tidy(mm): ModelSearch cleanup

- No need for it to by a pydantic model. Just a class now.
- Remove ABC, it made it hard to understand what was going on as attributes were spread across the ABC and implementation. Also, there is no other implementation.
- Add tests

tests/test_model_search.py

@@ -0,0 +1,142 @@
+from pathlib import Path
+
+import pytest
+
+from invokeai.backend.model_manager.search import ModelSearch
+
+
+@pytest.fixture
+def model_search(tmp_path: Path) -> tuple[ModelSearch, Path]:
+    search = ModelSearch()
+    return search, tmp_path
+
+
+def test_model_search_on_search_started(model_search: tuple[ModelSearch, Path]):
+    search, tmp_path = model_search
+    on_search_started_called_with: Path | None = None
+
+    def on_search_started_callback(path: Path) -> None:
+        nonlocal on_search_started_called_with
+        on_search_started_called_with = path
+
+    search.on_search_started = on_search_started_callback
+    search.search(tmp_path)
+
+    assert on_search_started_called_with == tmp_path
+
+
+def test_model_search_on_completed(model_search: tuple[ModelSearch, Path]):
+    search, tmp_path = model_search
+    on_search_completed_called_with: set[Path] | None = None
+    file1 = tmp_path / "file1.ckpt"
+    with open(file1, "w") as f:
+        f.write("")
+
+    def on_search_completed_callback(models: set[Path]) -> None:
+        nonlocal on_search_completed_called_with
+        on_search_completed_called_with = models
+
+    search.on_search_completed = on_search_completed_callback
+    expected = {file1}
+    found = search.search(tmp_path)
+
+    assert found == expected
+    assert on_search_completed_called_with == expected
+
+
+def test_model_search_handles_files(model_search: tuple[ModelSearch, Path]):
+    search, tmp_path = model_search
+    on_model_found_called_with: set[Path] = set()
+
+    file1 = tmp_path / "file1.ckpt"
+    file2 = tmp_path / "file2.ckpt"
+    file3 = tmp_path / "subfolder" / "file3.ckpt"
+    file4 = tmp_path / "subfolder" / "subfolder" / "file4.ckpt"
+    file5 = tmp_path / "not_a_model_file.txt"
+
+    file4.parent.mkdir(parents=True)
+    for file in [file1, file2, file3, file4, file5]:
+        with open(file, "w") as f:
+            f.write("")
+
+    def on_model_found_callback(path: Path) -> bool:
+        on_model_found_called_with.add(path)
+        return True
+
+    search.on_model_found = on_model_found_callback
+
+    expected = {file1, file2, file3, file4}
+    found = search.search(tmp_path)
+
+    assert on_model_found_called_with == expected
+    assert found == expected
+    assert search.stats.models_found == 4
+    assert search.stats.models_filtered == 4
+
+
+def test_model_search_filters_by_on_model_found(model_search: tuple[ModelSearch, Path]):
+    search, tmp_path = model_search
+    on_model_found_called_with: set[Path] = set()
+
+    file1 = tmp_path / "file1.ckpt"
+    file2 = tmp_path / "file2.ckpt"  # explicitly ignored
+
+    for file in [file1, file2]:
+        with open(file, "w") as f:
+            f.write("")
+
+    def on_model_found_callback(path: Path) -> bool:
+        if path == file2:
+            return False
+        on_model_found_called_with.add(path)
+        return True
+
+    search.on_model_found = on_model_found_callback
+
+    expected = {file1}
+    found = search.search(tmp_path)
+
+    assert on_model_found_called_with == expected
+    assert found == expected
+    assert search.stats.models_filtered == 1
+    assert search.stats.models_found == 2
+
+
+def test_model_search_handles_diffusers_model_dirs(model_search: tuple[ModelSearch, Path]):
+    search, tmp_path = model_search
+    on_model_found_called_with: set[Path] = set()
+
+    diffusers_dir = tmp_path / "diffusers_dir"
+    diffusers_dir_entry_point = diffusers_dir / "model_index.json"
+    diffusers_dir.mkdir()
+    with open(diffusers_dir_entry_point, "w") as f:
+        f.write("")
+
+    nested_diffusers_dir = tmp_path / "subfolder" / "nested_diffusers_dir"
+    nested_diffusers_dir_entry_point = nested_diffusers_dir / "model_index.json"
+    nested_diffusers_dir_ignore_me_file = nested_diffusers_dir / "ignore_me.ckpt"  # totally skipped
+    nested_diffusers_dir.mkdir(parents=True)
+    with open(nested_diffusers_dir_entry_point, "w") as f:
+        f.write("")
+    with open(nested_diffusers_dir_ignore_me_file, "w") as f:
+        f.write("")
+
+    not_a_diffusers_dir = tmp_path / "not_a_diffusers_dir"
+    not_a_diffusers_dir_entry_point = not_a_diffusers_dir / "not_model_index.json"
+    not_a_diffusers_dir.mkdir()
+    with open(not_a_diffusers_dir_entry_point, "w") as f:
+        f.write("")
+
+    def on_model_found_callback(path: Path) -> bool:
+        on_model_found_called_with.add(path)
+        return True
+
+    search.on_model_found = on_model_found_callback
+
+    expected = {diffusers_dir, nested_diffusers_dir}
+    found = search.search(tmp_path)
+
+    assert found == expected
+    assert on_model_found_called_with == expected
+    assert search.stats.models_found == 2
+    assert search.stats.models_filtered == 2