fix(dialyzer): resolve all dialyzer warnings

Chris Xu · claude · Chris Xu · commit c37aabb68ee4 · 2026-01-20T15:55:52.000+01:00
- Remove dead code patterns that could never match: - detect_root_type([]) in structural_parser.ex - append_lines(writer, [], _depth) in objects.ex - Define precise types to fix supertype warnings: - Add @type decoded in decode.ex - Add @type validated in options.ex - Use nonempty_list() in arrays.ex and strings.ex specs - Fix protocol fallback no_return warning: - Remove @SPEC from Toon.Encoder.Any encode/2 functions - Add .dialyzer_ignore.exs for intentional no_return behavior - Add edge case tests to verify behavior before dead code removal Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
diff --git a/.dialyzer_ignore.exs b/.dialyzer_ignore.exs
@@ -0,0 +1,8 @@
+# Dialyzer warnings to ignore
+#
+# Protocol fallback implementation that intentionally raises.
+# This is expected behavior - the Any implementation raises Protocol.UndefinedError
+# when a struct doesn't have an explicit Toon.Encoder implementation.
+[
+  {"lib/toon/encoder.ex", :no_return}
+]
diff --git a/README.md b/README.md
@@ -2,6 +2,7 @@
 
 [![Hex.pm](https://img.shields.io/hexpm/v/toon.svg)](https://hex.pm/packages/toon)
 [![Documentation](https://img.shields.io/badge/docs-hexdocs-blue.svg)](https://hexdocs.pm/toon)
+[![Coverage Status](https://coveralls.io/repos/github/xu-chris/toon_ex/badge.svg?branch=main)](https://coveralls.io/github/xu-chris/toon_ex?branch=main)
 
 **TOON (Token-Oriented Object Notation)** encoder and decoder for Elixir.
 
diff --git a/lib/toon/decode/decode.ex b/lib/toon/decode/decode.ex
@@ -8,6 +8,9 @@ defmodule Toon.Decode do
   alias Toon.Decode.{Options, StructuralParser}
   alias Toon.DecodeError
 
+  @typedoc "Decoded TOON value"
+  @type decoded :: nil | boolean() | binary() | number() | list() | map()
+
   @doc """
   Decodes a TOON format string to Elixir data.
 
@@ -94,7 +97,7 @@ defmodule Toon.Decode do
       iex> Toon.Decode.decode!("count: 42")
       %{"count" => 42}
   """
-  @spec decode!(String.t(), keyword()) :: term()
+  @spec decode!(String.t(), keyword()) :: decoded()
   def decode!(string, opts \\ []) when is_binary(string) do
     case decode(string, opts) do
       {:ok, result} -> result
@@ -104,7 +107,7 @@ defmodule Toon.Decode do
 
   # Private functions
 
-  @spec do_decode(String.t(), map()) :: term()
+  @spec do_decode(String.t(), map()) :: decoded()
   defp do_decode(string, opts) do
     # Use structural parser for full TOON support
     case StructuralParser.parse(string, opts) do
diff --git a/lib/toon/decode/structural_parser.ex b/lib/toon/decode/structural_parser.ex
@@ -157,8 +157,6 @@ defmodule Toon.Decode.StructuralParser do
     end
   end
 
-  defp detect_root_type([]), do: {:object, nil}
-
   # Parse root primitive value (single value without key)
   defp parse_root_primitive([%{content: content}], _opts) do
     # For root primitives, we parse directly without parser combinator
diff --git a/lib/toon/encode/arrays.ex b/lib/toon/encode/arrays.ex
@@ -49,7 +49,8 @@ defmodule Toon.Encode.Arrays do
       iex> IO.iodata_to_binary(result)
       "items[0]:"
   """
-  @spec encode_empty(String.t(), String.t() | nil) :: [iodata()]
+  @spec encode_empty(String.t(), String.t() | nil) ::
+          nonempty_list(nonempty_list(binary() | nonempty_list(binary())))
   def encode_empty(key, length_marker \\ nil) do
     marker = format_length_marker(0, length_marker)
     [[Strings.encode_key(key), "[", marker, "]", Constants.colon()]]
diff --git a/lib/toon/encode/objects.ex b/lib/toon/encode/objects.ex
@@ -17,7 +17,7 @@ defmodule Toon.Encode.Objects do
       iex> Toon.Encode.Objects.encode(map, 0, opts)
 
   """
-  @spec encode(map(), non_neg_integer(), map()) :: iodata()
+  @spec encode(map(), non_neg_integer(), map()) :: [iodata()]
   def encode(map, depth, opts) when is_map(map) do
     writer = Writer.new(opts.indent)
 
