compiletest: support auxiliaries with auxiliaries

To test behaviour that depends on the extern options of intermediate
crates, compiletest auxiliaries must have their own auxiliaries.

Auxiliary compilation previously did not trigger compilation of any
auxiliaries in the auxiliary's headers. In addition, those auxiliaries
would need to be in an `auxiliary/auxiliary` directory, which is
unnecessary and makes some crate graphs harder to write tests for,
such as when A depends on B and C, and B depends on C.

For a test `tests/ui/$path/root.rs`, with the following crate graph:

```
root
|-- grandparent
`-- parent
    `-- grandparent
```

then the intermediate outputs from compiletest will be:

```
build/$target/test/ui/$path/
|-- auxiliary
|   |-- libgrandparent.dylib
|   |-- libparent.dylib
|   |-- grandparent
|   |   |-- grandparent.err
|   |   `-- grandparent.out
|   `-- parent
|       |-- parent.err
|       `-- parent.out
|-- libroot.rmeta
|-- root.err
`-- root.out
```

Signed-off-by: David Wood <david@davidtw.co>

src/tools/compiletest/src/runtest.rs

@@ -1936,7 +1936,7 @@ fn compile_test_general(
     fn document(&self, out_dir: &Path) -> ProcRes {
         if self.props.build_aux_docs {
             for rel_ab in &self.props.aux_builds {
-                let aux_testpaths = self.compute_aux_test_paths(rel_ab);
+                let aux_testpaths = self.compute_aux_test_paths(&self.testpaths, rel_ab);
                 let aux_props =
                     self.props.from_aux_file(&aux_testpaths.file, self.revision, self.config);
                 let aux_cx = TestCx {
@@ -2092,24 +2092,18 @@ fn exec_compiled_test_general(
         proc_res
     }
 
-    /// For each `aux-build: foo/bar` annotation, we check to find the
-    /// file in an `auxiliary` directory relative to the test itself.
-    fn compute_aux_test_paths(&self, rel_ab: &str) -> TestPaths {
-        let test_ab = self
-            .testpaths
-            .file
-            .parent()
-            .expect("test file path has no parent")
-            .join("auxiliary")
-            .join(rel_ab);
+    /// For each `aux-build: foo/bar` annotation, we check to find the file in an `auxiliary`
+    /// directory relative to the test itself (not any intermediate auxiliaries).
+    fn compute_aux_test_paths(&self, of: &TestPaths, rel_ab: &str) -> TestPaths {
+        let test_ab =
+            of.file.parent().expect("test file path has no parent").join("auxiliary").join(rel_ab);
         if !test_ab.exists() {
             self.fatal(&format!("aux-build `{}` source not found", test_ab.display()))
         }
 
         TestPaths {
             file: test_ab,
-            relative_dir: self
-                .testpaths
+            relative_dir: of
                 .relative_dir
                 .join(self.output_testname_unique())
                 .join("auxiliary")
@@ -2135,7 +2129,7 @@ fn is_vxworks_pure_dynamic(&self) -> bool {
         self.config.target.contains("vxworks") && !self.is_vxworks_pure_static()
     }
 
-    fn build_all_auxiliary(&self, rustc: &mut Command) -> PathBuf {
+    fn aux_output_dir(&self) -> PathBuf {
         let aux_dir = self.aux_output_dir_name();
 
         if !self.props.aux_builds.is_empty() {
@@ -2143,22 +2137,26 @@ fn build_all_auxiliary(&self, rustc: &mut Command) -> PathBuf {
             create_dir_all(&aux_dir).unwrap();
         }
 
