Rollup merge of rust-lang#109162 - ozkanonur:extend_detect_src_and_out_test, r=jyn514

extend `detect_src_and_out` test

> I was thinking about the following cases when I wrote the comment in rust-lang#109055
>
> 1. Running bootstrap from the source root.
> 2. Running from a subdirectory of the source root.
> 3. Running from outside the source root.
> 4. Running on a different machine from where bootstrap was compiled (which will be important > for rust-lang#107812). You can mostly replicate this by renaming the source root so it no longer exists on disk.
> 5. Running with `--build-dir`.
> 6. Running with `$RUST_BOOTSTRAP_CONFIG` set in the environment and `build-dir` set in the file.

Tested all the topics mentioned above. All worked fine. The test is now also covers if build dir is manually specified in config.

r? `@jyn514`

helps rust-lang#109120 partially

Author: Dylan-DPC

src/bootstrap/config/tests.rs

@@ -33,35 +33,54 @@ fn download_ci_llvm() {
     ));
 }
 
+// FIXME(ozkanonur): extend scope of the test
+// refs:
+//   - https://github.com/rust-lang/rust/issues/109120
+//   - https://github.com/rust-lang/rust/pull/109162#issuecomment-1496782487
 #[test]
 fn detect_src_and_out() {
-    let cfg = parse("");
+    fn test(cfg: Config, build_dir: Option<&str>) {
+        // This will bring absolute form of `src/bootstrap` path
+        let current_dir = std::env::current_dir().unwrap();
 
-    // This will bring absolute form of `src/bootstrap` path
-    let current_dir = std::env::current_dir().unwrap();
+        // get `src` by moving into project root path
+        let expected_src = current_dir.ancestors().nth(2).unwrap();
+        assert_eq!(&cfg.src, expected_src);
 
-    // get `src` by moving into project root path
-    let expected_src = current_dir.ancestors().nth(2).unwrap();
+        // Sanity check for `src`
+        let manifest_dir = Path::new(env!("CARGO_MANIFEST_DIR"));
+        let expected_src = manifest_dir.ancestors().nth(2).unwrap();
+        assert_eq!(&cfg.src, expected_src);
 
-    assert_eq!(&cfg.src, expected_src);
+        // test if build-dir was manually given in config.toml
+        if let Some(custom_build_dir) = build_dir {
+            assert_eq!(&cfg.out, Path::new(custom_build_dir));
+        }
+        // test the native bootstrap way
+        else {
+            // This should bring output path of bootstrap in absolute form
+            let cargo_target_dir = env::var_os("CARGO_TARGET_DIR").expect(
+                "CARGO_TARGET_DIR must been provided for the test environment from bootstrap",
+            );
 
-    // This should bring output path of bootstrap in absolute form
-    let cargo_target_dir = env::var_os("CARGO_TARGET_DIR")
-        .expect("CARGO_TARGET_DIR must been provided for the test environment from bootstrap");
+            // Move to `build` from `build/bootstrap`
+            let expected_out = Path::new(&cargo_target_dir).parent().unwrap();
+            assert_eq!(&cfg.out, expected_out);
 
-    // Move to `build` from `build/bootstrap`
-    let expected_out = Path::new(&cargo_target_dir).parent().unwrap();
-    assert_eq!(&cfg.out, expected_out);
+            let args: Vec<String> = env::args().collect();
 
-    let args: Vec<String> = env::args().collect();
+            // Another test for `out` as a sanity check
+            //
+            // This will bring something similar to:
+            //     `{build-dir}/bootstrap/debug/deps/bootstrap-c7ee91d5661e2804`
+            // `{build-dir}` can be anywhere, not just in the rust project directory.
+            let dep = Path::new(args.first().unwrap());
+            let expected_out = dep.ancestors().nth(4).unwrap();
 
-    // Another test for `out` as a sanity check
-    //
-    // This will bring something similar to:
-    //     `{config_toml_place}/build/bootstrap/debug/deps/bootstrap-c7ee91d5661e2804`
-    // `{config_toml_place}` can be anywhere, not just in the rust project directory.
-    let dep = Path::new(args.first().unwrap());
-    let expected_out = dep.ancestors().nth(4).unwrap();
+            assert_eq!(&cfg.out, expected_out);
+        }
+    }
 
-    assert_eq!(&cfg.out, expected_out);
+    test(parse(""), None);
+    test(parse("build.build-dir = \"/tmp\""), Some("/tmp"));
 }