@@ -103,22 +103,14 @@ defmodule Toon.Encode.Objects do
 
   # Private helpers
 
-  defp append_lines(writer, [], _depth), do: writer
-
-  defp append_lines(writer, lines, depth) when is_list(lines) do
+  defp append_lines(writer, [header | data_rows], depth) do
     # For arrays, the first line is the header at current depth
     # Subsequent lines (data rows for tabular format) should be one level deeper
-    case lines do
-      [header | data_rows] ->
-        writer = Writer.push(writer, header, depth)
-
-        Enum.reduce(data_rows, writer, fn row, acc ->
-          Writer.push(acc, row, depth + 1)
-        end)
+    writer = Writer.push(writer, header, depth)
 
-      [] ->
-        writer
-    end
+    Enum.reduce(data_rows, writer, fn row, acc ->
+      Writer.push(acc, row, depth + 1)
+    end)
   end
 
   defp append_iodata(writer, iodata, _base_depth) do
diff --git a/lib/toon/encode/options.ex b/lib/toon/encode/options.ex
@@ -5,6 +5,15 @@ defmodule Toon.Encode.Options do
 
   alias Toon.Constants
 
+  @typedoc "Validated encoding options"
+  @type validated :: %{
+          indent: pos_integer(),
+          delimiter: String.t(),
+          length_marker: String.t() | nil,
+          key_order: term(),
+          indent_string: String.t()
+        }
+
   @options_schema [
     indent: [
       type: :pos_integer,
@@ -90,7 +99,7 @@ defmodule Toon.Encode.Options do
       iex> Toon.Encode.Options.validate!(indent: 4)
       %{indent: 4, delimiter: ",", length_marker: nil, indent_string: "    "}
   """
-  @spec validate!(keyword()) :: map()
+  @spec validate!(keyword()) :: validated()
   def validate!(opts) when is_list(opts) do
     case validate(opts) do
       {:ok, validated} ->
diff --git a/lib/toon/encode/strings.ex b/lib/toon/encode/strings.ex
@@ -24,7 +24,7 @@ defmodule Toon.Encode.Strings do
       iex> Toon.Encode.Strings.encode_string("line1\\nline2") |> IO.iodata_to_binary()
       ~s("line1\\\\nline2")
   """
-  @spec encode_string(String.t(), String.t()) :: iodata()
+  @spec encode_string(String.t(), String.t()) :: binary() | nonempty_list(binary())
   def encode_string(string, delimiter \\ ",") when is_binary(string) do
     if safe_unquoted?(string, delimiter) do
       string
diff --git a/lib/toon/encoder.ex b/lib/toon/encoder.ex
@@ -51,7 +51,6 @@ defimpl Toon.Encoder, for: Any do
     end
   end
 
-  @spec encode(struct(), keyword()) :: no_return()
   def encode(%_{} = struct, _opts) do
     raise Protocol.UndefinedError,
       protocol: @protocol,
@@ -71,7 +70,6 @@ defimpl Toon.Encoder, for: Any do
       """
   end
 
-  @spec encode(term(), keyword()) :: no_return()
   def encode(value, _opts) do
     raise Protocol.UndefinedError,
       protocol: @protocol,
diff --git a/mix.exs b/mix.exs
@@ -26,7 +26,8 @@ defmodule Toon.MixProject do
           :underspecs,
           :unmatched_returns,
           :unknown
-        ]
+        ],
+        ignore_warnings: ".dialyzer_ignore.exs"
       ],
       aliases: aliases()
     ]
diff --git a/test/toon/edge_cases_test.exs b/test/toon/edge_cases_test.exs
@@ -0,0 +1,47 @@
+defmodule Toon.EdgeCasesTest do
+  @moduledoc """
+  Tests for edge cases to ensure behavior is preserved after removing dead code.
+  """
+  use ExUnit.Case, async: true
+
+  describe "empty input decoding" do
+    test "empty string decodes to empty map" do
+      assert {:ok, %{}} = Toon.decode("")
+    end
+
+    test "whitespace-only string decodes to empty map" do
+      assert {:ok, %{}} = Toon.decode("   ")
+      assert {:ok, %{}} = Toon.decode("\n\n")
+      assert {:ok, %{}} = Toon.decode("  \n  \n  ")
+    end
+  end
+
+  describe "empty data encoding" do
+    test "empty map encodes to empty string" do
+      assert "" = Toon.encode!(%{})
+    end
+
+    test "empty list encodes with zero-length header" do
+      result = Toon.encode!(%{"items" => []})
+      assert result =~ "items[0]:"
+    end
+
+    test "nested empty structures" do
+      # Empty map inside map - produces key with colon
+      assert "nested:" = Toon.encode!(%{"nested" => %{}})
+
+      # Empty list inside map
+      result = Toon.encode!(%{"items" => []})
+      assert result =~ "[0]:"
+    end
+  end
+
+  describe "decode and encode roundtrip for edge cases" do
+    test "empty map roundtrip" do
+      original = %{}
+      encoded = Toon.encode!(original)
+      {:ok, decoded} = Toon.decode(encoded)
+      assert decoded == original
+    end
+  end
+end
