From 3a7a0b7564641921a758e88525a2c7a1ce671324 Mon Sep 17 00:00:00 2001
From: brandon s allbery kf8nh <allbery.b@gmail.com>
Date: Mon, 19 Aug 2024 22:43:55 -0400
Subject: [PATCH] make sure cabal-install is compatible with Cabal

See https://github.com/haskell/cabal/issues/9833

If a ghc ships with a compatible Cabal, it will be preferred by
the solver on `cabal install cabal-install`; the new `cabal-install`
should in fact be compatible. So we test this on release branches
that have had at least one release on Hackage. (Ideally we'd check
ghc instead, but we can't do that from GHA. Even checking Hackage
is pretty painful.)
---
 .github/workflows/check-sdist.yml | 82 +++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 .github/workflows/check-sdist.yml

diff --git a/.github/workflows/check-sdist.yml b/.github/workflows/check-sdist.yml
new file mode 100644
index 00000000000..d295ad0ccca
--- /dev/null
+++ b/.github/workflows/check-sdist.yml
@@ -0,0 +1,82 @@
+name: Check sdist
+
+# See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#concurrency.
+concurrency:
+  group: ${{ github.ref }}-${{ github.workflow }}
+  cancel-in-progress: true
+
+on:
+  push:
+    paths-ignore:
+      - "doc/**"
+      - "**/README.md"
+      - "CONTRIBUTING.md"
+    branches:
+      - master
+  pull_request:
+    paths-ignore:
+      - "doc/**"
+      - "**/README.md"
+      - "CONTRIBUTING.md"
+  release:
+    types:
+      - created
+
+jobs:
+
+  # Dogfood the generated sdist, to avoid bugs like https://github.com/haskell/cabal/issues/9833
+  # No caching, since the point is to verify they can be installed "from scratch"
+  # Don't run on master or a PR targeting master, because there's never an installable Cabal
+  dogfood-sdists:
+    name: Dogfood sdist on ${{ matrix.os }} ghc-${{ matrix.ghc }}
+    if: github.ref != 'refs/heads/master' && github.base_ref != 'master'
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        # this should be kept up to date with the list in validate.yml, but should be the
+        # *first* compiler release so we validate against what is hopefully the first
+        # release of a corresponding Cabal and friends. it can also be short since it's
+        # highly unlikely that we are releasing really old branches.
+        ghc:
+          [
+            "9.10.1",
+            "9.8.1",
+            "9.6.1",
+            "9.4.1",
+          ]
+
+    steps:
+
+      - uses: haskell-actions/setup@v2
+        id: setup-haskell
+        with:
+          ghc-version: ${{ matrix.ghc }}
+          cabal-version: latest
+
+      - uses: actions/checkout@v4
+
+      - name: Make sdist
+        run: cabal sdist cabal-install
+
+      - name: Install from sdist
+        run: |
+          # skip if a suitable Cabal isn't in this ghc's bootlibs, since that's the case
+          # that causes failures for users (otherwise cabal-install will install a matching
+          # version itself)
+          # we only want to test cabal-install, to ensure that it works with existing Cabals
+          # (don't look at this too closely)
+          sdist="$(ls dist-newstyle/sdist/cabal-install-*.tar.gz | sed -n '\,^dist-newstyle/sdist/cabal-install-[0-9.]*\.tar\.gz$,{;p;q;}')"
+          # extract the cabal-install major version
+          ver="$(echo "$sdist" | sed -n 's,^dist-newstyle/sdist/cabal-install-\([0-9][0-9]*\.[0-9][0-9]*\)\.[0-9.]*$,\1,p')"
+          # dunno if this will ever be extended to freebsd, but grep -q is a gnu-ism
+          if ghc-pkg --global --simple-output list Cabal | grep "^Cabal-$cbl\\." >/dev/null; then
+            # sigh, someone broke installing from tarballs
+            rm -rf cabal*.project Cabal Cabal-syntax cabal-install-solver cabal-install
+            tar xfz "$sdist"
+            cd "cabal-install-$cbl"*
+            cabal install
+          else
+            echo No matching bootlib Cabal version to test against.
+            exit 0
+          fi