From ef2941603c561c126720ffb75ccbba09b09b9a61 Mon Sep 17 00:00:00 2001
From: Michele Locati <michele@locati.it>
Date: Thu, 23 Jan 2020 13:48:18 +0100
Subject: [PATCH 1/3] Test that previously installed APT packages are restored

---
 .travis.yml              |  4 ++++
 scripts/invoke-shfmt     |  1 +
 scripts/test-restore-apt | 17 +++++++++++++++++
 3 files changed, 22 insertions(+)
 create mode 100755 scripts/test-restore-apt

diff --git a/.travis.yml b/.travis.yml
index 522d292..43d226f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -62,6 +62,10 @@ jobs:
       name: Test extensions on Debian 10 (buster)
       env: DOCKER_DISTRO=buster
 
+    - <<: *test-extensions-job-template
+      name: Test restoring previous packages
+      script: docker run --rm --volume "$TRAVIS_BUILD_DIR:/app" --workdir /app php:7.3-stretch ./scripts/test-restore-apt
+
     - stage: Update docs
       name: Update README.md
       if: branch = master AND type = push
diff --git a/scripts/invoke-shfmt b/scripts/invoke-shfmt
index 801c6f6..4c24e41 100755
--- a/scripts/invoke-shfmt
+++ b/scripts/invoke-shfmt
@@ -23,6 +23,7 @@ shfmt $PARAMS \
 	scripts/common \
 	scripts/invoke-shfmt \
 	scripts/lint \
+	scripts/test-restore-apt \
 	scripts/travisci-test-extensions \
 	scripts/travisci-update-readme \
 	scripts/update-readme
diff --git a/scripts/test-restore-apt b/scripts/test-restore-apt
new file mode 100755
index 0000000..6545a0e
--- /dev/null
+++ b/scripts/test-restore-apt
@@ -0,0 +1,17 @@
+#!/bin/sh
+
+# Let's set a sane environment
+set -o errexit
+set -o nounset
+
+apt-get update -qq
+apt-get install -qqy libssl-dev
+
+./install-php-extensions zip
+
+if test -z "$(dpkg --get-selections | grep -E '^libssl-dev[:\s].*install$')"; then
+	echo 'The libssl-dev APT package has not been restored.' >&2
+	exit 1
+fi
+
+echo 'The libssl-dev APT package has been correctly restored.'

From 8b5078f47fd44e8c2b1eee8e21d6c14ee1a36ccf Mon Sep 17 00:00:00 2001
From: Michele Locati <michele@locati.it>
Date: Thu, 23 Jan 2020 14:50:55 +0100
Subject: [PATCH 2/3] Restore previously installed APT packages

---
 install-php-extensions | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/install-php-extensions b/install-php-extensions
index 4b1d4eb..a0ebb61 100755
--- a/install-php-extensions
+++ b/install-php-extensions
@@ -199,6 +199,7 @@ sortModulesToInstall() {
 # Set:
 #   PACKAGES_PERSISTENT
 #   PACKAGES_VOLATILE
+#   PACKAGES_PREVIOUS
 buildRequiredPackageLists() {
 	buildRequiredPackageLists_persistent=''
 	buildRequiredPackageLists_volatile=''
@@ -634,6 +635,7 @@ buildRequiredPackageLists() {
 	done
 	PACKAGES_PERSISTENT=''
 	PACKAGES_VOLATILE=''
+	PACKAGES_PREVIOUS=''
 	if test -z "$buildRequiredPackageLists_persistent$buildRequiredPackageLists_volatile"; then
 		return
 	fi
@@ -643,7 +645,6 @@ buildRequiredPackageLists() {
 			;;
 		debian)
 			DEBIAN_FRONTEND=noninteractive apt-get update -q
-			DEBIAN_FRONTEND=noninteractive apt-get autoremove --purge -y -q
 			;;
 	esac
 	if test -n "$buildRequiredPackageLists_persistent"; then
@@ -665,6 +666,13 @@ buildRequiredPackageLists() {
 		done
 		PACKAGES_VOLATILE="${PACKAGES_VOLATILE# }"
 	fi
+	if test -n "$PACKAGES_PERSISTENT$PACKAGES_VOLATILE"; then
+		case "$buildRequiredPackageLists_distro" in
+			debian)
+				PACKAGES_PREVIOUS="$(dpkg --get-selections | grep -E '\sinstall$' | awk '{ print $1 }')"
+				;;
+		esac
+	fi
 }
 
 # Get the full list of APT/APK packages that will be installed, given the required packages
@@ -1290,6 +1298,14 @@ cleanup() {
 				;;
 		esac
 	fi
+	if test -n "$PACKAGES_PREVIOUS"; then
+		case "$cleanup_distro" in
+			debian)
+				printf '### RESTORING PREVIOUSLY INSTALLED PACKAGES ###\n'
+				DEBIAN_FRONTEND=noninteractive apt-get install -qqy $PACKAGES_PREVIOUS
+				;;
+		esac
+	fi
 	case "$cleanup_distro" in
 		alpine)
 			rm -rf /var/cache/apk/*

From dc2c90a66346337d95f02ed92178963bf58cda66 Mon Sep 17 00:00:00 2001
From: Michele Locati <michele@locati.it>
Date: Thu, 23 Jan 2020 14:54:42 +0100
Subject: [PATCH 3/3] Upgrade packages in test-restore-apt

---
 scripts/test-restore-apt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/test-restore-apt b/scripts/test-restore-apt
index 6545a0e..dd9f408 100755
--- a/scripts/test-restore-apt
+++ b/scripts/test-restore-apt
@@ -5,6 +5,7 @@ set -o errexit
 set -o nounset
 
 apt-get update -qq
+apt-get upgrade -qqy
 apt-get install -qqy libssl-dev
 
 ./install-php-extensions zip