Inspect.inspect/2 is undefined or private

Questions / Help
1

Hello all,
I am facing an intermittent error on a system I’m running with iex -S mix phx.server.

Every once in a while, a web request will fail with the error above Inspect.inspect/2 is undefined or private (either in rendering, or in Ecto). Other threads seem to be happy to use Inspect instead. I’m rather puzzled :wink:

Edit: every once in a while, I seem to get a similar error on Poison.Encoder.encode/2 (this one on a different thread, so not web-related). Like, 99.9% of the times it works. What could it be?

2

I think you need IO.inspect/2 instead.

3

Honest question: why should be that? either the function is present and it always works or it is not present, and it should always break. What I don’zt hget is why it breaks sometimes.

4

Try to locate where Inspect.inspect is… maybe it is not always called.

1 Like
5

Hey there and welcome to the forums!
Is 'Inspect.inspect` one of your own modules / functions? Or were you looking for Kernel.inspect or IO.inspect instead? (these are the only ones I know of in the core lib)

1 Like
6

There is also Inspect.inspect/2 in Inspect protocol.

2 Likes
7

From the Inspect.inspect/2 docs:

Converts term into an algebra document.

This function shouldn’t be invoked directly, unless when implementing a custom inspect_fun to be given to Inspect.Opts. Everywhere else, Inspect.Algebra.to_doc/2 should be preferred as it handles structs and exceptions.

8

From the IO.inspect/2 docs:

I assume you meant Inspect.inspect/2

1 Like
10

Actually it sometimes crashes when used by Ecto… and sometimes when rendering a web view. Is there a way to assert that the function is available or force its loading?

Like:

12:42:47.065 mfa=:telemetry.execute/3 [error] Handler {Phoenix.Logger, [:phoenix, :router_dispatch, :start]} has failed and has been
 detached. Class=:error
Reason=:undef
Stacktrace=[
  {Inspect, :inspect,
   [
     LogfwdWeb.PageController,
     %Inspect.Opts{
       base: :decimal,
       binaries: :infer,
       char_lists: :infer,
       charlists: :infer,
       custom_options: [],
       inspect_fun: &Inspect.inspect/2,
       limit: 50,
       pretty: false,
       printable_limit: 4096,
       safe: true,
       structs: true,
       syntax_colors: [],
       width: 80
     }
   ], []},
  {Kernel, :inspect, 2, [file: 'lib/kernel.ex', line: 2203]},
  {Phoenix.Logger, :"-phoenix_router_dispatch_start/4-fun-0-", 4,
   [file: 'lib/phoenix/logger.ex', line: 234]},
  {Logger, :__do_log__, 4, [file: 'lib/logger.ex', line: 777]},
  {:telemetry, :"-execute/3-fun-0-", 4,
   [file: '/root/src/LogFwd/deps/telemetry/src/telemetry.erl', line: 135]},
  {:lists, :foreach, 2, [file: 'lists.erl', line: 1342]},
  {Phoenix.Router, :__call__, 2, [file: 'lib/phoenix/router.ex', line: 345]},
  {LogfwdWeb.Endpoint, :plug_builder_call, 2,
   [file: 'lib/logfwd_web/endpoint.ex', line: 1]},
  {LogfwdWeb.Endpoint, :"call (overridable 3)", 2,
   [file: 'lib/plug/debugger.ex', line: 136]},
  {LogfwdWeb.Endpoint, :call, 2, [file: 'lib/logfwd_web/endpoint.ex', line: 1]},
  {Phoenix.Endpoint.Cowboy2Handler, :init, 4,
   [file: 'lib/phoenix/endpoint/cowboy2_handler.ex', line: 65]},
  {:cowboy_handler, :execute, 2,
   [file: '/root/src/LogFwd/deps/cowboy/src/cowboy_handler.erl', line: 37]},
  {:cowboy_stream_h, :execute, 3,
   [file: '/root/src/LogFwd/deps/cowboy/src/cowboy_stream_h.erl', line: 300]},
  {:cowboy_stream_h, :request_process, 3,
   [file: '/root/src/LogFwd/deps/cowboy/src/cowboy_stream_h.erl', line: 291]},
  {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 226]}
]

