Merge pull request #850 from projectsyn/fix/parallel-fetching-propaga…

…te-exceptions

Propagate exceptions raised while fetching dependencies

commodore/dependency_mgmt/__init__.py

@@ -110,7 +110,11 @@ def fetch_parallel(fetch_fun, cfg, to_fetch):
     Fetch dependencies in parallel threads with ThreadPoolExecutor.
     """
     with ThreadPoolExecutor() as exe:
-        exe.map(fetch_fun, itertools.repeat(cfg), to_fetch)
+        # We need to collect the results from the iterator produced by exe.map to ensure
+        # that any exceptions raised in `fetch_fun` are propagated, cf.
+        # https://docs.python.org/3/library/concurrent.futures.html#executor-objects. We
+        # do so by simply materializing the iterator into a list.
+        list(exe.map(fetch_fun, itertools.repeat(cfg), to_fetch))
 
 
 def register_components(cfg: Config):

tests/test_dependency_mgmt.py

@@ -197,6 +197,23 @@ def test_fetch_components_raises(
     )
 
 
+@patch("commodore.dependency_mgmt._read_components")
+@patch("commodore.dependency_mgmt._discover_components")
+def test_fetch_components_raises_giterror(
+    patch_discover, patch_read, config: Config, tmp_path: Path
+):
+    components = ["foo"]
+    patch_discover.return_value = (components, {})
+    read_retval = setup_components_upstream(tmp_path, components)
+    read_retval["foo"].version = "nonexistent"
+    patch_read.return_value = read_retval
+
+    with pytest.raises(Exception) as excinfo:
+        dependency_mgmt.fetch_components(config)
+
+    assert "Failed to checkout revision 'nonexistent'" in str(excinfo.value)
+
+
 @patch("commodore.dependency_mgmt._read_components")
 @patch("commodore.dependency_mgmt._discover_components")
 def test_fetch_components_is_minimal(