path: simplify code and remove obsolete checks

Either `end` is `-1` or `startPart` is not `0`. Therefore it's
possible to move the conditions in a way that we eliminate a few code
branches.

PR-URL: nodejs#25278
Reviewed-By: Michaël Zasso <[email protected]>

Author: BridgeAR

lib/path.js

@@ -960,21 +960,20 @@ const win32 = {
       }
     }
 
-    if (startDot === -1 ||
-        end === -1 ||
-        // We saw a non-dot character immediately before the dot
-        preDotState === 0 ||
-        // The (right-most) trimmed path component is exactly '..'
-        (preDotState === 1 &&
-         startDot === end - 1 &&
-         startDot === startPart + 1)) {
-      if (end !== -1) {
+    if (end !== -1) {
+      if (startDot === -1 ||
+          // We saw a non-dot character immediately before the dot
+          preDotState === 0 ||
+          // The (right-most) trimmed path component is exactly '..'
+          (preDotState === 1 &&
+           startDot === end - 1 &&
+           startDot === startPart + 1)) {
         ret.base = ret.name = path.slice(startPart, end);
+      } else {
+        ret.name = path.slice(startPart, startDot);
+        ret.base = path.slice(startPart, end);
+        ret.ext = path.slice(startDot, end);
       }
-    } else {
-      ret.name = path.slice(startPart, startDot);
-      ret.base = path.slice(startPart, end);
-      ret.ext = path.slice(startDot, end);
     }
 
     // If the directory is the root, use the entire root as the `dir` including
@@ -1380,29 +1379,21 @@ const posix = {
       }
     }
 
-    if (startDot === -1 ||
-        end === -1 ||
-        // We saw a non-dot character immediately before the dot
-        preDotState === 0 ||
-        // The (right-most) trimmed path component is exactly '..'
-        (preDotState === 1 &&
-         startDot === end - 1 &&
-         startDot === startPart + 1)) {
-      if (end !== -1) {
-        if (startPart === 0 && isAbsolute)
-          ret.base = ret.name = path.slice(1, end);
-        else
-          ret.base = ret.name = path.slice(startPart, end);
-      }
-    } else {
-      if (startPart === 0 && isAbsolute) {
-        ret.name = path.slice(1, startDot);
-        ret.base = path.slice(1, end);
+    if (end !== -1) {
+      const start = startPart === 0 && isAbsolute ? 1 : startPart;
+      if (startDot === -1 ||
+          // We saw a non-dot character immediately before the dot
+          preDotState === 0 ||
+          // The (right-most) trimmed path component is exactly '..'
+          (preDotState === 1 &&
+          startDot === end - 1 &&
+          startDot === startPart + 1)) {
+        ret.base = ret.name = path.slice(start, end);
       } else {
-        ret.name = path.slice(startPart, startDot);
-        ret.base = path.slice(startPart, end);
+        ret.name = path.slice(start, startDot);
+        ret.base = path.slice(start, end);
+        ret.ext = path.slice(startDot, end);
       }
-      ret.ext = path.slice(startDot, end);
     }
 
     if (startPart > 0)