pretty format terms in errors

lib/elixir/lib/access.ex

@@ -517,8 +517,8 @@ defmodule Access do
   An error is raised if the accessed structure is not a map or a struct:
 
       iex> get_in([], [Access.key(:foo)])
-      ** (BadMapError) expected a map, got: []
-
+      ** (BadMapError) expected a map, got:
+      ...
   """
   @spec key(key, term) :: access_fun(data :: struct | map, current_value :: term)
   def key(key, default \\ nil) do
@@ -556,7 +556,8 @@ defmodule Access do
       iex> pop_in(map, [Access.key!(:user), Access.key!(:name)])
       {"john", %{user: %{}}}
       iex> get_in(map, [Access.key!(:user), Access.key!(:unknown)])
-      ** (KeyError) key :unknown not found in: %{name: \"john\"}
+      ** (KeyError) key :unknown not found in:
+      ...
 
   The examples above could be partially written as:
 

lib/elixir/lib/exception.ex

@@ -177,6 +177,22 @@ defmodule Exception do
     end
   end
 
+  @doc false
+  @spec _format_message_with_term(String.t(), any) :: String.t()
+  def _format_message_with_term(message, term) do
+    inspected =
+      term
+      |> inspect(pretty: true)
+      |> String.split("\n")
+      |> Enum.map(fn
+        "" -> ""
+        line -> "    " <> line
+      end)
+      |> Enum.join("\n")
+
+    message <> "\n\n" <> inspected
+  end
+
   @doc """
   Attaches information to exceptions for extra debugging.
 
@@ -1431,7 +1447,10 @@ defmodule BadStructError do
 
   @impl true
   def message(exception) do
-    "expected a struct named #{inspect(exception.struct)}, got: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "expected a struct named #{inspect(exception.struct)}, got:",
+      exception.term
+    )
   end
 end
 
@@ -1451,7 +1470,10 @@ defmodule BadMapError do
 
   @impl true
   def message(exception) do
-    "expected a map, got: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "expected a map, got:",
+      exception.term
+    )
   end
 end
 
@@ -1470,7 +1492,10 @@ defmodule BadBooleanError do
 
   @impl true
   def message(exception) do
-    "expected a boolean on left-side of \"#{exception.operator}\", got: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "expected a boolean on left-side of \"#{exception.operator}\", got:",
+      exception.term
+    )
   end
 end
 
@@ -1492,7 +1517,10 @@ defmodule MatchError do
 
   @impl true
   def message(exception) do
-    "no match of right hand side value: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no match of right hand side value:",
+      exception.term
+    )
   end
 end
 
@@ -1518,7 +1546,10 @@ defmodule CaseClauseError do
 
   @impl true
   def message(exception) do
-    "no case clause matching: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no case clause matching:",
+      exception.term
+    )
   end
 end
 
@@ -1548,7 +1579,10 @@ defmodule WithClauseError do
 
   @impl true
   def message(exception) do
-    "no with clause matching: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no with clause matching:",
+      exception.term
+    )
   end
 end
 
@@ -1598,7 +1632,10 @@ defmodule TryClauseError do
 
   @impl true
   def message(exception) do
-    "no try clause matching: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no try clause matching:",
+      exception.term
+    )
   end
 end
 
@@ -2160,7 +2197,10 @@ defmodule KeyError do
           "make sure to add parentheses after the function name)"
 
       true ->
-        message <> " in: #{inspect(term, pretty: true, limit: :infinity)}"
+        Exception._format_message_with_term(
+          message <> " in:",
+          term
+        )
     end
   end
 
@@ -2202,7 +2242,7 @@ defmodule KeyError do
 
     case suggestions do
       [] -> []
-      suggestions -> [". Did you mean:\n\n" | format_suggestions(suggestions)]
+      suggestions -> ["\n\nDid you mean:\n\n" | format_suggestions(suggestions)]
     end
   end
 

lib/elixir/lib/kernel/special_forms.ex

@@ -742,7 +742,8 @@ defmodule Kernel.SpecialForms do
       iex> x = 1
       iex> ^x = List.first([1])
       iex> ^x = List.first([2])
-      ** (MatchError) no match of right hand side value: 2
+      ** (MatchError) no match of right hand side value:
+      ...
 
   Note that `^x` always refers to the value of `x` prior to the match. The
   following example will match:

lib/elixir/lib/keyword.ex

@@ -529,7 +529,8 @@ defmodule Keyword do
       iex> Keyword.get_and_update!([a: 1], :b, fn current_value ->
       ...>   {current_value, "new value!"}
       ...> end)
-      ** (KeyError) key :b not found in: [a: 1]
+      ** (KeyError) key :b not found in:
+      ...
 
       iex> Keyword.get_and_update!([a: 1], :a, fn _ ->
       ...>   :pop
@@ -596,7 +597,8 @@ defmodule Keyword do
       iex> Keyword.fetch!([a: 1], :a)
       1
       iex> Keyword.fetch!([a: 1], :b)
-      ** (KeyError) key :b not found in: [a: 1]
+      ** (KeyError) key :b not found in:
+      ...
 
