v0.2.6

0.2.6 - alpha - 2026-01-31

Breaking Changes

• when putting source instead of an FST or AST node directly as a slice to an expression, if the source is a delimited sequence then it will always be put as one node and not unpacked, previous behavior of .put_slice('[1, 2, 3]') being put as a slice of three distinct elements can be selected by passing one=None

Added

• coercion expanded greatly, can now put more nodes which are not the exact type but that "should work", e.g. TupleFST.elts = MatchSequenceFST.patterns.copy()
  • pattern, arguments, arg, alias, withitem, TypeVar and TypeVarTuple to expr
  • custom slice types _Assign_targets, _decorator_list, _arglikes, _comprehension_ifs, _aliases, _withitems and _type_params to Tuple, List or Set
  • all sequence types, custom and standard, to custom slice types
  • all expressions and custom slice types to pattern
  • keyword to arguments
• FST.as_(mode) for explicit coercion directly to mode (which can be an explicit type[AST] or a parse mode)
• FST(FST, mode) for constructor default non-destructive coerce copy from other FST node, a-la list(other_list) is not other_list
• FST(AST, mode) and FST.fromast(AST, type[AST] or mode) can use the new coercion to convert AST
  • with these changes, FST(x[, mode]) now works like list(x) in that it converts source, AST or FST to the given mode FST if possible, or just AN FST if mode not provided
• put slice as one=True for _Assign_targets, _decorator_list, _arglikes, _comprehension_ifs, _aliases, _withitems, _type_params and _expr_arglikes
• prescribed slicing for MatchClass.patterns
• prescribed slicing for arguments._all, e.g. FunctionDefFST.args[x:y] = 'a: int, /, b=c'
• unpar('invalid') can remove delimiters from List, Set, Dict, MatchMapping, ListComp, SetComp, DictComp and GeneratorExp, if needed for some reason

Changed

• FST.dump() returns self when not returning str or lines and those are now specified with out='str' or out='lines'
• concretized behavior of put slice with one=True for custom special slices, will not put multiple elements now in this mode when one requested
• parse_withitem('x,') now parses to singleton Tuple withitem instead of single Name withitem with trailing comma, makes more sense
• allow put Starred to value field of Expr, Return, AnnAssign and Yield even though not compilable, for consistency, our metric is parsability, not compilability
• REMOVED norm_put option as was too annoying to maintain everywhere needed for the little good it did, norm_self and norm_get remain
• improved put multiline slice aesthetics, specifically better needs-own-line detection and keeping line comment on pre-insert element line instead of moving it
• parse withitem and _withitems no longer accept single unparenthesized Yield, NamedExpr or Tuple as a convenience, causes too many problems downstream
• empty arguments now always have a location, having potentially zero-length arguments is less ugly than having arguments with no location
• Dict and MatchMapping slice views dereferenced with a single index will now return a view of that single key:value pair instead of raising

Fixed

• fixed comprehension_ifs and _arglikes coercions where unparenthesized tuple needed to be parenthesized
• FST.dump() will no longer output trailing whitespace on lines when the line is completely empty, better for tests
• fixed delimit of whole node at root when degenerate last line has line continuation without trailing newline
• fixed parse location correction of multiline unparenthesized tuple with group parenthesized first and / or last elements
• fixed parse of unparenthesized tuple with trailing comma to _Assign_targets
• don't accept Starred node for a withitem, _withitems normal or _comprehension_ifs coerce
• don't try to parse *starred = value as TypeVarTuple in place of Assign on py < 3.13
• allow put Starred to TypeVarTuple.default_value
• fixed parse withitem of a solo GeneratorExp
• will not parenthesize arg or arguments if putting multiline to a Lambda but instead parenthesize the Lambda
• will not parenthesize multiline withitem put to With.items with existing items but rather the whole items field
• fixed unpar(node=True) node if first and or last elements are parenthesized