Add assertions to the DSL #154
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| case .startOfSubject: fatalError("Not yet supported") | ||
| case .endOfSubjectBeforeNewline: fatalError("Not yet supported") | ||
| case .endOfSubject: fatalError("Not yet supported") | ||
| case .firstMatchingPositionInSubject: fatalError("Not yet supported") | ||
| case .textSegmentBoundary: return .notTextSegment | ||
| case .startOfLine: fatalError("Not yet supported") | ||
| case .endOfLine: fatalError("Not yet supported") |
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We don't currently have a representation for these negated assertions in the AST, since things like notWordBoundary are represented as specific individual cases. These fatalError'd cases don't have a regex literal equivalent, but would be available if we use an API like Assertion.wordBoundary.inverted.
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Why are we going to an AST here?
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DSLTree tracks assertions using AST.Atom.AssertionKind right now.
| case endOfLine | ||
| case wordBoundary | ||
| case lookahead(DSLTree.Node) | ||
| } |
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Is this meant to be a listing of built-in assertions, or are each of these the kinds of assertions someone could write?
| case .startOfSubject: fatalError("Not yet supported") | ||
| case .endOfSubjectBeforeNewline: fatalError("Not yet supported") | ||
| case .endOfSubject: fatalError("Not yet supported") | ||
| case .firstMatchingPositionInSubject: fatalError("Not yet supported") | ||
| case .textSegmentBoundary: return .notTextSegment | ||
| case .startOfLine: fatalError("Not yet supported") | ||
| case .endOfLine: fatalError("Not yet supported") |
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Why are we going to an AST here?
Tests/RegexTests/RegexDSLTests.swift
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| ("aaaaabc", nil), | ||
| captureType: Substring.self, ==) | ||
| { | ||
| Assertion.startOfLine |
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Many of the built-in ones are more commonly called "anchors", which might be worth considering too.
`lookahead` is moved to a free function, since it isn't an anchor like the others
natecook1000
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| var result = self | ||
| result.isInverted.toggle() | ||
| return result | ||
| } |
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Would we want an isInverted then? Also, is it the case that all anchors can be inverted?
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I don't know that a property makes sense if we aren't going to also expose kind as public API, and the purpose of this is just to carry the regex wrapper.
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Everything in this PR can be inverted, just need a little more plumbing. If we want to provide the functionality of a "reset match" assertion, that could just be a separate function or type, since it isn't an anchor anyway.
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natecook1000
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| } | ||
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| public func lookahead<R: RegexProtocol>( | ||
| isNegative: Bool = false, |
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While generally Boolean properties should read like an assertion about the receiver, I'm not sure it's quite as useful for function parameters. In this case, isNegative is not forming a phrase with the base name to produce Boolean result, but a dictation by the caller to modify the behavior of the callee. As such, I wonder if we should call it negative instead.
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You're right, this is like the second parameter in split(separator: "-", omittingEmptySubsequences: false). 👍🏻
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@swift-ci Please test Linux platform |
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@swift-ci Please test Linux platform |
This adds an
Anchortype that handles the different kinds of assertions supported by regular expression literals. Some spelling are different — instead of separate\wand\Wassertions, this design provides justAnchor.wordBoundaryas well as aninvertedproperty that is available on all assertions. (This property should perhaps be namednegatedinstead.) That is,\Win a regex literal maps toAnchor.wordBoundary.inverted.A
lookahead(isNegative:)function provides the positive/negative lookahead functionality from regex literals.