Conditionally mark the test cfg as a well known cfg

src/cargo/core/compiler/mod.rs

@@ -1391,17 +1391,22 @@ fn check_cfg_args(unit: &Unit) -> Vec<OsString> {
     }
     arg_feature.push("))");
 
-    // In addition to the package features, we also include the `test` cfg (since
-    // compiler-team#785, as to be able to someday apply yt conditionaly), as well
-    // the `docsrs` cfg from the docs.rs service.
+    // In addition to the package features, we also conditionaly include the `test` cfg
+    // based on the unit target "test" field (ie `lib.test = false`, `[[bin]] test = false` and
+    // others).
     //
-    // We include `docsrs` here (in Cargo) instead of rustc, since there is a much closer
+    // We also include `docsrs` here (in Cargo) instead of rustc, since there is a much closer
     // relationship between Cargo and docs.rs than rustc and docs.rs. In particular, all
     // users of docs.rs use Cargo, but not all users of rustc (like Rust-for-Linux) use docs.rs.
+    let arg_extra = if unit.target.tested() {
+        OsString::from("cfg(docsrs,test)")
+    } else {
+        OsString::from("cfg(docsrs)")
+    };
 
     vec![
         OsString::from("--check-cfg"),
-        OsString::from("cfg(docsrs,test)"),
+        arg_extra,
         OsString::from("--check-cfg"),
         arg_feature,
     ]

tests/testsuite/check_cfg.rs

@@ -336,17 +336,18 @@ fn test_false_lib() {
         .build();
 
     p.cargo("check -v")
-        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs,test"))
+        .with_stderr_does_not_contain(x!("rustc" => "cfg" of "docsrs,test"))
+        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs"))
         .run();
 
     p.cargo("clean").run();
     p.cargo("test -v")
-        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs,test"))
+        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs"))
         .run();
 
     p.cargo("clean").run();
     p.cargo("test --lib -v")
-        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs,test"))
+        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs"))
         .run();
 }
 
@@ -372,7 +373,8 @@ fn test_false_bins() {
         .build();
 
     p.cargo("check -v")
-        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs,test")) // for foo & deamon
+        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs,test")) // for foo
+        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs")) // for deamon
         .run();
 }
 
@@ -401,7 +403,8 @@ fn test_false_examples() {
         .build();
 
     p.cargo("check --examples -v")
-        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs,test"))
+        .with_stderr_does_not_contain(x!("rustc" => "cfg" of "docsrs,test"))
+        .with_stderr_contains(x!("rustc" => "cfg" of "docsrs"))
         .run();
 }