Fix highlighting of empty source ranges (#231)

Highlighting of empty ranges needs special handling at the ends of lines
as the source line of the end of the range can be less than the source
line at the start of the range.

Author: c42f

src/source_files.jl

@@ -183,17 +183,18 @@ function highlight(io::IO, source::SourceFile, range::UnitRange;
                             context_lines_before=context_lines_before,
                             context_lines_after=context_lines_inner)
     a,b = source_line_range(source, p)
-    c,d = source_line_range(source, q)
-    z,w = source_line_range(source, q;
+    q1 = max(q, p) # Ignore q for empty ranges
+    c,d = source_line_range(source, q1)
+    z,w = source_line_range(source, q1;
                             context_lines_before=context_lines_inner,
                             context_lines_after=context_lines_after)
 
     p_line = source_line(source, p)
-    q_line   = source_line(source, q)
+    q_line = source_line(source, q)
 
     marker_line_color = :light_black
 
-    if p_line == q_line
+    if p_line >= q_line
         # x-----------------
         # a---p-------q----b
         # #   └───────┘ ── note

test/source_files.jl

@@ -57,11 +57,22 @@ end
         αβγδ
         +-*/""")
 
+    # Empty ranges
+    @test sprint(highlight, src, 1:0) == "abcd\n└\nαβγδ\n+-*/"
+    @test sprint(highlight, src, 2:1) == "abcd\n#└\nαβγδ\n+-*/"
+    @test sprint(highlight, src, 3:2) == "abcd\n# └\nαβγδ\n+-*/"
+    @test sprint(highlight, src, 4:3) == "abcd\n#  └\nαβγδ\n+-*/"
+    @test sprint(highlight, src, 5:4) == "abcd\n#   └\nαβγδ\n+-*/"
+    @test sprint(highlight, src, 6:5) == "abcd\nαβγδ\n└\n+-*/"
+    @test sprint(highlight, src, 19:18) == "abcd\nαβγδ\n+-*/\n#   └"
+    @test sprint(io->highlight(io, src, 1:0, context_lines_after=0, note="hi")) ==
+        "abcd\n└ ── hi"
+
+    # Single line ranges
     @test sprint(highlight, src, 1:4) == "abcd\n└──┘\nαβγδ\n+-*/"
     @test sprint(highlight, src, 2:4) == "abcd\n#└─┘\nαβγδ\n+-*/"
     @test sprint(highlight, src, 3:4) == "abcd\n# └┘\nαβγδ\n+-*/"
     @test sprint(highlight, src, 4:4) == "abcd\n#  ╙\nαβγδ\n+-*/"
-    @test sprint(highlight, src, 4:3) == "abcd\n#  └\nαβγδ\n+-*/"
     @test sprint(highlight, src, 5:5) == "abcd\n#   └\nαβγδ\n+-*/"
 
     # multi-byte chars