Disallow proc-macro-crate being used in Buck builds

Summary: The `proc-macro-crate` crate involves looking at the filesystem for a Cargo.toml file in the directory given by $CARGO_MANIFEST_DIR, and parsing it to pick out names of crates. This crate is not possible to use correctly from a Buck build.

Reviewed By: capickett

Differential Revision: D61338693

fbshipit-source-id: 7236db8e54d9a872ab274678412fb57215fd27da

shed/facet/BUCK

@@ -34,12 +34,28 @@ rust_library(
     name = "facet_proc_macros",
     srcs = glob(["proc_macros/*.rs"]),
     autocargo = {
+        "cargo_toml_config": {
+            "dependencies_override": {
+                "dependencies": {
+                    "proc-macro-crate": {
+                        "version": "1.1.0",
+                    },
+                },
+            },
+            "lints": {
+                "rust": {
+                    "unexpected_cfgs": {
+                        "check-cfg": ["cfg(fb_buck_build)"],
+                        "level": "warn",
+                    },
+                },
+            },
+        },
         "cargo_toml_dir": "proc_macros",
     },
     crate_root = "proc_macros/lib.rs",
     proc_macro = True,
     deps = [
-        "fbsource//third-party/rust:proc-macro-crate",
         "fbsource//third-party/rust:proc-macro2",
         "fbsource//third-party/rust:quote",
         "fbsource//third-party/rust:syn",

shed/facet/proc_macros/Cargo.toml

@@ -20,3 +20,6 @@ proc-macro-crate = "1.1.0"
 proc-macro2 = { version = "1.0.70", features = ["span-locations"] }
 quote = "1.0.29"
 syn = { version = "2.0.38", features = ["extra-traits", "fold", "full", "visit", "visit-mut"] }
+
+[lints]
+rust = { unexpected_cfgs = { check-cfg = ["cfg(fb_buck_build)"], level = "warn" } }

shed/facet/proc_macros/lib.rs

@@ -13,19 +13,23 @@
 //!
 //! See the crate-level documentation for the `facet` crate for details.
 
-use proc_macro_crate::crate_name;
-use proc_macro_crate::FoundCrate;
-
 mod container_impl;
 mod facet_impl;
 mod factory_impl;
 mod util;
 
 fn facet_crate_name() -> String {
-    match crate_name("facet") {
-        Ok(FoundCrate::Name(n)) => n,
-        _ => "facet".to_string(),
+    #[cfg(not(fb_buck_build))]
+    {
+        use proc_macro_crate::crate_name;
+        use proc_macro_crate::FoundCrate;
+
+        if let Ok(FoundCrate::Name(name)) = crate_name("facet") {
+            return name;
+        }
     }
+
+    "facet".to_string()
 }
 
 /// Mark a `struct` as a facet container.  See the crate-level documentation