add a reason to masquerade_as_nightly_cargo so it is searchable

crates/cargo-test-support/src/lib.rs

@@ -806,9 +806,14 @@ impl Execs {
         p.build_command()
     }
 
-    pub fn masquerade_as_nightly_cargo(&mut self) -> &mut Self {
+    /// Enables nightly features for testing
+    ///
+    /// The list of reasons should be why nightly cargo is needed. If it is
+    /// becuase of an unstable feature put the name of the feature as the reason,
+    /// e.g. `&["print-im-a-teapot"]`
+    pub fn masquerade_as_nightly_cargo(&mut self, reasons: &[&str]) -> &mut Self {
         if let Some(ref mut p) = self.process_builder {
-            p.masquerade_as_nightly_cargo();
+            p.masquerade_as_nightly_cargo(reasons);
         }
         self
     }
@@ -1139,17 +1144,20 @@ fn _process(t: &OsStr) -> ProcessBuilder {
 
 /// Enable nightly features for testing
 pub trait ChannelChanger {
-    fn masquerade_as_nightly_cargo(self) -> Self;
+    /// The list of reasons should be why nightly cargo is needed. If it is
+    /// becuase of an unstable feature put the name of the feature as the reason,
+    /// e.g. `&["print-im-a-teapot"]`.
+    fn masquerade_as_nightly_cargo(self, _reasons: &[&str]) -> Self;
 }
 
 impl ChannelChanger for &mut ProcessBuilder {
-    fn masquerade_as_nightly_cargo(self) -> Self {
+    fn masquerade_as_nightly_cargo(self, _reasons: &[&str]) -> Self {
         self.env("__CARGO_TEST_CHANNEL_OVERRIDE_DO_NOT_USE_THIS", "nightly")
     }
 }
 
 impl ChannelChanger for snapbox::cmd::Command {
-    fn masquerade_as_nightly_cargo(self) -> Self {
+    fn masquerade_as_nightly_cargo(self, _reasons: &[&str]) -> Self {
         self.env("__CARGO_TEST_CHANNEL_OVERRIDE_DO_NOT_USE_THIS", "nightly")
     }
 }

src/cargo/core/features.rs

@@ -86,7 +86,9 @@
 //!      `CliUnstable. Remove the `(unstable)` note in the clap help text if
 //!      necessary.
 //! 2. Remove `masquerade_as_nightly_cargo` from any tests, and remove
-//!    `cargo-features` from `Cargo.toml` test files if any.
+//!    `cargo-features` from `Cargo.toml` test files if any. You can
+//!     quickly find what needs to be removed by searching for the name
+//!     of the feature, e.g. `print_im_a_teapot`
 //! 3. Update the docs in unstable.md to move the section to the bottom
 //!    and summarize it similar to the other entries. Update the rest of the
 //!    documentation to add the new feature.

src/doc/contrib/src/tests/writing.md

@@ -71,11 +71,11 @@ fn <description>() {
 #### Testing Nightly Features
 
 If you are testing a Cargo feature that only works on "nightly" Cargo, then
-you need to call `masquerade_as_nightly_cargo` on the process builder like
-this:
+you need to call `masquerade_as_nightly_cargo` on the process builder and pass 
+the name of the feature as the reason, like this:
 
 ```rust,ignore
-p.cargo("build").masquerade_as_nightly_cargo()
+p.cargo("build").masquerade_as_nightly_cargo(&["print-im-a-teapot"])
 ```
 
 If you are testing a feature that only works on *nightly rustc* (such as
@@ -192,12 +192,12 @@ Be sure to check the snapshots to make sure they make sense.
 #### Testing Nightly Features
 
 If you are testing a Cargo feature that only works on "nightly" Cargo, then
-you need to call `masquerade_as_nightly_cargo` on the process builder like
-this:
+you need to call `masquerade_as_nightly_cargo` on the process builder and pass
+the name of the feature as the reason, like this:
 
 ```rust,ignore
     snapbox::cmd::Command::cargo()
-        .masquerade_as_nightly_cargo()
+        .masquerade_as_nightly_cargo(&["print-im-a-teapot"])
 ```
 
 If you are testing a feature that only works on *nightly rustc* (such as

tests/build-std/main.rs

@@ -32,7 +32,7 @@ fn enable_build_std(e: &mut Execs, arg: Option<&str>) {
         None => "-Zbuild-std".to_string(),
     };
     e.arg(arg);
-    e.masquerade_as_nightly_cargo();
+    e.masquerade_as_nightly_cargo(&["build-std"]);
 }
 
 // Helper methods used in the tests below

tests/testsuite/advanced_env.rs

@@ -31,7 +31,7 @@ fn source_config_env() {
     let path = paths::root().join("registry");
 
     p.cargo("check -Zadvanced-env")
-        .masquerade_as_nightly_cargo()
+        .masquerade_as_nightly_cargo(&["advanced-env"])
         .env("CARGO_SOURCE_crates-io_REPLACE_WITH", "my-local-source")
         .env("CARGO_SOURCE_my-local-source_LOCAL_REGISTRY", path)
         .run();