From e08fd73f1d8e84540d5ebdc5fdf98c047da0976e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Thu, 23 Jun 2022 03:57:23 +0200
Subject: Wrote (and fixed) tests for filename-extension.

---
 module/hnh/util/path.scm |  8 +++++++-
 tests/test/util.scm      | 34 +++++++++++++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/module/hnh/util/path.scm b/module/hnh/util/path.scm
index ac6df491..ea081e85 100644
--- a/module/hnh/util/path.scm
+++ b/module/hnh/util/path.scm
@@ -66,7 +66,13 @@
        (char=? #\. (string-ref base 0))))
 
 (define (filename-extension filename)
-  (car (reverse (string-split filename #\.))))
+  (let ((components (-> filename
+                        ;; Path split removes potential trailing directory separator
+                        path-split last
+                        basename
+                        (string-split #\.))))
+    (if (>= 1 (length components))
+        "" (last components))))
 
 (define (realpath filename)
   (unless (string? filename)
diff --git a/tests/test/util.scm b/tests/test/util.scm
index 3fd926f2..e6b0c214 100644
--- a/tests/test/util.scm
+++ b/tests/test/util.scm
@@ -10,7 +10,11 @@
   :use-module (hnh util)
   :use-module (hnh util env)
   :use-module ((hnh util path)
-               :select (path-append path-split file-hidden? realpath)))
+               :select (path-append
+                        path-split
+                        file-hidden?
+                        realpath
+                        filename-extension)))
 
 (test-equal "when"
   1 (when #t 1))
@@ -274,6 +278,8 @@
 (test-assert (not (file-hidden? "/visible/.in/hidden")))
 (test-assert (not (file-hidden? "")))
 
+;; TODO test realpath with .. and similar
+
 (test-equal "Realpath for path fragment"
   "/home/hugo"
   (with-working-directory
@@ -291,3 +297,29 @@
   (with-working-directory
    "/tmp"
    (lambda () (realpath "/home/hugo"))))
+
+
+(test-equal "Extension of simple file"
+  "txt" (filename-extension "file.txt"))
+
+(test-equal "Extension of file with directory"
+  "txt" (filename-extension "/direcotry/file.txt"))
+
+(test-equal "Extension of file with multiple"
+  "gz" (filename-extension "filename.tar.gz"))
+
+(test-equal "Filename extension when none is present"
+  "" (filename-extension "filename"))
+
+(test-equal "Filename extension when none is present, but directory has"
+  "" (filename-extension "config.d/filename"))
+
+(test-equal "Filename extension of directory"
+  "d" (filename-extension "config.d/"))
+
+
+(test-equal "Extension of hidden file"
+  "sh" (filename-extension ".bashrc.sh"))
+
+(test-equal "Extension of hidden file without extension"
+  "bashrc" (filename-extension ".bashrc"))
-- 
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