or

** (UndefinedFunctionError) function Inspect.inspect/2 is undefined or private
    (elixir 1.12.2) Inspect.inspect({:ok, %{.......}, %Inspect.Opts{base: :decimal, binaries: :infer, char_lists: :infer, charlists: :infer, custom_options: [], inspect_fun: &Inspect.inspect/2, limit: 50, pretty: false, printable_limit: 4096, safe: true, structs: true, syntax_colors: [], width: 80})
    (elixir 1.12.2) lib/kernel.ex:2203: Kernel.inspect/2
    (logfwd 0.3.12) lib/logfwd/tools.ex:424: Logfwd.Tools.jsonHttp/5
    (logfwd 0.3.12) lib/logfwd/tx/apis.ex:929: Logfwd.Teams.Apis.jsonCallGet/3
    (logfwd 0.3.12) lib/logfwd/tx/subs.ex:144: Logfwd.Teams.Subs.listSubscriptions/1
    (logfwd 0.3.12) lib/logfwd/tx/subs.ex:161: Logfwd.Teams.Subs.listSubscriptionsAsSubs/2
    (elixir 1.12.2) lib/enum.ex:2385: Enum."-reduce/3-lists^foldl/2-0-"/3
    (logfwd 0.3.12) lib/logfwd/tx/subsrv.ex:385: Logfwd.Teams.SubsSrv.handle_call/3
    (stdlib 3.15.1) gen_server.erl:721: :gen_server.try_handle_call/4
    (stdlib 3.15.1) gen_server.erl:750: :gen_server.handle_msg/6
    (stdlib 3.15.1) proc_lib.erl:226: :proc_lib.init_p_do_apply/3

or this coming from Ecto:

** (UndefinedFunction
Error) function Inspect.inspect/2 is undefined or private
    (elixir 1.12.2) Inspect.inspect("t_calls", %Inspect.Opts{base: :decimal, binaries: :infer, char_lists: :infer, charlists: :infer, custom_options: [], inspect_fun: &Inspect.inspect/2, limit: 50, pretty: false, printable_limit: 4096, safe: true, structs: true, syntax_colors: [], width: 80})
    (elixir 1.12.2) lib/kernel.ex:2203: Kernel.inspect/2
    (ecto_sql 3.5.4) lib/ecto/adapters/sql.ex:998: Ecto.Adapters.SQL.log_ok_source/1
    (ecto_sql 3.5.4) lib/ecto/adapters/sql.ex:982: Ecto.Adapters.SQL.log_iodata/2
    (logger 1.12.2) lib/logger.ex:777: Logger.__do_log__/4
    (ecto_sql 3.5.4) lib/ecto/adapters/sql.ex:948: Ecto.Adapters.SQL.log/4
    (db_connection 2.3.1) lib/db_connection.ex:1401: DBConnection.log/5
    (myxql 0.4.5) lib/myxql.ex:243: MyXQL.do_query/4
    (ecto_sql 3.5.4) lib/ecto/adapters/sql.ex:717: Ecto.Adapters.SQL.execute!/4
    (ecto_sql 3.5.4) lib/ecto/adapters/sql.ex:684: Ecto.Adapters.SQL.execute/5
    (ecto 3.5.6) lib/ecto/repo/queryable.ex:229: Ecto.Repo.Queryable.execute/4
    (ecto 3.5.6) lib/ecto/repo/queryable.ex:17: Ecto.Repo.Queryable.all/3
    (logfwd 0.3.12) lib/logfwd/tx/db/dbcall.ex:358: Logfwd.Teams.Db.DbCall.fetch_open_call_if_exists/2
    (logfwd 0.3.12) lib/logfwd/tx/db/dbcall.ex:162: Logfwd.Teams.Db.DbCall.new_call_notification/2
    (logfwd 0.3.12) lib/logfwd/tx/calltrackersrv.ex:154: Logfwd.Teams.CallTrackerSrv.call_received/3
    (logfwd 0.3.12) lib/logfwd_web/controllers/page_controller.ex:122: LogfwdWeb.PageController.notifyTenantOfCall/3
    (logfwd 0.3.12) lib/logfwd_web/controllers/page_controller.ex:108: anonymous fn/2 in LogfwdWeb.PageController.downloadEntries/1
    (elixir 1.12.2) lib/enum.ex:2385: Enum."-reduce/3-lists^foldl/2-0-"/3
11

