[stdlib] Require explicit byte= keyword for String/StringSlice span indexing

[mahendrarathore1742]

…an indexing

Fixes #6024 — String/StringSlice slice syntax like s[0:1] silently did byte-level indexing. Now requires s[byte=0:1] to make byte-based slicing explicit. Updated all stdlib callers and tests.

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[mahendrarathore1742]

I have read the CLA Document and I hereby sign the CLA

[Copilot]

Pull request overview

This PR addresses #6024 by making byte-based slicing of String / StringSlice explicit, preventing accidental UTF-8-invalid slicing via implicit byte indexing.

Changes:

• Make StringSlice.__getitem__ span slicing keyword-only ([byte=...]) to disallow implicit byte slicing.
• Update String.__getitem__ span slicing to forward to StringSlice using the explicit byte= keyword.
• Update stdlib call sites and tests to use [byte=...] where byte-based slicing is intended.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
mojo/stdlib/test/collections/string/test_string_unicode_panic.mojo	Updates a unicode boundary panic test to use explicit byte slicing.
mojo/stdlib/test/collections/string/test_string_slice.mojo	Updates StringSlice byte-slicing tests to use [byte=...].
mojo/stdlib/test/collections/string/test_string.mojo	Updates String slicing/indexing tests to use explicit byte slicing.
mojo/stdlib/test/builtin/test_string_literal.mojo	Updates comparisons that slice StringSlice inputs to use [byte=...].
mojo/stdlib/test/builtin/test_print.mojo	Updates output trimming/prefix checks to use explicit byte slicing.
mojo/stdlib/test/builtin/test_file.mojo	Updates exception-message prefix extraction to use explicit byte slicing.
mojo/stdlib/std/python/python_object.mojo	Updates inplace-method name construction to slice via [byte=2:].
mojo/stdlib/std/pathlib/path.mojo	Updates path substring extraction to use explicit byte slicing.
mojo/stdlib/std/os/path/path.mojo	Updates root/suffix splitting logic to use explicit byte slicing.
mojo/stdlib/std/collections/string/string_slice.mojo	Makes span slicing keyword-only and updates docs/examples accordingly.
mojo/stdlib/std/collections/string/string.mojo	Makes span slicing keyword-only and forwards to StringSlice via byte=.
mojo/stdlib/std/collections/string/_parsing_numbers/parsing_floats.mojo	Updates sign stripping to use explicit byte slicing.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.

[barcharcraz]

This looks good, this is the second PR to do this (actually the third, I had one internally). It's about time we got one merged. I'll have to migrate the rest of max internally so expect some additional changes.

[barcharcraz]

!sync

[modularbot]

✅🟣 This contribution has been merged 🟣✅

Your pull request has been merged to the internal upstream Mojo sources. It will be reflected here in the Mojo repository on the main branch during the next Mojo nightly release, typically within the next 24-48 hours.

We use Copybara to merge external contributions, click here to learn more.

[modularbot]

Landed in b90e36f! Thank you for your contribution 🎉