Lexer start of line is false only for Mode::Expression

[dhruvmanila]

Summary

This PR fixes the bug in the lexer where the Mode::Ipython wasn't being considered when initializing the soft keyword transformer which wraps the lexer. This means that if the source code starts with either match or type keyword, then the keywords were being considered as name tokens instead. For example,

match foo:
    case bar:
        pass

This would transform the match keyword into an identifier if the mode is Ipython.

The fix is to reverse the condition in the soft keyword initializer so that any new modes are by default considered as the lexer being at start of line.

Test Plan

Add a new test case for Mode::Ipython and verify the snapshot.

fixes: #8870

[dhruvmanila]

Current dependencies on/for this PR:

• main
  • PR Lexer start of line is false only for Mode::Expression #8880 👈

This stack of pull requests is managed by Graphite.

[charliermarsh]

Wow, that's devious

[github-actions]

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