Breaking change in the header! macro not documented

[mhristache]

I updated to 0.3.15 and my code is now failing due to changes in header! macro:

src/lib.rs:250:43: 250:44 error: unexpected end of macro invocation
src/lib.rs:250 header!{ (TenantId, "TenantId") => [String] }

This is most likely due to commits efd6c96 and a27e681 which are not listed as breaking changes.

With the new header! implementation It seems I must also add a dummy test function when implementing the header which is, IMHO, an unnecessary complication and makes the header! macro harder to use. E.g. for my example above:

header!{ (TenantId, "TenantId") => [String] test1 {} }

Is this the intended behaviour?

[mhristache]

cc @pyfisch as he is the one which added the commits mentioned above

[seanmonstar]

I'd say this was an oversight. We shouldn't have made a breaking change. A reason making it easier to miss is that all of our internal uses do include a test function.

I think part of a fix so as to make sure we don't break the exported header! macro in the future is to use it in the examples/ directory.

[pyfisch]

Sorry, I forgot to add BREAKING CHANGE warnings to the commits. The current behaviour is the intended behaviour.

It is impossible (I think so) to add optional parts to a macro without duplicating the definition, since every header should have tests this is no problem for the core of hyper. I think also external headers should have tests, they have been proven useful to discover bugs in header parsing and formatting inside hyper. Using the test_header! macro makes it really easy to test headers but it requires to be inside the header! macro. #489 will allow external code to use it in tests, but you can also write your own test functions inside the header! macro test section.

[seanmonstar]

@pyfisch can't the macro be written such that without the test pattern, a dummy empty one is created?

macro_rules! header {
  ( $foo:ty $bar:ty ) => ( header! { $foo $bar test_dummy {} } )
}

[pyfisch]

@seanmonstar yes this will probably work.

[pyfisch]

There is one problem: you can't have multiple headers with no tests in one module, because there will be multiple test_dummy modules.

[mhristache]

I guess you can append the identto the name of the test function as the ident has to be unique anyhow.

[pyfisch]

Joining identifiers like function or module names does not work.

[reem]

grumbles something about macros not being hygienic even though they are supposed to be