Auto merge of #9128 - poliorcetics:respect-shortness-rustdoc, r=ehuss

Pass the error message format to rustdoc

- Goes with rust-lang/rust#81675.
- Will help with rust-lang/rust#81662.

This is my first PR to Cargo and I haven't finished reading the contributor guide yet, how should I add tests for this ? Did I had the code in the correct place ?

src/cargo/core/compiler/context/mod.rs

@@ -228,6 +228,7 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
                 let mut unstable_opts = false;
                 let mut args = compiler::extern_args(&self, unit, &mut unstable_opts)?;
                 args.extend(compiler::lto_args(&self, unit));
+
                 for feature in &unit.features {
                     args.push("--cfg".into());
                     args.push(format!("feature=\"{}\"", feature).into());
@@ -242,6 +243,16 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
                     }
                 }
                 args.extend(self.bcx.rustdocflags_args(unit).iter().map(Into::into));
+
+                use super::MessageFormat;
+                let format = match self.bcx.build_config.message_format {
+                    MessageFormat::Short => "short",
+                    MessageFormat::Human => "human",
+                    MessageFormat::Json { .. } => "json",
+                };
+                args.push("--error-format".into());
+                args.push(format.into());
+
                 self.compilation.to_doc_test.push(compilation::Doctest {
                     unit: unit.clone(),
                     args,

tests/testsuite/message_format.rs

@@ -1,6 +1,6 @@
 //! Tests for --message-format flag.
 
-use cargo_test_support::{basic_manifest, project};
+use cargo_test_support::{basic_lib_manifest, basic_manifest, is_nightly, project};
 
 #[cargo_test]
 fn cannot_specify_two() {
@@ -109,3 +109,30 @@ fn cargo_renders_ansi() {
         .with_stdout_contains("[..]\\u001b[38;5;9merror[..]")
         .run();
 }
+
+#[cargo_test]
+fn cargo_renders_doctests() {
+    if !is_nightly() {
+        // --error-format=short support added in 1.51
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_lib_manifest("foo"))
+        .file(
+            "src/lib.rs",
+            "\
+            /// ```rust
+            /// bar()
+            /// ```
+            pub fn bar() {}
+            ",
+        )
+        .build();
+
+    p.cargo("test --doc --message-format short")
+        .with_status(101)
+        .with_stdout_contains("src/lib.rs:2:1: error[E0425]:[..]")
+        .with_stdout_contains("[..]src/lib.rs - bar (line 1)[..]")
+        .run();
+}