links: File.info(a).inode == File.info(b).inode;
detecting symlinks: File.real_path(a) == File.real_path(b);
detecting hard links through potential symlinks:
File.info(a, follow_symlinks: true).inode == File.info(b, follow_symlinks: true).inode.

Simple, does the job, no confusing behavior, and allows finer grained detection. All it needs is to expose a value that we already have.

RX14 · 2018-05-31T10:38:51Z

@bcardiff having a follow_symlinks in File.same is fine because symlinks are a property of a path, which File.same is working with. It's not fine to have File#info with a follow_symlinks option because you've already dereferenced the symlink and got to a specific device and inode when you call open(2).

@ysbaddaden the reason why I want to only expose equality only is because your examples are wrong! You must compare device and inode to be sure they're the same file. If even you get this wrong, then surely thats a fantastic reason to expose this nicely instead of just expose the platform-specific inode (which won't even exist on windows).

Let's add File.same with a follow_symlinks option, then move File::Info#== to File#== so it's just file == file and skip the .info step (it reads badly and is a bit weird).

bcardiff · 2018-06-04T10:48:30Z

PR sent for this. I don't think we need to expose inode for file comparison in order to stay posix independent for this api.

Users are free to go to info and extract more information, but for comparison File.same? is good API.

ysbaddaden · 2018-06-04T11:59:08Z

My wrong, you're both right. Let's go with File.same?.

RX14 added topic:stdlib kind:refactor breaking-change labels Jan 13, 2018

RX14 requested a review from asterite January 13, 2018 22:39

straight-shoota reviewed Jan 13, 2018

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RX14 force-pushed the feature/file-info branch 2 times, most recently from 030495b to 148b1f6 Compare January 13, 2018 23:03

lbguilherme reviewed Jan 13, 2018

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asterite approved these changes Jan 13, 2018

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RX14 mentioned this pull request Jan 18, 2018

Add cache control headers to http static file handler + a few more mi… #2470

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RX14 force-pushed the feature/file-info branch from 148b1f6 to 7c874b8 Compare January 21, 2018 00:44

RX14 force-pushed the feature/file-info branch from 7c874b8 to f8e9bd5 Compare January 21, 2018 16:22

RX14 mentioned this pull request Jan 21, 2018

Implement File and Dir for win32 #5623

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RX14 force-pushed the feature/file-info branch from f8e9bd5 to d9f73d4 Compare January 21, 2018 16:40

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RX14 added 2 commits April 9, 2018 15:57

Rename and rework File::Stat as File::Info

db94fda

fixup! Rename and rework File::Stat as File::Info

7541889

RX14 force-pushed the feature/file-info branch from 3372d31 to 7541889 Compare April 9, 2018 14:57

fixup! Rename and rework File::Stat as File::Info

3cfdfb5

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sdogruyol merged commit 96bcc34 into crystal-lang:master Apr 14, 2018

sdogruyol added this to the Next milestone Apr 14, 2018

bcardiff mentioned this pull request May 23, 2018

Proposal: Rename File::Stat to FileInfo #3828

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bcardiff mentioned this pull request Jun 4, 2018

Add File.same?(path1, path2) with follow_symlinks option #6161

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Blacksmoke16 mentioned this pull request Jun 11, 2018

Get ready for Crystal 0.25.0 amberframework/granite#226

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This was referenced Jun 15, 2018

Update to crystal 0.25.0 amberframework/granite#228

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Change stat by info [breaking-change] faustinoaq/watcher#6

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RX14 mentioned this pull request Jul 4, 2018

Targeting windows cross-compile: can't find file 'File/stat' #6326

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hkalexling mentioned this pull request Jun 3, 2020

[Feature Request] Home screen (easy access to entries you're reading and recently added) getmango/Mango#37

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straight-shoota mentioned this pull request Sep 11, 2022

File creation time stx_btime #12416

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straight-shoota mentioned this pull request May 11, 2023

Fine-grained file permissions on Windows #13233

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Rename and rework File::Stat as File::Info #5584

Rename and rework File::Stat as File::Info #5584

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