Problem:    Setting buffer local mapping with mapset() changes global mapping.
Solution:   Only set the local mapping. (closes #8143)

Problem:    Missing test coverage.
Solution:   Improve test coverage for completion with different encodings,
            mapset(), and term function failures. (Dominique Pellé,
            closes #7877)

Problem:    Crash when calling mapset() with a list as first argument.
Solution:   Check for NULL. (closes #7040)

Problem:    Vim9: Some tests are still using :let.
Solution:   Change the last few declarations to use :var.

Problem:    Vim9: using :call where it is not needed.
Solution:   Remove :call. (closes #6892)

Problem:    Vim9: return type of maparg() not adjusted for fourth argument.
Solution:   Check if fourth argument is present. (closes #6645)

Problem:    maparg() does not provide enough information for mapset().
Solution:   Add "lhsraw" and "lhsrawalt" items.  Drop "simplified"

Problem:    mapset() does not properly handle <> notation.
Solution:   Convert <> codes. (closes #6116)

Problem:    Cannot easily restore a mapping.
Solution:   Add mapset().

Problem:    Cannot recognize a <script> mapping using maparg().
Solution:   Add the "script" key. (closes #5873)