Add test fixtures for renderAsBuilderDSL

Tests/RegexTests/RenderDSLTests.swift

@@ -0,0 +1,117 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import XCTest
+import _RegexParser
+@_spi(PatternConverter) @testable
+import _StringProcessing
+
+class RenderDSLTests: XCTestCase {}
+
+func testConversion(
+  _ regex: String,
+  _ expectedDSL: String,
+  file: StaticString = #file, line: UInt = #line
+) throws {
+  let ast = try _RegexParser.parse(regex, .semantic, .traditional)
+  let actualDSL = renderAsBuilderDSL(ast: ast)._trimmingSuffix(while: \.isWhitespace)
+  XCTAssertEqual(actualDSL, expectedDSL[...], file: file, line: line)
+}
+
+extension RenderDSLTests {
+  func testSimpleConversions() throws {
+    try testConversion(#"ab+c"#, """
+      Regex {
+        "a"
+        OneOrMore {
+          "b"
+        }
+        "c"
+      }
+      """)
+
+    try testConversion(#"(?:a*)b?(c+)"#, """
+      Regex {
+        ZeroOrMore {
+          "a"
+        }
+        Optionally {
+          "b"
+        }
+        Capture {
+          OneOrMore {
+            "c"
+          }
+        }
+      }
+      """)
+
+    try testConversion(#"\d+"#, """
+      Regex {
+        OneOrMore {
+          .digit
+        }
+      }
+      """)
+    try XCTExpectFailure("Invalid leading dot syntax in non-initial position") {
+      try testConversion(#":\d:"#, """
+        Regex {
+          ":"
+          CharacterClass.digit
+          ":"
+        }
+        """)
+    }
+  }
+
+  func testOptions() throws {
+    try XCTExpectFailure("Options like '(?i)' aren't converted") {
+      try testConversion(#"(?i)abc"#, """
+        Regex {
+          "abc"
+        }.ignoresCase()
+        """)
+    }
+
+    try XCTExpectFailure("Options like '(?i:...)' aren't converted") {
+      try testConversion(#"(?i:abc)"#, """
+        Regex {
+          "abc"
+        }.ignoresCase()
+        """)
+    }
+  }
+
+  func testAlternations() throws {
+    try testConversion(#"a|b"#, """
+      Regex {
+        ChoiceOf {
+          "a"
+          "b"
+        }
+      }
+      """)
+
+    try XCTExpectFailure("Concatenations in alternations aren't grouped") {
+      try testConversion(#"\da|b"#, """
+        Regex {
+          ChoiceOf {
+            Regex {
+              .digit
+              "a"
+            }
+            "bc"
+          }
+        }
+        """)
+    }
+  }
+}

Tests/RegexTests/UTS18Tests.swift

@@ -62,7 +62,7 @@ fileprivate func expectFirstMatch<Output: Equatable>(
 }
 
 #if os(Linux)
-func XCTExpectFailure(_ message: String? = nil, body: () -> Void) {}
+func XCTExpectFailure(_ message: String? = nil, body: () throws -> Void) rethrows {}
 #endif
 
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