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bevy_input is now optional, but there's no way to enable it #18397

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rparrett opened this issue Mar 18, 2025 · 6 comments · Fixed by #18638
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bevy_input is now optional, but there's no way to enable it #18397

rparrett opened this issue Mar 18, 2025 · 6 comments · Fixed by #18638
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A-Input Player input via keyboard, mouse, gamepad, and more C-Bug An unexpected or incorrect behavior D-Straightforward Simple bug fixes and API improvements, docs, test and examples S-Needs-Design This issue requires design work to think about how it would best be accomplished

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@rparrett
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rparrett commented Mar 18, 2025 •
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Bevy version

main, since #17955

What you did

Attempted to migrate a crate dealing with input and using default-features = false to Bevy 0.16-dev

What went wrong

error[E0433]: failed to resolve: could not find `input` in `bevy`
  --> src/lib.rs:28:5
   |
28 |     input::keyboard::{Key, KeyboardInput},
   |     ^^^^^ could not find `input` in `bevy`

And there doesn't appear to be any way of rectifying this. It seems that we need a new bevy_input feature, but it's also possible that bevy_input becoming optional was a mistake. I haven't been following the no_std effort closely, so I'm not sure.

A bad workaround is to add the std feature, which includes bevy_input. (This may be a separate bug. Seems like with bevy_input optional, bevy_internal/std should be using bevy_input?/std).
@rparrett rparrett added C-Bug An unexpected or incorrect behavior S-Needs-Triage This issue needs to be labelled labels Mar 18, 2025
@rparrett rparrett added this to the 0.16 milestone Mar 18, 2025
@alice-i-cecile alice-i-cecile added A-Input Player input via keyboard, mouse, gamepad, and more D-Straightforward Simple bug fixes and API improvements, docs, test and examples and removed S-Needs-Triage This issue needs to be labelled labels Mar 18, 2025
@alice-i-cecile
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@bushrat011899 may know better, but my instincts say we're just missing a feature flag.

@alice-i-cecile alice-i-cecile added the S-Needs-Design This issue requires design work to think about how it would best be accomplished label Mar 18, 2025
@bushrat011899
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Tl;Dr enable either std or libm and you'll get bevy_input.

The problem is bevy_math, bevy_inout, etc. need a floating point backend, so you must enable either libm or std. To allow no-default-features to still compile, the only option is to make those crates optional.

I'll give this another look though and see if there's a way to make this more intuitive!

@alice-i-cecile alice-i-cecile removed this from the 0.16 milestone Mar 18, 2025
@alice-i-cecile
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Cutting from the milestone: that's a good enough workaround for me to be comfortable shipping it. Rust please give us enum features 🥺

@rparrett
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rparrett commented Mar 18, 2025 •
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Tl;Dr enable either std or libm and you'll get bevy_input.

Gotcha, thanks. So the play for maximum compatibility would be to add a matching std and libm feature to my crate? (and include std in my own default features?)

Side note: we may want to amend https://bevyengine.org/learn/quick-start/plugin-development/#small-crate-size

@bushrat011899
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Yep! In the release notes we'll call out a newly added example in examples/no_std/library (which you should check as well!) which shows how to make a maximally compatible Bevy library, and some suggestions for how to test it for no_std compatibility.

@alice-i-cecile
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Pre-RFC for a cargo feature in this space: https://internals.rust-lang.org/t/pre-rfc-mutually-excusive-global-features/19618

@bushrat011899 bushrat011899 mentioned this issue Mar 22, 2025
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@bushrat011899 bushrat011899 mentioned this issue Mar 31, 2025
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github-merge-queue bot pushed a commit that referenced this issue Mar 31, 2025
@bushrat011899
Upgrade to Glam 0.29.3 and Simplify Feature Gating (#18638)
45e2398 
# Objective

- Fixes #18397
- Supersedes #18474
- Simplifies 0.16 migration

## Solution

- Upgrade to Glam 0.29.3, which has backported the `nostd-libm` feature.
- Expose a similar feature in `bevy_math` and enable it in
`bevy_internal`, allowing `bevy_math`, `bevy_input`, and
`bevy_transform` to be unconditional dependencies again.

## Testing

- CI

---

## Notes

- This includes `libm` as a dependency, but this was already the case in
the common scenario where `rand` or many other features were enabled.
Considering `libm` is an official Rust crate, it's a very low-risk
dependency to unconditionally include.
- For users who do not want `libm` included, simply import Bevy's
subcrates directly, since `bevy_math/nostd-libm` will not be enabled.
- I know we are _very_ late in the RC cycle for 0.16, but this has a
substantial impact on the usability of `bevy` that I consider worth
including.
mockersf pushed a commit that referenced this issue Mar 31, 2025
@bushrat011899 @mockersf
Upgrade to Glam 0.29.3 and Simplify Feature Gating (#18638)
a2b1498 
- Fixes #18397
- Supersedes #18474
- Simplifies 0.16 migration

- Upgrade to Glam 0.29.3, which has backported the `nostd-libm` feature.
- Expose a similar feature in `bevy_math` and enable it in
`bevy_internal`, allowing `bevy_math`, `bevy_input`, and
`bevy_transform` to be unconditional dependencies again.

- CI

---

- This includes `libm` as a dependency, but this was already the case in
the common scenario where `rand` or many other features were enabled.
Considering `libm` is an official Rust crate, it's a very low-risk
dependency to unconditionally include.
- For users who do not want `libm` included, simply import Bevy's
subcrates directly, since `bevy_math/nostd-libm` will not be enabled.
- I know we are _very_ late in the RC cycle for 0.16, but this has a
substantial impact on the usability of `bevy` that I consider worth
including.
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A-Input Player input via keyboard, mouse, gamepad, and more C-Bug An unexpected or incorrect behavior D-Straightforward Simple bug fixes and API improvements, docs, test and examples S-Needs-Design This issue requires design work to think about how it would best be accomplished
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