assert expected json files in rust-docs-json component

Signed-off-by: onur-ozkan <work@onurozkan.dev>

src/bootstrap/src/core/build_steps/dist.rs

@@ -102,6 +102,21 @@ impl Step for JsonDocs {
 
     /// Builds the `rust-docs-json` installer component.
     fn run(self, builder: &Builder<'_>) -> Option<GeneratedTarball> {
+        fn is_tier_1_target(target: &TargetSelection) -> bool {
+            const T1_TARGETS: &[&str] = &[
+                "aarch64-unknown-linux-gnu",
+                "i686-pc-windows-gnu",
+                "i686-pc-windows-msvc",
+                "i686-unknown-linux-gnu",
+                "x86_64-unknown-linux-gnu",
+                "x86_64-apple-darwin",
+                "x86_64-pc-windows-gnu",
+                "x86_64-pc-windows-msvc",
+            ];
+
+            T1_TARGETS.contains(&target.triple.to_string().as_str())
+        }
+
         let host = self.host;
         builder.ensure(crate::core::build_steps::doc::Std::new(
             builder.top_stage,
@@ -110,11 +125,19 @@ impl Step for JsonDocs {
         ));
 
         let dest = "share/doc/rust/json";
+        let out = builder.json_doc_out(host);
+
+        if is_tier_1_target(&host) {
+            // On tier 1 targets, make sure these are present in the component.
+            for f in ["alloc.json", "core.json", "std.json"] {
+                assert!(out.join(f).exists(), "rust-docs-json is missing `{f}`.");
+            }
+        }
 
         let mut tarball = Tarball::new(builder, "rust-docs-json", &host.triple);
         tarball.set_product_name("Rust Documentation In JSON Format");
         tarball.is_preview(true);
-        tarball.add_bulk_dir(builder.json_doc_out(host), dest);
+        tarball.add_bulk_dir(out, dest);
         Some(tarball.generate())
     }
 }