Another crash on valid Erlang module

[michalmuskala]

Given this module:

-module(test).
-moduledoc "".

-export_type([
    enum/0,
    union/0,
    entity/0
]).

-type enum() :: foo.
-type union() :: bar.
-type entity() :: enum() | union().

compiled with erlc +debug_info -o test_ebin test.erl

and placing this file as test.app inside test_ebin

{application, test, [
    {applications, [kernel, stdlib]},
    {modules, [test]}
]}.

Calling the escript as ./ex_doc -f html foobar 1.0.0 test_ebin crashes with:

17:51:37.035 [error] Task #PID<0.116.0> started from #PID<0.112.0> terminating
** (Enum.EmptyError) empty error
    (elixir 1.18.2) lib/enum.ex:2489: Enum.reduce/2
    (elixir 1.18.2) lib/enum.ex:1714: Enum."-map/2-lists^map/1-1-"/2
    (elixir 1.18.2) lib/enum.ex:1714: Enum."-map/2-lists^map/1-1-"/2
    (elixir 1.18.2) lib/code/typespec.ex:302: Code.Typespec.typespec_to_quoted/1
    (elixir 1.18.2) lib/code/typespec.ex:72: Code.Typespec.type_to_quoted/1
    (ex_doc 0.37.0-rc.2) lib/ex_doc/language/erlang.ex:240: ExDoc.Language.Erlang.autolink_spec/2
    (elixir 1.18.2) lib/enum.ex:1714: Enum."-map/2-lists^map/1-1-"/2
    (ex_doc 0.37.0-rc.2) lib/ex_doc/formatter/html.ex:109: anonymous fn/5 in ExDoc.Formatter.HTML.render_all/5
Function: &:erlang.apply/2
    Args: [#Function<18.71509929/1 in ExDoc.Formatter.HTML.render_all/5>, [%ExDoc.ModuleNode{id: "test", title: "test", nested_context: nil, nested_title: nil, module: :test, group: nil, deprecated: nil, doc_format: "text/markdown", doc: [], source_doc: %{"en" => ""}, rendered_doc: nil, moduledoc_line: 2, moduledoc_file: "test.erl", source_path: nil, source_url: nil, docs_groups: ["Types", "Callbacks", "Functions"], docs: [%ExDoc.DocNode{id: "t:entity/0", name: :entity, arity: 0, defaults: [], deprecated: nil, doc: nil, source_doc: :none, rendered_doc: nil, type: :type, signature: "entity()", specs: [{:attribute, [file: "/Users/micmus/github/elixir-lang/ex_doc/test.erl", location: {12, 2}], :type, {:entity, {:type, {12, 19}, :union, [{:type, {12, 19}, :enum, []}, {:type, {12, 28}, :union, []}]}, []}}], annotations: [], group: "Types", doc_line: 12, doc_file: "test.erl", source_url: nil}, %ExDoc.DocNode{id: "t:enum/0", name: :enum, arity: 0, defaults: [], deprecated: nil, doc: nil, source_doc: :none, rendered_doc: nil, type: :type, signature: "enum()", specs: [{:attribute, [file: "/Users/micmus/github/elixir-lang/ex_doc/test.erl", location: {10, 2}], :type, {:enum, {:atom, {10, 17}, :foo}, []}}], annotations: [], group: "Types", doc_line: 10, doc_file: "test.erl", source_url: nil}, %ExDoc.DocNode{id: "t:union/0", name: :union, arity: 0, defaults: [], deprecated: nil, doc: nil, source_doc: :none, rendered_doc: nil, type: :type, signature: "union()", specs: [{:attribute, [file: "/Users/micmus/github/elixir-lang/ex_doc/test.erl", location: {11, 2}], :type, {:union, {:atom, {11, 18}, :bar}, []}}], annotations: [], group: "Types", doc_line: 11, doc_file: "test.erl", source_url: nil}], typespecs: [], type: :module, language: ExDoc.Language.Erlang, annotations: [], metadata: %{otp_doc_vsn: {1, 0, 0}, kind: :module}}]]
** (EXIT from #PID<0.112.0>) an exception was raised:
    ** (Enum.EmptyError) empty error
        (elixir 1.18.2) lib/enum.ex:2489: Enum.reduce/2
        (elixir 1.18.2) lib/enum.ex:1714: Enum."-map/2-lists^map/1-1-"/2
        (elixir 1.18.2) lib/enum.ex:1714: Enum."-map/2-lists^map/1-1-"/2
        (elixir 1.18.2) lib/code/typespec.ex:302: Code.Typespec.typespec_to_quoted/1
        (elixir 1.18.2) lib/code/typespec.ex:72: Code.Typespec.type_to_quoted/1
        (ex_doc 0.37.0-rc.2) lib/ex_doc/language/erlang.ex:240: ExDoc.Language.Erlang.autolink_spec/2
        (elixir 1.18.2) lib/enum.ex:1714: Enum."-map/2-lists^map/1-1-"/2
        (ex_doc 0.37.0-rc.2) lib/ex_doc/formatter/html.ex:109: anonymous fn/5 in ExDoc.Formatter.HTML.render_all/5

This is on latest master and following elixir --version:

Erlang/OTP 27 [erts-15.2.1] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit] [dtrace]

Elixir 1.18.2 (compiled with Erlang/OTP 27)

[josevalim]

I will take a look, thank you. Btw, in the long term, we should stop translating Erlang typespecs into Elixir. We should either:

1. Add a function to Erlang/OTP to pretty print typespecs with links
2. Tranverse the Erlang AST instead when generating links

This way we can evolve the Erlang components of ExDoc without depending on Elixir. Contributions around those areas would be very welcome.

[garazdawi]

@michalmuskala Do you know if it be possible to run https://github.com/WhatsApp/erlfuzz and see if there are any more cases that need to be covered?