Change first and last character when it doesn't match

builder/googlecompute/template_funcs.go

@@ -34,6 +34,12 @@ func templateCleanImageName(s string) string {
 			newb[i] = '-'
 		}
 	}
+	if !('a' <= newb[0] && newb[0] <= 'z') {
+		newb[0] = 'a'
+	}
+	if newb[l-1] == '-' {
+		newb[l-1] = 'a'
+	}
 	return string(newb)
 }
 

builder/googlecompute/template_funcs_test.go

@@ -20,8 +20,16 @@ func Test_templateCleanImageName(t *testing.T) {
 			expected: "abcde-012345v1-0-0",
 		},
 		{
-			origName: "0123456789012345678901234567890123456789012345678901234567890123456789",
-			expected: "012345678901234567890123456789012345678901234567890123456789012",
+			origName: "a123456789012345678901234567890123456789012345678901234567890123456789",
+			expected: "a12345678901234567890123456789012345678901234567890123456789012",
+		},
+		{
+			origName: "01234567890123456789012345678901234567890123456789012345678901.",
+			expected: "a1234567890123456789012345678901234567890123456789012345678901a",
+		},
+		{
+			origName: "01234567890123456789012345678901234567890123456789012345678901-",
+			expected: "a1234567890123456789012345678901234567890123456789012345678901a",
 		},
 	}