From 28f7e6fa69ee5fe1275deb4c7cf2ecac18a370ed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?F=C3=A9lix=20Bourbonnais?=
 <felix.bourbonnais@imaginary-spaces.com>
Date: Wed, 8 Dec 2021 15:49:14 -0500
Subject: [PATCH] Add has_value to cell_iterator

When iterating over a range that doesn't ignore null rows/columns,
the operator*() throws when dereferencing an iterator to a null cell.
Add has_value() to cell_iterator to be able to make a check without
relying on exceptions.
And add a test case.
---
 include/xlnt/worksheet/cell_iterator.hpp | 14 +++++++++++++
 source/worksheet/cell_iterator.cpp       |  8 ++++++++
 tests/worksheet/worksheet_test_suite.cpp | 26 ++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/include/xlnt/worksheet/cell_iterator.hpp b/include/xlnt/worksheet/cell_iterator.hpp
index e0770448..0e324d09 100644
--- a/include/xlnt/worksheet/cell_iterator.hpp
+++ b/include/xlnt/worksheet/cell_iterator.hpp
@@ -136,6 +136,13 @@ public:
     /// </summary>
     cell_iterator operator++(int);
 
+    /// <summary>
+    /// When iterating over a range that doesn't ignore null cells, operator*()
+    /// will throw when trying to access the cells that are null. This method
+    /// checks the existence of a cell.
+    /// </summary>
+    bool has_value() const;
+
 private:
     /// <summary>
     /// If true, cells that don't exist in the worksheet will be skipped during iteration.
@@ -263,6 +270,13 @@ public:
     /// </summary>
     const_cell_iterator operator++(int);
 
+    /// <summary>
+    /// When iterating over a range that doesn't ignore null cells, operator*()
+    /// will throw when trying to access the cells that are null. This method
+    /// checks the existence of a cell.
+    /// </summary>
+    bool has_value() const;
+
 private:
     /// <summary>
     /// If true, cells that don't exist in the worksheet will be skipped during iteration.
diff --git a/source/worksheet/cell_iterator.cpp b/source/worksheet/cell_iterator.cpp
index 1d950a5b..b89863e5 100644
--- a/source/worksheet/cell_iterator.cpp
+++ b/source/worksheet/cell_iterator.cpp
@@ -278,4 +278,12 @@ const const_cell_iterator::reference const_cell_iterator::operator*() const
 {
     return ws_.cell(cursor_);
 }
+
+bool cell_iterator::has_value() const{
+    return ws_.has_cell(cursor_);
+}
+
+bool const_cell_iterator::has_value() const{
+    return ws_.has_cell(cursor_);
+}
 } // namespace xlnt
diff --git a/tests/worksheet/worksheet_test_suite.cpp b/tests/worksheet/worksheet_test_suite.cpp
index 64b47da1..6580142f 100644
--- a/tests/worksheet/worksheet_test_suite.cpp
+++ b/tests/worksheet/worksheet_test_suite.cpp
@@ -78,6 +78,7 @@ public:
         register_test(test_lowest_row_or_props);
         register_test(test_highest_row);
         register_test(test_highest_row_or_props);
+        register_test(test_iterator_has_value);
         register_test(test_const_iterators);
         register_test(test_const_reverse_iterators);
         register_test(test_column_major_iterators);
@@ -584,6 +585,31 @@ public:
         xlnt_assert_equals(ws.highest_row_or_props(), 11);
     }
 
+    void test_iterator_has_value()
+    {
+        xlnt::workbook wb;
+        auto ws = wb.active_sheet();
+
+        // make a worksheet with a blank row and column
+        ws.cell("A1").value("A1");
+        ws.cell("A3").value("A3");
+        ws.cell("C1").value("C1");
+
+        xlnt_assert_equals(ws.columns(false)[0].begin().has_value(), true);
+        xlnt_assert_equals(ws.rows(false)[0].begin().has_value(), true);
+
+        xlnt_assert_equals(ws.columns(false)[1].begin().has_value(), false);
+        xlnt_assert_equals(ws.rows(false)[1].begin().has_value(), false);
+
+        // also test const interators.
+        xlnt_assert_equals(ws.columns(false)[0].cbegin().has_value(), true);
+        xlnt_assert_equals(ws.rows(false)[0].cbegin().has_value(), true);
+
+        xlnt_assert_equals(ws.columns(false)[1].cbegin().has_value(), false);
+        xlnt_assert_equals(ws.rows(false)[1].cbegin().has_value(), false);
+
+    }
+
     void test_const_iterators()
     {
         xlnt::workbook wb;