fix: respect latest only if ignoring unstable

lib/manager/npm/lookup/filter.js

@@ -6,7 +6,6 @@ const {
 
 module.exports = {
   filterVersions,
-  filterUnstable,
   filterLatest,
 };
 
@@ -15,42 +14,40 @@ function filterVersions(config, fromVersion, latestVersion, versions) {
   if (!fromVersion) {
     return [];
   }
+
   // Leave only versions greater than current
   let filteredVersions = versions.filter(version =>
     isGreaterThan(version, fromVersion)
   );
-  filteredVersions = filterUnstable(
+
-    ignoreUnstable,
+  // Return all versions if we aren't ignore unstable. Also ignore latest
-    fromVersion,
+  if (ignoreUnstable === false) {
-    filteredVersions
+    return filteredVersions;
-  );
+  }
-  filteredVersions = filterLatest(
+
+  // if current is unstable then allow unstable in the current major only
+  if (!isStable(fromVersion)) {
+    // Allow unstable only in current major
+    return filteredVersions.filter(
+      version =>
+        isStable(version) || getMajor(version) === getMajor(fromVersion)
+    );
+  }
+
+  // Normal case: remove all unstable
+  filteredVersions = filteredVersions.filter(isStable);
+
+  return filterLatest(
     respectLatest,
     fromVersion,
     latestVersion,
     filteredVersions
   );
-  return filteredVersions;
-}
-
-function filterUnstable(ignoreUnstable, fromVersion, versions) {
-  // Filter nothing out if we are not ignoring unstable
-  if (ignoreUnstable === false) {
-    return versions;
-  }
-  // Filter out all unstable if fromVersion is stable
-  if (isStable(fromVersion)) {
-    // Remove all unstable
-    return versions.filter(isStable);
-  }
-  // Allow unstable only in current major
-  return versions.filter(
-    version => isStable(version) || getMajor(version) === getMajor(fromVersion)
-  );
 }
 
 function filterLatest(respectLatest, fromVersion, latestVersion, versions) {
   // No filtering if no latest
+  // istanbul ignore if
   if (!latestVersion) {
     return versions;
   }