Fix if-else formatting for JSDoc type casting (#16798)

Keep block comment position for block less else

src/language-js/comments/handle-comments.js

@@ -198,25 +198,39 @@ function handleIfStatementComments({
     precedingNode === enclosingNode.consequent &&
     followingNode === enclosingNode.alternate
   ) {
-    if (precedingNode.type === "BlockStatement") {
-      addTrailingComment(precedingNode, comment);
-    } else {
-      const isSingleLineComment =
-        isLineComment(comment) ||
-        comment.loc.start.line === comment.loc.end.line;
-      const isSameLineComment =
-        comment.loc.start.line === precedingNode.loc.start.line;
-      if (isSingleLineComment && isSameLineComment) {
-        // example:
-        //   if (cond1) expr1; // comment A
-        //   else if (cond2) expr2; // comment A
-        //   else expr3;
+    const maybeElseTokenIndex = getNextNonSpaceNonCommentCharacterIndex(
+      text,
+      locEnd(enclosingNode.consequent),
+    );
+    // With the above conditions alone, this code would also match. This is a false positive.
+    // So, ignore cases where the token "else" appears immediately after the consequent:
+    //
+    //   if (cond) a;
+    //   else /* foo */ b;
+    if (
+      locStart(comment) < maybeElseTokenIndex ||
+      enclosingNode.alternate.type === "BlockStatement"
+    ) {
+      if (precedingNode.type === "BlockStatement") {
         addTrailingComment(precedingNode, comment);
       } else {
-        addDanglingComment(enclosingNode, comment);
+        const isSingleLineComment =
+          isLineComment(comment) ||
+          comment.loc.start.line === comment.loc.end.line;
+        const isSameLineComment =
+          comment.loc.start.line === precedingNode.loc.start.line;
+        if (isSingleLineComment && isSameLineComment) {
+          // example:
+          //   if (cond1) expr1; // comment A
+          //   else if (cond2) expr2; // comment A
+          //   else expr3;
+          addTrailingComment(precedingNode, comment);
+        } else {
+          addDanglingComment(enclosingNode, comment);
+        }
       }
+      return true;
     }
-    return true;
   }
 
   if (followingNode.type === "BlockStatement") {

tests/format/js/comments/16398.js

@@ -0,0 +1,5 @@
+if (foo) a = b;
+/* foo */ else foo.split;
+
+if (foo) a = b;
+else /* foo */ foo.split;

tests/format/js/comments/__snapshots__/format.test.js.snap

@@ -321,6 +321,51 @@ void (
 ================================================================================
 `;
 
+exports[`16398.js - {"semi":false} format 1`] = `
+====================================options=====================================
+parsers: ["babel", "flow", "typescript"]
+printWidth: 80
+semi: false
+                                                                                | printWidth
+=====================================input======================================
+if (foo) a = b;
+/* foo */ else foo.split;
+
+if (foo) a = b;
+else /* foo */ foo.split;
+
+=====================================output=====================================
+if (foo) a = b
+/* foo */ else foo.split
+
+if (foo) a = b
+else /* foo */ foo.split
+
+================================================================================
+`;
+
+exports[`16398.js format 1`] = `
+====================================options=====================================
+parsers: ["babel", "flow", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+if (foo) a = b;
+/* foo */ else foo.split;
+
+if (foo) a = b;
+else /* foo */ foo.split;
+
+=====================================output=====================================
+if (foo) a = b;
+/* foo */ else foo.split;
+
+if (foo) a = b;
+else /* foo */ foo.split;
+
+================================================================================
+`;
+
 exports[`arrow.js - {"semi":false} format 1`] = `
 ====================================options=====================================
 parsers: ["babel", "flow", "typescript"]