Auto merge of #10918 - ehuss:fix-formats_source, r=Eh2406

Fix formats_source test requiring rustfmt.

The requirements added in #9892 that `rustfmt` must be present doesn't work in the `rust-lang/rust` environment. There are two issues:

* Cargo is run without using rustup. If you also have rustup installed, the test will fail because the `rustfmt` binary found in `PATH` will fail to choose a toolchain because HOME points to the sandbox home which does not have a rustup configuration.
* rust-lang/rust CI uninstalls rustup, and does not have rustfmt in PATH at all.  It is not practical to make rustfmt available there.

The solution here is to just revert the behavior back to where it was where it checks if it can run `rustfmt` in the sandbox. This should work for anyone who has a normal rustup installation (including Cargo's CI). If running the testsuite without rustup, then the test will be skipped.

This also includes a small enhancement to provide better error information when rustfmt fails.

src/cargo/ops/cargo_new.rs

@@ -10,8 +10,7 @@ use std::collections::BTreeMap;
 use std::fmt;
 use std::io::{BufRead, BufReader, ErrorKind};
 use std::path::{Path, PathBuf};
-use std::process::Command;
-use std::str::{from_utf8, FromStr};
+use std::str::FromStr;
 use toml_edit::easy as toml;
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -830,14 +829,12 @@ mod tests {
             paths::write(&path_of_source_file, default_file_content)?;
 
             // Format the newly created source file
-            match Command::new("rustfmt").arg(&path_of_source_file).output() {
-                Err(e) => log::warn!("failed to call rustfmt: {}", e),
-                Ok(output) => {
-                    if !output.status.success() {
-                        log::warn!("rustfmt failed: {:?}", from_utf8(&output.stdout));
-                    }
-                }
-            };
+            if let Err(e) = cargo_util::ProcessBuilder::new("rustfmt")
+                .arg(&path_of_source_file)
+                .exec_with_output()
+            {
+                log::warn!("failed to call rustfmt: {:#}", e);
+            }
         }
     }
 

tests/testsuite/init/formats_source/mod.rs

@@ -1,11 +1,19 @@
 use cargo_test_support::compare::assert_ui;
 use cargo_test_support::prelude::*;
-use cargo_test_support::Project;
+use cargo_test_support::{process, Project};
 
 use cargo_test_support::curr_dir;
 
-#[cargo_test(requires_rustfmt)]
+#[cargo_test]
 fn formats_source() {
+    // This cannot use `requires_rustfmt` because rustfmt is not available in
+    // the rust-lang/rust environment. Additionally, if running cargo without
+    // rustup (but with rustup installed), this test also fails due to HOME
+    // preventing the proxy from choosing a toolchain.
+    if let Err(e) = process("rustfmt").arg("-V").exec_with_output() {
+        eprintln!("skipping test, rustfmt not available:\n{e:?}");
+        return;
+    }
     let project = Project::from_template(curr_dir!().join("in"));
     let project_root = &project.root();