fix(utils): narrow bare except Exception in merge_json_files (#4189)

merge_json_files's read of the existing JSON file caught bare
`Exception` around `json5.load`, so a real bug there (e.g. a
`TypeError`/`AttributeError`) was silently treated the same as a normal
parse failure -- `None` returned, existing settings preserved untouched,
nothing surfaced unless `verbose`. Only `OSError` (inaccessible file) and
`ValueError` (malformed JSON5 -- json5's decode error is a `ValueError`
subclass) are expected outcomes here; anything else should propagate.

Same bug, same fix shape, as the caller `handle_vscode_settings`, whose
own bare `except Exception` was just narrowed to `(OSError, ValueError,
KeyError)` in commit 16f4577 (PR #3844) with the same rationale
("let programming errors like TypeError or AttributeError propagate").
That PR's own regression test monkeypatched `merge_json_files` to prove
the caller's narrowing works; this fixes and tests the callee itself,
which still had the original bare-except bug.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

src/specify_cli/_utils.py

@@ -249,7 +249,7 @@ def merge_json_files(existing_path: Path, new_content: Any, verbose: bool = Fals
         except FileNotFoundError:
             # Handle race condition where file is deleted after exists() check
             exists = False
-        except Exception as e:
+        except (OSError, ValueError) as e:
             if verbose:
                 console.print(f"[yellow]Warning: Could not read or parse existing JSON in {existing_path.name} ({e}).[/yellow]")
             # Skip merge to preserve existing file if unparseable or inaccessible (e.g. PermissionError)

tests/test_merge.py

@@ -212,3 +212,29 @@ def test_handle_vscode_settings_propagates_programming_errors(tmp_path):
             )
     finally:
         utils_mod.merge_json_files = original_merge
+
+
+def test_merge_json_files_propagates_programming_errors(tmp_path, monkeypatch):
+    """Unexpected programming errors reading the existing file must propagate.
+
+    ``merge_json_files``'s own read of the existing JSON file caught bare
+    ``Exception`` around ``json5.load``, so a real bug there (e.g. a
+    ``TypeError``) was silently treated the same as a normal parse failure --
+    ``None`` returned, existing settings preserved, nothing logged unless
+    ``verbose``. Only ``OSError`` (inaccessible file) and ``ValueError``
+    (malformed JSON5 -- json5's decode error is a ``ValueError`` subclass)
+    are expected outcomes here; anything else must propagate, matching the
+    narrowing already applied to the caller, ``handle_vscode_settings``.
+    """
+    existing_file = tmp_path / "settings.json"
+    existing_file.write_text('{"a": 1}\n', encoding="utf-8")
+
+    import specify_cli._utils as utils_mod
+
+    def _boom(*_a, **_kw):
+        raise TypeError("boom")
+
+    monkeypatch.setattr(utils_mod.json5, "load", _boom)
+
+    with pytest.raises(TypeError):
+        merge_json_files(existing_file, {"b": 2})