Ensure an engine-only ruby-version picks the latest stable version and not a preview or RC

Author: eregon

common.js

@@ -28,6 +28,10 @@ export function isHeadVersion(rubyVersion) {
   return rubyVersion === 'head' || rubyVersion === 'debug' || rubyVersion === 'mingw' || rubyVersion === 'mswin'
 }
 
+export function isStableVersion(rubyVersion) {
+  return /^\d+(\.\d+)*$/.test(rubyVersion)
+}
+
 export async function hashFile(file) {
   // See https://github.com/actions/runner/blob/master/src/Misc/expressionFunc/hashFiles/src/hashFiles.ts
   const hash = crypto.createHash('sha256')

dist/index.js

@@ -132,7 +132,7 @@ function validateRubyEngineAndVersion(platform, engineVersions, engine, parsedVe
   let version = parsedVersion
   if (!engineVersions.includes(parsedVersion)) {
     const latestToFirstVersion = engineVersions.slice().reverse()
-    const found = latestToFirstVersion.find(v => !common.isHeadVersion(v) && v.startsWith(parsedVersion))
+    const found = latestToFirstVersion.find(v => common.isStableVersion(v) && v.startsWith(parsedVersion))
     if (found) {
       version = found
     } else {