From 165b4fe9025607b7b716f08241ee17085a711079 Mon Sep 17 00:00:00 2001
From: Christian Heimes <christian@python.org>
Date: Fri, 3 Dec 2021 13:38:26 +0100
Subject: [PATCH 1/2] bpo-45695: Test out-of-tree builds on GHA

The Ubuntu test runner now configures and compiles CPython out of tree.
The source directory is a read-only bind mount to ensure that the build
cannot create or modify any files in the source tree.

For testing the source directory is re-mounted writable. 15 test modules
depend on writable sources and lack of .pyc files slows CI down.

Signed-off-by: Christian Heimes <christian@python.org>
---
 .github/workflows/build.yml                   | 21 ++++++++++++++++---
 .../2021-12-03-14-19-16.bpo-45695.QKBn2E.rst  |  3 +++
 2 files changed, 21 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index fe4b14828699c7..fbf7bb6fe2128a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -179,13 +179,28 @@ jobs:
         echo "PATH=/usr/lib/ccache:$PATH" >> $GITHUB_ENV
     - name: Configure ccache action
       uses: hendrikmuhs/ccache-action@v1
-    - name: Configure CPython
-      run: ./configure --with-pydebug --with-openssl=$OPENSSL_DIR
-    - name: Build CPython
+    - name: Setup directory envs for out-of-tree builds
+      run: |
+        echo "CPYTHON_RO_SRCDIR=$(realpath -m ${GITHUB_WORKSPACE}/../cpython-ro-srcdir)" >> $GITHUB_ENV
+        echo "CPYTHON_BUILDDIR=$(realpath -m ${GITHUB_WORKSPACE}/../cpython-builddir)" >> $GITHUB_ENV
+    - name: Create directories for read-only out-of-tree builds
+      run: mkdir -p $CPYTHON_RO_SRCDIR $CPYTHON_BUILDDIR
+    - name: Bind mount sources read-only
+      run: sudo mount --bind -o ro $GITHUB_WORKSPACE $CPYTHON_RO_SRCDIR
+    - name: Configure CPython out-of-tree
+      working-directory: ${{ env.CPYTHON_BUILDDIR }}
+      run: ../cpython-ro-srcdir/configure --with-pydebug --with-openssl=$OPENSSL_DIR
+    - name: Build CPython out-of-tree
+      working-directory: ${{ env.CPYTHON_BUILDDIR }}
       run: make -j4
     - name: Display build info
+      working-directory: ${{ env.CPYTHON_BUILDDIR }}
       run: make pythoninfo
+    - name: Remount sources writable for tests
+      # some tests write to srcdir, lack of pyc files slows down testing
+      run: sudo mount $CPYTHON_RO_SRCDIR -oremount,rw
     - name: Tests
+      working-directory: ${{ env.CPYTHON_BUILDDIR }}
       run: xvfb-run make buildbottest TESTOPTS="-j4 -uall,-cpu"
 
   build_ubuntu_ssltests:
diff --git a/Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst b/Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst
new file mode 100644
index 00000000000000..e334855d0f6d60
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst
@@ -0,0 +1,3 @@
+The Ubuntu test runner now configures and compiles CPython out of tree. The
+source directory is a read-only bind mount to ensure that the build cannot
+create or modify any files in the source tree.

From 0381848559f28af91f8ec542120f7dc742e441a3 Mon Sep 17 00:00:00 2001
From: Christian Heimes <christian@python.org>
Date: Fri, 3 Dec 2021 23:16:17 +0100
Subject: [PATCH 2/2] Simplify news entry

---
 .../next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst       | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst b/Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst
index e334855d0f6d60..14ecd923dbd553 100644
--- a/Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst
+++ b/Misc/NEWS.d/next/Tests/2021-12-03-14-19-16.bpo-45695.QKBn2E.rst
@@ -1,3 +1 @@
-The Ubuntu test runner now configures and compiles CPython out of tree. The
-source directory is a read-only bind mount to ensure that the build cannot
-create or modify any files in the source tree.
+Out-of-tree builds with a read-only source directory are now tested by CI.