The fix that landed in #6557 was unfortunately the wrong subset of the
work I had been doing locally, and users of the attached bugs are still
reporting problems with Terraform v0.6.16.
At the very last step, I attempted to scope down both the failing test
and the implementation to their bare essentials, but ended up with a
test that did not exercise the root of the problem and a subset of the
implementation that was insufficient for a full bugfix.
The key thing I removed from the test was a _referencing output_ for the
module, which is what breaks down the #6557 solution.
I've re-tested the examples in #5440 and #3268 to verify this solution
does indeed solve the problem.
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.
These tests demonstrates a problem where the types to a module input are
not checked. For example, if a module - inner - defines a variable
"should_be_a_map" as a map, or with a default variable of map, we do not
fail if the user sets the variable value in the outer module to a string
value. This is also a problem in nested modules.
The implementation changes add a type checking step into the graph
evaluation process to ensure invalid types are not passed.
