This changes the representation of maps in the interpolator from the
dotted flatmap form of a string variable named "var.variablename.key"
per map element to use native HIL maps instead.
This involves porting some of the interpolation functions in order to
keep the tests green, and adding support for map outputs.
There is one backwards incompatibility: as a result of an implementation
detail of maps, one could access an indexed map variable using the
syntax "${var.variablename.key}".
This is no longer possible - instead HIL native syntax -
"${var.variablename["key"]}" must be used. This was previously
documented, (though not heavily used) so it must be noted as a backward
compatibility issue for Terraform 0.7.
Had to handle a lot of implicit leaning on a few properties of the old
representation:
* Old representation allowed plain strings to be treated as lists
without problem (i.e. shoved into strings.Split), now strings need to
be checked whether they are a list before they are treated as one
(i.e. shoved into StringList(s).Slice()).
* Tested behavior of 0 and 1 length lists in formatlist() was a side
effect of the representation. Needs to be special cased now to
maintain the behavior.
* Found a pretty old context test failure that was wrong in several
different ways. It's covered by TestContext2Apply_multiVar so I
removed it.
This is the initial pure "all tests passing without a diff" stage. The
plan is to change the internal representation of StringList to include a
suffix delimiter, which will allow us to recognize empty and
single-element lists.
James Nugent