scripts: generate_rust_analyzer: provide `cfg`s for `core` and `alloc`

Both `core` and `alloc` have their `cfgs` (such as `no_rc`) missing
in `rust-project.json`.

To remedy this, pass the flags to `generate_rust_analyzer.py` for
them to be added to a dictionary where each key corresponds to
a crate and each value to a list of `cfg`s. The dictionary is then
used to pass the `cfg`s to each crate in the generated file (for
`core` and `alloc` only).

Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Link: https://lore.kernel.org/r/20230804171448.54976-1-yakoyoku@gmail.com
[ Removed `Suggested-by` as discussed in mailing list. ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/Makefile

@@ -374,6 +374,7 @@ quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L
 
 rust-analyzer:
 	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
+		--cfgs='core=$(core-cfgs)' --cfgs='alloc=$(alloc-cfgs)' \
 		$(abs_srctree) $(abs_objtree) \
 		$(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
 		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json

scripts/generate_rust_analyzer.py

@@ -10,7 +10,15 @@ import os
 import pathlib
 import sys
 
-def generate_crates(srctree, objtree, sysroot_src, external_src):
+def args_crates_cfgs(cfgs):
+    crates_cfgs = {}
+    for cfg in cfgs:
+        crate, vals = cfg.split("=", 1)
+        crates_cfgs[crate] = vals.replace("--cfg", "").split()
+
+    return crates_cfgs
+
+def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs):
     # Generate the configuration list.
     cfg = []
     with open(objtree / "include" / "generated" / "rustc_cfg") as fd:
@@ -24,6 +32,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src):
     # Avoid O(n^2) iterations by keeping a map of indexes.
     crates = []
     crates_indexes = {}
+    crates_cfgs = args_crates_cfgs(cfgs)
 
     def append_crate(display_name, root_module, deps, cfg=[], is_workspace_member=True, is_proc_macro=False):
         crates_indexes[display_name] = len(crates)
@@ -45,6 +54,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src):
         "core",
         sysroot_src / "core" / "src" / "lib.rs",
         [],
+        cfg=crates_cfgs.get("core", []),
         is_workspace_member=False,
     )
 
@@ -58,6 +68,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src):
         "alloc",
         srctree / "rust" / "alloc" / "lib.rs",
         ["core", "compiler_builtins"],
+        cfg=crates_cfgs.get("alloc", []),
     )
 
     append_crate(
@@ -131,6 +142,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src):
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument('--verbose', '-v', action='store_true')
+    parser.add_argument('--cfgs', action='append', default=[])
     parser.add_argument("srctree", type=pathlib.Path)
     parser.add_argument("objtree", type=pathlib.Path)
     parser.add_argument("sysroot_src", type=pathlib.Path)
@@ -143,7 +155,7 @@ def main():
     )
 
     rust_project = {
-        "crates": generate_crates(args.srctree, args.objtree, args.sysroot_src, args.exttree),
+        "crates": generate_crates(args.srctree, args.objtree, args.sysroot_src, args.exttree, args.cfgs),
         "sysroot_src": str(args.sysroot_src),
     }