VCC now has type-driven properties
phk at phk.freebsd.dk
Tue Jun 4 07:16:37 UTC 2019
As you may have spotted in recent commits and notably 2962375b4ed80e,
VCC now has type driven properties.
This means that subexpressions of a given type can express that
property, no matter how we got to it in the first place.
If we defined a type driven property from DURATION called
"foobar" it would be possible to write:
set beresp.http.qqq = (beresp.ttl + 4m).foobar;
Right now, this has not changed the syntax of VCL, we're still 4.1
because the only use is for the storage.*.* variables for which
the syntax remains the exact same.
If we want to, some of the stuff in vmod_std can now be made
slightly more intutive syntax-wise:
BACKEND.healthy -> BOOL
IP.port -> INT
Note that these are *properties* `EXPR.name` they do not take any
VCL arguments beside the expression they work on. (The C-implementation
can of course take other args, like VRT_CTX)
It would not be too hard to also do *methods* `EXPR.func(args)`,
so that one could also do things like:
set bereq.http.qqq = beres.ttl.format("%.3f")
But I am not going to implement that until we have more convincing
use cases than that.
A bit more work would be to allow vmods to implement type driven
properties and methods, but again: Convincing use cases ?.
Proposals and ideas are welcome.
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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