Auto merge of #139731 - jieyouxu:rmake-rustdoc-auto-cross, r=<try>

[WIP] Enable automatic cross-compilation for run-make rustdoc tests

Extracted out of #139244.
Helps with #138066.

r? `@ghost`

try-job: armhf-gnu
try-job: test-various
try-job: x86_64-msvc-1
try-job: i686-msvc-1
try-job: x86_64-mingw-1
try-job: aarch64-apple
try-job: x86_64-apple-1

Author: bors

src/tools/run-make-support/src/external_deps/rustdoc.rs

@@ -3,21 +3,35 @@ use std::path::Path;
 
 use crate::command::Command;
 use crate::env::env_var;
+use crate::target;
 use crate::util::set_host_compiler_dylib_path;
 
-/// Construct a new `rustdoc` invocation.
+/// Construct a new `rustdoc` invocation with target automatically set to cross-compile target. Use
+/// [`bare_rustdoc`] to avoid this.
 #[track_caller]
 pub fn rustdoc() -> Rustdoc {
     Rustdoc::new()
 }
 
+/// Bare `rustdoc` invocation, no args set.
+#[track_caller]
+pub fn bare_rustdoc() -> Rustdoc {
+    Rustdoc::bare()
+}
+
 #[derive(Debug)]
 #[must_use]
 pub struct Rustdoc {
     cmd: Command,
+    target: Option<String>,
 }
 
-crate::macros::impl_common_helpers!(Rustdoc);
+// Only fill in the target just before execution, so that it can be overridden.
+crate::macros::impl_common_helpers!(Rustdoc, |rustdoc: &mut Rustdoc| {
+    if let Some(target) = &rustdoc.target {
+        rustdoc.cmd.arg(&format!("--target={target}"));
+    }
+});
 
 #[track_caller]
 fn setup_common() -> Command {
@@ -28,11 +42,19 @@ fn setup_common() -> Command {
 }
 
 impl Rustdoc {
-    /// Construct a bare `rustdoc` invocation.
+    /// Construct a new `rustdoc` invocation with target automatically set to cross-compile target.
+    /// Use [`bare_rustdoc`] to avoid this.
     #[track_caller]
     pub fn new() -> Self {
         let cmd = setup_common();
-        Self { cmd }
+        Self { cmd, target: Some(target()) }
+    }
+
+    /// Bare `rustdoc` invocation, no args set.
+    #[track_caller]
+    pub fn bare() -> Self {
+        let cmd = setup_common();
+        Self { cmd, target: None }
     }
 
     /// Specify where an external library is located.
@@ -85,8 +107,9 @@ impl Rustdoc {
 
     /// Specify the target triple, or a path to a custom target json spec file.
     pub fn target<S: AsRef<str>>(&mut self, target: S) -> &mut Self {
-        let target = target.as_ref();
-        self.cmd.arg(format!("--target={target}"));
+        // We store the target as a separate field, so that it can be specified multiple times.
+        // This is in particular useful to override the default target set in `Rustdoc::new()`.
+        self.target = Some(target.as_ref().to_string());
         self
     }
 

src/tools/run-make-support/src/lib.rs

@@ -70,7 +70,7 @@ pub use llvm::{
 };
 pub use python::python_command;
 pub use rustc::{bare_rustc, rustc, rustc_path, Rustc};
-pub use rustdoc::{rustdoc, Rustdoc};
+pub use rustdoc::{bare_rustdoc, rustdoc, Rustdoc};
 
 /// [`diff`][mod@diff] is implemented in terms of the [similar] library.
 ///

tests/run-make/rustdoc-default-output/rmake.rs

@@ -3,10 +3,11 @@
 // ensures the output of rustdoc's help menu is as expected.
 // See https://github.com/rust-lang/rust/issues/88756
 
-use run_make_support::{diff, rustdoc};
+use run_make_support::{bare_rustdoc, diff};
 
 fn main() {
-    let out = rustdoc().run().stdout_utf8();
+    // Use `bare_rustdoc` to ensure no `--target` is set.
+    let out = bare_rustdoc().run().stdout_utf8();
     diff()
         .expected_file("output-default.stdout")
         .actual_text("actual", out)