Rollup merge of #146150 - weihanglo:rustdoc-emit, r=aDotInTheVoid

fix(rustdoc): match rustc `--emit` precedence
Resolves#141664
This changes rustdoc's `--emit` to allow only one instance of each type, regardless of the actual data that `--emit` carries. This matches rustc's `--emit` behavior.
As of the writing, only `dep-info` emit type carries extra data.

Author: Zalathar

src/librustdoc/config.rs

@@ -454,15 +454,22 @@ impl Options {
 returnNone;
 }
 
-letmut emit = Vec::new();
+letmut emit = FxIndexMap::<_,EmitType>::default();
 for list in matches.opt_strs("emit"){
 for kind in list.split(','){
 match kind.parse(){
-Ok(kind) => emit.push(kind),
+Ok(kind) => {
+// De-duplicate emit types and the last wins.
+// Only one instance for each type is allowed
+// regardless the actual data it carries.
+// This matches rustc's `--emit` behavior.
+ emit.insert(std::mem::discriminant(&kind), kind);
+}
 Err(()) => dcx.fatal(format!("unrecognized emission type: {kind}")),
 }
 }
 }
+let emit = emit.into_values().collect::<Vec<_>>();
 
 let show_coverage = matches.opt_present("show-coverage");
 let output_format_s = matches.opt_str("output-format");

tests/run-make/rustdoc-dep-info/rmake.rs

@@ -33,4 +33,16 @@ fn main() {
 // Now we check that we can provide a file name to the `dep-info` argument.
 rustdoc().input("lib.rs").arg("-Zunstable-options").emit("dep-info=bla.d").run();
 assert!(path("bla.d").exists());
+
+// The last emit-type wins. The same behavior as rustc.
+rustdoc()
+.input("lib.rs")
+.arg("-Zunstable-options")
+.emit("dep-info=precedence1.d")
+.emit("dep-info=precedence2.d")
+.emit("dep-info=precedence3.d")
+.run();
+assert!(!path("precedence1.d").exists());
+assert!(!path("precedence2.d").exists());
+assert!(path("precedence3.d").exists());
 }