Simplify markdown_input fn and subsequent logic

src/librustdoc/config.rs

@@ -3,6 +3,7 @@ use std::ffi::OsStr;
 use std::fmt;
 use std::io;
 use std::io::Read;
+use std::path::Path;
 use std::path::PathBuf;
 use std::str::FromStr;
 
@@ -816,12 +817,10 @@ impl Options {
     }
 
     /// Returns `true` if the file given as `self.input` is a Markdown file.
-    pub(crate) fn markdown_input(&self) -> bool {
+    pub(crate) fn markdown_input(&self) -> Option<&Path> {
         self.input
             .opt_path()
-            .map(std::path::Path::extension)
-            .flatten()
-            .is_some_and(|e| e == "md" || e == "markdown")
+            .filter(|p| matches!(p.extension(), Some(e) if e == "md" || e == "markdown"))
     }
 }
 

src/librustdoc/lib.rs

@@ -730,18 +730,13 @@ fn main_args(
         core::new_dcx(options.error_format, None, options.diagnostic_width, &options.unstable_opts);
 
     match (options.should_test, options.markdown_input()) {
-        (true, true) => return wrap_return(&diag, markdown::test(options)),
-        (true, false) => return doctest::run(&diag, options),
-        (false, true) => {
+        (true, Some(_)) => return wrap_return(&diag, markdown::test(options)),
+        (true, None) => return doctest::run(&diag, options),
+        (false, Some(input)) => {
+            let input = input.to_owned();
             let edition = options.edition;
             let config = core::create_config(options, &render_options, using_internal_features);
 
-            use rustc_session::config::Input;
-            let input = match &config.input {
-                Input::File(path) => path.clone(),
-                Input::Str { .. } => unreachable!("only path to markdown are supported"),
-            };
-
             // `markdown::render` can invoke `doctest::make_test`, which
             // requires session globals and a thread pool, so we use
             // `run_compiler`.
@@ -752,7 +747,7 @@ fn main_args(
                 }),
             );
         }
-        (false, false) => {}
+        (false, None) => {}
     }
 
     // need to move these items separately because we lose them by the time the closure is called,