From 2a6cb0cb4c7c212151addc677e3707655f40222b Mon Sep 17 00:00:00 2001
From: wesleyel <48174882+wesleyel@users.noreply.github.com>
Date: Tue, 7 Apr 2026 10:04:11 +0800
Subject: [PATCH] Fix boundary handling in Parser and update tests for empty
 cases

---
 .../SwiftUIMath/Internal/Syntax/Parser.swift  | 12 +++++++++++
 .../Internal/Syntax/ParserTests.swift         | 20 +++++++++++++------
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/Sources/SwiftUIMath/Internal/Syntax/Parser.swift b/Sources/SwiftUIMath/Internal/Syntax/Parser.swift
index aa9cb1b..af01f93 100644
--- a/Sources/SwiftUIMath/Internal/Syntax/Parser.swift
+++ b/Sources/SwiftUIMath/Internal/Syntax/Parser.swift
@@ -764,6 +764,12 @@ extension Math {
         // reinstate the old inner atom.
         let newInner = currentInnerAtom
         currentInnerAtom = oldInner
+        if newInner?.leftBoundary?.nucleus.isEmpty == true {
+          newInner?.leftBoundary = nil
+        }
+        if newInner?.rightBoundary?.nucleus.isEmpty == true {
+          newInner?.rightBoundary = nil
+        }
         return newInner
       } else if command == "overline" {
         // The overline command has 1 arguments
@@ -1162,6 +1168,12 @@ extension Math {
         }
         let newInner = self.currentInnerAtom
         currentInnerAtom = oldInner
+        if newInner?.leftBoundary?.nucleus.isEmpty == true {
+          newInner?.leftBoundary = nil
+        }
+        if newInner?.rightBoundary?.nucleus.isEmpty == true {
+          newInner?.rightBoundary = nil
+        }
         return newInner
       } else if command == "overline" {
         let over = Overline()
diff --git a/Tests/SwiftUIMathTests/Internal/Syntax/ParserTests.swift b/Tests/SwiftUIMathTests/Internal/Syntax/ParserTests.swift
index cb37f17..2aa782a 100644
--- a/Tests/SwiftUIMathTests/Internal/Syntax/ParserTests.swift
+++ b/Tests/SwiftUIMathTests/Internal/Syntax/ParserTests.swift
@@ -594,13 +594,21 @@ struct ParserTests {
       let innerList = try #require(inner.innerList)
       checkAtomTypes(innerList, types: testCase.type2)
 
-      let leftBoundary = try #require(inner.leftBoundary)
-      #expect(leftBoundary.type == .boundary)
-      #expect(leftBoundary.nucleus == testCase.left)
+      if testCase.left.isEmpty {
+        #expect(inner.leftBoundary == nil)
+      } else {
+        let leftBoundary = try #require(inner.leftBoundary)
+        #expect(leftBoundary.type == .boundary)
+        #expect(leftBoundary.nucleus == testCase.left)
+      }
 
-      let rightBoundary = try #require(inner.rightBoundary)
-      #expect(rightBoundary.type == .boundary)
-      #expect(rightBoundary.nucleus == testCase.right)
+      if testCase.right.isEmpty {
+        #expect(inner.rightBoundary == nil)
+      } else {
+        let rightBoundary = try #require(inner.rightBoundary)
+        #expect(rightBoundary.type == .boundary)
+        #expect(rightBoundary.nucleus == testCase.right)
+      }
 
       // convert it back to latex
       let latex = Math.Parser.atomListToString(list)