Add code coverage

.github/workflows/coverage.yml

@@ -0,0 +1,53 @@
+---
+on:
+  pull_request:
+
+name: Code coverage
+
+permissions:
+  issues: write
+  pull-requests: write
+
+jobs:
+  coverage-report:
+    name: Generate test coverage report
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v3
+        with:
+          ref: ${{ github.head_ref }}
+
+      - uses: cachix/install-nix-action@v22
+        with:
+          extra_nix_config: |
+            extra-experimental-features = nix-command flakes
+            accept-flake-config = true
+
+      - name: Fetch code coverage report
+        id: fetch-coverage
+        run: |
+          COVERAGE_PATH=$(nix build '.#coverage' --print-build-logs --print-out-paths --no-link)
+          echo "coverage-path=$COVERAGE_PATH" >> "$GITHUB_OUTPUT"
+
+      - name: Read coverage summary
+        id: coverage-summary
+        uses: juliangruber/read-file-action@v1
+        with:
+          path: ${{ steps.fetch-coverage.outputs.coverage-path }}/coverage-summary.txt
+
+      - name: Comment with coverage information
+        uses: peter-evans/create-or-update-comment@v3
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          edit-mode: replace
+          body: |
+            Code coverage:
+            ```
+            ${{ steps.coverage-summary.outputs.content }}
+            ```
+
+      - uses: actions/upload-artifact@v3
+        with:
+          name: coverage-report
+          path: ${{ steps.fetch-coverage.outputs.coverage-path }}/coverage-report

.gitignore

@@ -0,0 +1 @@
+/target

.luacov

@@ -0,0 +1,9 @@
+return {
+  modules = {
+    ["broot"] = "lua/broot/init.lua",
+    ["broot.*"] = "lua",
+  },
+  statsfile = "target/coverage.stats",
+  reportfile = "target/coverage.lcov",
+  tick = true,
+}

Makefile

@@ -5,13 +5,44 @@ ifdef file
 NVIM_COMMAND = "lua MiniTest.run_file([["$(file)"]])"
 endif
 
-# Run all test files
-.PHONY: test
-test:
-	nvim --headless --noplugin -u ./scripts/mini_test_init.lua -c $(NVIM_COMMAND)
+ifdef coverage
+export COVERAGE = 1
+endif
+
+# Clean out temporary files or other artifacts.
+.PHONY: clean
+clean:
+	rm -rf target
 
 # Format code
 .PHONY: format
 format:
 	stylua .
 	alejandra .
+
+# Run all test files, or the file specified by `file=`.
+.PHONY: test
+test: target
+	nvim --headless --noplugin -u ./scripts/mini_test_init.lua -c $(NVIM_COMMAND)
+ifdef COVERAGE
+	make target/coverage-report
+endif
+
+# Generate an HTML coverage report and fail if there are untested lines.
+target/coverage-report target/coverage-summary.txt: target target/coverage.lcov
+	genhtml target/coverage.lcov \
+		--no-function-coverage \
+		--no-branch-coverage \
+		--output-directory target/coverage-report
+	lcov --summary target/coverage.lcov \
+		--fail-under-lines 100 \
+		| tee target/coverage-summary.txt
+	lcov --list target/coverage.lcov \
+		| tee --append target/coverage-summary.txt
+
+target/coverage.lcov: target/coverage.stats
+	luacov -r lcov
+
+# Create the `target` directory.
+target:
+	mkdir -p target

flake.nix

@@ -3,22 +3,44 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs";
+
+    # Neovim test framework.
     mini-nvim = {
       url = "github:echasnovski/mini.nvim";
       flake = false;
     };
+
+    # Vimhelp->HTML generation. Used for the GitHub pages site.
     vimhelp = {
       url = "github:c4rlo/vimhelp";
       flake = false;
     };
+
+    # Tool for running `lua-language-server` in check mode for type-checking.
     lualscheck = {
       url = "github:9999years/lualscheck";
       flake = false;
     };
+
+    # Neovim Lua API type stubs.
     neodev = {
       url = "github:folke/neodev.nvim";
       flake = false;
     };
+
+    # Lua code coverage.
+    luacov = {
+      url = "github:lunarmodules/luacov";
+      flake = false;
+    };
+    cluacov = {
+      url = "github:mpeterv/cluacov";
+      flake = false;
+    };
+    luacov-reporter-lcov = {
+      url = "github:daurnimator/luacov-reporter-lcov";
+      flake = false;
+    };
   };
 
   nixConfig = {
@@ -34,6 +56,9 @@
     vimhelp,
     lualscheck,
     neodev,
+    luacov,
+    cluacov,
+    luacov-reporter-lcov,
   }: let
     forAllSystems = function:
       nixpkgs.lib.genAttrs [
@@ -54,6 +79,7 @@
         mkCheck = pkgs.callPackage ./nix/mkCheck.nix {
           luarc = self.packages.${pkgs.system}.luarc;
         };
+        luaPkgs = pkgs.lua5_1.pkgs;
       in {
         # mini.nvim unit tests.
         tests = mkCheck {
@@ -73,6 +99,27 @@
           '';
         };
 
