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Improve error on module case mismatch #5665

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20 changes: 19 additions & 1 deletion lib/elixir/lib/exception.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -640,8 +640,26 @@ defmodule UndefinedFunctionError do
end

def message(%{reason: :"module could not be loaded", module: module, function: function, arity: arity}) do
suffix =
case :code.get_object_code(module) do
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@josevalim josevalim Jan 17, 2017 •
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This will probably be cleaner if you use the with construct. Also keep in mind we can pass the second argument from :code.get_object_code to :beam_lib. Here is one suggestion:

suffix =
  with {_, binary, _} <- :code.get_object_code(module),
       {:ok, {alt_module, _}} <- :beam_lib.chunks(binary, []) do
    exports = exports_for(alt_module)
    if ... do ... else ... end
  else
    _ -> ""
  end

{_, _, path} ->
case :beam_lib.info(path) do
info when is_list(info) ->
alt_module = Keyword.get(info, :module)
exports = exports_for(alt_module)
if {function, arity} in exports do
". Did you mean:\n\n * " <>
Exception.format_mfa(alt_module, function, arity) <> "\n"
else
". Did you mean #{inspect alt_module}?"
end
_ -> ""
end
_ -> ""
end
"function " <> Exception.format_mfa(module, function, arity) <>
" is undefined (module #{inspect module} is not available)"
" is undefined (module #{inspect module} is not available)" <>
suffix
end

def message(%{reason: :"function not exported", module: module, function: function, arity: arity, exports: exports}) do
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7 changes: 7 additions & 0 deletions lib/elixir/test/elixir/exception_test.exs
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Expand Up @@ -387,6 +387,13 @@ defmodule ExceptionTest do
* get_cookie/0
* set_cookie/2
"""
assert %UndefinedFunctionError{module: Genserver, function: :start_link, arity: 3} |> message == """
function Genserver.start_link/3 is undefined (module Genserver is not available). Did you mean:

* GenServer.start_link/3
"""
assert %UndefinedFunctionError{module: Genserver, function: :start_link, arity: 1} |> message ==
"function Genserver.start_link/1 is undefined (module Genserver is not available). Did you mean GenServer?"
end

test "UndefinedFunctionError when the mfa is a macro but require wasn't called" do
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8 changes: 6 additions & 2 deletions lib/mix/lib/mix/tasks/xref.ex
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Expand Up @@ -240,8 +240,12 @@ defmodule Mix.Tasks.Xref do
end

defp format_warning(file, {lines, :unknown_module, module, function, arity, _}) do
["function ", Exception.format_mfa(module, function, arity),
" is undefined (module #{inspect module} is not available)\n" | format_file_lines(file, lines)]
message =
[module: module, function: function, arity: arity, reason: :"module could not be loaded"]
|> UndefinedFunctionError.exception()
|> Exception.message()

[message, "\n" | format_file_lines(file, lines)]
end

defp format_file_lines(file, [line]) do
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15 changes: 15 additions & 0 deletions lib/mix/test/mix/tasks/xref_test.exs
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Expand Up @@ -63,6 +63,21 @@ defmodule Mix.Tasks.XrefTest do
"""
end

test "warnings: reports module case mismatch" do
assert_warnings """
defmodule A do
def a, do: Genserver.start_link(A, [], [])
end
""", """
warning: function Genserver.start_link/3 is undefined (module Genserver is not available). Did you mean:

* GenServer.start_link/3

lib/a.ex:2

"""
end

test "warnings: reports missing captures" do
assert_warnings """
defmodule A do
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