[SPARK-58136][INFRA] Automate downloads.md and versions.json updates in the release script

dev/create-release/release-build.sh

@@ -302,7 +302,73 @@ EOF
     echo "Edited js/downloads.js"
   fi
 
-  # 3. Add news post
+  # 3. Update the latest stable version in downloads.md and site/static/versions.json.
+  #    site/downloads.html is regenerated from downloads.md by the jekyll build below,
+  #    so it does not need to be edited here.
+  if [[ "$RELEASE_VERSION" =~ -preview[0-9]*$ ]]; then
+    echo "Skipping downloads.md and versions.json for preview release: $RELEASE_VERSION"
+  else
+    python3 <<EOF
+import json
+import re
+
+release_version = "${RELEASE_VERSION}"
+
+def parse_version(v):
+    return [int(p) for p in v.strip().split(".")]
+
+def vercmp(v1, v2):
+    a = parse_version(v1)
+    b = parse_version(v2)
+    return (a > b) - (a < b)
+
+# downloads.md: bump the Maven coordinate example to the latest stable version.
+# Only update when this release is newer than the version currently shown, so a
+# maintenance release on an older branch does not downgrade the coordinate.
+with open("downloads.md") as f:
+    lines = f.readlines()
+
+with open("downloads.md", "w") as f:
+    in_maven_block = False
+    for line in lines:
+        if re.match(r"\s*artifactId:\s*spark-core", line):
+            in_maven_block = True
+        m = re.match(r"(\s*version:\s*)(\d+\.\d+\.\d+)(\s*)$", line)
+        if in_maven_block and m:
+            if vercmp(release_version, m.group(2)) > 0:
+                line = f"{m.group(1)}{release_version}{m.group(3)}"
+            in_maven_block = False
+        f.write(line)
+
+# site/static/versions.json: add (or replace) the entry for this release, keeping
+# the list sorted in descending version order (it drives the API docs version picker).
+path = "site/static/versions.json"
+with open(path) as f:
+    versions = json.load(f)
+
+entry = {
+    "name": release_version,
+    "version": release_version,
+    "url": f"https://spark.apache.org/docs/{release_version}/api/python/",
+}
+
+versions = [v for v in versions if v.get("version") != release_version]
+insert_at = len(versions)
+for i, v in enumerate(versions):
+    if vercmp(release_version, v.get("version", "0.0.0")) > 0:
+        insert_at = i
+        break
+versions.insert(insert_at, entry)
+
+with open(path, "w") as f:
+    json.dump(versions, f, indent=4)
+    f.write("\n")
+EOF
+
+    echo "Edited downloads.md and site/static/versions.json"
+  fi
+
+  # 4. Add news post
   RELEASE_DATE=$(TZ=America/Los_Angeles date +"%Y-%m-%d")
   FILENAME="news/_posts/${RELEASE_DATE}-spark-${RELEASE_VERSION//./-}-released.md"
   mkdir -p news/_posts
@@ -356,7 +422,7 @@ EOF
 
   echo "Created $FILENAME"
 
-  # 4. Add release notes with Python to extract JIRA version ID
+  # 5. Add release notes with Python to extract JIRA version ID
   if [[ "$RELEASE_VERSION" =~ -preview[0-9]*$ ]]; then
     echo "Skipping JIRA release notes for preview release: $RELEASE_VERSION"
   else
@@ -430,11 +496,11 @@ EOF
     echo "Created $FILENAME"
   fi
 
-  # 5. Build the website
+  # 6. Build the website
   bundle install
   bundle exec jekyll build
 
-  # 6. Update latest or preview symlink
+  # 7. Update latest or preview symlink
   IFS='.' read -r rel_maj rel_min rel_patch <<< "$RELEASE_VERSION"
 
   if [[ "$RELEASE_VERSION" =~ -preview[0-9]*$ ]]; then