Rollup merge of #94154 - Urgau:rustdoc-check-cfg, r=GuillaumeGomez

Wire up unstable rustc --check-cfg to rustdoc

This pull-request wire up the new unstable `--check-cfg` option from `rustc` to `rustdoc` as [requested](https://github.com/rust-lang/rust/pull/93915#discussion_r807560445) in the [pull-request](https://github.com/rust-lang/rust/pull/93915) that introduce `--check-cfg`.

The motivation was describe in the original PR by ``@jyn514`` who wrote https://github.com/rust-lang/rust/pull/89346#issuecomment-930129761:
> > add plumbing to pass --check-cfg from rustdoc (do we want this one?)
>
> It would be useful, I think, it catches issues like cfg(doctst) or something (and in general I would like expansion to match rustc as closely as possible).

4 files changed, 16 insertions, 2 deletions

diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 6e483d27f33..93f90b90e0a 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -80,6 +80,8 @@ crate struct Options {
     crate extern_strs: Vec<String>,
     /// List of `cfg` flags to hand to the compiler. Always includes `rustdoc`.
     crate cfgs: Vec<String>,
+    /// List of check cfg flags to hand to the compiler.
+    crate check_cfgs: Vec<String>,
     /// Codegen options to hand to the compiler.
     crate codegen_options: CodegenOptions,
     /// Codegen options strings to hand to the compiler.
@@ -172,6 +174,7 @@ impl fmt::Debug for Options {
             .field("libs", &self.libs)
             .field("externs", &FmtExterns(&self.externs))
             .field("cfgs", &self.cfgs)
+            .field("check-cfgs", &self.check_cfgs)
             .field("codegen_options", &"...")
             .field("debugging_options", &"...")
             .field("target", &self.target)
@@ -506,6 +509,7 @@ impl Options {
         };
 
         let cfgs = matches.opt_strs("cfg");
+        let check_cfgs = matches.opt_strs("check-cfg");
 
         let extension_css = matches.opt_str("e").map(|s| PathBuf::from(&s));
 
@@ -677,6 +681,7 @@ impl Options {
             externs,
             extern_strs,
             cfgs,
+            check_cfgs,
             codegen_options,
             codegen_options_strs,
             debugging_opts,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index c2f6f7aea75..2b82575f710 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -192,6 +192,7 @@ crate fn create_config(
         libs,
         externs,
         mut cfgs,
+        check_cfgs,
         codegen_options,
         debugging_opts,
         target,
@@ -219,6 +220,7 @@ crate fn create_config(
         // these are definitely not part of rustdoc, but we want to warn on them anyway.
         rustc_lint::builtin::RENAMED_AND_REMOVED_LINTS.name.to_string(),
         rustc_lint::builtin::UNKNOWN_LINTS.name.to_string(),
+        rustc_lint::builtin::UNEXPECTED_CFGS.name.to_string(),
     ];
     lints_to_show.extend(crate::lint::RUSTDOC_LINTS.iter().map(|lint| lint.name.to_string()));
 
@@ -253,7 +255,7 @@ crate fn create_config(
     interface::Config {
         opts: sessopts,
         crate_cfg: interface::parse_cfgspecs(cfgs),
-        crate_check_cfg: interface::parse_check_cfg(vec![]),
+        crate_check_cfg: interface::parse_check_cfg(check_cfgs),
         input,
         input_path: cpath,
         output_file: None,
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index dc9ce052cb5..13253312901 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -91,7 +91,7 @@ crate fn run(options: RustdocOptions) -> Result<(), ErrorReported> {
     let config = interface::Config {
         opts: sessopts,
         crate_cfg: interface::parse_cfgspecs(cfgs),
-        crate_check_cfg: interface::parse_check_cfg(vec![]),
+        crate_check_cfg: interface::parse_check_cfg(options.check_cfgs.clone()),
         input,
         input_path: None,
         output_file: None,
@@ -321,6 +321,12 @@ fn run_test(
     for cfg in &rustdoc_options.cfgs {
         compiler.arg("--cfg").arg(&cfg);
     }
+    if !rustdoc_options.check_cfgs.is_empty() {
+        compiler.arg("-Z").arg("unstable-options");
+        for check_cfg in &rustdoc_options.check_cfgs {
+            compiler.arg("--check-cfg").arg(&check_cfg);
+        }
+    }
     if let Some(sysroot) = rustdoc_options.maybe_sysroot {
         compiler.arg("--sysroot").arg(sysroot);
     }
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 9d3e58a3a66..d7e1f90bcf1 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -259,6 +259,7 @@ fn opts() -> Vec<RustcOptGroup> {
             o.optmulti("L", "library-path", "directory to add to crate search path", "DIR")
         }),
         stable("cfg", |o| o.optmulti("", "cfg", "pass a --cfg to rustc", "")),
+        unstable("check-cfg", |o| o.optmulti("", "check-cfg", "pass a --check-cfg to rustc", "")),
         stable("extern", |o| o.optmulti("", "extern", "pass an --extern to rustc", "NAME[=PATH]")),
         unstable("extern-html-root-url", |o| {
             o.optmulti(