add file_prefix method to std::path #85166

mbhall88 · 2021-05-11T00:42:58Z

This is an initial implementation of std::path::Path::file_prefix. It is effectively a "left" variant of the existing file_stem method. An illustration of the difference is

use std::path::Path;

let path = Path::new("foo.tar.gz");
assert_eq!(path.file_stem(), Some("foo.tar"));
assert_eq!(path.file_prefix(), Some("foo"));

In my own development, I generally find I almost always want the prefix, rather than the stem, so I thought it might be best to suggest it's addition to libstd.

Of course, as this is my first contribution, I expect there is probably more work that needs to be done. Additionally, if the libstd team feel this isn't appropriate then so be it.

There has been some discussion about this on Zulip and a user there suggested I open a PR to see whether someone in the libstd team thinks it is worth pursuing.

rust-highfive · 2021-05-11T00:43:01Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @dtolnay (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

dtolnay

Thanks for the PR. I am on board with adding a method like this. Please update the implementation and open a new tracking issue.

library/std/src/path.rs

dtolnay

#85166 (comment) + #85166 (comment)

JohnCSimon · 2021-07-12T00:07:39Z

Ping from triage:
@mbhall88 - can you please mark dtolnay's change requests as addressed?

mbhall88 · 2021-07-12T00:48:12Z

Ping from triage:
@mbhall88 - can you please mark dtolnay's change requests as addressed?

@JohnCSimon I have already marked all of the comments as resolved...? Is there some other way of marking the changes as resolved?

dtolnay · 2021-08-15T01:00:37Z

library/std/src/path.rs

+    pub fn file_prefix(&self) -> Option<&OsStr> {
+        self.file_name()
+            .map(split_file_at_dot)
+            .and_then(|(before, after)| if before.is_empty() { after } else { Some(before) })


The first branch on this line (when before is empty) has no test coverage. What is this case for?

Good point. I had it in there for the case where the filename was a single . or empty, but this is inherently handled by file_name already, so we never actually try and split on . for these cases. I've removed the branch and all tests pass. I also added another test case.

dtolnay

Looks good. Thanks!

dtolnay · 2021-08-21T21:42:53Z

@bors r+

bors · 2021-08-21T21:42:55Z

📌 Commit 51cf318 has been approved by dtolnay

bors · 2021-08-22T05:19:51Z

⌛ Testing commit 51cf318 with merge 2ad56d5...

bors · 2021-08-22T08:03:41Z

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing 2ad56d5 to master...

Ziris85 · 2022-02-07T19:25:17Z

Hello, I just wanted to inquire about this specific function. According to the above, it was merged and should (if I'm understanding this correctly) be available as of rust v1.56.0. However, that doesn't appear to be the case, since as of rust 1.58.1, cargo will not compile code with that function, claiming it's not found:

error[E0599]: no method named `file_prefix` found for struct `PathBuf` in the current scope

>rustc -V
rustc 1.58.1 (db9d1b20b 2022-01-20)

>cargo -V
cargo 1.58.0 (f01b232bc 2022-01-19)

Just wondering if perhaps I'm simply misunderstanding when this function will be available? Thank you for your time.

CryZe · 2022-02-07T19:32:35Z

It's not stable yet: #86319

Ziris85 · 2022-02-07T19:42:48Z

Thanks for the quick response! The original author seems unsure what he's supposed to do next with regards to making it stable:

I don't know how these tracking issues work. The PR for this feature was merged a while ago, but I have no idea if I'm supposed to do something with this issue? @dtolnay as you were the reviewer/merger of that PR are you able to answer this?

He may need some assistance/guidance in that regard 🙂

add file_prefix method to std::path This is an initial implementation of `std::path::Path::file_prefix`. It is effectively a "left" variant of the existing [`file_stem`](https://doc.rust-lang.org/std/path/struct.Path.html#method.file_stem) method. An illustration of the difference is ```rust use std::path::Path; let path = Path::new("foo.tar.gz"); assert_eq!(path.file_stem(), Some("foo.tar")); assert_eq!(path.file_prefix(), Some("foo")); ``` In my own development, I generally find I almost always want the prefix, rather than the stem, so I thought it might be best to suggest it's addition to libstd. Of course, as this is my first contribution, I expect there is probably more work that needs to be done. Additionally, if the libstd team feel this isn't appropriate then so be it. There has been some [discussion about this on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/file_lstem/near/238076313) and a user there suggested I open a PR to see whether someone in the libstd team thinks it is worth pursuing.

add file_prefix method

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rust-highfive assigned dtolnay May 11, 2021

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add missing windows tests

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dtolnay requested changes May 22, 2021

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dtolnay added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 7, 2021

simplify logic for split_file_at_dot

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mbhall88 mentioned this pull request Jun 15, 2021

Tracking Issue for Path::file_prefix #86319

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3 tasks

add explicit hidden file name tests

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mbhall88 requested a review from dtolnay June 21, 2021 03:54

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mbhall88 added 2 commits June 24, 2021 13:45

change return signature for split_file_at_dot

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make docs clearer about how hidden files are dealt with

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mbhall88 requested a review from dtolnay June 24, 2021 04:27

JohnCSimon added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 12, 2021

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remove unnecessary empty check

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 21, 2021

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 22, 2021

bors merged commit 2ad56d5 into rust-lang:master Aug 22, 2021

rustbot added this to the 1.56.0 milestone Aug 22, 2021

EvanCarroll mentioned this pull request May 18, 2022

add file_suffix method to std::path #97134

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add file_prefix method to std::path #85166

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add file_prefix method to std::path #85166

add file_prefix method to std::path #85166

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