grammar attempts to load "impossible" rule

[asottile]

this file (t.jac) causes the grammar to recurse into a rule named "impossible" which does not exist:

f'''

the grammar source is here:

jac-vscode/syntaxes/jac.tmLanguage.json

Line 1541 in 468a529

"include": "#impossible"

(that include goes nowhere though, there's no rule repository named impossible)

in babi this results in a crash (via babi-textmate-demo t.jac):

$ babi-textmate-demo t.jac 

Traceback (most recent call last):
  File "/home/asottile/opt/venv/bin/babi-textmate-demo", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/textmate_demo.py", line 66, in main
    return _highlight_output(theme, compiler, args.filename)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/textmate_demo.py", line 44, in _highlight_output
    state, regions = highlight_line(compiler, state, line, first_line)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 748, in highlight_line
    search_res = state.cur.rule.search(
                 ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 362, in search
    return _do_regset(idx, match, self, compiler, state, pos)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 331, in _do_regset
    target_rule = compiler.compile_rule(rule.u_rules[idx])
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 632, in compile_rule
    ret = self._c_rules[rule] = self._compile_rule(grammar, rule)
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 600, in _compile_rule
    regs, rules = self._patterns(grammar, rule.patterns)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 564, in _patterns_
    tmp_regs, tmp_rules = self._include(
                          ^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 546, in _include_
    return self._patterns(grammar, (repository[s[1:]],))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 570, in _patterns_
    tmp_regs, tmp_rules = self._patterns(grammar, rule.patterns)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 564, in _patterns_
    tmp_regs, tmp_rules = self._include(
                          ^^^^^^^^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/highlight.py", line 546, in _include_
    return self._patterns(grammar, (repository[s[1:]],))
                                    ~~~~~~~~~~^^^^^^^
  File "/home/asottile/opt/venv/lib/python3.12/site-packages/babi/fdict.py", line 45, in __getitem__
    raise KeyError(key)
KeyError: 'impossible'

[RedCMD]

technically babi-textmate should gracefully handle missing includes: just same as VSCode, TextMate 2.0 and GitHub etc

I don't understand why the rule is there
I doubt it did anything useful

possibly the rule did exist at one point
but is long gone

[asottile]

it could accept invalid grammars but I don't think that's a good idea