feat(cli): flatten nested fields in table and CSV output

cli/utils/output.py

@@ -40,6 +40,7 @@ def _table(self, data: Any) -> None:
             self._console.print_json(json.dumps(data, default=str))
             return
 
+        rows = _flatten_rows(rows)
         columns = list(rows[0].keys())
         numeric_cols = _detect_numeric_columns(rows, columns)
 
@@ -61,11 +62,38 @@ def _csv(self, data: Any) -> None:
             )
             sys.exit(EXIT_ERROR)
 
+        rows = _flatten_rows(rows)
         columns = list(rows[0].keys())
         writer = csv.DictWriter(sys.stdout, fieldnames=columns)
         writer.writeheader()
         for row in rows:
-            writer.writerow({k: str(v) for k, v in row.items()})
+            writer.writerow(
+                {
+                    k: json.dumps(v, default=str)
+                    if isinstance(v, (dict, list))
+                    else str(v)
+                    for k, v in row.items()
+                }
+            )
+
+
+def _flatten_rows(rows: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    """Flatten nested dicts into dot-notation columns (one level deep)."""
+    if not rows:
+        return rows
+    flat: list[dict[str, Any]] = []
+    for row in rows:
+        new_row: dict[str, Any] = {}
+        for key, value in row.items():
+            if isinstance(value, dict):
+                for sub_key, sub_value in value.items():
+                    new_row[f"{key}.{sub_key}"] = sub_value
+            elif isinstance(value, list):
+                new_row[key] = json.dumps(value, default=str)
+            else:
+                new_row[key] = value
+        flat.append(new_row)
+    return flat
 
 
 def _extract_rows(data: Any) -> list[dict[str, Any]]:

tests/test_output.py

@@ -0,0 +1,111 @@
+from __future__ import annotations
+
+import io
+import json
+import sys
+from unittest.mock import patch
+
+from cli.types.enums import OutputFormat
+from cli.utils.output import OutputRenderer, _flatten_rows
+
+
+class TestFlattenRows:
+    def test_nested_dicts_produce_dot_notation_keys(self):
+        rows = [
+            {"id": 1, "info": {"name": "Tether USD", "symbol": "USDT"}},
+            {"id": 2, "info": {"name": "USD Coin", "symbol": "USDC"}},
+        ]
+        result = _flatten_rows(rows)
+        assert result == [
+            {"id": 1, "info.name": "Tether USD", "info.symbol": "USDT"},
+            {"id": 2, "info.name": "USD Coin", "info.symbol": "USDC"},
+        ]
+
+    def test_lists_serialized_as_json(self):
+        rows = [{"id": 1, "tags": ["stablecoin", "erc20"]}]
+        result = _flatten_rows(rows)
+        assert result == [{"id": 1, "tags": '["stablecoin", "erc20"]'}]
+        # Verify it's valid JSON
+        assert json.loads(result[0]["tags"]) == ["stablecoin", "erc20"]
+
+    def test_flat_data_passes_through_unchanged(self):
+        rows = [
+            {"id": 1, "name": "Tether", "price": "1.00"},
+            {"id": 2, "name": "Ethereum", "price": "3000.00"},
+        ]
+        result = _flatten_rows(rows)
+        assert result == rows
+
+    def test_empty_rows_returns_empty(self):
+        assert _flatten_rows([]) == []
+
+    def test_mixed_nested_and_flat_values(self):
+        rows = [
+            {
+                "id": 1,
+                "name": "Token",
+                "info": {"symbol": "TKN"},
+                "tags": ["defi"],
+                "price": "1.50",
+            }
+        ]
+        result = _flatten_rows(rows)
+        assert result == [
+            {
+                "id": 1,
+                "name": "Token",
+                "info.symbol": "TKN",
+                "tags": '["defi"]',
+                "price": "1.50",
+            }
+        ]
+
+
+class TestCsvOutput:
+    def test_csv_no_python_repr(self):
+        """CSV output should use JSON (double quotes) not Python repr (single quotes)."""
+        data = [
+            {
+                "id": 1,
+                "info": {"name": "Tether USD", "symbol": "USDT"},
+                "tags": ["stablecoin"],
+            }
+        ]
+        buf = io.StringIO()
+        renderer = OutputRenderer()
+        with patch.object(sys, "stdout", buf):
+            renderer.render(data, OutputFormat.CSV)
+
+        output = buf.getvalue()
+        # Should not contain Python-style single-quoted dicts
+        assert "{'name'" not in output
+        assert "'symbol'" not in output
+        # Flattened dict keys should appear as columns
+        assert "info.name" in output
+        assert "info.symbol" in output
+        assert "Tether USD" in output
+        # Tags should be valid JSON
+        lines = output.strip().split("\n")
+        assert len(lines) == 2  # header + 1 row
+
+
+class TestTableOutput:
+    def test_table_with_nested_data_shows_flattened_columns(self):
+        """Table output should show flattened dot-notation columns."""
+        from rich.console import Console
+
+        buf = io.StringIO()
+        console = Console(file=buf, width=200)
+        renderer = OutputRenderer(console=console)
+
+        data = [
+            {"id": 1, "info": {"name": "Tether", "symbol": "USDT"}},
+            {"id": 2, "info": {"name": "Ethereum", "symbol": "ETH"}},
+        ]
+        renderer.render(data, OutputFormat.TABLE)
+
+        output = buf.getvalue()
+        assert "info.name" in output
+        assert "info.symbol" in output
+        assert "Tether" in output
+        assert "ETH" in output