The expression upgrade functionality mostly ignores comments because in
the old language the syntax prevented comments from appearing in the
middle of expressions, but there was one exception: object expressions.
Because HCL 1 used ObjectType both for blocks and for object expressions,
that is the one situation where something we consider to be an expression
could have inline attached comments in the old language.
We migrate these here so we don't lose these comments that don't appear
anywhere else. Other comments get gathered up into a general comments
set maintained inside the analysis object and so will be printed out as
required _between_ expressions, just as they did before.
Aside from the two special meta-arguments "connection" and "provisioner"
this is just our standard mapping from schema to conversion rules, using
the provisioner's configuration schema.
This is a temporary implementation of these rules just so that these can
be passed through verbatim (rather than generating an error) while we
do testing of other features.
A subsequent commit will finish these with their own custom rulesets.
Some further rules are required here to deal with the meta-arguments we
accept inside these blocks, but this is good enough to pass through most
module blocks using the standard attribute-expression-based mapping.
The old parser was forgiving in allowing the use of block syntax where a
map attribute was expected, but the new parser is not (in order to allow
for dynamic map keys, for expressions, etc) and so the upgrade tool must
fix these to use attribute syntax.
This covers all of the expression node types in HIL's AST, and also
includes initial support for some of our top-level blocks so that we can
easily test that.
The initial implementations of the "variable" and "output" blocks are
pretty redundant and messy, so we can hopefully improve on these in a
later pass.
This package will do all of its work in-memory so that it can avoid making
partial updates and then failing, so we need to be able to load the
sources files from a particular directory into memory.
The upgrade process isn't idempotent, so we also attempt to detect
heuristically whether an upgrade has already been performed (can parse
with the new parser and has a version constraint that prevents versions
earlier than 0.12) so that the CLI tool that will eventually wrap this
will be able to produce a warning and prompt for confirmation in that
case.
Martin Atkins