   """
   @spec fetch!(t, key) :: value
@@ -879,7 +881,8 @@ defmodule Keyword do
       [a: 1, b: :new, c: 3]
 
       iex> Keyword.replace!([a: 1], :b, 2)
-      ** (KeyError) key :b not found in: [a: 1]
+      ** (KeyError) key :b not found in:
+      ...
 
   """
   @doc since: "1.5.0"
@@ -1135,7 +1138,8 @@ defmodule Keyword do
       [a: 1, b: 4, c: 3]
 
       iex> Keyword.update!([a: 1], :b, &(&1 * 2))
-      ** (KeyError) key :b not found in: [a: 1]
+      ** (KeyError) key :b not found in:
+      ...
 
   """
   @spec update!(t, key, (current_value :: value -> new_value :: value)) :: t
@@ -1348,7 +1352,8 @@ defmodule Keyword do
       iex> Keyword.pop!([a: 1, a: 2], :a)
       {1, []}
       iex> Keyword.pop!([a: 1], :b)
-      ** (KeyError) key :b not found in: [a: 1]
+      ** (KeyError) key :b not found in:
+      ...
 
   """
   @doc since: "1.10.0"

lib/elixir/lib/map.ex

@@ -54,7 +54,8 @@ defmodule Map do
       map.foo
       #=> "bar"
       map.non_existing_key
-      ** (KeyError) key :non_existing_key not found in: %{baz: "bong", foo: "bar"}
+      ** (KeyError) key :non_existing_key not found in:
+      ...
 
   > #### Avoid parentheses {: .warning}
   >
@@ -388,7 +389,8 @@ defmodule Map do
       %{a: 3, b: 2}
 
       iex> Map.replace!(%{a: 1}, :b, 2)
-      ** (KeyError) key :b not found in: %{a: 1}
+      ** (KeyError) key :b not found in:
+      ...
 
   """
   @doc since: "1.5.0"
@@ -725,7 +727,8 @@ defmodule Map do
       iex> Map.pop!(%{a: 1, b: 2}, :a)
       {1, %{b: 2}}
       iex> Map.pop!(%{a: 1}, :b)
-      ** (KeyError) key :b not found in: %{a: 1}
+      ** (KeyError) key :b not found in:
+      ...
 
   """
   @doc since: "1.10.0"
@@ -911,7 +914,8 @@ defmodule Map do
       %{a: 2}
 
       iex> Map.update!(%{a: 1}, :b, &(&1 * 2))
-      ** (KeyError) key :b not found in: %{a: 1}
+      ** (KeyError) key :b not found in:
+      ...
 
   """
   @spec update!(map, key, (existing_value :: value -> new_value :: value)) :: map
@@ -986,7 +990,8 @@ defmodule Map do
       iex> Map.get_and_update!(%{a: 1}, :b, fn current_value ->
       ...>   {current_value, "new value!"}
       ...> end)
-      ** (KeyError) key :b not found in: %{a: 1}
+      ** (KeyError) key :b not found in:
+      ...
 
       iex> Map.get_and_update!(%{a: 1}, :a, fn _ ->
       ...>   :pop

lib/elixir/test/elixir/exception_test.exs

@@ -701,33 +701,69 @@ defmodule ExceptionTest do
       message = blame_message(%{first: nil, second: nil}, fn map -> map.firts end)
 
       assert message == """
-             key :firts not found in: %{first: nil, second: nil}. Did you mean:
+             key :firts not found in:
+
+                 %{first: nil, second: nil}
+
+             Did you mean:
 
                    * :first
              """
 
       message = blame_message(%{"first" => nil, "second" => nil}, fn map -> map.firts end)
 
-      assert message == "key :firts not found in: %{\"first\" => nil, \"second\" => nil}"
+      assert message == """
+             key :firts not found in:
+
+                 %{"first" => nil, "second" => nil}\
+             """
 
       message =
         blame_message(%{"first" => nil, "second" => nil}, fn map -> Map.fetch!(map, "firts") end)
 
-      assert message == "key \"firts\" not found in: %{\"first\" => nil, \"second\" => nil}"
+      assert message ==
+               """
+               key "firts" not found in:
+
+                   %{"first" => nil, "second" => nil}\
+               """
 
       message =
-        blame_message([first: nil, second: nil], fn kwlist -> Keyword.fetch!(kwlist, :firts) end)
+        blame_message(
+          [
+            created_at: nil,
+            updated_at: nil,
+            deleted_at: nil,
+            started_at: nil,
+            finished_at: nil
+          ],
+          fn kwlist ->
+            Keyword.fetch!(kwlist, :inserted_at)
+          end
+        )
 
       assert message == """
-             key :firts not found in: [first: nil, second: nil]. Did you mean:
+             key :inserted_at not found in:
 
-                   * :first
+                 [
+                   created_at: nil,
+                   updated_at: nil,
+                   deleted_at: nil,
+                   started_at: nil,
+                   finished_at: nil
+                 ]
+
+             Did you mean:
+
+                   * :created_at
+                   * :finished_at
+                   * :started_at
              """
     end
 
     test "annotates key error with suggestions for structs" do
       message = blame_message(%URI{}, fn map -> map.schema end)
-      assert message =~ "key :schema not found in: %URI{"
+      assert message =~ "key :schema not found in:\n\n    %URI{"
       assert message =~ "Did you mean:"
       assert message =~ "* :scheme"
     end