Surface untested source files at 0% coverage in reports

.gitignore

@@ -2,6 +2,10 @@
 bazel-*
 .bazel-*
 
+# Generated coverage reports (output from `bazel run @score_cpp_policies//coverage:generate_coverage_html`)
+cpp_coverage/
+*/cpp_coverage/
+
 # IDE files
 .vscode/
 .idea/

MODULE.bazel

@@ -17,3 +17,26 @@ bazel_dep(name = "bazel_skylib", version = "1.8.2")
 bazel_dep(name = "platforms", version = "0.0.10")
 bazel_dep(name = "rules_cc", version = "0.2.17")
 bazel_dep(name = "aspect_rules_lint", version = "2.5.0")
+
+# ---------------------------------------------------------------------------
+# Coverage tooling (//coverage/...). Hosts the merger/reporter/justify/
+# effective_coverage Python binaries and the shell driver. Consumers do not
+# need rules_python themselves to use //coverage:reporter — it is wired in
+# here once for the whole policies module.
+# ---------------------------------------------------------------------------
+bazel_dep(name = "rules_python", version = "1.8.5")
+bazel_dep(name = "rules_shell", version = "0.3.0")
+
+python = use_extension("@rules_python//python/extensions:python.bzl", "python")
+python.toolchain(
+    python_version = "3.12",
+    is_default = True,
+)
+
+pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip")
+pip.parse(
+    hub_name = "score_cpp_policies_pip",
+    python_version = "3.12",
+    requirements_lock = "//coverage:requirements_lock.txt",
+)
+use_repo(pip, "score_cpp_policies_pip")

README.md

@@ -1,10 +1,10 @@
 # score_cpp_policies
 
 Centralized C++ quality tool policies for Eclipse S-CORE, providing sanitizer
-configurations and clang-tidy integration reusable across all S-CORE modules
-(logging, communication, baselibs, etc.).
+configurations, clang-tidy integration and source-based code coverage
+reusable across all S-CORE modules (logging, communication, baselibs, etc.).
 
-Planned: clang-format, code coverage policies.
+Planned: clang-format.
 
 ## What This Provides
 
@@ -15,6 +15,10 @@ Planned: clang-format, code coverage policies.
 - **Constraint system** — `target_compatible_with` settings for sanitizer-incompatible targets
 - **`clang_tidy/.clang-tidy`** — centralized default check set (conservative baseline, tailorable per module)
 - **`clang_tidy/clang_tidy.bazelrc`** — `--config=clang-tidy` bazelrc config consumers can import
+- **`//coverage:reporter` + `score_coverage_reporter` macro** — llvm-cov source-based
+coverage with a shared baseline of ignore regexes (test/mock/fake/external), pluggable 
+per-module extensions and an effective-coverage justification post-processor.
+See [`coverage/README.md`](coverage/README.md) for the seven-step adoption guide.
 
 ## Available Sanitizer Configurations
 
@@ -54,6 +58,10 @@ bazel_dep(name = "score_cpp_policies")
 
 Copy [`sanitizers/sanitizers.bazelrc`](sanitizers/sanitizers.bazelrc) into your repository's `.bazelrc`.
 
+### Configure Coverage
+
+See [`coverage/README.md`](coverage/README.md).
+
 ### Run Tests
 
 ```bash

coverage/BUILD.bazel

@@ -0,0 +1,97 @@
+# *******************************************************************************
+# 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("@rules_python//python:defs.bzl", "py_binary", "py_library")
+load("@rules_shell//shell:sh_binary.bzl", "sh_binary")
+
+package(default_visibility = ["//visibility:public"])
+
+# Files consumers may reference directly (e.g. .bazelrc imports, custom macros).
+exports_files([
+    "coverage.bazelrc",
+    "filter_regexes.txt",
+    "generate_coverage_html.sh",
+])
+
+# ---------------------------------------------------------------------------
+# Per-test coverage merger.
+# Bazel calls this as --coverage_output_generator once per test; it takes
+# profraw files + the source-file manifest, merges them with llvm-profdata
+# and packages everything (profdata + object-file list) into a zip that the
+# reporter later aggregates.
+# ---------------------------------------------------------------------------
+py_binary(
+    name = "merger",
+    srcs = ["merger.py"],
+)
+
+# ---------------------------------------------------------------------------
+# Final coverage reporter (HTML / LCOV / text).
+# Invoked indirectly via the per-consumer wrapper produced by
+# `score_coverage_reporter` (see defs.bzl). Reads per-test zips, merges all
+# profdata, then calls llvm-cov to render the combined report.
+#
+# Note: this target intentionally does NOT carry the llvm-cov / llvm-profdata
+# binaries in its `data` — the consumer-side wrapper supplies them by label,
+# letting each consumer pick its own llvm_toolchain repository name and
+# version (see score_coverage_reporter in coverage/defs.bzl).
+# ---------------------------------------------------------------------------
+py_library(
+    name = "reporter_lib",
+    srcs = ["reporter.py"],
+    imports = [".."],
+    deps = ["@rules_python//python/runfiles"],
+)
+
+py_binary(
+    name = "reporter",
+    srcs = ["reporter.py"],
+    deps = ["@rules_python//python/runfiles"],
+)
+
+# ---------------------------------------------------------------------------
+# Coverage justification processor.
+# Reads a YAML database of justifications + scans source for COV_JUSTIFIED
+# markers and emits a manifest of (file, line) -> justification.
+# ---------------------------------------------------------------------------
+py_binary(
+    name = "justify",
+    srcs = ["justify.py"],
+    deps = [
+        "@score_cpp_policies_pip//pyyaml",
+    ],
+)
+
+# ---------------------------------------------------------------------------
+# Effective coverage calculator + HTML post-processor.
+# Takes the llvm-cov HTML report and the resolved justification manifest;
+# rewrites the HTML to highlight justified lines and emits effective
+# coverage statistics.
+# ---------------------------------------------------------------------------
+py_binary(
+    name = "effective_coverage",
+    srcs = ["effective_coverage.py"],
+)
+
+# ---------------------------------------------------------------------------
+# Generic post-`bazel coverage` driver. Consumers invoke this via
+# `bazel run @score_cpp_policies//coverage:generate_coverage_html -- [flags]`.
+# ---------------------------------------------------------------------------
+sh_binary(
+    name = "generate_coverage_html",
+    srcs = ["generate_coverage_html.sh"],
+    data = [
+        ":justify",
+        ":effective_coverage",
+    ],
+)