Display environment variables for rustc commands

This picks up on the work done in PR #5683.

The extra output is only displayed with `-vv`.

The Windows output has the form `set FOO=foo && BAR=bar rustc ...` instead of
the form that suggested in #5683 to make escaping easier and since it's
simpler.

src/cargo/core/compiler/compilation.rs

@@ -89,6 +89,9 @@ impl<'cfg> Compilation<'cfg> {
         } else {
             bcx.rustc.process()
         };
+        if bcx.config.extra_verbose() {
+            rustc.display_env_vars();
+        }
         for (k, v) in bcx.build_config.extra_rustc_env.iter() {
             rustc.env(k, v);
         }

src/cargo/util/process_builder.rs

@@ -27,11 +27,28 @@ pub struct ProcessBuilder {
     ///
     /// [jobserver_docs]: https://docs.rs/jobserver/0.1.6/jobserver/
     jobserver: Option<Client>,
+    /// Whether to include environment variable in display
+    display_env_vars: bool
 }
 
 impl fmt::Display for ProcessBuilder {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "`{}", self.program.to_string_lossy())?;
+        write!(f, "`")?;
+
+        if self.display_env_vars {
+            for (key, val) in self.env.iter() {
+                if let Some(val) = val {
+                    let val = escape(val.to_string_lossy());
+                    if cfg!(windows) {
+                        write!(f, "set {}={} && ", key, val)?;
+                    } else {
+                        write!(f, "{}={} ", key, val)?;
+                    }
+                }
+            }
+        }
+
+        write!(f, "{}", self.program.to_string_lossy())?;
 
         for arg in &self.args {
             write!(f, " {}", escape(arg.to_string_lossy()))?;
@@ -129,6 +146,12 @@ impl ProcessBuilder {
         self
     }
 
+    /// Enable environment variable display
+    pub fn display_env_vars(&mut self) -> &mut Self {
+        self.display_env_vars = true;
+        self
+    }
+
     /// Run the process, waiting for completion, and mapping non-success exit codes to an error.
     pub fn exec(&self) -> CargoResult<()> {
         let mut command = self.build_command();
@@ -316,6 +339,7 @@ pub fn process<T: AsRef<OsStr>>(cmd: T) -> ProcessBuilder {
         cwd: None,
         env: HashMap::new(),
         jobserver: None,
+        display_env_vars: false,
     }
 }
 

tests/testsuite/build.rs

@@ -1553,6 +1553,40 @@ fn crate_authors_env_vars() {
     p.cargo("test -v").run();
 }
 
+#[test]
+fn vv_prints_rustc_env_vars() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [project]
+            name = "foo"
+            version = "0.0.1"
+            authors = ["escape='\"@example.com"]
+        "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    let mut b = p.cargo("build -vv");
+
+    if cfg!(windows) {
+        b.with_stderr_contains(
+            "[RUNNING] `[..]set CARGO_PKG_NAME=foo && [..]rustc [..]`"
+        ).with_stderr_contains(
+            r#"[RUNNING] `[..]set CARGO_PKG_AUTHORS="escape='\"@example.com" && [..]rustc [..]`"#
+        )
+    } else {
+        b.with_stderr_contains(
+            "[RUNNING] `[..]CARGO_PKG_NAME=foo [..]rustc [..]`"
+        ).with_stderr_contains(
+            r#"[RUNNING] `[..]CARGO_PKG_AUTHORS='escape='\''"@example.com' [..]rustc [..]`"#
+        )
+    };
+
+    b.run();
+}
+
 // The tester may already have LD_LIBRARY_PATH=::/foo/bar which leads to a false positive error
 fn setenv_for_removing_empty_component(mut execs: Execs) -> Execs {
     let v = dylib_path_envvar();

tests/testsuite/build_script.rs

@@ -2965,13 +2965,13 @@ fn warnings_printed_on_vv() {
 [DOWNLOADING] crates ...
 [DOWNLOADED] bar v0.1.0 ([..])
 [COMPILING] bar v0.1.0
-[RUNNING] `rustc [..]`
+[RUNNING] `[..] rustc [..]`
 [RUNNING] `[..]`
 warning: foo
 warning: bar
-[RUNNING] `rustc [..]`
+[RUNNING] `[..] rustc [..]`
 [COMPILING] foo v0.5.0 ([..])
-[RUNNING] `rustc [..]`
+[RUNNING] `[..] rustc [..]`
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
 ",
         )
@@ -3010,10 +3010,10 @@ fn output_shows_on_vv() {
         .with_stderr(
             "\
 [COMPILING] foo v0.5.0 ([..])
-[RUNNING] `rustc [..]`
+[RUNNING] `[..] rustc [..]`
 [RUNNING] `[..]`
 [foo 0.5.0] stderr
-[RUNNING] `rustc [..]`
+[RUNNING] `[..] rustc [..]`
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
 ",
         )