Add JDK 17 fallback to mvn-spotless-apply.sh

scripts/mvn-spotless-apply.sh previously exec'd `mvn spotless:apply`
directly, so when the default JDK was older than 17 (the minimum required
by the pinned google-java-format 1.27.0) it failed with no recovery.

Mirror the `make fmt` -> `make fmt-jdk17` fallback: try the selected JDK
first, and if that fails retry under an explicit JDK 17 install, always
applying the javac --add-exports flags GJF needs on JDK 16+.

To keep the fallback honest and portable:
- detect the JDK version from the JVM Maven actually uses ($JAVA_HOME/bin/java
  if JAVA_HOME is set, else `java` on PATH), so the add-exports gating matches
  the running JDK and re-running with JAVA_HOME=<jdk17> succeeds on the first
  attempt;
- allow the fallback location to be overridden via JDK17_HOME for non-Debian
  layouts, and error clearly (pointing at JDK17_HOME / JAVA_HOME) when no
  JDK 17 is found.

Author: Divyansh-db

scripts/mvn-spotless-apply.sh

@@ -4,25 +4,67 @@
 # google-java-format on JDK 16+. Without these, GJF fails on JDK 17+ with either
 # IllegalAccessError or NoSuchMethodError when it reaches into com.sun.tools.javac.*.
 # On JDK <= 15 the flags are unrecognized and would break Maven startup, so we only
-# set them when detected JDK major version is >= 16.
+# set them when the detected JDK major version is >= 16.
+#
+# If that JDK can't run google-java-format (most often because it's older than JDK 17,
+# which the pinned GJF 1.27.0 requires), we retry under an explicit JDK 17 install —
+# mirroring the `make fmt` -> `make fmt-jdk17` fallback. Override the fallback location
+# with JDK17_HOME, or just point JAVA_HOME at a JDK 17+ and re-run.
 
 set -euo pipefail
 
-JDK_VERSION_OUTPUT=$(java -version 2>&1 | head -1)
-# Matches `"1.8.0_xxx"` (legacy) and `"17.0.1"` / `"25"` (modern) forms.
-JDK_MAJOR=$(echo "$JDK_VERSION_OUTPUT" | sed -E 's/.*version "([0-9]+)(\.[0-9]+)?.*/\1/')
-if [ "$JDK_MAJOR" = "1" ]; then
-  JDK_MAJOR=$(echo "$JDK_VERSION_OUTPUT" | sed -E 's/.*version "1\.([0-9]+).*/\1/')
-fi
+# Location used by the JDK 17 fallback. Override for non-Debian layouts, e.g.
+# `JDK17_HOME=$(/usr/libexec/java_home -v 17) bash scripts/mvn-spotless-apply.sh`.
+JDK17_HOME="${JDK17_HOME:-/usr/lib/jvm/java-17-openjdk-amd64}"
 
-if [ "${JDK_MAJOR:-0}" -ge 16 ]; then
-  export MAVEN_OPTS="${MAVEN_OPTS:-} \
+# The --add-exports flags google-java-format needs to reach into com.sun.tools.javac.*
+# on JDK 16+.
+GJF_ADD_EXPORTS="\
 --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED \
 --add-exports=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED \
 --add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED \
 --add-exports=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED \
 --add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED \
 --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED"
+
+# Detect the major version of the JDK Maven will actually use: $JAVA_HOME/bin/java when
+# JAVA_HOME is set, otherwise `java` from PATH. mvn resolves its JVM the same way, so the
+# add-exports gating below matches what the first attempt really runs (and re-running with
+# JAVA_HOME pointed at a JDK 17+ makes that attempt succeed without hitting the fallback).
+JAVA_BIN="java"
+if [ -n "${JAVA_HOME:-}" ] && [ -x "${JAVA_HOME}/bin/java" ]; then
+  JAVA_BIN="${JAVA_HOME}/bin/java"
+fi
+
+JDK_VERSION_OUTPUT=$("$JAVA_BIN" -version 2>&1 | head -1)
+# Matches `"1.8.0_xxx"` (legacy) and `"17.0.1"` / `"25"` (modern) forms.
+JDK_MAJOR=$(echo "$JDK_VERSION_OUTPUT" | sed -E 's/.*version "([0-9]+)(\.[0-9]+)?.*/\1/')
+if [ "$JDK_MAJOR" = "1" ]; then
+  JDK_MAJOR=$(echo "$JDK_VERSION_OUTPUT" | sed -E 's/.*version "1\.([0-9]+).*/\1/')
+fi
+
+DEFAULT_OPTS="${MAVEN_OPTS:-}"
+if [ "${JDK_MAJOR:-0}" -ge 16 ]; then
+  DEFAULT_OPTS="$DEFAULT_OPTS $GJF_ADD_EXPORTS"
+fi
+
+# First attempt: the JDK selected above (JAVA_HOME or PATH).
+if MAVEN_OPTS="$DEFAULT_OPTS" mvn spotless:apply; then
+  exit 0
+fi
+
+echo ""
+echo "==> default JDK could not run google-java-format (likely < JDK 17). Retrying with JDK 17..."
+echo ""
+
+if [ ! -x "$JDK17_HOME/bin/java" ]; then
+  echo "error: JDK 17 not found at $JDK17_HOME" >&2
+  echo "       install it, set JDK17_HOME to a JDK 17 install, or point JAVA_HOME" >&2
+  echo "       at a JDK 17+ and re-run." >&2
+  exit 1
 fi
 
-exec mvn spotless:apply
+# JDK 17 is always >= 16, so the add-exports flags are always required here.
+exec env JAVA_HOME="$JDK17_HOME" \
+  MAVEN_OPTS="${MAVEN_OPTS:-} $GJF_ADD_EXPORTS" \
+  mvn spotless:apply