From bae8a0a45393518bbf7914b10bf36139a977cda6 Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fischer@muhq.space>
Date: Sat, 11 Jan 2025 15:37:12 +0100
Subject: handle special cases in util.dirname

---
 util.lua      | 22 +++++++++++++++++++++-
 util_test.lua | 18 ++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100755 util_test.lua

diff --git a/util.lua b/util.lua
index 8d9df9b..de5ad07 100644
--- a/util.lua
+++ b/util.lua
@@ -127,7 +127,27 @@ end
 -- @param the pathname
 -- @return the pathname up to the last '/'
 function util.dirname(name)
-  return name:match('(.*[/])')
+  if name == '.' or name == '..' or name == '/' then
+    return name
+  end
+
+  -- strip a trailing path separator
+  if name:sub(#name, #name) == '/' then
+    name = name:sub(1, #name - 1)
+  end
+
+  local dirname = name:match('(.*)[/]')
+  -- There was no path separator in name.
+  if not dirname then
+    return '.'
+  end
+
+  -- The name started with the root dir.
+  if dirname == '' then
+    return '/'
+  end
+
+  return dirname
 end
 
 --- Create an iterator yielding the nth line of a file
diff --git a/util_test.lua b/util_test.lua
new file mode 100755
index 0000000..fd6570d
--- /dev/null
+++ b/util_test.lua
@@ -0,0 +1,18 @@
+#!/usr/bin/env lua5.4
+
+-- mock vis global
+vis = {} -- luacheck: ignore 111
+local util = require('util')
+
+local lunatest = require('lunatest')
+
+function test_dirname() -- luacheck: ignore 111
+  lunatest.assert_equal('/usr', util.dirname('/usr/lib'))
+  lunatest.assert_equal('/', util.dirname('/usr/'))
+  lunatest.assert_equal('.', util.dirname('usr'))
+  lunatest.assert_equal('.', util.dirname('.'))
+  lunatest.assert_equal('..', util.dirname('..'))
+  lunatest.assert_equal('/', util.dirname('/'))
+end
+
+lunatest.run()
-- 
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