[rules score] fix architecture validation

bazel/rules/rules_score/test/BUILD

@@ -622,25 +622,70 @@ dependable_element(
 
 # Minimal dependable element used as a dependency target to test
 # the deps attribute of dependable_element (i.e. SEooC depending on another SEooC).
+# Composed of a single component/unit pair so it satisfies the
+# non-empty-composition validation (see check_non_empty_composition).
+unit(
+    name = "dep_unit",
+    testonly = True,
+    scope = ["//:mock_lib1"],
+    tests = [],
+    unit_design = [":test_unit_design"],
+    implementation = [":mock_lib1"],
+)
+
+component(
+    name = "dep_component",
+    testonly = True,
+    components = [":dep_unit"],
+    requirements = [
+        ":comp_req",
+        ":feat_req",
+    ],
+    tests = [],
+)
+
 dependable_element(
     name = "dep_seooc_lib",
     architectural_design = [":arch_design_dep"],
     assumptions_of_use = [":aous"],
-    components = [],
+    components = [":dep_component"],
     dependability_analysis = [":dependability_analysis_target"],
     integrity_level = "B",
+    maturity = "development",
     requirements = [":feat_req"],
     tests = [],
     deps = [],
 )
 
+unit(
+    name = "seooc_test_unit",
+    testonly = True,
+    scope = ["//:mock_lib1"],
+    tests = [],
+    unit_design = [":test_unit_design"],
+    implementation = [":mock_lib1"],
+)
+
+component(
+    name = "seooc_test_component",
+    testonly = True,
+    components = [":seooc_test_unit"],
+    requirements = [
+        ":comp_req",
+        ":feat_req",
+    ],
+    tests = [],
+)
+
+# maturity = "development": same rationale as dep_seooc_lib above.
 dependable_element(
     name = "seooc_test_lib",
     architectural_design = [":arch_design"],
     assumptions_of_use = [":aous"],
-    components = [],
+    components = [":seooc_test_component"],
     dependability_analysis = [":dependability_analysis_target"],
     integrity_level = "B",
+    maturity = "development",
     requirements = [":feat_req"],
     tests = [],
     deps = [":dep_seooc_lib"],  # dependency to other seoocs/score_components

bazel/rules/rules_score/test/fixtures/dep_seooc_lib.puml

@@ -13,6 +13,10 @@
 
 @startuml dep_seooc_lib
 
-package "Dependency SEooC Library" as dep_seooc_lib <<SEooC>>
+package "Dependency SEooC Library" as dep_seooc_lib <<SEooC>> {
+    component "Dep Component" as dep_component <<component>> {
+        component "Dep Unit" as dep_unit <<unit>>
+    }
+}
 
 @enduml

bazel/rules/rules_score/test/fixtures/seooc_test_lib.puml

@@ -13,6 +13,10 @@
 
 @startuml seooc_test_lib
 
-package "SEooC Test Library" as seooc_test_lib <<SEooC>>
+package "SEooC Test Library" as seooc_test_lib <<SEooC>> {
+    component "SEooC Test Component" as seooc_test_component <<component>> {
+        component "SEooC Test Unit" as seooc_test_unit <<unit>>
+    }
+}
 
 @enduml

validation/core/docs/requirements/tool_requirements.trlc

@@ -72,6 +72,16 @@ section "Tool Requirements" {
                 satisfied_by = Verifier
             }
 
+            ToolQualification.ToolRequirement BazelComponentNonEmptyComposition {
+                description = '''The validator shall report an error when a
+                Bazel `dependable_element` or `component` target decomposes
+                into zero nested `component` or `unit` targets, even when the
+                corresponding PlantUML entity likewise shows no nested
+                elements.'''
+                derived_from = [UseCases.Validate_Architecture_Specification_Documents]
+                satisfied_by = Verifier
+            }
+
         }
 
         section "Component Sequence Validator" {

validation/core/docs/specifications/bazel_component.md

@@ -127,6 +127,25 @@ entity defined in the same component diagram. An entity referencing an
 undefined parent is rejected with a `[Design]` error naming the missing
 parent ID.
 
