[python] - cpython - prev. version fallback - fix (#907)

* [python] - cpython - prev. version fallback - fix

* according to comments

src/python/devcontainer-feature.json

 {
   "id": "python",
-  "version": "1.4.1",
+  "version": "1.4.2",
   "name": "Python",
   "documentationURL": "https://github.com/devcontainers/features/tree/main/src/python",
   "description": "Installs the provided version of Python, as well as PIPX, and other common Python utilities.  JupyterLab is conditionally installed with the python feature. Note: May require source code compilation.",

src/python/install.sh

@@ -248,6 +248,48 @@ find_version_from_git_tags() {
     echo "${variable_name}=${!variable_name}"
 }
 
+# Use semver logic to decrement a version number then look for the closest match
+find_prev_version_from_git_tags() {
+    local variable_name=$1
+    local current_version=${!variable_name}
+    local repository=$2
+    # Normally a "v" is used before the version number, but support alternate cases
+    local prefix=${3:-"tags/v"}
+    # Some repositories use "_" instead of "." for version number part separation, support that
+    local separator=${4:-"."}
+    # Some tools release versions that omit the last digit (e.g. go)
+    local last_part_optional=${5:-"false"}
+    # Some repositories may have tags that include a suffix (e.g. actions/node-versions)
+    local version_suffix_regex=$6
+    # Try one break fix version number less if we get a failure. Use "set +e" since "set -e" can cause failures in valid scenarios.
+    set +e
+        major="$(echo "${current_version}" | grep -oE '^[0-9]+' || echo '')"
+        minor="$(echo "${current_version}" | grep -oP '^[0-9]+\.\K[0-9]+' || echo '')"
+        breakfix="$(echo "${current_version}" | grep -oP '^[0-9]+\.[0-9]+\.\K[0-9]+' 2>/dev/null || echo '')"
+
+        if [ "${minor}" = "0" ] && [ "${breakfix}" = "0" ]; then
+            ((major=major-1))
+            declare -g ${variable_name}="${major}"
+            # Look for latest version from previous major release
+            find_version_from_git_tags "${variable_name}" "${repository}" "${prefix}" "${separator}" "${last_part_optional}"
+        # Handle situations like Go's odd version pattern where "0" releases omit the last part
+        elif [ "${breakfix}" = "" ] || [ "${breakfix}" = "0" ]; then
+            ((minor=minor-1))
+            declare -g ${variable_name}="${major}.${minor}"
+            # Look for latest version from previous minor release
+            find_version_from_git_tags "${variable_name}" "${repository}" "${prefix}" "${separator}" "${last_part_optional}"
+        else
+            ((breakfix=breakfix-1))
+            if [ "${breakfix}" = "0" ] && [ "${last_part_optional}" = "true" ]; then
+                declare -g ${variable_name}="${major}.${minor}"
+            else 
+                declare -g ${variable_name}="${major}.${minor}.${breakfix}"
+            fi
+        fi
+    set -e
+}
+
+
 # Use Oryx to install something using a partial version match
 oryx_install() {
     local platform=$1
@@ -368,6 +410,29 @@ install_openssl3() {
     rm -rf /tmp/openssl3
 }
 
+install_prev_vers_cpython() {
+    VERSION=$1
+    echo -e "\n(!) Failed to fetch the latest artifacts for cpython ${VERSION}..."
+    find_prev_version_from_git_tags VERSION https://github.com/python/cpython
+    echo -e "\nAttempting to install ${VERSION}"
+    install_cpython "${VERSION}"
+}
+
+install_cpython() {
+    VERSION=$1
+    INSTALL_PATH="${PYTHON_INSTALL_PATH}/${VERSION}"
+    if [ -d "${INSTALL_PATH}" ]; then
+        echo "(!) Python version ${VERSION} already exists."
+        exit 1
+    fi
+    mkdir -p /tmp/python-src ${INSTALL_PATH}
+    cd /tmp/python-src
+    cpython_tgz_filename="Python-${VERSION}.tgz"
+    cpython_tgz_url="https://www.python.org/ftp/python/${VERSION}/${cpython_tgz_filename}"
+    echo "Downloading ${cpython_tgz_filename}..."
+    curl -sSL -o "/tmp/python-src/${cpython_tgz_filename}" "${cpython_tgz_url}"
+}
+
 install_from_source() {
     VERSION=$1  
     echo "(*) Building Python ${VERSION} from source..."
@@ -378,13 +443,6 @@ install_from_source() {
     # Find version using soft match
     find_version_from_git_tags VERSION "https://github.com/python/cpython"
 
