From 621e027b2ac38a9cfc775a2afdff5235167b8b22 Mon Sep 17 00:00:00 2001
From: Luc Briand <34173752+Keluaa@users.noreply.github.com>
Date: Sun, 21 Apr 2024 18:12:05 +0200
Subject: [PATCH] Fix tab alignment

---
 src/display.jl   | 4 ++--
 test/runtests.jl | 6 ++++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/display.jl b/src/display.jl
index 43acf4a..96c73f5 100644
--- a/src/display.jl
+++ b/src/display.jl
@@ -5,9 +5,9 @@ function print_str_with_tabs(io::IO, str, tab_replacement)
     str_pos = 1
     column_pos = 1
     while (tab_pos = findnext('\t', str, str_pos); !isnothing(tab_pos))
-        str_part_len = (tab_pos - 1) - str_pos
+        str_part_len = (tab_pos - 1) - str_pos + 1
         column_pos += str_part_len
-        tab_len = full_tab_len - mod(column_pos, full_tab_len)
+        tab_len = full_tab_len - mod(column_pos - 1, full_tab_len)
         print(io, @view(str[str_pos:tab_pos - 1]), @view(tab_replacement[1:tab_len]))
         column_pos += tab_len
         str_pos = tab_pos + 1
diff --git a/test/runtests.jl b/test/runtests.jl
index 69058c9..d4752d3 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -407,6 +407,12 @@ end
                 @test str == expected_str
             end
         end
+
+        # Lines with changes use another code path for tabs alignment
+        diff = CodeDiffs.compare_show("\tabc\t123\n\tabc\t456", "\tabc\t126\n\tabc\t456")
+        diff_str = split(display_str(diff; color=false), '\n')
+        @test startswith(diff_str[1], "    abc 1")
+        @test startswith(diff_str[2], "    abc 4")
     end
 
     @testset "@code_diff" begin