Set up a simple CI profiling step using nixprof

https://github.com/Kha/nixprof

.github/workflows/pipeline.yml

@@ -14,8 +14,10 @@ defaults:
     shell: bash
 
 # do we really want nixos-unstable?
-env: 
+env:
   NIX_PATH: "nixpkgs=channel:nixos-unstable"
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  PR_NUMBER: ${{ github.event.number }}
 
 jobs:
   nix-build:
@@ -246,3 +248,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - run: nix build ./nix-tools#checks.x86_64-linux.truncate-index --accept-flake-config
+
+  nixprof:
+    runs-on: [self-hosted, linux]
+    steps:
+      - uses: actions/checkout@v3
+      - name: "Run tests with ghc8107: Profile flakes development shell ..."
+        run: nix shell github:Kha/nixprof -c ./test/tests.sh ghc8107 nixprof

test/tests.sh

@@ -228,4 +228,26 @@ if [ "$TESTS" == "docs" ] || [ "$TESTS" == "all" ]; then
   popd
 fi
 
+if [ "$TESTS" == "nixprof" ]; then
+    printf "*** Profile flakes development shell ...\n" >& 2
+    cat > Dockerfile <<EOF
+FROM nixos/nix
+RUN nix-channel --update
+RUN echo "experimental-features = nix-command flakes" >> /etc/nix/nix.conf
+RUN nix profile install github:Kha/nixprof
+RUN nix profile install nixpkgs#time
+WORKDIR /workspace
+CMD ["sh", "-c", "nixprof record nix develop --accept-flake-config"]
+EOF
+    docker build -t nixprof .
+    docker run --mount type=bind,source="$(pwd)/..",target=/workspace nixprof
+    pushd ..
+    nixprof report -p
+    nixprof report -a
+    nixprof report -s
+    popd
+    # FIXME: is that the right way to publish a report on GitHub?
+    # curl -s -H "Authorization: token $GITHUB_TOKEN" -X POST -d "{\"body\": \"$report\"}" "https://api.github.com/repos/input-output-hk/haskell.nix/issues/$PR_NUMBER/comments"
+fi
+
 printf "\n*** Finished successfully\n" >& 2