A bit of clean-up on io.lua

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extra : rebase_source : 155b4170270d978c7a4577e25c505f6a494f96a6
Expose target name builder for extension modules

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extra : rebase_source : 1b5dedf09b3c486ee521da794ac69536c8e1fbaf
Show name of action in the missing field error message

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extra : rebase_source : ade279873e4a79ddfcf59e99c9a24a8ae4393726