All of the other subdivisions of a block were already nodes, but we'd
represented the labels as an undifferentiated set of nodes belonging
directly to the block's child node list.
Now that we support replacing the labels in the public API, that's a good
excuse to refactor this slightly to make the labels their own node. As
well as being consistent with everything else in Block, this also makes
it easier to implement the Block.SetLabels operation because we can
just change the children of the labels node, rather than having to
carefully identify and extract the individual child nodes of the block
that happen to represent labels.
Internally this models the labels in a similar sort of way as the content
of a body, although we've kept the public API directly on the Block type
here because that's a more straightforward model for the use-cases we
currently know and matches better with the API of hcl.Block. This is just
an internal change for consistency.
I also added a few tests for having comments interspersed with labels
while I was here, because that helped to better exercise the new
parseBlockLabels function.
While implementing Block.SetLabels(), I found a new hclwrite parser bug.
The NewBlock() method records positions of TokenOBrace / TokenCBrace.
Nevertheless when generating blocks via hclwrite.ParseConfig(),
they were not recorded.
The position of TokenOBrace is needed for Block.SetLabels(),
so I also fixed this existing bug.
Although our underlying parse tree retains all of the token content, it
doesn't necessarily retain all of the spacing information under editing,
and so formatting on save ensures that we'll produce a canonical result
even if some edits have been applied that have changed the expected
alignment of objects, etc.
For now, this is the only way to set an attribute, and so attributes can
only be set to literal values.
Later this will be generalized so that this is just a helper wrapper
around a "SetAttribute" method that just uses a given expression, which
then helps by constructing the expression from the value first.
The original prototype of hclwrite tried to track both the tokens and
the AST as two parallel data structures. This quickly exploded in
complexity, leading to lots of messy code to manage keeping those two
structures in sync.
This new approach melds the two structures together, creating first a
physical token tree (made of "node" objects, and hidden from the caller)
and then attaching the AST nodes to that token tree as additional sidecar
data.
The result is much easier to work with, leading to less code in the parser
and considerably less complex data structures in the parser's tests.
This commit is enough to reach feature parity with the previous prototype,
but it remains a prototype. With a more usable foundation, we'll evolve
this into a more complete implementation in subsequent commits.
This will allow for use-cases such as renaming a variable (changing the
content of the first token) and replacing variable references with
constant values that they evaluate to for debug purposes.
This is a super-invasive update since the "zcl" package in particular
is referenced all over.
There are probably still a few zcl references hanging around in comments,
etc but this takes care of most of it.
The main "zcl" package requires a bit more care because of how many
callers it has and because of its two subpackages, so we'll take care
of that one separately.
