HCL uses a number of upstream libraries that implement algorithms defined
in Unicode. This commit is updating those libraries all to versions that
have Unicode 13 support.
The main implication of this for HCL directly is that when it returns
column numbers in source locations it will count characters using the
Unicode 13 definition of "character", which includes various new
multi-codeunit characters added in Unicode 13.
These new version dependencies will also make Unicode 13 support available
for other functionality that HCL callers might use, such as the stdlib
functions in upstream cty, even though HCL itself does not directly use
those.
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.)
Martin Atkins