fix(table): don't crash on --query lists mixing scalars and objects

.changes/next-release/bugfix-table-output-mixed-list.json

@@ -0,0 +1,5 @@
+{
+  "category": "``table`` output",
+  "description": "Fix ``ValueError`` when ``--output table`` renders a list that contains both a scalar and an object, which a ``--query`` multi-select list such as ``[InstanceId, State]`` produces",
+  "type": "bugfix"
+}

awscli/formatter.py

@@ -137,10 +137,27 @@ def _build_table(self, title, current, indent_level=0):
         if title is not None:
             self.table.new_section(title, indent_level=indent_level)
         if isinstance(current, list):
-            if isinstance(current[0], dict):
+            if all(isinstance(el, dict) for el in current):
                 self._build_sub_table_from_list(current, indent_level, title)
             else:
-                for item in current:
+                # The elements don't all share a shape, so a dict can't be
+                # rendered as a row alongside them.  Give it a section of
+                # its own, and start a new one for whatever follows it.
+                needs_new_section = False
+                for i, item in enumerate(current):
+                    if isinstance(item, dict):
+                        if i > 0:
+                            self.table.new_section(
+                                title, indent_level=indent_level
+                            )
+                        self._build_sub_table_from_dict(item, indent_level)
+                        needs_new_section = True
+                        continue
+                    if needs_new_section:
+                        self.table.new_section(
+                            title, indent_level=indent_level
+                        )
+                        needs_new_section = False
                     if self._scalar_type(item):
                         self.table.add_row([item])
                     elif all(self._scalar_type(el) for el in item):

tests/unit/output/test_table_formatter.py

@@ -362,6 +362,41 @@
 """
 
 
+# A --query multi-select list such as '[InstanceId, State]' returns a list
+# holding both a scalar and an object.
+MIXED_SCALAR_FIRST = ["i-123", {"Code": 16, "Name": "running"}]
+
+MIXED_SCALAR_FIRST_TABLE = """\
+---------------------
+|   OperationName   |
++-------------------+
+|  i-123            |
++-------------------+
+|   OperationName   |
++-------+-----------+
+| Code  |   Name    |
++-------+-----------+
+|  16   |  running  |
++-------+-----------+
+"""
+
+MIXED_DICT_FIRST = [{"Code": 16, "Name": "running"}, "i-123"]
+
+MIXED_DICT_FIRST_TABLE = """\
+---------------------
+|   OperationName   |
++-------+-----------+
+| Code  |   Name    |
++-------+-----------+
+|  16   |  running  |
++-------+-----------+
+|   OperationName   |
++-------------------+
+|  i-123            |
++-------------------+
+"""
+
+
 class Object(object):
     def __init__(self, **kwargs):
         self.__dict__.update(kwargs)
@@ -425,3 +460,11 @@ def test_jmespath_filtered_response(self):
     def test_jmespath_filtered_dict_response(self):
         self.assert_data_renders_to(data=JMESPATH_FILTERED_RESPONSE_DICT,
                                     table=JMESPATH_FILTERED_RESPONSE_DICT_TABLE)
+
+    def test_mixed_list_with_leading_scalar(self):
+        self.assert_data_renders_to(data=MIXED_SCALAR_FIRST,
+                                    table=MIXED_SCALAR_FIRST_TABLE)
+
+    def test_mixed_list_with_leading_dict(self):
+        self.assert_data_renders_to(data=MIXED_DICT_FIRST,
+                                    table=MIXED_DICT_FIRST_TABLE)