textinput: fix deleteWord with an only whitespace

Fix a panic in the textinput.deleteWord when text is a whitespace
symbol.

Add tests for textinput.

Fixes: https://todo.sr.ht/~rjarry/aerc/183
Signed-off-by: Oskar Sharipov <oskargit@riseup.net>
Acked-by: Robin Jarry <robin@jarry.cc>

2 files changed, 73 insertions, 1 deletions

diff --git a/lib/ui/textinput.go b/lib/ui/textinput.go
index e41cff75..dd946aec 100644
--- a/lib/ui/textinput.go
+++ b/lib/ui/textinput.go
@@ -220,7 +220,7 @@ func (ti *TextInput) deleteWord() {
 	for i >= 0 && ti.text[i] == ' ' {
 		i--
 	}
-	if strings.ContainsRune(separators, ti.text[i]) {
+	if i >= 0 && strings.ContainsRune(separators, ti.text[i]) {
 		for i >= 0 && strings.ContainsRune(separators, ti.text[i]) {
 			i--
 		}
diff --git a/lib/ui/textinput_test.go b/lib/ui/textinput_test.go
new file mode 100644
index 00000000..47a4c294
--- /dev/null
+++ b/lib/ui/textinput_test.go
@@ -0,0 +1,72 @@
+package ui
+
+import "testing"
+
+func TestDeleteWord(t *testing.T) {
+	tests := []struct {
+		name     string
+		text     string
+		expected string
+	}{
+		{
+			name:     "hello-world",
+			text:     "hello world",
+			expected: "hello ",
+		},
+		{
+			name:     "empty",
+			text:     "",
+			expected: "",
+		},
+		{
+			name:     "quoted",
+			text:     `"hello"`,
+			expected: `"hello`,
+		},
+		{
+			name:     "hello-and-space",
+			text:     "hello ",
+			expected: "",
+		},
+		{
+			name:     "space-and-hello",
+			text:     " hello",
+			expected: " ",
+		},
+		{
+			name:     "only-quote",
+			text:     `"`,
+			expected: "",
+		},
+		{
+			name:     "only-space",
+			text:     " ",
+			expected: "",
+		},
+		{
+			name:     "space-and-quoted",
+			text:     " 'hello",
+			expected: " '",
+		},
+		{
+			name:     "paths",
+			text:     "foo/bar/baz",
+			expected: "foo/bar/",
+		},
+		{
+			name:     "space-and-paths",
+			text:     " /foo",
+			expected: " /",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			textinput := NewTextInput(test.text, nil)
+			textinput.deleteWord()
+			if string(textinput.text) != test.expected {
+				t.Errorf("word was deleted incorrectly: got %s but expected %s", string(textinput.text), test.expected)
+			}
+		})
+	}
+}