Can't get pest to compile for thumbv7em-none-eabihf target

[seanybaggins]

Describe the bug
Can't get pest to compile for thumbv7em-none-eabihf target.

To Reproduce

1. clone the repo
2. Make sure you have the thumbv7em-none-eabihf target on your toolchain by using the following command

rustup target add aarch64-linux-android

3. Try to build

cargo build --target thumbv7em-none-eabihf --no-default-features

Expected behavior
The library to build with no compiler errors.

Looks like dependencies are still looking for std.

Actual Behavior

   Compiling once_cell v1.17.0
   Compiling bytes v1.4.0
   Compiling ucd-trie v0.1.5
   Compiling memchr v2.5.0
   Compiling socket2 v0.4.7
   Compiling openssl-sys v0.9.80
   Compiling mio v0.8.5
   Compiling futures-core v0.3.26
   Compiling num_cpus v1.15.0
   Compiling fnv v1.0.7
   Compiling thiserror v1.0.38
   Compiling slab v0.4.7
   Compiling futures-task v0.3.26
   Compiling hashbrown v0.12.3
   Compiling pest_meta v2.5.5 (/home/demo/forks/pest/meta)
   Compiling native-tls v0.2.11
error[E0583]: file not found for module `sys`
   --> /home/demo/.cargo/registry/src/github.com-1ecc6299db9ec823/socket2-0.4.7/src/lib.rs:124:1
    |
124 | mod sys;
    | ^^^^^^^^
    |
    = help: to create the module `sys`, create file "/home/demo/.cargo/registry/src/github.com-1ecc6299db9ec823/socket2-0.4.7/src/sys.rs" or "/home/demo/.cargo/registry/src/github.com-1ecc6299db9ec823/socket2-0.4.7/src/sys/mod.rs"

error[E0463]: can't find crate for `std`
  |
  = note: the `thumbv7em-none-eabihf` target may not support the standard library
  = note: `std` is required by `ucd_trie` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

...

[tomtau]

native-tls is a dependency of reqwest; so that's likely due to this new feature in pest_debugger: #779 by @Jamalam360

@seanybaggins do you need to compile pest_debugger CLI for thumbv7em-none-eabihf or pest (or other crates) are fine? If the latter, perhaps you can try cargo build --target thumbv7em-none-eabihf --no-default-features -p pest (or whichever crate is needed, besides pest_debugger)?

if the former, maybe we can feature-guard that version check in pest_debugger?

[Jamalam360]

Making it a default feature that can therefore be disabled does sound like a good thing to do

[seanybaggins]

@tomtau
cargo build --target thumbv7em-none-eabihf --no-default-features -p pest works.

cargo build --target thumbv7em-none-eabihf --no-default-features -p pest_derive does not work.

cargo build --target thumbv7em-none-eabihf --no-default-features -p pest_derive
   Compiling syn v1.0.107
   Compiling ucd-trie v0.1.5
   Compiling once_cell v1.17.0
   Compiling thiserror v1.0.38
   Compiling pest_meta v2.5.5 (/home/demo/forks/pest/meta)
error: failed to run custom build command for `pest_meta v2.5.5 (/home/demo/forks/pest/meta)`

Caused by:
  process didn't exit successfully: `/home/demo/forks/pest/target/debug/build/pest_meta-7a0831d7849d17e7/build-script-build` (exit status: 101)
  --- stdout
  rerun-if-changed=src/grammar.pest
  Bootstrapping `meta/src/grammar.rs`

  --- stderr
  thread 'main' panicked at 'Bootstrap failed because no bootstrap executable was found. Please run `cargo build --package pest_bootstrap` or `cargo bootstrap` and then try again.', meta/build.rs:50:21
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...

cargo build --target thumbv7em-none-eabihf --no-default-features -p pest_bootstrap
   Compiling syn v1.0.107
   Compiling proc-macro2 v1.0.51
   Compiling unicode-ident v1.0.6
   Compiling quote v1.0.23
   Compiling ucd-trie v0.1.5
   Compiling once_cell v1.17.0
error[E0463]: can't find crate for `std`
  |
  = note: the `thumbv7em-none-eabihf` target may not support the standard library
  = note: `std` is required by `ucd_trie` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

[tomtau]

'Bootstrap failed because no bootstrap executable was found. Please run cargo build --package pest_bootstrap or cargo bootstrap and then try again.'

@seanybaggins did you run the bootstrap first?

[tomtau]

you can run the bootstrap without --target thumbv7em-none-eabihf

[tomtau]

I just tried:

✗ cargo bootstrap
...
✗ cargo build --target thumbv7em-none-eabihf --no-default-features -p pest_derive
   Compiling pest_meta v2.5.5 (.../pest/meta)
   Compiling pest_generator v2.5.5 (.../pest/generator)
   Compiling pest_derive v2.5.5 (.../pest/derive)
    Finished dev [unoptimized + debuginfo] target(s) in 1.57s

for feature-guarding pest_debugger, I find that it'd also need changing pest_vm etc. I'll add a note to docs about the no_std support -- if there's a need to support no_std on pest crates that currently don't support it (like pest_vm or pest_meta), feel free to open an issue for it