Validate optimizations when a match fails

This allows us to catch the case where a match
occurs without optimizations, but doesn't occur
with optimizations. Additionally fix the `xfail`
param such that it can't be used on tests that
actually match expectations.

Author: hamishknight

Tests/RegexTests/MatchTests.swift

@@ -25,23 +25,33 @@ func _firstMatch(
   input: String,
   validateOptimizations: Bool,
   syntax: SyntaxOptions = .traditional
-) throws -> (String, [String?]) {
+) throws -> (String, [String?])? {
   var regex = try Regex(regexStr, syntax: syntax)
-  guard let result = try regex.firstMatch(in: input) else {
-    throw MatchError("match not found for \(regexStr) in \(input)")
-  }
-  let caps = result.output.slices(from: input)
-  
+  let result = try regex.firstMatch(in: input)
+
   if validateOptimizations {
     regex._setCompilerOptionsForTesting(.disableOptimizations)
-    guard let unoptResult = try regex.firstMatch(in: input) else {
+    let unoptResult = try regex.firstMatch(in: input)
+    if result != nil && unoptResult == nil {
       throw MatchError("match not found for unoptimized \(regexStr) in \(input)")
     }
-    XCTAssertEqual(
-      String(input[result.range]),
-      String(input[unoptResult.range]),
-      "Unoptimized regex returned a different result")
+    if result == nil && unoptResult != nil {
+      throw MatchError("match not found in optimized \(regexStr) in \(input)")
+    }
+    if let result = result, let unoptResult = unoptResult {
+      let optMatch = String(input[result.range])
+      let unoptMatch = String(input[unoptResult.range])
+      if optMatch != unoptMatch {
+        throw MatchError("""
+
+        Unoptimized regex returned: '\(unoptMatch)'
+        Optimized regex returned: '\(optMatch)'
+        """)
+      }
+    }
   }
+  guard let result = result else { return nil }
+  let caps = result.output.slices(from: input)
   return (String(input[result.range]), caps.map { $0.map(String.init) })
 }
 
@@ -147,21 +157,19 @@ func firstMatchTest(
   line: UInt = #line
 ) {
   do {
-    let (found, _) = try _firstMatch(
+    let found = try _firstMatch(
       regex,
       input: input,
       validateOptimizations: validateOptimizations,
-      syntax: syntax)
+      syntax: syntax)?.0
 
     if xfail {
       XCTAssertNotEqual(found, match, file: file, line: line)
     } else {
       XCTAssertEqual(found, match, file: file, line: line)
     }
   } catch {
-    // FIXME: This allows non-matches to succeed even when xfail'd
-    // When xfail == true, this should report failure for match == nil
-    if !xfail && match != nil {
+    if !xfail {
       XCTFail("\(error)", file: file, line: line)
     }
     return
@@ -421,8 +429,7 @@ extension RegexTests {
       "a++a",
       ("babc", nil),
       ("baaabc", nil),
-      ("bb", nil),
-      xfail: true)
+      ("bb", nil))
     firstMatchTests(
       "a+?a",
       ("babc", nil),
@@ -498,23 +505,19 @@ extension RegexTests {
       ("baabc", nil),
       ("bb", nil))
 
-    // XFAIL'd versions of the above
     firstMatchTests(
       "a{2,4}+a",
-      ("baaabc", nil),
-      xfail: true)
+      ("baaabc", nil))
     firstMatchTests(
       "a{,4}+a",
       ("babc", nil),
       ("baabc", nil),
-      ("baaabc", nil),
-      xfail: true)
+      ("baaabc", nil))
     firstMatchTests(
       "a{2,}+a",
       ("baaabc", nil),
       ("baaaaabc", nil),
-      ("baaaaaaaabc", nil),
-      xfail: true)
+      ("baaaaaaaabc", nil))
 
     // XFAIL'd possessive tests
     firstMatchTests(
@@ -709,6 +712,11 @@ extension RegexTests {
     }
     firstMatchTest(#"[\t-\t]"#, input: "\u{8}\u{A}\u{9}", match: "\u{9}")
 
+    // FIXME: This produces a different result with and without optimizations.
+    firstMatchTest(#"[1-2]"#, input: "1️⃣", match: nil, xfail: true)
+    firstMatchTest(#"[1-2]"#, input: "1️⃣", match: nil,
+                   validateOptimizations: false)
+
     // Currently not supported in the matching engine.
     for c: UnicodeScalar in ["a", "b", "c"] {
       firstMatchTest(#"[\c!-\C-#]"#, input: "def\(c)", match: "\(c)",
@@ -1054,8 +1062,8 @@ extension RegexTests {
     // TODO: Oniguruma \y and \Y
     firstMatchTests(
       #"\u{65}"#,             // Scalar 'e' is present in both
-      ("Cafe\u{301}", nil),   // but scalar mode requires boundary at end of match
-      xfail: true)
+      ("Cafe\u{301}", nil))   // but scalar mode requires boundary at end of match
+
     firstMatchTests(
       #"\u{65}"#,             // Scalar 'e' is present in both
       ("Sol Cafe", "e"))      // standalone is okay
@@ -1647,19 +1655,15 @@ extension RegexTests {
     firstMatchTest(#"\u{65 301}$"#, input: eComposed, match: eComposed)
 
     // FIXME: Implicit \y at end of match
-    firstMatchTest(#"\u{65}"#, input: eDecomposed, match: nil,
-      xfail: true)
+    firstMatchTest(#"\u{65}"#, input: eDecomposed, match: nil)
     firstMatchTest(#"\u{65}$"#, input: eDecomposed, match: nil)
-    // FIXME: \y is unsupported
-    firstMatchTest(#"\u{65}\y"#, input: eDecomposed, match: nil,
-      xfail: true)
+    firstMatchTest(#"\u{65}\y"#, input: eDecomposed, match: nil)
 
     // FIXME: Unicode scalars are only matched at the start of a grapheme cluster
     firstMatchTest(#"\u{301}"#, input: eDecomposed, match: "\u{301}",
       xfail: true)
-    // FIXME: \y is unsupported
-    firstMatchTest(#"\y\u{301}"#, input: eDecomposed, match: nil,
-      xfail: true)
+
+    firstMatchTest(#"\y\u{301}"#, input: eDecomposed, match: nil)
   }
 
   func testCanonicalEquivalence() throws {
@@ -1717,13 +1721,11 @@ extension RegexTests {
     // \s
     firstMatchTest(#"\s"#, input: " ", match: " ")
     // FIXME: \s shouldn't match a number composed with a non-number character
-    firstMatchTest(#"\s\u{305}"#, input: " ", match: nil,
-              xfail: true)
+    firstMatchTest(#"\s\u{305}"#, input: " ", match: nil)
     // \p{Whitespace}
     firstMatchTest(#"\s"#, input: " ", match: " ")
-    // FIXME: \p{Whitespace} shouldn't match whitespace composed with a non-whitespace character
-    firstMatchTest(#"\s\u{305}"#, input: " ", match: nil,
-              xfail: true)
+    // \p{Whitespace} shouldn't match whitespace composed with a non-whitespace character
+    firstMatchTest(#"\s\u{305}"#, input: " ", match: nil)
   }
 
   func testCanonicalEquivalenceCustomCharacterClass() throws {