generalized code, better error message and link update

nf_core/pipeline-template/lib/Utils.groovy

@@ -21,19 +21,26 @@ class Utils {
         }
 
         // Check that all channels are present
-        def required_channels = ['conda-forge', 'bioconda', 'defaults']
-        def conda_check_failed = !required_channels.every { ch -> ch in channels }
+        // This channel list is ordered by required channel priority.
+        def required_channels_in_order = ['conda-forge', 'bioconda', 'defaults']
+        def channels_missing = ((required_channels_in_order as Set) - (channels as Set)) as Boolean
 
         // Check that they are in the right order
-        conda_check_failed |= !(channels.indexOf('conda-forge') < channels.indexOf('bioconda'))
-        conda_check_failed |= !(channels.indexOf('bioconda') < channels.indexOf('defaults'))
+        def channel_priority_violation = false
+        def n = required_channels_in_order.size()
+        for (int i = 0; i < n - 1; i++) {
+            channel_priority_violation |= !(channels.indexOf(required_channels_in_order[i]) < channels.indexOf(required_channels_in_order[i+1]))
+        }
 
-        if (conda_check_failed) {
+        if (channels_missing | channel_priority_violation) {
             log.warn "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n" +
                 "  There is a problem with your Conda configuration!\n\n" +
                 "  You will need to set-up the conda-forge and bioconda channels correctly.\n" +
-                "  Please refer to https://bioconda.github.io/user/install.html#set-up-channels\n" +
-                "  NB: The order of the channels matters!\n" +
+                "  Please refer to https://bioconda.github.io/\n" +
+                "  The observed channel order is \n" +
+                "  ${channels}" +
+                "  but the following channel order is required:\n" +
+                "  ${required_channels}\n" +
                 "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
         }
     }