+        aux_dir
+    }
+
+    fn build_all_auxiliary(&self, of: &TestPaths, aux_dir: &Path, rustc: &mut Command) {
         for rel_ab in &self.props.aux_builds {
-            self.build_auxiliary(rel_ab, &aux_dir);
+            self.build_auxiliary(of, rel_ab, &aux_dir);
         }
 
         for (aux_name, aux_path) in &self.props.aux_crates {
-            let is_dylib = self.build_auxiliary(&aux_path, &aux_dir);
+            let is_dylib = self.build_auxiliary(of, &aux_path, &aux_dir);
             let lib_name =
                 get_lib_name(&aux_path.trim_end_matches(".rs").replace('-', "_"), is_dylib);
             rustc.arg("--extern").arg(format!("{}={}/{}", aux_name, aux_dir.display(), lib_name));
         }
-
-        aux_dir
     }
 
     fn compose_and_run_compiler(&self, mut rustc: Command, input: Option<String>) -> ProcRes {
-        let aux_dir = self.build_all_auxiliary(&mut rustc);
+        let aux_dir = self.aux_output_dir();
+        self.build_all_auxiliary(&self.testpaths, &aux_dir, &mut rustc);
+
         self.props.unset_rustc_env.iter().fold(&mut rustc, Command::env_remove);
         rustc.envs(self.props.rustc_env.clone());
         self.compose_and_run(
@@ -2172,10 +2170,10 @@ fn compose_and_run_compiler(&self, mut rustc: Command, input: Option<String>) ->
     /// Builds an aux dependency.
     ///
     /// Returns whether or not it is a dylib.
-    fn build_auxiliary(&self, source_path: &str, aux_dir: &Path) -> bool {
-        let aux_testpaths = self.compute_aux_test_paths(source_path);
+    fn build_auxiliary(&self, of: &TestPaths, source_path: &str, aux_dir: &Path) -> bool {
+        let aux_testpaths = self.compute_aux_test_paths(of, source_path);
         let aux_props = self.props.from_aux_file(&aux_testpaths.file, self.revision, self.config);
-        let aux_output = TargetLocation::ThisDirectory(self.aux_output_dir_name());
+        let aux_output = TargetLocation::ThisDirectory(aux_dir.to_path_buf());
         let aux_cx = TestCx {
             config: self.config,
             props: &aux_props,
@@ -2193,6 +2191,7 @@ fn build_auxiliary(&self, source_path: &str, aux_dir: &Path) -> bool {
             LinkToAux::No,
             Vec::new(),
         );
+        aux_cx.build_all_auxiliary(of, aux_dir, &mut aux_rustc);
 
         for key in &aux_props.unset_rustc_env {
             aux_rustc.env_remove(key);
@@ -3034,7 +3033,8 @@ fn compare_to_default_rustdoc(&mut self, out_dir: &Path) {
             LinkToAux::Yes,
             Vec::new(),
         );
-        new_rustdoc.build_all_auxiliary(&mut rustc);
+        let aux_dir = new_rustdoc.aux_output_dir();
+        new_rustdoc.build_all_auxiliary(&new_rustdoc.testpaths, &aux_dir, &mut rustc);
 
         let proc_res = new_rustdoc.document(&compare_dir);
         if !proc_res.status.success() {

tests/ui/compiletest-self-test/aux-aux.rs

@@ -0,0 +1,14 @@
+//@ aux-crate: aux_aux_foo=aux_aux_foo.rs
+//@ aux-crate: aux_aux_bar=aux_aux_bar.rs
+//@ edition: 2021
+//@ compile-flags: --crate-type lib
+//@ check-pass
+
+use aux_aux_foo::Bar as IndirectBar;
+use aux_aux_bar::Bar as DirectBar;
+
+fn foo(x: IndirectBar) {}
+
+fn main() {
+    foo(DirectBar);
+}

tests/ui/compiletest-self-test/auxiliary/aux_aux_bar.rs

@@ -0,0 +1,3 @@
+//@ edition: 2021
+
+pub struct Bar;

tests/ui/compiletest-self-test/auxiliary/aux_aux_foo.rs

@@ -0,0 +1,4 @@
+//@ aux-crate: aux_aux_bar=aux_aux_bar.rs
+//@ edition: 2021
+
+pub use aux_aux_bar::Bar;