add a flag to `cargo add` to make it show all features

[yshui]

Problem

Currently when a crate has too many features, cargo add only shows part of them and prints "X deactivated features". this is useful if i want to see a concise summary, but sometimes i actually want to see all the available features to see what i can enable.

Proposed Solution

add an new flag to make cargo add print all features. or perhaps make it do so when -v/--verbose is specified.

Notes

No response

[epage]

Can you provide an example of a crate with that large of a feature list that you want to browse?

If we don't support this already, the two most ways to support this that are aligned with cargo would be

• show it with -v
• show it with -F (nothing else) except this command takes a positional and we generally don't mix flag/option hybrids with positionals

[yshui]

Can you provide an example of a crate with that large of a feature list that you want to browse?

reqwest

right now it shows:

    Updating crates.io index
      Adding reqwest v0.12.12 to dependencies
             Features:
             + __tls
             + charset
             + default-tls
             + h2
             + http2
             + macos-system-configuration
             27 deactivated features

[epage]

Doing a quick look to see how short-term vs long term that feature count is

There are 4 "private" features which would be aided by #10882.

They are using dep: for each optional dependency, so no accidental features exist

It looks like the different backends are not mutually exclusive but I suspect some aspects might benefit from https://internals.rust-lang.org/t/pre-rfc-mutually-excusive-global-features/19618, reducing the number of features.

[epage]

Looking at that example, another option is that we bump the max feature count. The number we chose (30) was arbitrary and was meant to avoid cases like windows with its ~700 features for which a -v or -F may still not be too helpful.

[yshui]

i found a ugly workaround: by specifying a non-existent feature, cargo will list all features:

$ cargo add --features sadfasdf rustix
    Updating crates.io index
      Adding rustix v0.38.44 to dependencies
error: unrecognized feature for crate rustix: sadfasdf
disabled features:
    all-apis, cc, compiler_builtins, core, event, io_uring, itoa, libc, libc_errno
    linux_4_11, linux_latest, mm, mount, net, once_cell, param, pipe, process
    procfs, pty, rand, runtime, rustc-dep-of-std, rustc-std-workspace-alloc, shm
    stdio, system, termios, thread, time, try_close, use-explicitly-provided-auxv
    use-libc
enabled features:
    alloc, fs, libc-extra-traits, std, use-libc-auxv

[epage]

#15200 added a cap on that though its in favor of showing deactivated features.

[tcanabrava]

i found a ugly workaround: by specifying a non-existent feature, cargo will list all features:

$ cargo add --features sadfasdf rustix
    Updating crates.io index
      Adding rustix v0.38.44 to dependencies
error: unrecognized feature for crate rustix: sadfasdf
disabled features:
    all-apis, cc, compiler_builtins, core, event, io_uring, itoa, libc, libc_errno
    linux_4_11, linux_latest, mm, mount, net, once_cell, param, pipe, process
    procfs, pty, rand, runtime, rustc-dep-of-std, rustc-std-workspace-alloc, shm
    stdio, system, termios, thread, time, try_close, use-explicitly-provided-auxv
    use-libc
enabled features:
    alloc, fs, libc-extra-traits, std, use-libc-auxv

it will not. the amount of features displayed is also governed by the same constant. you just picked up a crate that has a lower count.