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fix(swift): scan expression identifiers by UAX 31 XID_Continue - #3547
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The Swift expression parser decided which characters belong to a path,
function name, argument name or keyword with Character.isLetter and
isNumber. isNumber also accepts characters such as ½ and ², so Swift
parsed ${a½} as a path and ${add(½: 1)} as a call, while web_core, Dart
and Python reject both.
Scan by UAX 31 XID_Continue instead, like the other engines: a
character counts when all of its scalars are XID_Continue. Paths still
allow /, . and -.
Add shared cases to conformance/core/expressions.yaml for non-ASCII
paths, function names, argument names and keyword boundaries, and for
rejecting ½. They pass in the Swift, web_core, Dart and Python runners.
Part of a2ui-project#2838
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This pull request updates the Swift expression parser to support non-ASCII characters in paths, identifiers, and function/argument names using the UAX #31 XID_Continue standard, and adds corresponding conformance tests. Feedback on the changes suggests optimizing the isIdentifierCharacter method with a fast-path check for ASCII characters to prevent potential performance overhead from Unicode scalar property lookups.
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…ombining marks A Swift Character is a grapheme cluster, so a '/', '.' or '-' followed by a combining mark such as U+0301 arrives as one Character and was rejected, while web_core, Dart and Python accept it. Check path characters scalar by scalar, fold the scan predicates into the while-let conditions, and flatten matchesKeyword with a guard. Add shared conformance cases for combining marks (including right after a slash or dot), a supplementary-plane XID_Continue character, and a supplementary-plane character outside XID_Continue.
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Description
The Swift expression parser used
Character.isLetter || isNumberto scan paths, function names, argument names and the character aftertrue/false/null.isNumberalso accepts characters such as½and², so Swift parsed${a½}as a path and${add(½: 1)}as a call. web_core, Dart and Python scan by UAX 31XID_Continueand reject both.This PR makes Swift scan by
XID_Continuetoo: aCharactercounts when all of its scalars areXID_Continue. Paths still allow/,.and-, and are also checked per scalar, because a SwiftCharacteris a grapheme cluster and a separator followed by a combining mark such as U+0301 arrives as oneCharacter. Like the other parsers, it does not requireXID_Startfor the first character.It also adds eight shared cases to
conformance/core/expressions.yaml: non-ASCII path, function and argument names, a keyword followed byß, combining marks (including right after/and.) and the supplementary-plane𠮷are accepted, and½in a path, after a keyword and in an argument name, and🚀in a path are rejected.Testing:
swift testpasses (685 tests; the only issues are the 4 existing known issues inAdapterConformanceTests). Without the parser change, the three½cases and the combining-mark path case fail.expression_parser.conformance.test.js), Dart (expressions_conformance_test.dart) and Python (test_conformance.py) pass the new cases without changes.swift-format lint --strictis clean.Part of #2838
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