unwrapping contents of in message and wrapping contents of out message about stratisd HOT 5 CLOSED

There is a question of types. Looking at the Python version that does the wrapping, and imagining the same actions...

• A simple type is easy, I think. |_:T| |x: u16| MessageItem::UInt16(x) should do it, assuming a signature of 'q' The type is obvious.
• An array is tricky, maybe. We have to take a function arg, the function for handling the array elements. So, something like: |func| |vec: Vec<T>| MessageItem::Array(<calling func on each element>). What is the type of func? T -> MessageItem, presumably.

The parameter type of the inner functiion will vary. Ultimately, it will depend on the signature.
But it will end up being applied to something of the correct type.

Of course, whether or not there is a Rust parser that will do the trick is not yet known.

There is not an obviously better way, though.

Probably the best way to use such a function would be to define methods that simply returned the message values as a tuple of native Rust types.

Then define a generic function that takes a return message and the arguments, transforms the arguments, and appends them to the message before returning.

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rust peg would work just fine: https://github.com/kevinmehall/rust-peg

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This blog article gives a long list of other: http://smallcultfollowing.com/babysteps/blog/2015/09/14/lalrpop/.

• nom is definitely overkill
• oak looks thorough and is embeddable as an extension, which is nice
• nailgun is not ready, says the developer
• peggler, ditto
• combine looks promising
• LALRPOP might be excessive
• racc is not ready
• lemon_rust doesn't look bad either

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Well, it turns out that the CLI approach is absolutely impossible, because it would require Rust to have dependent types, which it doesn't.

It also turns out that the dbus-rs has functionality that is supposed to make this much easier, but it seems to prevent our distinguishing between missing arguments and arguments with the wrong type.
See: diwic/dbus-rs#51.

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Closed by #76.

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