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raise compile error when inspect protocol options don't match struct #11801

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Merged
merged 2 commits into from
May 8, 2022
Merged

raise compile error when inspect protocol options don't match struct #11801

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952ce9b
raise compile error when inspect protocol options don't match struct
jwharrow May 6, 2022
dc203bf
change CompileError to ArgumentError. Update error message
jwharrow May 6, 2022
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12 changes: 12 additions & 0 deletions lib/elixir/lib/inspect.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -455,6 +455,9 @@ defimpl Inspect, for: Any do
only = Keyword.get(options, :only, fields)
except = Keyword.get(options, :except, [])

:ok = validate_option(only, fields, module, __CALLER__)
:ok = validate_option(except, fields, module, __CALLER__)

filtered_fields =
fields
|> Enum.reject(&(&1 in except))
Expand All @@ -478,6 +481,15 @@ defimpl Inspect, for: Any do
end
end

defp validate_option(option_list, fields, module, caller) do
if not Enum.empty?(option_list -- fields) do
description = "When deriving inspect protocol of #{module}, values must match struct fields"
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Suggested change
description = "When deriving inspect protocol of #{module}, values must match struct fields"
description = "unknown fields #{inspect(...)} given when deriving the Inspect protocol for #{inspect(module)}. :only and :except values must match struct fields"

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Originally i had something like this, but the problem is that inspect/1 is not yet available. I looked at some of the erlang :io_lib libraries and at :erlang.display/1 but those weren't exactly right. I'll take another stab at it using Enum.join/2 which will trim off the :s

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Oh, we unimport inspect to avoid conflcit. You can use Kernel.inspect(module) instead. :)

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Oh, we unimport inspect to avoid conflcit. You can use Kernel.inspect(module) instead. :)

Thanks! it's wild how tricky it gets when i think I'm missing one function :)
updated: dc203bf

raise CompileError, file: caller.file, line: caller.line, description: description
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This can be a regular ArgumentError :) CompileError is typically only raise from within the compiler.

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It would also be nice to show which fields do not match. Perhaps convert the if to a case and pattern match accordingly.

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updated dc203bf

end

:ok
end

def inspect(%module{} = struct, opts) do
try do
module.__struct__()
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24 changes: 24 additions & 0 deletions lib/elixir/test/elixir/inspect_test.exs
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Original file line number Diff line number Diff line change
Expand Up @@ -694,6 +694,30 @@ defmodule Inspect.MapTest do
"%Inspect.MapTest.StructWithAllFieldsInOnlyOption{\n a: 1,\n b: 2\n}"
end

test "struct missing fields in the :only option" do
message =
~r"When deriving inspect protocol of Elixir.Inspect.MapTest.StructMissingFieldsInOnlyOption, values must match struct fields"

assert_raise CompileError, message, fn ->
defmodule StructMissingFieldsInOnlyOption do
@derive {Inspect, only: [:c]}
defstruct [:a, :b]
end
end
end

test "struct missing fields in the :except option" do
message =
~r"When deriving inspect protocol of Elixir.Inspect.MapTest.StructMissingFieldsInExceptOption, values must match struct fields"

assert_raise CompileError, message, fn ->
defmodule StructMissingFieldsInExceptOption do
@derive {Inspect, except: [:c]}
defstruct [:a, :b]
end
end
end

defmodule StructWithExceptOption do
@derive {Inspect, except: [:b, :c]}
defstruct [:a, :b, :c, :d]
Expand Down