Rollup merge of #99055 - GuillaumeGomez:rustdoc-help-options, r=jyn514

Fix rustdoc help options

Fixes #98976.

Since you're the one who found out about the problem and also provided the solution (thanks for both!):

r? ```@jyn514```

src/librustdoc/config.rs

@@ -329,6 +329,17 @@ impl Options {
             return Err(0);
         }
 
+        let z_flags = matches.opt_strs("Z");
+        if z_flags.iter().any(|x| *x == "help") {
+            print_flag_list("-Z", config::DB_OPTIONS);
+            return Err(0);
+        }
+        let c_flags = matches.opt_strs("C");
+        if c_flags.iter().any(|x| *x == "help") {
+            print_flag_list("-C", config::CG_OPTIONS);
+            return Err(0);
+        }
+
         let color = config::parse_color(matches);
         let config::JsonConfig { json_rendered, json_unused_externs, .. } =
             config::parse_json(matches);
@@ -343,17 +354,6 @@ impl Options {
         // check for deprecated options
         check_deprecated_options(matches, &diag);
 
-        let z_flags = matches.opt_strs("Z");
-        if z_flags.iter().any(|x| *x == "help") {
-            print_flag_list("-Z", config::DB_OPTIONS);
-            return Err(0);
-        }
-        let c_flags = matches.opt_strs("C");
-        if c_flags.iter().any(|x| *x == "help") {
-            print_flag_list("-C", config::CG_OPTIONS);
-            return Err(0);
-        }
-
         if matches.opt_strs("passes") == ["list"] {
             println!("Available passes for running rustdoc:");
             for pass in passes::PASSES {

src/test/rustdoc-ui/c-help.rs

@@ -0,0 +1,4 @@
+// check-pass
+// compile-flags: -Chelp
+
+pub struct Foo;

src/test/rustdoc-ui/c-help.stdout

@@ -0,0 +1,51 @@
+    -C                       ar=val -- this option is deprecated and does nothing
+    -C               code-model=val -- choose the code model to use (`rustc --print code-models` for details)
+    -C            codegen-units=val -- divide crate into N units to optimize in parallel
+    -C       control-flow-guard=val -- use Windows Control Flow Guard (default: no)
+    -C         debug-assertions=val -- explicitly enable the `cfg(debug_assertions)` directive
+    -C                debuginfo=val -- debug info emission level (0 = no debug info, 1 = line tables only, 2 = full debug info with variable and type information; default: 0)
+    -C default-linker-libraries=val -- allow the linker to link its default libraries (default: no)
+    -C            embed-bitcode=val -- emit bitcode in rlibs (default: yes)
+    -C           extra-filename=val -- extra data to put in each output filename
+    -C     force-frame-pointers=val -- force use of the frame pointers
+    -C      force-unwind-tables=val -- force use of unwind tables
+    -C              incremental=val -- enable incremental compilation
+    -C         inline-threshold=val -- set the threshold for inlining a function
+    -C      instrument-coverage=val -- instrument the generated code to support LLVM source-based code coverage reports (note, the compiler build config must include `profiler = true`); implies `-C symbol-mangling-version=v0`. Optional values are:
+        `=all` (implicit value)
+        `=except-unused-generics`
+        `=except-unused-functions`
+        `=off` (default)
+    -C                 link-arg=val -- a single extra argument to append to the linker invocation (can be used several times)
+    -C                link-args=val -- extra arguments to append to the linker invocation (space separated)
+    -C           link-dead-code=val -- keep dead code at link time (useful for code coverage) (default: no)
+    -C      link-self-contained=val -- control whether to link Rust provided C objects/libraries or rely
+        on C toolchain installed in the system
+    -C                   linker=val -- system linker to link outputs with
+    -C            linker-flavor=val -- linker flavor
+    -C        linker-plugin-lto=val -- generate build artifacts that are compatible with linker-based LTO
+    -C                llvm-args=val -- a list of arguments to pass to LLVM (space separated)
+    -C                      lto=val -- perform LLVM link-time optimizations
+    -C                 metadata=val -- metadata to mangle symbol names with
+    -C    no-prepopulate-passes=val -- give an empty list of passes to the pass manager
+    -C               no-redzone=val -- disable the use of the redzone
+    -C           no-stack-check=val -- this option is deprecated and does nothing
+    -C       no-vectorize-loops=val -- disable loop vectorization optimization passes
+    -C         no-vectorize-slp=val -- disable LLVM's SLP vectorization pass
+    -C                opt-level=val -- optimization level (0-3, s, or z; default: 0)
+    -C          overflow-checks=val -- use overflow checks for integer arithmetic
+    -C                    panic=val -- panic strategy to compile crate with
+    -C                   passes=val -- a list of extra LLVM passes to run (space separated)
+    -C           prefer-dynamic=val -- prefer dynamic linking to static linking (default: no)
+    -C         profile-generate=val -- compile the program with profiling instrumentation
+    -C              profile-use=val -- use the given `.profdata` file for profile-guided optimization
+    -C         relocation-model=val -- control generation of position-independent code (PIC) (`rustc --print relocation-models` for details)
+    -C                   remark=val -- print remarks for these optimization passes (space separated, or "all")
+    -C                    rpath=val -- set rpath values in libs/exes (default: no)
+    -C               save-temps=val -- save all temporary output files during compilation (default: no)
+    -C               soft-float=val -- use soft float ABI (*eabihf targets only) (default: no)
+    -C          split-debuginfo=val -- how to handle split-debuginfo, a platform-specific option
+    -C                    strip=val -- tell the linker which information to strip (`none` (default), `debuginfo` or `symbols`)
+    -C  symbol-mangling-version=val -- which mangling version to use for symbol names ('legacy' (default) or 'v0')
+    -C               target-cpu=val -- select target processor (`rustc --print target-cpus` for details)
+    -C           target-feature=val -- target specific attributes. (`rustc --print target-features` for details). This feature is unsafe.

src/test/rustdoc-ui/z-help.rs

@@ -0,0 +1,4 @@
+// check-pass
+// compile-flags: -Zhelp
+
+pub struct Foo;