fix: make warning and error level output prefix consistent

lib/core.js

@@ -183,13 +183,13 @@ const fetchPackageDependencies = async function({ name, version, deep }) {
         // handle version not exist
         if (!versions.find(x => x == entry.version)) {
           log.warn(
-            `[WARN] package ${entry.name}@${
+            `package ${entry.name}@${
               entry.version
             } is not a valid choice of ${versions.reverse().join(", ")}`
           );
           // eslint-disable-next-line require-atomic-updates
           validDep.version = entry.version = getLatestVersion(pkgInfo);
-          log.warn(`[WARN] fall back to ${entry.name}@${entry.version}`);
+          log.warn(`fall back to ${entry.name}@${entry.version}`);
         }
         // add dependencies to pending list
         if (validDep.self || deep) {

lib/logger.js

@@ -1,14 +1,24 @@
 const log = require("loglevel");
 const prefix = require("loglevel-plugin-prefix");
 
+prefix.reg(log);
 if (process.env.NODE_ENV == "test") {
-  prefix.reg(log);
   prefix.apply(log, {
     // eslint-disable-next-line no-unused-vars
     format(level, name, timestamp) {
       return "[test]";
     }
   });
+} else {
+  prefix.apply(log, {
+    // eslint-disable-next-line no-unused-vars
+    format(level, name, timestamp) {
+      if (level == "ERROR" || level == "WARN") {
+        return `[${level}]`;
+      }
+      return "";
+    }
+  });
 }
 
 module.exports = log;