+### Non-Empty Composition
+
+Every Bazel `dependable_element` and `component` target must decompose into
+at least one nested `component` or `unit`. A target with an empty
+`components` attribute (and, for components, no nested `unit`) is reported
+even if the PlantUML diagram agrees and shows the same element as empty --
+the set-difference checks above only compare presence between Bazel and
+PlantUML, so a childless entry that matches on both sides would otherwise go
+unnoticed.
+*(Requirement: {requirement:downstream-ref}`Tools.BazelComponentNonEmptyComposition`)*
+
+```starlark
+# Flagged: component_example has no nested unit() or component().
+component(
+  name = "component_example",
+  components = [],
+)
+```
+
 ## Failure Cases
 
 | Failure case | Validation rule |
@@ -141,6 +160,8 @@ parent ID.
 | Duplicate Bazel entity key (same name/parent from different labels) | Duplicate Entity Detection |
 | Duplicate PlantUML entity ID (case-insensitive collision) | Duplicate Entity Detection |
 | PlantUML entity references an undefined parent | Parent Reference Validity |
+| Empty dependable element in Bazel build graph | Non-Empty Composition |
+| Empty component in Bazel build graph | Non-Empty Composition |
 
 ## PlantUML Stereotype Reference
 

validation/core/integration_test/bazel_component/BUILD

@@ -19,6 +19,7 @@ filegroup(
         "//validation/core/integration_test/bazel_component/negative_duplicate_component_key:case_data",
         "//validation/core/integration_test/bazel_component/negative_duplicate_dependable_element_key:case_data",
         "//validation/core/integration_test/bazel_component/negative_duplicate_unit_key:case_data",
+        "//validation/core/integration_test/bazel_component/negative_empty_component:case_data",
         "//validation/core/integration_test/bazel_component/negative_empty_target_name_label:case_data",
         "//validation/core/integration_test/bazel_component/negative_extra_component:case_data",
         "//validation/core/integration_test/bazel_component/negative_extra_unit:case_data",

validation/core/integration_test/bazel_component/bazel_component_suite.rs

@@ -104,3 +104,8 @@ fn negative_duplicate_component_key_suite_case() {
 fn negative_empty_target_name_label_suite_case() {
     assert_case("negative_empty_target_name_label");
 }
+
+#[test]
+fn negative_empty_component_suite_case() {
+    assert_case("negative_empty_component");
+}

validation/core/integration_test/bazel_component/negative_empty_component/BUILD

@@ -0,0 +1,37 @@
+# *******************************************************************************
+# Copyright (c) 2026 Contributors to the Eclipse Foundation
+#
+# See the NOTICE file(s) distributed with this work for additional
+# information regarding copyright ownership.
+#
+# This program and the accompanying materials are made available under the
+# terms of the Apache License Version 2.0 which is available at
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# SPDX-License-Identifier: Apache-2.0
+# *******************************************************************************
+
+load("//bazel/rules/rules_score:rules_score.bzl", "architectural_design")
+load("//validation/core/integration_test:puml_fixture.bzl", "provider_fbs_fixture_bundle")
+
+architectural_design(
+    name = "design",
+    static = ["component_diagram.puml"],
+    visibility = ["//visibility:private"],
+)
+
+provider_fbs_fixture_bundle(
+    name = "fbs",
+    visibility = ["//visibility:public"],
+    deps = [":design"],
+)
+
+filegroup(
+    name = "case_data",
+    srcs = [
+        "architecture.json",
+        "expected.yaml",
+        ":fbs",
+    ],
+    visibility = ["//visibility:public"],
+)

validation/core/integration_test/bazel_component/negative_empty_component/architecture.json

@@ -0,0 +1,14 @@
+{
+    "components": {
+        "safety_software_seooc_example": {
+            "units": [],
+            "components": [
+                "@//bazel/rules/rules_score/examples/seooc:component_example"
+            ]
+        },
+        "@//bazel/rules/rules_score/examples/seooc:component_example": {
+            "units": [],
+            "components": []
+        }
+    }
+}

validation/core/integration_test/bazel_component/negative_empty_component/component_diagram.puml

@@ -0,0 +1,21 @@
+' *******************************************************************************
+' Copyright (c) 2026 Contributors to the Eclipse Foundation
+'
+' See the NOTICE file(s) distributed with this work for additional
+' information regarding copyright ownership.
+'
+' This program and the accompanying materials are made available under the
+' terms of the Apache License Version 2.0 which is available at
+' https://www.apache.org/licenses/LICENSE-2.0
+'
+' SPDX-License-Identifier: Apache-2.0
+' *******************************************************************************
+
+@startuml component_diagram
+
+package "Sample Seooc" as safety_software_seooc_example <<SEooC>> {
+    component "Component Example" as component_example <<component>> {
+    }
+}
+
+@enduml

validation/core/integration_test/bazel_component/negative_empty_component/expected.yaml

@@ -0,0 +1,16 @@
+# *******************************************************************************
+# Copyright (c) 2026 Contributors to the Eclipse Foundation
+#
+# See the NOTICE file(s) distributed with this work for additional
+# information regarding copyright ownership.
+#
+# This program and the accompanying materials are made available under the
+# terms of the Apache License Version 2.0 which is available at
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# SPDX-License-Identifier: Apache-2.0
+# *******************************************************************************
+should_pass: false
+error_contains:
+  - "Empty component in Bazel build graph"
+  - 'Alias          : "component_example"'