FIX: string length expression

[klauer]

Context

Closes #70

Building on @engineerjoe440 's branch

Changes

Continuous Integration

• CI will only test on Python 3.9+ going forward.
  • 3.7 and 3.8 will be considered unsupported - but some/most of blark may still work on them

Grammar

• Added bracketed_expression used solely for string lengths as in STRING[255]
• Grammar change - terminal STRING_TYPE -> is now a rule string_type_specification as it must support expressions for length and not just simple integers/constants/terminals
• string_spec_length added to support both flavors of string type declaration lengths STRING[255] and STRING(255)

Dataclasses

• Adjusted dataclasses to support the grammar changes
• SimpleSpecification gets a bit more complicated as its type is no longer just a string Token

Test suite

• Added a bunch of TwinCAT-approved string declarations, which went beyond what I expected to compile
• Added some TwinCAT disapproved string declarations and commented them out, but perhaps they should be added and marked as strict xfail. blark might be more permissive here than it should be, though.

[codecov-commenter]

Codecov Report

Merging #72 (39c32d0) into master (1e09713) will increase coverage by 0.2%.
The diff coverage is 90.0%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master     #72     +/-   ##
========================================
+ Coverage    72.2%   72.5%   +0.2%     
========================================
  Files          18      18             
  Lines        3816    3835     +19     
========================================
+ Hits         2758    2783     +25     
+ Misses       1058    1052      -6     

Impacted Files	Coverage Δ
blark/tests/conftest.py	83.6% <0.0%> (ø)
blark/transform.py	98.9% <92.0%> (-0.2%)	⬇️
blark/tests/test_transformer.py	94.5% <100.0%> (+0.1%)	⬆️

... and 2 files with indirect coverage changes

[klauer]

@engineerjoe440 mind taking a look before I merge this?

[engineerjoe440]

The changes all look good and seem clear, to me. I won't have a chance to run this up in test until Friday of this week (at the earliest), because I'm helping with a youth conference. But I still think this looks nice! 😃

[klauer]

Ah, no rush - blark is low priority for all involved. :) If you're willing to take a look later I'm happy to wait to merge. I'll be out for about a week starting tomorrow, also.

Have fun with the conference!

[engineerjoe440]

Thank you! I'll give it a run-down on Friday. Can't wait!

[engineerjoe440]

Just gave this a quick run and it's looking pretty nice! Thank you, again!