Edition 2015 is used if .rustfmt without edition is present

[saecki]

• rust.vim version:
  Latest master
  commit hash: 4aa69b84c8a58fcec6b6dad6fe244b916b1cf830

Steps to reproduce:

1. Create a .rustfmt.toml without an explicit edition key defined.
2. Use any feature from the Rust 2018 edition. For example the async keyword.
3. Run the :RustFmt command

Expected behavior

The expected behavior would be that rust.vim either defaults to the edition that is specified in the Cargo.toml or the 2018 edition, like when no .rustfmt.toml file is present.

Actual behavior

The actual behavior is that no edition option is passed to rustfmt and the 2015 edition is used.

Paste debugging info from the Rust Vim plugin via one of the following
commands: :RustInfo, :RustInfoToClipboard, or :RustInfoToFile <filename>.

:RustInfo

let g:loaded_syntastic_rust_cargo_checker = v:null
let g:loaded_syntastic_rust_filetype = v:null
let g:loaded_syntastic_rust_rustc_checker = v:null
let g:rust_bang_comment_leader = v:null
let g:rust_cargo_avoid_whole_workspace = v:null
let g:rust_clip_command = v:null
let g:rust_conceal = v:null
let g:rust_conceal_mod_path = v:null
let g:rust_conceal_pub = v:null
let g:rust_fold = v:null
let g:rust_last_args = v:null
let b:rust_last_args = []
let g:rust_last_rustc_args = v:null
let b:rust_last_rustc_args = []
let g:rust_original_delimitMate_excluded_regions = v:null
let g:rust_playpen_url = v:null
let g:rust_prev_delimitMate_quotes = v:null
let g:rust_recent_nearest_cargo_tol = v:null
let g:rust_recent_root_cargo_toml = v:null
let g:rust_recommended_style = 0
let g:rust_set_conceallevel = v:null
let g:rust_set_conceallevel=1 = v:null
let g:rust_set_foldmethod = v:null
let g:rust_set_foldmethod=1 = v:null
let g:rust_shortener_url = v:null
let g:rustc_makeprg_no_percent = v:null
let g:rustc_path = v:null
let g:rustfmt_autosave = 0
let g:rustfmt_autosave_if_config_present = v:null
let g:rustfmt_command = 'rustfmt'
let g:rustfmt_emit_files = 1
let g:rustfmt_fail_silently = 0
let g:rustfmt_options = ''
let g:syntastic_extra_filetypes = ['rust']
let g:syntastic_rust_cargo_fname = v:null
rustfmt 1.4.37-stable (f1edd04 2021-11-29)
rustc 1.57.0 (f1edd0429 2021-11-29)
cargo 1.57.0 (b2e52d7ca 2021-10-21)

NVIM v0.6.0
Build type: RelWithDebInfo
LuaJIT 2.1.0-beta3
Compilation: /usr/bin/gcc-11 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 -DNVIM_TS_HAS_SET_MATCH_LIMIT -O2 -g -Og -g -Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion -Wmissing-prototypes -Wimplic
it-fallthrough -Wvla -fstack-protector-strong -fno-common -fdiagnostics-color=always -DINCLUDE_GENERATED_DECLARATIONS -D_GNU_SOURCE -DNVIM_MSGPACK_HAS_FLOAT32 -DNVIM_UNIBI_HAS_VAR_FROM -DMIN_LOG_LEVEL=3 -I/home/runner/work/neovim/neovim/bu
ild/config -I/home/runner/work/neovim/neovim/src -I/home/runner/work/neovim/neovim/.deps/usr/include -I/usr/include -I/home/runner/work/neovim/neovim/build/src/nvim/auto -I/home/runner/work/neovim/neovim/build/include
Compiled by runner@fv-az65-618

Features: +acl +iconv +tui
See ":help feature-compile"

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "/home/runner/work/neovim/neovim/build/nvim.AppDir/usr/share/nvim"

Run :checkhealth for more info

[vhakulinen]

FWIW, you can do let g:rustfmt_options = '--edition 2021 to "force" the used edition.

[saecki]

I've since switched to nvim-lsp formatting, but good to know!