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Don't parse a character property containing a backslash #301

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Merged
merged 1 commit into from
Apr 19, 2022
Merged

Don't parse a character property containing a backslash #301

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8 changes: 8 additions & 0 deletions Sources/_RegexParser/Regex/Parse/LexicalAnalysis.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1176,6 +1176,14 @@ extension Source {
// character property name anyway, and it's nice not to have diverging
// logic for these cases.
return true
case "\\":
// An escape sequence, which may include e.g '\Q :] \E'. ICU bails here
// for all its known escape sequences (e.g '\a', '\e' '\f', ...). It
// seems character class escapes e.g '\d' are excluded, however it's not
// clear that is intentional. Let's apply the rule for any escape, as a
// backslash would never be a valid character property name, and we can
// diagnose any invalid escapes when parsing as a character class.
return true
default:
// We may want to handle other metacharacters here, e.g '{', '(', ')',
// as they're not valid character property names. However for now
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21 changes: 20 additions & 1 deletion Tests/RegexTests/ParseTests.swift
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Expand Up @@ -503,6 +503,25 @@ extension RegexTests {
parseTest(#"[[:{]]"#, charClass(charClass(":", "{")))
parseTest(#"[[:}:]]"#, charClass(charClass(":", "}", ":")))

parseTest(
#"[:[:space:]:]"#,
charClass(":", posixProp_m(.binary(.whitespace)), ":")
)
parseTest(
#"[:a[:space:]b:]"#,
charClass(":", "a", posixProp_m(.binary(.whitespace)), "b", ":")
)

// ICU parses a custom character class if it sees any of its known escape
// sequences in a POSIX character property (though it appears to exclude
// character class escapes e.g '\d'). We do so for any escape sequence as
// '\' is not a valid character property character.
parseTest(#"[:\Q:]\E]"#, charClass(":", quote_m(":]")))
parseTest(#"[:\a:]"#, charClass(":", atom_m(.escaped(.alarm)), ":"))
parseTest(#"[:\d:]"#, charClass(":", atom_m(.escaped(.decimalDigit)), ":"))
parseTest(#"[:\\:]"#, charClass(":", "\\", ":"))
parseTest(#"[:\:]"#, charClass(":", ":"))

parseTest(
#"\D\S\W"#,
concat(
Expand Down Expand Up @@ -2319,7 +2338,7 @@ extension RegexTests {
diagnosticTest(#"\p{x=y}"#, .unknownProperty(key: "x", value: "y"))
diagnosticTest(#"\p{aaa(b)}"#, .unknownProperty(key: nil, value: "aaa(b)"))
diagnosticTest("[[:a():]]", .unknownProperty(key: nil, value: "a()"))
diagnosticTest(#"\p{aaa\p{b}}"#, .unknownProperty(key: nil, value: #"aaa\p{b"#))
diagnosticTest(#"\p{aaa\p{b}}"#, .unknownProperty(key: nil, value: "aaa"))
diagnosticTest(#"[[:{:]]"#, .unknownProperty(key: nil, value: "{"))

// MARK: Matching options
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