Cin's review note: typing artist_name as plain `str` forced callers
that didn't have a name to pass `""` as a placeholder, which leaks the
parameter's emptiness contract into every call site and reads badly in
tests. Switching to `Optional[str] = None` lets callers omit it.
The function body's `if artist_name and active_server:` check already
handles None and "" identically, so no body changes were needed. Tests
that previously passed `artist_name=""` drop the argument; one new test
covers the omitted-arg path explicitly.
The web_server.py wrapper takes the same default for symmetry.
Cin pointed out that the prior version of test_artist_source_lookup.py
AST-parsed web_server.py to verify a constant and to string-match a
function's response keys. That was a workaround for the fact that
web_server.py can't be imported at test time (it boots Spotify,
Soulseek, Plex, etc.) — the right answer is to move the logic into a
side-effect-free module so it can be imported and tested directly.
This commit:
- adds core/artist_source_lookup.py containing the SOURCE_ID_FIELD
map, the SOURCE_ONLY_ARTIST_SOURCES set, and find_library_artist_for_source
- replaces the inline definitions in web_server.py with imports +
a thin wrapper that injects the active media server
- rewrites the tests to import from the core module directly:
* mapping correctness is now a plain equality assertion
* lookup behaviour is exercised against a real MusicDatabase
* the AST parse and the string-matching contract test class are
gone
- drops the _build_source_only_artist_detail contract test entirely
(the weakest of the four — it was just string-matching the function
body); when that function moves to core/ it can get a real
behavioural test alongside.
Test runtime drops from ~161s to ~5.8s. All 18 tests pass.
