Fix the union type that contains an extra empty line (#18197)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: fisker <lionkay@gmail.com>

changelog_unreleased/typescript/18197.md

@@ -0,0 +1,21 @@
+#### Remove extra empty line in union type (#18197 by @Dunqing)
+
+<!-- prettier-ignore -->
+```tsx
+// Input
+type SuperLongTypeNameLoremIpsumLoremIpsumBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBla =
+  Fooo1000 | Baz2000 | BarLoooooooooooooooooooooooooooooooooooooooooooooooooLong;
+
+// Prettier stable
+type SuperLongTypeNameLoremIpsumLoremIpsumBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBla =
+
+    | Fooo1000
+    | Baz2000
+    | BarLoooooooooooooooooooooooooooooooooooooooooooooooooLong;
+
+// Prettier main
+type SuperLongTypeNameLoremIpsumLoremIpsumBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBla =
+  | Fooo1000
+  | Baz2000
+  | BarLoooooooooooooooooooooooooooooooooooooooooooooooooLong;
+```

src/document/printer/printer.js

@@ -62,6 +62,7 @@ function fits(
   }
 
   let restCommandsIndex = restCommands.length;
+  let hasPendingSpace = false;
   /** @type {Array<Omit<Command, 'indent'>>} */
   const commands = [next];
   // `output` is only used for width counting because `trim` requires to look
@@ -82,6 +83,12 @@ function fits(
     switch (docType) {
       case DOC_TYPE_STRING:
         if (doc) {
+          if (hasPendingSpace) {
+            output += " ";
+            remainingWidth -= 1;
+            hasPendingSpace = false;
+          }
+
           output += doc;
           remainingWidth -= getStringWidth(doc);
         }
@@ -142,8 +149,7 @@ function fits(
           return true;
         }
         if (!doc.soft) {
-          output += " ";
-          remainingWidth--;
+          hasPendingSpace = true;
         }
         break;
 

tests/format/typescript/union/consistent-with-flow/__snapshots__/format.test.js.snap

@@ -142,10 +142,9 @@ type A3 = // dir, exp, arg, modifiers
     [string, ExpressionNode, ExpressionNode, ObjectExpression];
 
 type SuperLongTypeNameLoremIpsumLoremIpsumBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBla =
-
-    | Fooo1000
-    | Baz2000
-    | BarLoooooooooooooooooooooooooooooooooooooooooooooooooLong;
+  | Fooo1000
+  | Baz2000
+  | BarLoooooooooooooooooooooooooooooooooooooooooooooooooLong;
 
 type SuperLongTypeNameLoremIpsumLoremIpsumBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBlaBl2 =
   Fooo1000 &