chore: add code coverage

.github/workflows/ci.yaml

@@ -23,3 +23,24 @@ jobs:
         run: |
           cat regression.out
           cat regression.diffs
+
+  coverage:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: true
+      - uses: cachix/install-nix-action@v18
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - name: Run coverage
+        run: nix-shell --run "nxpg-16 nxpg-tmp nxpg-coverage"
+
+      - name: Send coverage to Coveralls
+        uses: coverallsapp/github-action@v2.3.6
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          files: ./coverage.info

Makefile

@@ -12,6 +12,9 @@ SRC = $(wildcard src/*.c)
 OBJS = $(patsubst src/%.c, src/%.o, $(SRC))
 SHLIB_LINK = -lmustach
 PG_CFLAGS = -std=c99 -Wno-declaration-after-statement -Wall -Werror -Wshadow
+ifeq ($(COVERAGE), 1)
+PG_CFLAGS += --coverage
+endif
 
 TESTS = $(wildcard test/sql/*.sql)
 REGRESS = $(patsubst test/sql/%.sql,%,$(TESTS))

nix/nxpg.nix

@@ -1,4 +1,4 @@
-{ writeShellScriptBin, findutils, entr, callPackage, postgresql_17, postgresql_16, postgresql_15, postgresql_14, postgresql_13, postgresql_12 } :
+{ writeShellScriptBin, findutils, entr, callPackage, lcov, postgresql_17, postgresql_16, postgresql_15, postgresql_14, postgresql_13, postgresql_12 } :
 let
   prefix = "nxpg";
   supportedPgs = [
@@ -24,7 +24,26 @@ let
       make
       make installcheck
     '';
+  cov =
+    writeShellScriptBin "${prefix}-coverage" ''
+      set -euo pipefail
+
+      info_file="coverage.info"
+      out_dir="coverage_html"
+
+      make clean
+      make COVERAGE=1
+      make installcheck
+      ${lcov}/bin/lcov --capture --directory . --output-file "$info_file"
+
+      # remove postgres headers on the nix store, otherwise they show on the output
+      ${lcov}/bin/lcov --remove "$info_file" '/nix/*' --output-file "$info_file" || true
 
+      ${lcov}/bin/lcov --list coverage.info
+      ${lcov}/bin/genhtml "$info_file" --output-directory "$out_dir"
+
+      echo "${prefix}-coverage: To see the results, visit file://$(pwd)/$out_dir/index.html on your browser"
+    '';
   watch =
     writeShellScriptBin "${prefix}-watch" ''
       set -euo pipefail
@@ -80,6 +99,7 @@ in
 [
   build
   test
+  cov
   watch
   tmpDb
   allPgPaths