LibCST 0.4.0 Release - 2022-01-12

This release contains a new parsing infrastructure that is turned off by default. You
can enable it by setting the LIBCST_PARSER_TYPE environment variable to native
before parsing an input with the usual LibCST APIs. Parsing Python 3.10 documents is
only supported in this new mode.

Note: the new parser is built as a native extension, so LibCST will ship with binary
wheels from now on.

Added

• Implement a Python PEG parser in Rust by @zsol in #566
• implement PEP-654: except* by @zsol in #571
• Implement PEP-634 - Match statement by @zsol in #568
• Add instructions to codegen test failures by @stroxler in #582
• Support Parenthesized With Statements by @stroxler in #584
• Support relative imports in AddImportsVisitor by @martindemello in #585
• Codemod for PEP 484 Assign w / type comments -> PEP 526 AnnAssign by @stroxler in #594

Updated

• Update license headers by @zsol in #560
• Use precise signature matching when inserting function type annotations by @martindemello in #591