ci: enforce a format style with clang-format and black

On PR, we could use git-clang-format instead.

.clang-format

@@ -0,0 +1,47 @@
+---
+BasedOnStyle: WebKit
+AlignAfterOpenBracket: DontAlign
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlines: Left
+AlignOperands: false
+AlignTrailingComments: true
+AllowAllArgumentsOnNextLine: false
+AllowAllParametersOfDeclarationOnNextLine: false
+AllowShortBlocksOnASingleLine: Never
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: InlineOnly
+AllowShortIfStatementsOnASingleLine: WithoutElse
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakAfterReturnType: TopLevelDefinitions
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: MultiLine
+BinPackArguments: true
+BinPackParameters: true
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: WebKit
+BreakBeforeTernaryOperators: false
+BreakStringLiterals: false
+PenaltyBreakBeforeFirstCallParameter: 100
+CompactNamespaces: true
+DerivePointerAlignment: false
+DisableFormat: false
+ForEachMacros:
+  - TAILQ_FOREACH
+IndentCaseLabels: false
+IndentPPDirectives: AfterHash
+PPIndentWidth: 2
+Language: Cpp
+NamespaceIndentation: None
+PointerAlignment: Right
+ContinuationIndentWidth: 4
+IndentWidth: 8
+TabWidth: 8
+ColumnLimit: 88
+UseTab: Always
+SpaceAfterCStyleCast: false
+SortIncludes: false
+KeepEmptyLinesAtTheStartOfBlocks: true
+TypenameMacros:
+  - TAILQ_ENTRY
+  - TAILQ_HEAD

.dir-locals.el

@@ -1 +1,3 @@
-((nix-mode . ((mode . apheleia))))
+((nix-mode    . ((mode . format-all)))
+ (c-mode      . ((mode . format-all)))
+ (python-mode . ((mode . format-all))))

.github/workflows/style.yml

@@ -0,0 +1,17 @@
+---
+name: Code style
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+jobs:
+  style-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: cachix/install-nix-action@v17
+      - name: Check Python/C style
+        run: |
+          nix develop --command ci-helper format-c format-python
+          git diff --exit-code

flake.nix

@@ -9,11 +9,11 @@
         pkgs = inputs.nixpkgs.legacyPackages."${system}";
       in
       {
-        defaultPackage = pkgs.stdenv.mkDerivation rec {
+        packages.default = pkgs.stdenv.mkDerivation rec {
           name = "lldpd";
           # We should be able to just use ./., but we have libevent as a submodule.
-          # Currently, an alternative would be to use:
-          #  nix build "git+file://$(pwd)?submodules=1"
+          # Currently, we should use:
+          #  nix build ".?submodules=1"
           # See:
           # - https://github.com/NixOS/nix/pull/5434
           # - https://github.com/NixOS/nix/pull/5497
@@ -29,5 +29,51 @@
           buildInputs = with pkgs; [ libevent readline net-snmp openssl ];
           outputs = [ "out" "dev" "man" "doc" ];
         };
+        apps = {
+          # Use:
+          #  nix run ".?submodules=1#lldpcli" -- --help
+          lldpd = {
+            type = "app";
+            program = "${self.packages."${system}".default}/bin/lldpd";
+          };
+          lldpcli = {
+            type = "app";
+            program = "${self.packages."${system}".default}/bin/lldpcli";
+          };
+        };
+        devShells.default =
+          let
+            llvm = pkgs.llvmPackages_14;
+            clang-tools = pkgs.clang-tools.override { llvmPackages = llvm; };
+          in
+          pkgs.mkShell {
+            name = "lldpd-dev";
+            buildInputs =
+              self.packages."${system}".default.nativeBuildInputs ++
+              self.packages."${system}".default.buildInputs ++ [
+                clang-tools # clang-format (C)
+                llvm.libclang.python # git-clang-format (C)
+                pkgs.python3Packages.black # black (Python)
+
+                # CI helper
+                (pkgs.writeShellScriptBin "ci-helper" ''
+                  set -eu
+                  while [ $# -gt 0 ]; do
+                    case $1 in
+                      format-c)
+                        echo "Run clang-format on C code..."
+                        ${pkgs.git}/bin/git ls-files '*.c' '*.h' \
+                          | xargs ${clang-tools}/bin/clang-format -i
+                        ;;
+                      format-python)
+                        echo "Run black on Python code..."
+                        ${pkgs.python3Packages.black}/bin/black tests/integration
+                        ;;
+                    esac
+                    shift
+                  done
+                '')
+              ];
+          };
       });
 }

include/.clang-format

@@ -0,0 +1,3 @@
+---
+DisableFormat: true
+SortIncludes: false