-    INSTALL_PATH="${PYTHON_INSTALL_PATH}/${VERSION}"
-    
-    if [ -d "${INSTALL_PATH}" ]; then
-        echo "(!) Python version ${VERSION} already exists."
-        exit 1
-    fi
-
     # Some platforms/os versions need modern versions of openssl installed
     # via common package repositories, for now rhel-7 family, use case statement to 
     # make it easy to expand
@@ -396,23 +454,21 @@ install_from_source() {
             ;;
     esac
 
-    # Download tgz of source
-    mkdir -p /tmp/python-src ${INSTALL_PATH}
-    cd /tmp/python-src
-    local tgz_filename="Python-${VERSION}.tgz"
-    local tgz_url="https://www.python.org/ftp/python/${VERSION}/${tgz_filename}"
-    echo "Downloading ${tgz_filename}..."
-    curl -sSL -o "/tmp/python-src/${tgz_filename}" "${tgz_url}"
-
+    install_cpython "${VERSION}"
+    if [ -f "/tmp/python-src/${cpython_tgz_filename}" ]; then 
+        if grep -q "404 Not Found" "/tmp/python-src/${cpython_tgz_filename}"; then
+            install_prev_vers_cpython "${VERSION}"
+        fi
+    fi;
     # Verify signature
     if [[ ${VERSION_CODENAME} = "centos7" ]] || [[ ${VERSION_CODENAME} = "rhel7" ]]; then
         receive_gpg_keys_centos7 PYTHON_SOURCE_GPG_KEYS
     else
         receive_gpg_keys PYTHON_SOURCE_GPG_KEYS
     fi
-    echo "Downloading ${tgz_filename}.asc..."
-    curl -sSL -o "/tmp/python-src/${tgz_filename}.asc" "${tgz_url}.asc"
-    gpg --verify "${tgz_filename}.asc"
+    echo "Downloading ${cpython_tgz_filename}.asc..."
+    curl -sSL -o "/tmp/python-src/${cpython_tgz_filename}.asc" "${cpython_tgz_url}.asc"
+    gpg --verify "${cpython_tgz_filename}.asc"
 
     # Update min protocol for testing only - https://bugs.python.org/issue41561
     if [ -f /etc/pki/tls/openssl.cnf ]; then
@@ -424,7 +480,7 @@ install_from_source() {
     export OPENSSL_CONF=/tmp/python-src/openssl.cnf
 
     # Untar and build
-    tar -xzf "/tmp/python-src/${tgz_filename}" -C "/tmp/python-src" --strip-components=1
+    tar -xzf "/tmp/python-src/${cpython_tgz_filename}" -C "/tmp/python-src" --strip-components=1
     local config_args=""
     if [ "${OPTIMIZE_BUILD_FROM_SOURCE}" = "true" ]; then
         config_args="${config_args} --enable-optimizations"

test/python/scenarios.json

 {
+    "install_cpython_fallback_prev_version_test": {
+        "image": "python:3.12",
+        "features": {
+            "python": {
+                "version": "3.12",
+                "installTools": false,
+                "skipVulnerabilityPatching": true
+            }
+        }
+    },
     "install_python310_skipVulnerabilityPatching_true": {
         "image": "python:3.10",
         "features": {