Add unit tests for crate_package_default_visibility

Two tests in rendering.rs:
- render_crate_package_default_visibility: verifies custom visibility
  appears in the generated BUILD file instead of //visibility:public
- render_default_visibility_when_not_configured: verifies the default
  behavior (//visibility:public) when the option is not set

Use skip_serializing_if on the new field to preserve lockfile digest
compatibility when the option is not set (None).

Author: Tamas Vajk

crate_universe/src/config.rs

@@ -111,6 +111,7 @@ pub(crate) struct RenderConfig {
     /// The default_visibility for individual crate BUILD packages. If None,
     /// defaults to ["//visibility:public"]. Set to restrict direct references
     /// to crate targets so that consumers must use the top-level aliases.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub(crate) crate_package_default_visibility: Option<Vec<String>>,
 }
 

crate_universe/src/rendering.rs

@@ -2366,4 +2366,97 @@ mod test {
             "proc-macro lib must appear in proc_macro_deps:\n{binary_section}"
         );
     }
+
+    #[test]
+    fn render_crate_package_default_visibility() {
+        let mut context = Context::default();
+        let crate_id = CrateId::new("mock_crate".to_owned(), VERSION_ZERO_ONE_ZERO);
+        context.crates.insert(
+            crate_id.clone(),
+            CrateContext {
+                name: crate_id.name,
+                version: crate_id.version,
+                package_url: None,
+                repository: None,
+                targets: BTreeSet::from([Rule::Library(mock_target_attributes())]),
+                library_target_name: None,
+                common_attrs: CommonAttributes::default(),
+                build_script_attrs: None,
+                license: None,
+                license_ids: BTreeSet::default(),
+                license_file: None,
+                additive_build_file_content: None,
+                disable_pipelining: false,
+                extra_aliased_targets: BTreeMap::default(),
+                alias_rule: None,
+                override_targets: BTreeMap::default(),
+            },
+        );
+
+        let config = Arc::new(RenderConfig {
+            repository_name: "test_rendering".to_owned(),
+            regen_command: "cargo_bazel_regen_command".to_owned(),
+            crate_package_default_visibility: Some(vec![
+                "//third_party/rust:__subpackages__".to_owned()
+            ]),
+            ..RenderConfig::default()
+        });
+        let renderer = Renderer::new(config, mock_supported_platform_triples());
+        let output = renderer.render(&context, None).unwrap();
+
+        let build_file_content = output
+            .get(&PathBuf::from("BUILD.mock_crate-0.1.0.bazel"))
+            .unwrap();
+
+        assert!(
+            build_file_content.contains("//third_party/rust:__subpackages__"),
+            "Expected custom visibility in BUILD file:\n{}",
+            build_file_content
+        );
+        assert!(
+            !build_file_content.contains("//visibility:public"),
+            "Expected no public visibility in BUILD file:\n{}",
+            build_file_content
+        );
+    }
+
+    #[test]
+    fn render_default_visibility_when_not_configured() {
+        let mut context = Context::default();
+        let crate_id = CrateId::new("mock_crate".to_owned(), VERSION_ZERO_ONE_ZERO);
+        context.crates.insert(
+            crate_id.clone(),
+            CrateContext {
+                name: crate_id.name,
+                version: crate_id.version,
+                package_url: None,
+                repository: None,
+                targets: BTreeSet::from([Rule::Library(mock_target_attributes())]),
+                library_target_name: None,
+                common_attrs: CommonAttributes::default(),
+                build_script_attrs: None,
+                license: None,
+                license_ids: BTreeSet::default(),
+                license_file: None,
+                additive_build_file_content: None,
+                disable_pipelining: false,
+                extra_aliased_targets: BTreeMap::default(),
+                alias_rule: None,
+                override_targets: BTreeMap::default(),
+            },
+        );
+
+        let renderer = Renderer::new(mock_render_config(None), mock_supported_platform_triples());
+        let output = renderer.render(&context, None).unwrap();
+
+        let build_file_content = output
+            .get(&PathBuf::from("BUILD.mock_crate-0.1.0.bazel"))
+            .unwrap();
+
+        assert!(
+            build_file_content.contains("//visibility:public"),
+            "Expected public visibility in BUILD file:\n{}",
+            build_file_content
+        );
+    }
 }