moved cross-compiling doctests behind the doctest-xcompile feature flag

Author: Goirad

src/cargo/core/features.rs

@@ -336,6 +336,7 @@ pub struct CliUnstable {
     pub binary_dep_depinfo: bool,
     pub build_std: Option<Vec<String>>,
     pub timings: Option<Vec<String>>,
+    pub doctest_xcompile: bool,
 }
 
 impl CliUnstable {
@@ -393,6 +394,7 @@ impl CliUnstable {
                 self.build_std = Some(crate::core::compiler::standard_lib::parse_unstable_flag(v))
             }
             "timings" => self.timings = Some(parse_timings(v)),
+            "doctest-xcompile" => self.doctest_xcompile = true,
             _ => failure::bail!("unknown `-Z` flag specified: {}", k),
         }
 

src/cargo/ops/cargo_test.rs

@@ -140,7 +140,16 @@ fn run_doc_tests(
     let mut errors = Vec::new();
     let config = options.compile_opts.config;
 
-    let runtool = compilation.target_runner();
+    // The unstable doctest-xcompile feature enables both per-target-ignores and
+    // cross-compiling doctests. As a side effect, this feature also gates running
+    // doctests with runtools when target == host.
+    let doctest_xcompile = config.cli_unstable().doctest_xcompile;
+    let mut runtool: &Option<(std::path::PathBuf, Vec<String>)> = &None;
+    if doctest_xcompile {
+        runtool = compilation.target_runner();
+    } else if compilation.host != compilation.target {
+        return Ok((Test::Doc, errors));
+    }
 
     for doctest_info in &compilation.to_doc_test {
         let Doctest {
@@ -155,9 +164,10 @@ fn run_doc_tests(
             .arg("--crate-name")
             .arg(&target.crate_name());
 
-        p.arg("-Z");
-        p.arg("unstable-options");
-        p.arg("--enable-per-target-ignores");
+        if doctest_xcompile {
+            p.arg("-Zunstable-options");
+            p.arg("--enable-per-target-ignores");
+        }
 
         runtool.as_ref().map(|(runtool, runtool_args)| {
             p.arg("--target").arg(&compilation.target);

tests/testsuite/cross_compile.rs

@@ -535,8 +535,7 @@ fn cross_tests() {
 [COMPILING] foo v0.0.0 ([CWD])
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
 [RUNNING] target/{triple}/debug/deps/foo-[..][EXE]
-[RUNNING] target/{triple}/debug/deps/bar-[..][EXE]
-[DOCTEST] Skipping doctests, no runner defined for target",
+[RUNNING] target/{triple}/debug/deps/bar-[..][EXE]",
             triple = target
         ))
         .with_stdout_contains("test test_foo ... ok")
@@ -596,7 +595,6 @@ fn no_cross_doctests() {
 [COMPILING] foo v0.0.1 ([CWD])
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
 [RUNNING] target/{triple}/debug/deps/foo-[..][EXE]
-[DOCTEST] Skipping doctests, no runner defined for target
 ",
             triple = target
         ))
@@ -1225,8 +1223,7 @@ fn cross_test_dylib() {
 [COMPILING] foo v0.0.1 ([CWD])
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
 [RUNNING] target/{arch}/debug/deps/foo-[..][EXE]
-[RUNNING] target/{arch}/debug/deps/test-[..][EXE]
-[DOCTEST] Skipping doctests, no runner defined for target",
+[RUNNING] target/{arch}/debug/deps/test-[..][EXE]",
             arch = cross_compile::alternate()
         ))
         .with_stdout_contains_n("test foo ... ok", 2)