Make every clang-tidy finding an error

Task: MIL-007#4

CHANGELOG.md

@@ -27,7 +27,8 @@ Each release lists its changes in these groups, in this order:
   (inputs `clang-format-version`, `clang-tidy-version`), with the inputs
   `working-directory`, `std`, `compile-commands-dir` and `tools-ref`. The
   repository needs a `.clang-format`; without a `.clang-tidy` the checks
-  `clang-diagnostic-*` and `clang-analyzer-*` run.
+  `clang-diagnostic-*` and `clang-analyzer-*` run, and every clang-tidy finding
+  is an error (`--warnings-as-errors=*`).
 - Reusable workflow `quality-checks-csharp.yml` (ADR-0008): `dotnet format
   --verify-no-changes` and `dotnet build -warnaserror` on an exact .NET SDK 10
   or later (input `dotnet-sdk-version`, default `10.0.401`), with the inputs

guides/quality-checks-cpp.md

@@ -56,7 +56,7 @@ version of a tool is a new release of this repository, not a silent change.
 | Files | Tool | What it reports |
 | --- | --- | --- |
 | tracked `*.c`, `*.cc`, `*.cpp`, `*.cxx`, `*.h`, `*.hh`, `*.hpp`, `*.hxx` | `clang-format --dry-run -Werror` | formatting that differs from `.clang-format` |
-| the same files | `clang-tidy` | findings of the checks of `.clang-tidy` (or of `clang-diagnostic-*` and `clang-analyzer-*` without one); `*.c` files are checked as C17, the other files as the C++ standard of `std` |
+| the same files | `clang-tidy` | findings of the checks of `.clang-tidy` (or of `clang-diagnostic-*` and `clang-analyzer-*` without one); `*.c` files are checked as C17, the other files as the C++ standard of `std`; every finding is an error (`--warnings-as-errors=*`), so a warning fails the run |
 
 Untracked files are not checked. A repository without these files passes with a
 notice. There is no `cppcheck`: only an old version of it is available as a

tests/test_quality_workflows_cpp_csharp.py

@@ -312,6 +312,31 @@ class TestCppRun:
         assert len(calls) == 2
         assert not any("--checks=" in call for call in calls)
 
+    @pytest.mark.parametrize(
+        ("files", "extra", "tidy_calls"),
+        [
+            (("a.cpp", "lib/c.c"), {}, 2),
+            (("a.cpp", ".clang-tidy"), {}, 1),
+            (("a.cpp", "build/compile_commands.json"), {"COMPILE_COMMANDS_DIR": "build"}, 1),
+        ],
+        ids=["no-clang-tidy-file", "clang-tidy-file", "compile-database"],
+    )
+    def test_every_clang_tidy_call_treats_warnings_as_errors(
+        self,
+        repo: Path,
+        tmp_path: Path,
+        cpp_bin: Path,
+        files: tuple[str, ...],
+        extra: dict[str, str],
+        tidy_calls: int,
+    ) -> None:
+        add_files(repo, *files)
+        _, calls = self.run(repo, tmp_path, cpp_bin, **extra)
+        tidy = [c for c in calls if c.startswith("clang-tidy")]
+        assert len(tidy) == tidy_calls
+        assert all("--warnings-as-errors=*" in call for call in tidy)
+        assert "--warnings-as-errors" not in calls[0] and calls[0].startswith("clang-format")
+
     def test_no_default_checks_when_a_clang_tidy_file_is_above_the_working_directory(
         self,
         repo: Path,

tools/quality-checks-cpp.sh

@@ -127,7 +127,9 @@ run_checks() {
 
   # Without a .clang-tidy, clang-tidy enables no check and refuses to run, so
   # the project gets the compiler diagnostics and the static analyzer.
-  local tidy_args=(--quiet)
+  # clang-tidy exits 0 on a warning, so every finding is made an error: a
+  # finding must fail the check, as a failing tool does for the other languages.
+  local tidy_args=(--quiet "--warnings-as-errors=*")
   if ! find_config_upwards .clang-tidy _clang-tidy; then
     tidy_args+=("--checks=${DEFAULT_TIDY_CHECKS}")
   fi

wiki/QualityChecksCpp.da.md

@@ -1,4 +1,4 @@
-<!-- translation of QualityChecksCpp.md, source sha256 fd8bb0d71906 -->
+<!-- translation of QualityChecksCpp.md, source sha256 baf659e82523 -->
 
 > Dette er en oversættelse af [`QualityChecksCpp`](QualityChecksCpp). Den engelske side er autoritativ, og ændringer her bliver overskrevet, næste gang wikien publiceres.
 
