snap: Only treat --- as an info separator when it's preceded by newline (#7046)

* Only treat `---` as an info separator when it's preceded by newline

The code for splitting the output of `snap info` for multiple snaps
can't assume that `---` separates snaps any time it appears in the
output; it needs to treat that as the separator only when it's at the
start of a line. Otherwise it breaks if any snap uses `---` in its
description text, which, e.g., the `bw` snap does as of the date of
this commit.

Fixes #7045.

* Add changelog fragment

* Add a comment explaining why \n is necessary before ---

* Update changelogs/fragments/7046-snap-newline-before-separator.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Jonathan Kamens <jik@jik5.kamens.us>
Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>
Co-authored-by: Felix Fontein <felix@fontein.de>

changelogs/fragments/7046-snap-newline-before-separator.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - snap - fix crash when multiple snaps are specified and one has ``---`` in its description (https://github.com/ansible-collections/community.general/pull/7046).

plugins/modules/snap.py

@@ -303,7 +303,10 @@ class Snap(StateModuleHelper):
             return [name]
 
         def process_many(rc, out, err):
-            outputs = out.split("---")
+            # This needs to be "\n---" instead of just "---" because otherwise
+            # if a snap uses "---" in its description then that will incorrectly
+            # be interpreted as a separator between snaps in the output.
+            outputs = out.split("\n---")
             res = []
             for sout in outputs:
                 res.extend(process_one(rc, sout, ""))