The following expression caused a panic in hclwrite:
a = foo.*
This was due to the unusual dotted form of a full splat (where the splat
operator is at the end of the expression) being generated with an
invalid source range. In the full splat case, the end of the range was
uninitialized, which caused the token slice to be empty, and thus the
panic.
This commit fixes the bug, adds test coverage, and includes some bonus
tests for other splat expression cases.
HCL uses grapheme cluster segmentation to produce accurate "column"
indications in diagnostic messages and other human-oriented source
location information. Each new major version of Unicode introduces new
codepoints, some of which are defined to combine with other codepoints to
produce a single visible character (grapheme cluster).
We were previously using the rules from Unicode 9.0.0. This change
switches to using the segmentation rules from Unicode 12.0.0, which is
the latest version at the time of this commit and is also the version of
Unicode used for other purposes by the Go 1.14 runtime.
HCL does not use text segmentation results for any purpose that would
affect the meaning of decoded data extracted from HCL files, so this
change will only affect the human-oriented source positions generated for
files containing characters that were newly-introduced in Unicode 10, 11,
or 12. (Machine-oriented uses of source location information are based on
byte offsets and not affected by text segmentation.)
To allow easir adaptation of data already serialized as JSON, HCL native
syntax allows both equals signs _and_ colons for object constructors.
This was already implemented, but not reflected in the pseudo-BNF in
the specification.
Most of the time, the standard expression decoding built in to HCL is
sufficient. Sometimes though, it's useful to be able to customize the
decoding of certain arguments where the application intends to use them
in a very specific way, such as in static analysis.
This extension is an approximate analog of gohcl's support for decoding
into an hcl.Expression, allowing hcldec-based applications and
applications with custom functions to similarly capture and manipulate
the physical expressions used in arguments, rather than their values.
This includes one example use-case: the typeexpr extension now includes
a cty.Function called ConvertFunc that takes a type expression as its
second argument. A type expression is not evaluatable in the usual sense,
but thanks to cty capsule types we _can_ produce a cty.Value from one
and then make use of it inside the function implementation, without
exposing this custom type to the broader language:
convert(["foo"], set(string))
This mechanism is intentionally restricted only to "argument-like"
locations where there is a specific type we are attempting to decode into.
For now, that's hcldec AttrSpec/BlockAttrsSpec -- analogous to gohcl
decoding into hcl.Expression -- and in arguments to functions.
Some HCL callers make the (reasonable) assumption that the overall source
range of an expression will be a superset of all of the ranges of its
child expressions, for purposes such as extraction of source code
snippets, parse tree annotation in hclwrite, text editor analysis
functions like "go to reference", etc.
The IndexExpr type was not previously honoring that assumption, since its
source range was placed around only the bracket portion. That is a good
region to use when reporting errors relating to the index operation, but
it is not a faithful representation of the full extent of the expression.
In order to meet both of these requirements at once, IndexExpr now has
both SrcRange covering the entire expression and BracketRange covering
the index part delimited by brackets. We can then use BracketRange in
our error messages but return SrcRange as the result of the general
Range method that is common to all expression types.
In previous versions we had some bugs around template sequence escapes.
These tests show that they no longer seem to be present, and should
hopefully avoid them regressing in future.
Our error message for the ambiguous situation recommends doing this, but
the parser didn't actually previously allow it. Now we'll accept the form
that the error message recommends.
As before, we also accept a template with an interpolation sequence as
a disambiguation, but the error message doesn't mention that because it's
no longer idiomatic to use an inline string template containing just a
single interpolation sequence.
