Beautify doctest path

compiler/rustc_span/src/lib.rs

@@ -451,6 +451,16 @@ impl FileName {
             _ => None,
         }
     }
+
+    /// Returns the path suitable for reading from the file system on the local host,
+    /// if this information exists.
+    pub fn remapped_path_if_available(&self) -> Option<&Path> {
+        match self {
+            FileName::Real(path) => Some(path.remapped_path_if_available()),
+            FileName::DocTest(path, _) => Some(path),
+            _ => return None,
+        }
+    }
 }
 
 /// Represents a span.

src/librustdoc/doctest.rs

@@ -5,7 +5,7 @@ mod rust;
 
 use std::fs::File;
 use std::io::{self, Write};
-use std::path::{Path, PathBuf};
+use std::path::{Component, Path, PathBuf};
 use std::process::{self, Command, Stdio};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
@@ -713,6 +713,22 @@ impl IndividualTestOptions {
     }
 }
 
+fn beautify_path(path: &Path) -> PathBuf {
+    let mut beautiful_path = PathBuf::new();
+
+    for component in path.components().filter(|c| !matches!(c, Component::CurDir)) {
+        if matches!(component, Component::ParentDir) {
+            if beautiful_path.parent().is_none() {
+                return path.canonicalize().unwrap_or_else(|_| path.to_path_buf());
+            }
+            beautiful_path.pop();
+        } else {
+            beautiful_path.push(component.as_os_str());
+        }
+    }
+    beautiful_path
+}
+
 /// A doctest scraped from the code, ready to be turned into a runnable test.
 ///
 /// The pipeline goes: [`clean`] AST -> `ScrapedDoctest` -> `RunnableDoctest`.
@@ -743,8 +759,12 @@ impl ScrapedDocTest {
         if !item_path.is_empty() {
             item_path.push(' ');
         }
-        let name =
-            format!("{} - {item_path}(line {line})", filename.prefer_remapped_unconditionaly());
+        let name = match filename.remapped_path_if_available() {
+            Some(path) => format!("{} - {item_path}(line {line})", beautify_path(path).display()),
+            None => {
+                format!("{} - {item_path}(line {line})", filename.prefer_remapped_unconditionaly())
+            }
+        };
 
         Self { filename, line, langstr, text, name }
     }

tests/run-make/rustdoc-test-path/foo.rs

@@ -0,0 +1,2 @@
+#![doc = include_str!("./sub/bar.md")]
+#![doc = include_str!("sub/../sub/bar.md")]

tests/run-make/rustdoc-test-path/rmake.rs

@@ -0,0 +1,14 @@
+// This test ensures that the file paths displayed in doctests are "beautified",
+// meaning they don't contain ".." or "." characters.
+
+use run_make_support::rustdoc;
+
+fn main() {
+    rustdoc()
+        .input("foo.rs")
+        .arg("--test")
+        .run_fail()
+        .assert_stdout_not_contains("-- ../")
+        .assert_stdout_not_contains("-- ./")
+        .assert_stdout_contains("-- sub/bar.md ");
+}

tests/run-make/rustdoc-test-path/sub/bar.md

@@ -0,0 +1,7 @@
+With a code sample, that has an error:
+
+```rust
+fn main() {
+    let x = 234 // no semicolon here! oh no!
+}
+```