+        luacov = self.checks.${pkgs.system}.tests.override (old: {
+          name = "luacov";
+
+          nativeCheckInputs =
+            (old.nativeCheckInputs or [])
+            ++ [
+              self.packages.${pkgs.system}.luacov
+              self.packages.${pkgs.system}.cluacov
+              pkgs.lcov
+            ];
+
+          COVERAGE = true;
+
+          installPhase = ''
+            mkdir $out
+            cp target/coverage.lcov $out/
+            cp target/coverage-summary.txt $out/
+            cp --recursive target/coverage-report $out/
+          '';
+        });
+
         # Check diagnostics and type annotations with `lua-language-server`.
         luals = mkCheck {
           name = "lua-language-server";
@@ -116,7 +163,7 @@
         luacheck = mkCheck {
           name = "luacheck";
 
-          nativeCheckInputs = [pkgs.lua5_1.pkgs.luacheck];
+          nativeCheckInputs = [luaPkgs.luacheck];
 
           checkPhase = ''
             luacheck .
@@ -135,16 +182,27 @@
       };
 
       luarc = pkgs.callPackage ./nix/luarc.nix {inherit neodev;};
+
+      luacov = pkgs.callPackage ./nix/luacov.nix {
+        inherit luacov;
+        luacov-reporter-lcov = self.packages.${pkgs.system}.luacov-reporter-lcov;
+      };
+      cluacov = pkgs.callPackage ./nix/cluacov.nix {
+        inherit cluacov;
+        luacov = self.packages.${pkgs.system}.luacov;
+      };
+      luacov-reporter-lcov = pkgs.callPackage ./nix/luacov-reporter-lcov.nix {
+        inherit luacov-reporter-lcov;
+      };
+
+      coverage = self.checks.${pkgs.system}.luacov;
     });
 
     devShells = forAllSystems (pkgs: {
       default = pkgs.mkShell {
         MINI_NVIM = "${mini-nvim}";
 
         inputsFrom = builtins.attrValues self.checks.${pkgs.system};
-        packages = [
-          pkgs.lua5_1.pkgs.luacheck
-        ];
 
         shellHook = ''
           ${self.packages.${pkgs.system}.luarc.link-to-cwd}

nix/cluacov.nix

@@ -0,0 +1,15 @@
+{
+  lua5_1,
+  luacov,
+  cluacov,
+}:
+lua5_1.pkgs.buildLuarocksPackage {
+  pname = "cluacov";
+  version = "scm-1";
+  src = cluacov;
+
+  propagatedBuildInputs = [
+    lua5_1
+    luacov
+  ];
+}

nix/luacov-reporter-lcov.nix

@@ -0,0 +1,17 @@
+{
+  lua5_1,
+  luacov-reporter-lcov,
+}:
+lua5_1.pkgs.buildLuarocksPackage {
+  pname = "luacov-reporter-lcov";
+  version = "scm-0";
+  src = luacov-reporter-lcov;
+
+  patches = [
+    ./patches/luacov-reporter-lcov.diff
+  ];
+
+  propagatedBuildInputs = [
+    lua5_1
+  ];
+}

nix/luacov.nix

@@ -0,0 +1,25 @@
+{
+  lua5_1,
+  luacov,
+  luacov-reporter-lcov,
+}:
+lua5_1.pkgs.buildLuarocksPackage {
+  pname = "luacov";
+  version = "scm-1";
+  src = luacov;
+
+  propagatedBuildInputs = [
+    lua5_1
+    luacov-reporter-lcov
+  ];
+
+  patches = [
+    ./patches/luacov.diff
+  ];
+
+  # Tell `luacov` where to find its assets.
+  preConfigure = ''
+    substituteInPlace src/luacov/reporter/html.lua \
+      --subst-var-by assetDir "$out/$rocksSubdir/$pname/$version"
+  '';
+}