Does GNU GRUB support BLS (Boot Loader Specification)?

Question

I'm a Fedora user and recently (from Fedora 33) I noted that GRUB switched to Boot Loader Specification (BLS) when it comes to managing boot entries.

My question: Is it a Fedora customization or a regular feature of GNU GRUB?

Answer 1

GNU GRUB does not support BLS natively:

# git clone https://git.savannah.gnu.org/git/grub.git
# cd grub/
# find . -type f -print0 | xargs -0 fgrep -ai "boot loader spec" 
Exit 123
# find . -type f -print0 | xargs -0 fgrep -ai "bootloaderspec"
Exit 123
# find . -type f -print0 | xargs -0 fgrep -ail "bls"
./themes/starfield/starfield.png
./tests/gettext_strings_test.in
./grub-core/lib/libgcrypt/mpi/m68k/syntax.h
./grub-core/lib/libgcrypt/mpi/m68k/mpih-rshift.S
./grub-core/lib/libgcrypt/mpi/m68k/mpih-lshift.S
./grub-core/kern/arm/startup.S
./grub-core/commands/i386/coreboot/cbls.c
./grub-core/Makefile.core.def
./Makefile.am
./ChangeLog-2015
./.git/index
./.git/objects/pack/pack-d7b2418ef08f0a88570f360b4f27dfb38f96f4a0.pack

There have, however, been forks to implement the functionality

https://github.com/endlessm/grub/blob/master/grub-core/commands/blscfg.c

Answer 2

In addition to @Ned64 answer you can simply check the source files https://src.fedoraproject.org/rpms/grub2/tree/rawhide and see that Fedora does extensively patch GRUB to offer this feature.