DEVX-141: feat: add promtool to install_tools for alert rule validation

src/devx/tools/install_tools.py

@@ -8,6 +8,7 @@ Handles installation of:
 - tea (Gitea CLI — official command-line tool for Gitea API operations)
 - hadolint (Dockerfile linter)
 - vale (prose linter for documentation quality)
+- promtool (Prometheus rule validator)
 
 Each tool is installed to ``~/.local/bin`` if not already on PATH.
 Idempotent: skips tools that are already available.
@@ -47,6 +48,8 @@ TOFU_VERSION = "1.12.3"
 
 VALE_VERSION = "3.15.1"
 
+PROMTOOL_VERSION = "3.5.5"
+
 
 def _arch() -> str:
     """Return the architecture string used by release assets (delegates to shared utility)."""
@@ -212,7 +215,26 @@ def install_vale() -> bool:
     return True
 
 
-TOOL_NAMES = ["actionlint", "git-cliff", "act_runner", "tea", "hadolint", "tofu", "vale"]
+def install_promtool() -> bool:
+    """Install promtool (Prometheus rule validator) if not already present.
+
+    Downloads the official Prometheus release tarball from GitHub and
+    extracts the ``promtool`` binary to ``~/.local/bin``.
+    """
+    if _is_installed("promtool"):
+        click.echo("promtool: already installed")
+        return True
+    arch = _arch()
+    url = (
+        f"https://github.com/prometheus/prometheus/releases/download/"
+        f"v{PROMTOOL_VERSION}/prometheus-{PROMTOOL_VERSION}.linux-{arch}.tar.gz"
+    )
+    dest = _download_and_extract_tarball(url, "promtool")
+    click.echo(f"promtool: installed to {dest}")
+    return True
+
+
+TOOL_NAMES = ["actionlint", "git-cliff", "act_runner", "tea", "hadolint", "tofu", "vale", "promtool"]
 
 
 def _install_tool(name: str) -> bool:
@@ -231,6 +253,8 @@ def _install_tool(name: str) -> bool:
         return install_tofu()
     if name == "vale":
         return install_vale()
+    if name == "promtool":
+        return install_promtool()
     raise click.ClickException(f"Unknown tool: {name}")
 
 

tests/unit/test_install_tools.py

@@ -297,6 +297,47 @@ class TestInstallVale:
         assert (tmp_path / "vale").exists()
 
 
+class TestInstallPromtool:
+    def test_already_installed(self) -> None:
+        with patch.object(install_tools, "_is_installed", return_value=True):
+            assert install_tools.install_promtool() is True
+
+    def test_install(self, tmp_path: Path) -> None:
+        import io
+        import tarfile
+
+        tarball_path = tmp_path / "archive.tar.gz"
+        binary_content = b"fake promtool"
+        with tarfile.open(tarball_path, "w:gz") as tar:
+            info = tarfile.TarInfo(name="promtool")
+            info.size = len(binary_content)
+            tar.addfile(info, io.BytesIO(binary_content))
+
+        with patch.object(install_tools, "_is_installed", return_value=False):
+            with patch.object(install_tools, "TARGET_DIR", tmp_path):
+                with patch.object(install_tools, "_arch", return_value="amd64"):
+                    with patch.object(
+                        install_tools,
+                        "_download",
+                        side_effect=lambda url, dest: Path(dest).write_bytes(tarball_path.read_bytes()),
+                    ):
+                        assert install_tools.install_promtool() is True
+        assert (tmp_path / "promtool").exists()
+
+    def test_url_contains_version(self, tmp_path: Path) -> None:
+        """Verify the download URL includes the correct promtool version."""
+        captured_url = []
+
+        def fake_extract(url: str, binary_name: str) -> Path:
+            captured_url.append(url)
+            return tmp_path / binary_name
+
+        with patch.object(install_tools, "_is_installed", return_value=False):
+            with patch.object(install_tools, "_download_and_extract_tarball", side_effect=fake_extract):
+                install_tools.install_promtool()
+        assert any(f"v{install_tools.PROMTOOL_VERSION}" in url for url in captured_url)
+
+
 class TestListTools:
     def test_list(self, tmp_path: Path) -> None:
         with patch.object(install_tools, "TARGET_DIR", tmp_path):
@@ -341,6 +382,11 @@ class TestInstallTool:
             assert install_tools._install_tool("vale") is True
         mock.assert_called_once()
 
+    def test_promtool(self) -> None:
+        with patch.object(install_tools, "install_promtool", return_value=True) as mock:
+            assert install_tools._install_tool("promtool") is True
+        mock.assert_called_once()
+
     def test_unknown_tool(self) -> None:
         with pytest.raises(ClickException, match="Unknown tool"):
             install_tools._install_tool("unknown")
@@ -359,7 +405,7 @@ class TestMain:
         with patch.object(install_tools, "_install_tool", return_value=True) as mock_install:
             result = runner.invoke(install_tools.main, [])
         assert result.exit_code == 0
-        assert mock_install.call_count == 7
+        assert mock_install.call_count == 8
 
     def test_install_specific_tool(self) -> None:
         runner = CliRunner()