ansible-galaxy - add pre-release hint to dependency resolution error (#81147)

* add pre-release hint to dependency resolution error if --pre wasn't provided

Co-authored-by: Sviatoslav Sydorenko <wk.cvs.github@sydorenko.org.ua>

changelogs/fragments/pre-release-hint-for-dep-resolution-error.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - ansible-galaxy - add note to the collection dependency resolver error message about pre-releases if ``--pre`` was not provided (https://github.com/ansible/ansible/issues/80048).

lib/ansible/galaxy/collection/__init__.py

@@ -1809,6 +1809,11 @@ def _resolve_depenency_map(
         elif not req.specifier.contains(RESOLVELIB_VERSION.vstring):
             raise AnsibleError(f"ansible-galaxy requires {req.name}{req.specifier}")
 
+    if allow_pre_release:
+        pre_release_hint = ''
+    else:
+        pre_release_hint = 'Hint: Pre-releases are not installed by default unless the specific version is given. To enable pre-releases, use --pre.'
+
     collection_dep_resolver = build_collection_dependency_resolver(
         galaxy_apis=galaxy_apis,
         concrete_artifacts_manager=concrete_artifacts_manager,
@@ -1844,6 +1849,7 @@ def _resolve_depenency_map(
             ),
             conflict_causes,
         ))
+        error_msg_lines.append(pre_release_hint)
         raise AnsibleError('\n'.join(error_msg_lines)) from dep_exc
     except CollectionDependencyInconsistentCandidate as dep_exc:
         parents = [
@@ -1870,6 +1876,7 @@ def _resolve_depenency_map(
             error_msg_lines.append(
                 '* {req.fqcn!s}:{req.ver!s}'.format(req=req)
             )
+        error_msg_lines.append(pre_release_hint)
 
         raise AnsibleError('\n'.join(error_msg_lines)) from dep_exc
     except ValueError as exc:

test/integration/targets/ansible-galaxy-collection/tasks/fail_fast_resolvelib.yml

@@ -1,5 +1,5 @@
 # resolvelib>=0.6.0 added an 'incompatibilities' parameter to find_matches
-# If incompatibilities aren't removed from the viable candidates, this example causes infinite resursion
+# If incompatibilities aren't removed from the viable candidates, this example causes infinite recursion
 - name: test resolvelib removes incompatibilites in find_matches and errors quickly (prevent infinite recursion)
   block:
     - name: create collection dir

test/integration/targets/ansible-galaxy-collection/tasks/install.yml

@@ -165,6 +165,9 @@
   failed_when:
   - '"Could not satisfy the following requirements" not in fail_dep_mismatch.stderr'
   - '" fail_dep2.name:<0.0.5 (dependency of fail_namespace.fail_collection:2.1.2)" not in fail_dep_mismatch.stderr'
+  - 'pre_release_hint not in fail_dep_mismatch.stderr'
+  vars:
+    pre_release_hint: 'Hint: Pre-releases are not installed by default unless the specific version is given. To enable pre-releases, use --pre.'
 
 - name: Find artifact url for namespace3.name
   uri: