Fixed errors related to unsupported cell languages (#3026)

## Changes
Our current implementation logs warnings when encountering notebook
cells that are not Python or SQL
This PR fixes that

### Linked issues
Resolves #2977 

### Functionality
None

### Tests
- [x] manually tested
- [x] added unit tests

Co-authored-by: Eric Vergnaud <[email protected]>

Author: ericvergnaud

src/databricks/labs/ucx/source_code/jobs.py

@@ -4,7 +4,7 @@
 import shutil
 import tempfile
 from abc import ABC, abstractmethod
-from collections.abc import Generator, Iterable
+from collections.abc import Generator, Iterable, Callable
 from contextlib import contextmanager
 from dataclasses import dataclass
 from datetime import datetime, timezone
@@ -651,14 +651,15 @@ def _collect_from_source(
         path: Path,
         inherited_tree: Tree | None,
     ) -> Iterable[T]:
-        iterable: Iterable[T] | None = None
-        if language is CellLanguage.SQL:
-            iterable = self._collect_from_sql(source)
         if language is CellLanguage.PYTHON:
             iterable = self._collect_from_python(source, inherited_tree)
-        if iterable is None:
-            logger.warning(f"Language {language.name} not supported yet!")
-            return
+        else:
+            fn: Callable[[str], Iterable[T]] | None = getattr(self, f"_collect_from_{language.name.lower()}", None)
+            if not fn:
+                raise ValueError(f"Language {language.name} not supported yet!")
+            # the below is for disabling a false pylint positive
+            # pylint: disable=not-callable
+            iterable = fn(source)
         src_timestamp = datetime.fromtimestamp(path.stat().st_mtime, timezone.utc)
         src_id = str(path)
         for item in iterable:
@@ -667,8 +668,28 @@ def _collect_from_source(
     @abstractmethod
     def _collect_from_python(self, source: str, inherited_tree: Tree | None) -> Iterable[T]: ...
 
-    @abstractmethod
-    def _collect_from_sql(self, source: str) -> Iterable[T]: ...
+    def _collect_from_sql(self, _source: str) -> Iterable[T]:
+        return []
+
+    def _collect_from_r(self, _source: str) -> Iterable[T]:
+        logger.warning("Language R not supported yet!")
+        return []
+
+    def _collect_from_scala(self, _source: str) -> Iterable[T]:
+        logger.warning("Language scala not supported yet!")
+        return []
+
+    def _collect_from_shell(self, _source: str) -> Iterable[T]:
+        return []
+
+    def _collect_from_markdown(self, _source: str) -> Iterable[T]:
+        return []
+
+    def _collect_from_run(self, _source: str) -> Iterable[T]:
+        return []
+
+    def _collect_from_pip(self, _source: str) -> Iterable[T]:
+        return []
 
 
 class DfsaCollectorWalker(_CollectorWalker[DirectFsAccess]):

tests/unit/source_code/linters/test_directfs.py

@@ -1,11 +1,18 @@
+from collections.abc import Iterable
+from pathlib import Path
+from unittest.mock import create_autospec
+
 import pytest
 
-from databricks.labs.ucx.source_code.base import Deprecation, Advice, CurrentSessionState, Failure
+from databricks.labs.ucx.source_code.base import Deprecation, Advice, CurrentSessionState, Failure, DirectFsAccess
+from databricks.labs.ucx.source_code.graph import DependencyGraph
+from databricks.labs.ucx.source_code.jobs import DfsaCollectorWalker
 from databricks.labs.ucx.source_code.linters.directfs import (
     DIRECT_FS_ACCESS_PATTERNS,
     DirectFsAccessPyLinter,
     DirectFsAccessSqlLinter,
 )
+from databricks.labs.ucx.source_code.notebooks.cells import CellLanguage
 
 
 @pytest.mark.parametrize(
@@ -145,3 +152,18 @@ def test_dfsa_queries_failure(query: str) -> None:
             end_col=1024,
         ),
     ]
+
+
+class _TestCollectorWalker(DfsaCollectorWalker):
+    # inherit from DfsaCollectorWalker because it's public
+
+    def collect_from_source(self, language: CellLanguage) -> Iterable[DirectFsAccess]:
+        return self._collect_from_source("empty", language, Path(""), None)
+
+
+@pytest.mark.parametrize("language", list(iter(CellLanguage)))
+def test_collector_supports_all_cell_languages(language, mock_path_lookup, migration_index):
+    graph = create_autospec(DependencyGraph)
+    graph.assert_not_called()
+    collector = _TestCollectorWalker(graph, set(), mock_path_lookup, CurrentSessionState(), migration_index)
+    list(collector.collect_from_source(language))