From 0ca8a493e42a3dbaa2d9560ba772dc12c9ef50ab Mon Sep 17 00:00:00 2001
From: Jos de Jong <wjosdejong@gmail.com>
Date: Thu, 15 Feb 2024 10:14:44 +0100
Subject: [PATCH] fix: improve the logic to determine whether a JSON document
 needs formatting

---
 src/lib/utils/jsonUtils.test.ts | 13 +++++++++----
 src/lib/utils/jsonUtils.ts      |  9 +++++----
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/lib/utils/jsonUtils.test.ts b/src/lib/utils/jsonUtils.test.ts
index 4e2d4fa0..5c610abf 100644
--- a/src/lib/utils/jsonUtils.test.ts
+++ b/src/lib/utils/jsonUtils.test.ts
@@ -406,8 +406,7 @@ describe('jsonUtils', () => {
 
       expect(needsFormatting('')).toBe(false)
       expect(needsFormatting('[\n1,\n  2,\n  3\n]')).toBe(false)
-      expect(needsFormatting('{\n  "a":true,\n  "b":false\n}')).toBe(false)
-      expect(needsFormatting('\n[1,2,3]')).toBe(false)
+      expect(needsFormatting('{\n  "a": true,\n  "b": false\n}')).toBe(false)
 
       expect(needsFormatting('1234')).toBe(false)
       expect(needsFormatting('"abc"')).toBe(false)
@@ -415,9 +414,15 @@ describe('jsonUtils', () => {
       expect(needsFormatting('false')).toBe(false)
       expect(needsFormatting('null')).toBe(false)
 
-      // cannot detect partially formatted content
-      expect(needsFormatting('[1, 2, 3]')).toBe(true)
+      expect(needsFormatting('[1, 2, 3]')).toBe(false)
+      expect(needsFormatting('{"a": 1, "b": 2}')).toBe(false)
       expect(needsFormatting('{"a":1, "b":2}')).toBe(true)
+      expect(needsFormatting('{\n  "a": "some:message"\n}')).toBe(false)
+      expect(needsFormatting('{\n  "a": "some,message"\n}')).toBe(false)
+
+      // a colon or comma inside a string gives a false positive (when the text doesn't contain a return character)
+      expect(needsFormatting('{"a": "some:message"}')).toBe(true)
+      expect(needsFormatting('{"a": "some,message"}')).toBe(true)
     })
   })
 
diff --git a/src/lib/utils/jsonUtils.ts b/src/lib/utils/jsonUtils.ts
index 9cd92555..716a6949 100644
--- a/src/lib/utils/jsonUtils.ts
+++ b/src/lib/utils/jsonUtils.ts
@@ -484,9 +484,10 @@ export function isEqualParser(a: JSONParser, b: JSONParser): boolean {
  * Apply a fast and cheap heuristic to determine whether the content needs formatting (i.e. is compact).
  */
 export function needsFormatting(jsonText: string): boolean {
-  // the check for the length>2 is because an empty array or object does not need formatting
-  return NEEDS_FORMATTING_REGEX.test(jsonText) && jsonText.length > 2
+  const maxLength = 999
+  const head = jsonText.substring(0, maxLength)
+  return !head.includes('\n') && DELIMITER_WITHOUT_SPACING_REGEX.test(head)
 }
 
-// regex that matches the start of an object or array, followed by a non-whitespace character
-const NEEDS_FORMATTING_REGEX = /^[[{]\S/
+// This regex matches cases of a comma or colon NOT followed by a whitespace
+const DELIMITER_WITHOUT_SPACING_REGEX = /[,:]\S/