From 7c803006afaf67a3314cdc72e0878b11956c6640 Mon Sep 17 00:00:00 2001
From: dngr2 <denisgregor2@protonmail.com>
Date: Tue, 18 Aug 2026 02:45:25 +0300
Subject: [PATCH] Do not glue a property-access dot onto an integer literal

Formatting a numeric property access glued the object and the "." with no
space (1 . x -> 1.x). In dialects where 1. is a valid number literal, 1. then
re-lexes as a number and swallows the operator, so the output re-parses to a
different tree and re-formatting is not idempotent. Insert a space in that case
(as the layout already does to avoid gluing - onto - into a comment).
Identifiers ending in a digit (t1.x) and decimals (1.5) are unaffected.
---
 src/formatter/Layout.ts | 12 ++++++++++++
 test/mysql.test.ts      | 12 ++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/src/formatter/Layout.ts b/src/formatter/Layout.ts
index 39fd4071b7..e6b0a37237 100644
--- a/src/formatter/Layout.ts
+++ b/src/formatter/Layout.ts
@@ -63,6 +63,13 @@ export default class Layout {
           if (item.startsWith('-') && this.lastItemEndsWith('-')) {
             this.items.push(WS.SPACE);
           }
+          // Don't glue a "." onto a bare integer literal: "1." re-lexes as a number
+          // and absorbs the property-access operator, so "1 . x" would collapse to
+          // "1.x" and re-parse as a different expression. Identifiers that merely end
+          // in a digit ("t1.x") are unaffected.
+          if (item.startsWith('.') && this.lastItemIsIntegerLiteral()) {
+            this.items.push(WS.SPACE);
+          }
           this.items.push(item);
       }
     }
@@ -73,6 +80,11 @@ export default class Layout {
     return typeof lastItem === 'string' && lastItem.endsWith(suffix);
   }
 
+  private lastItemIsIntegerLiteral(): boolean {
+    const lastItem = last(this.items);
+    return typeof lastItem === 'string' && /^[0-9]+$/.test(lastItem);
+  }
+
   private trimHorizontalWhitespace() {
     while (isHorizontalWhitespace(last(this.items))) {
       this.items.pop();
diff --git a/test/mysql.test.ts b/test/mysql.test.ts
index e6bcd37af9..0d99ab5816 100644
--- a/test/mysql.test.ts
+++ b/test/mysql.test.ts
@@ -98,6 +98,18 @@ describe('MySqlFormatter', () => {
     `);
   });
 
+  it('keeps a numeric property access idempotent', () => {
+    // "1 ." must not glue into "1." which re-lexes as a number literal and
+    // swallows the property-access operator.
+    const sql = 'SELECT 1 . /*x*/ 5e';
+    const result = dedent`
+      SELECT
+        1 ./*x*/ 5e
+    `;
+    expect(format(sql)).toBe(result);
+    expect(format(result)).toBe(result);
+  });
+
   it('formats ALTER TABLE ... ALTER COLUMN', () => {
     expect(
       format(