Insert new featurePrefix after general cache key prefix

Author: mbg

lib/analyze-action.js

@@ -524,8 +524,14 @@ async function cachePrefix(
   // experimental features that affect the cache contents.
   const featurePrefix = await getFeaturePrefix(codeql, features, language);
 
-  // Assemble the cache key.
-  return `${featurePrefix}${prefix}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
+  // Assemble the cache key. For backwards compatibility with the JAR minification experiment's existing
+  // feature prefix usage, we add that feature prefix at the start. Other feature prefixes are inserted
+  // after the general CodeQL dependency cache prefix.
+  if (featurePrefix === "minify-") {
+    return `${featurePrefix}${prefix}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
+  } else {
+    return `${prefix}-${featurePrefix}${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
+  }
 }
 
 /** Represents information about our overall cache usage for CodeQL dependency caches. */