I have an update, but I’m still puzzled (or just too much of a n00b): the errors above came from a system that was run as iex -S mix phx.server. Now, it’s a couple of days that it runs under a proper release, and I have zero of these issues appearing vs hundreds per day.

So it makes me think that it has something to do with code preloading and/or protocol consolidation (as Inspect is a protocol). This said, the system was running with an open but unused iex shell, so it did no recompiling at runtime or anything.

Anybody has any hints?

12

What is your project/0 configuration in your mix.exs?

13

Like:


  def project do
    [
      app: :logfwd,
      version: "0.3.27-211130d",
      elixir: "~> 1.7",
      elixirc_paths: elixirc_paths(Mix.env()),
      compilers: [:phoenix, :gettext] ++ Mix.compilers(),
      start_permanent: Mix.env() == :prod,
      aliases: aliases(),
      deps: deps(),
      docs: docs()
    ]
  end

?

14

Looks like a bug, because you say it works most of the times.

What specific Phoenix version are you using?

All i can suggest is install:

and run
mix decompile Elixir.Inspect --to expanded

and post the share somewhere the contents of Elixir.Inspect.ex

If you could share a reduced cased of your code, and if you know under what circumstances the error happens… that will be helpful.

15

I’ll try that…

I am running on Elixir 1.12.2 - Phoenix 1.5.7 - Erlang/OTP 24 [erts-12.0.2] [source] [64-bit] [smp:1:1] [ds:1:1:10] [async-threads:1] [jit] [x86_64-pc-linux-gnu] - I am pretty sure I saw it happen on my machine (Mac M1) once or twice.

My line of reasoning was that it could maybe break if some code was being reloaded on a different thread, but I don’t get why it could/should happen - nothing that I’m aware of would trigger a reload.

16

Here is what I did:

  • stopped my release
  • installed Decompile
  • mix clean
  • iex -S mix phx.server
  • mix decompile Elixir.Inspect --to expanded

In the few minutes that I run the project I got 8 errors from a number of places (mostly from Ecto), all of them function Inspect.inspect/2 is undefined or private.

defmodule Inspect do
  defp struct_impl_for(struct) do
    target = Module.concat(Inspect, struct)

    try do
      target.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def inspect(term, arg2) do
    impl_for!(term).inspect(term, arg2)
  end

  def impl_for!(data) do
    impl_for(data)
  end

  def impl_for(%struct{}) do
    struct_impl_for(struct)
  end

  def impl_for(data) do
    try do
      Inspect.Tuple.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.Atom.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.List.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.Map.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.BitString.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.Integer.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.Float.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.Function.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.PID.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.Port.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(data) do
    try do
      Inspect.Reference.__impl__(:target)
    rescue
      _ in [UndefinedFunctionError] ->
        Inspect.Any.__impl__(:target)
    end
  end

  def impl_for(_) do
    Inspect.Any.__impl__(:target)
  end

  def __protocol__(:module) do
    Inspect
  end

  def __protocol__(:functions) do
    [inspect: 2]
  end

  def __protocol__(:consolidated?) do
    false
  end

  def __protocol__(:impls) do
    :not_consolidated
  end
end