refactor: move check to class, expand error message

nf_core/__main__.py

@@ -4,7 +4,6 @@
 import logging
 import os
 import re
-import requests
 import rich.console
 import rich.logging
 import rich.traceback
@@ -693,15 +692,19 @@ def mulled(specifications, build_number):
     that image, this command can generate it for you.
 
     """
-    image_name = nf_core.modules.mulled.MulledImageNameGenerator.generate_image_name(
-        nf_core.modules.mulled.MulledImageNameGenerator.parse_targets(specifications), build_number=build_number
+    from nf_core.modules.mulled import MulledImageNameGenerator
+
+    image_name = MulledImageNameGenerator.generate_image_name(
+        MulledImageNameGenerator.parse_targets(specifications), build_number=build_number
     )
     print(image_name)
-    response = requests.get(f"https://quay.io/biocontainers/{image_name}/", allow_redirects=True)
-    if response.status_code != 200:
+    if not MulledImageNameGenerator.image_exists(image_name):
         log.error(
-            "The generated multi-tool container image does not seem to exist yet. Are you sure that you provided the "
-            "right combination of tools and versions?"
+            "The generated multi-tool container image name does not seem to exist yet. Please double check that your "
+            "provided combination of tools and versions exists in the file:\n"
+            "https://github.com/BioContainers/multi-package-containers/blob/master/combinations/hash.tsv\n"
+            "If it does not, please add your desired combination as detailed at:\n"
+            "https://github.com/BioContainers/multi-package-containers\n"
         )
         sys.exit(1)
 

nf_core/modules/mulled.py

@@ -6,6 +6,7 @@
 from packaging.version import Version, InvalidVersion
 from typing import Iterable, Tuple, List
 
+import requests
 from galaxy.tool_util.deps.mulled.util import build_target, v2_image_name
 
 
@@ -57,3 +58,10 @@ def generate_image_name(cls, targets: Iterable[Tuple[str, str]], build_number: i
 
         """
         return v2_image_name([build_target(name, version) for name, version in targets], image_build=str(build_number))
+
+    @classmethod
+    def image_exists(cls, image_name: str) -> bool:
+        """Check whether a given BioContainers image name exists via a call to the quay.io API."""
+        response = requests.get(f"https://quay.io/biocontainers/{image_name}/", allow_redirects=True)
+        log.debug(response.text)
+        return response.status_code == 200