@@ -49,7 +49,7 @@ Henvis til workflowet ved major-tagget (`@v1`) eller et præcist tag, aldrig ved
 | Filer | Værktøj | Hvad det melder |
 | --- | --- | --- |
 | sporede `*.c`, `*.cc`, `*.cpp`, `*.cxx`, `*.h`, `*.hh`, `*.hpp`, `*.hxx` | `clang-format --dry-run -Werror` | formatering, der afviger fra `.clang-format` |
-| de samme filer | `clang-tidy` | fund fra kontrollerne i `.clang-tidy` (eller fra `clang-diagnostic-*` og `clang-analyzer-*` uden en); `*.c`-filer kontrolleres som C17, de øvrige filer som C++-standarden i `std` |
+| de samme filer | `clang-tidy` | fund fra kontrollerne i `.clang-tidy` (eller fra `clang-diagnostic-*` og `clang-analyzer-*` uden en); `*.c`-filer kontrolleres som C17, de øvrige filer som C++-standarden i `std`; hvert fund er en fejl (`--warnings-as-errors=*`), så en advarsel får kørslen til at fejle |
 
 Usporede filer kontrolleres ikke. Et repository uden disse filer består med en bemærkning. Der er ingen `cppcheck`: kun en gammel version findes som pakke, og gamle værktøjer køres ikke (ADR-0008).
 

wiki/QualityChecksCpp.md

@@ -62,7 +62,7 @@ version of a tool is a new release of this repository, not a silent change.
 | Files | Tool | What it reports |
 | --- | --- | --- |
 | tracked `*.c`, `*.cc`, `*.cpp`, `*.cxx`, `*.h`, `*.hh`, `*.hpp`, `*.hxx` | `clang-format --dry-run -Werror` | formatting that differs from `.clang-format` |
-| the same files | `clang-tidy` | findings of the checks of `.clang-tidy` (or of `clang-diagnostic-*` and `clang-analyzer-*` without one); `*.c` files are checked as C17, the other files as the C++ standard of `std` |
+| the same files | `clang-tidy` | findings of the checks of `.clang-tidy` (or of `clang-diagnostic-*` and `clang-analyzer-*` without one); `*.c` files are checked as C17, the other files as the C++ standard of `std`; every finding is an error (`--warnings-as-errors=*`), so a warning fails the run |
 
 Untracked files are not checked. A repository without these files passes with a
 notice. There is no `cppcheck`: only an old version of it is available as a

wiki/QualityChecksCpp.ms.md

@@ -1,4 +1,4 @@
-<!-- translation of QualityChecksCpp.md, source sha256 fd8bb0d71906 -->
+<!-- translation of QualityChecksCpp.md, source sha256 baf659e82523 -->
 
 > Ini ialah terjemahan [`QualityChecksCpp`](QualityChecksCpp). Halaman bahasa Inggeris ialah teks yang sah, dan perubahan di sini akan ditimpa pada penerbitan wiki yang seterusnya.
 
@@ -49,7 +49,7 @@ Rujuk aliran kerja pada tag major (`@v1`) atau pada tag tepat, jangan sekali-kal
 | Fail | Alat | Apa yang dilaporkan |
 | --- | --- | --- |
 | `*.c`, `*.cc`, `*.cpp`, `*.cxx`, `*.h`, `*.hh`, `*.hpp`, `*.hxx` yang dijejaki | `clang-format --dry-run -Werror` | pemformatan yang berbeza daripada `.clang-format` |
-| fail yang sama | `clang-tidy` | dapatan semakan dalam `.clang-tidy` (atau `clang-diagnostic-*` dan `clang-analyzer-*` tanpanya); fail `*.c` disemak sebagai C17, fail lain sebagai piawaian C++ dalam `std` |
+| fail yang sama | `clang-tidy` | dapatan semakan dalam `.clang-tidy` (atau `clang-diagnostic-*` dan `clang-analyzer-*` tanpanya); fail `*.c` disemak sebagai C17, fail lain sebagai piawaian C++ dalam `std`; setiap dapatan ialah ralat (`--warnings-as-errors=*`), jadi amaran menggagalkan larian |
 
 Fail yang tidak dijejaki tidak disemak. Repositori tanpa fail ini lulus dengan satu notis. Tiada `cppcheck`: hanya versi lama tersedia sebagai pakej, dan alat lama tidak dijalankan (ADR-0008).