address comments

src/dotnet/install.sh

@@ -33,6 +33,16 @@ DOTNET_VERSION_CODENAMES_REQUIRE_OLDER_LIBSSL_1="buster bullseye bionic focal hi
 # alongside DOTNET_VERSION, but not set as default.
 ADDITIONAL_VERSIONS=${ADDITIONALVERSIONS:-""}
 
+APT_PREFERENCES_CONTENT="$(cat << 'EOF'
+Package: *
+Pin: origin "packages.microsoft.com"
+Pin-Priority: 1001
+EOF
+)"
+
+APT_PREFERENCES_FILE_ADDED="false"
+APT_PREFERENCES_UPDATED="false"
+
 set -e
 
 # Clean up
@@ -149,7 +159,7 @@ apt_cache_package_and_version_soft_match() {
 
     apt-get update -y
     major_minor_version="$(echo "${requested_version}" | cut -d "." --field=1,2)"
-    package_name="$(apt-cache search "${partial_package_name}-[0-9].[0-9]" | awk -F" - " '{print $1}' | grep -v "source-built-artifacts" | grep -m 1 "${partial_package_name}-${major_minor_version}")"
+    package_name="$(apt-cache search "${partial_package_name}-[0-9].[0-9]$" | awk -F" - " '{print $1}' | grep -m 1 "${partial_package_name}-${major_minor_version}")"
     dot_escaped="${requested_version//./\\.}"
     dot_plus_escaped="${dot_escaped//+/\\+}"
     # Regex needs to handle debian package version number format: https://www.systutorials.com/docs/linux/man/5-deb-version/
@@ -194,13 +204,11 @@ install_using_apt() {
         curl -sSL ${MICROSOFT_GPG_KEYS_URI} | gpg --dearmor > /usr/share/keyrings/microsoft-archive-keyring.gpg
         echo "deb [arch=${architecture} signed-by=/usr/share/keyrings/microsoft-archive-keyring.gpg] https://packages.microsoft.com/repos/microsoft-${ID}-${VERSION_CODENAME}-prod ${VERSION_CODENAME} main" > /etc/apt/sources.list.d/microsoft.list
 
-        # See https://github.com/dotnet/core/issues/7699
-        cat << 'EOF' >> /etc/apt/preferences
-Package: *
-Pin: origin "packages.microsoft.com"
-Pin-Priority: 1001
-EOF
+        [ ! -f /etc/apt/preferences ] && APT_PREFERENCES_FILE_ADDED="true"
+        APT_PREFERENCES_UPDATED="true"
 
+        # See https://github.com/dotnet/core/issues/7699
+        echo "${APT_PREFERENCES_CONTENT}" >> /etc/apt/preferences
         apt-get update -y
     fi
 
@@ -471,6 +479,14 @@ if [ "${CHANGE_OWNERSHIP}" = "true" ]; then
 fi
 
 # Clean up
+if [ "${APT_PREFERENCES_UPDATED}" = "true" ]; then
+    if [ "${APT_PREFERENCES_FILE_ADDED}" = "true" ]; then
+        rm -f /etc/apt/preferences
+    else
+        head -n -3 /etc/apt/preferences > /tmp/preferences-temp && mv /tmp/preferences-temp /etc/apt/preferences
+    fi
+fi
+
 rm -rf /var/lib/apt/lists/*
 
 echo "Done!"

test/dotnet/install_dotnet_7_jammy.sh

@@ -5,6 +5,9 @@ set -e
 # Optional: Import test library
 source dev-container-features-test-lib
 
+cat /etc/apt/preferences
+
+
 check "dotnet sdks" dotnet --list-sdks
 check "some major version of dotnet 7 is installed" bash -c "dotnet --list-sdks |  grep '7\.[0-9]*\.[0-9]*'"
 check "dotnet version 7 installed"  bash -c "ls -l /usr/lib/dotnet/sdk | grep '7\.[0-9]*\.[0-9]*'"