Extend validations for tabular list to enforce the same columns (#19)

Author: greg-rychlewski

lib/table/reader/enumerable.ex

@@ -37,7 +37,7 @@ defmodule Table.Reader.Enumerable do
         case columns_for(head) do
           {:ok, columns} ->
             meta = %{columns: columns}
-            enum = Table.Mapper.map(enum, &record_values(&1, columns))
+            enum = Table.Mapper.map(enum, &record_values(&1, columns, head))
             {:rows, meta, enum}
 
           :error ->
@@ -70,11 +70,17 @@ defmodule Table.Reader.Enumerable do
   defp keyval_columns([{key, _} | rest], columns), do: keyval_columns(rest, [key | columns])
   defp keyval_columns(_list, _columns), do: :error
 
-  defp record_values(record, columns) when is_list(record) do
+  defp record_values(record, columns, _head_record) when is_list(record) do
     keyval_values(record, columns)
   end
 
-  defp record_values(record, columns) when is_map(record) do
+  defp record_values(record, columns, head_record) when is_map(record) do
+    if map_size(record) > map_size(head_record) do
+      missing_columns = Map.keys(record) -- columns
+
+      raise "map records must have the same columns, missing column(s) #{inspect(missing_columns)} in #{inspect(head_record)}"
+    end
+
     Enum.map(columns, fn column ->
       case record do
         %{^column => value} ->
@@ -86,7 +92,7 @@ defmodule Table.Reader.Enumerable do
     end)
   end
 
-  defp record_values(record, _columns) do
+  defp record_values(record, _columns, _head_record) do
     raise "invalid table record: #{inspect(record)}"
   end
 
@@ -96,6 +102,14 @@ defmodule Table.Reader.Enumerable do
     [value | keyval_values(rest, columns)]
   end
 
+  defp keyval_values([], [column | _columns]) do
+    raise "key-value records must have the same columns, missing #{inspect(column)}"
+  end
+
+  defp keyval_values([{column, _value}], []) do
+    raise "key-value records must have the same columns, missing #{inspect(column)}"
+  end
+
   defp keyval_values([{actual, _value} | _rest], [column | _columns]) do
     raise "key-value records must have columns in the same order, expected #{inspect(column)}, but got #{inspect(actual)}"
   end

test/table/reader_test.exs

@@ -74,6 +74,7 @@ defmodule Table.ReaderTest do
     end
 
     test "enumerating rows raises on missing map element" do
+      # First row has more columns than later rows
       assert {:rows, %{}, enum} =
                Table.Reader.init([
                  %{"x" => 1, "y" => 1},
@@ -85,6 +86,19 @@ defmodule Table.ReaderTest do
                    fn ->
                      Enum.to_list(enum)
                    end
+
+      # Later row has more columns than first row
+      assert {:rows, %{}, enum} =
+               Table.Reader.init([
+                 %{"x" => 2},
+                 %{"x" => 1, "y" => 1}
+               ])
+
+      assert_raise RuntimeError,
+                   ~s/map records must have the same columns, missing column(s) ["y"] in %{"x" => 2}/,
+                   fn ->
+                     Enum.to_list(enum)
+                   end
     end
 
     test "enumerating rows raises on keyval order mismatch" do
@@ -112,6 +126,34 @@ defmodule Table.ReaderTest do
         Enum.to_list(enum)
       end
     end
+
+    test "enumerating rows raises on missing keyval element" do
+      # First row has more columns than later rows
+      assert {:rows, %{}, enum} =
+               Table.Reader.init([
+                 [{"x", 1}, {"y", 1}],
+                 [{"x", 2}]
+               ])
+
+      assert_raise RuntimeError,
+                   ~s/key-value records must have the same columns, missing "y"/,
+                   fn ->
+                     Enum.to_list(enum)
+                   end
+
+      # Later row has more columns than first row
+      assert {:rows, %{}, enum} =
+               Table.Reader.init([
+                 [{"x", 2}],
+                 [{"x", 1}, {"y", 1}]
+               ])
+
+      assert_raise RuntimeError,
+                   ~s/key-value records must have the same columns, missing "y"/,
+                   fn ->
+                     Enum.to_list(enum)
+                   end
+    end
   end
 
   describe "map init/1" do