[llvm] d1d2932 - [Support][NFC] Add test documenting that empty `Regex` pattern matches nothing. (#83849)

[via llvm-commits]

Author: martinboehme
Date: 2024-03-05T12:34:17+01:00
New Revision: d1d2932cb1dc24e0c8149f07b75599981ac405a7

URL: https://github.com/llvm/llvm-project/commit/d1d2932cb1dc24e0c8149f07b75599981ac405a7
DIFF: https://github.com/llvm/llvm-project/commit/d1d2932cb1dc24e0c8149f07b75599981ac405a7.diff

LOG: [Support][NFC] Add test documenting that empty `Regex` pattern matches nothing. (#83849)

I was wondering about this when I recently used `Regex`, and I thought
it would
be nice to have a test documenting this behavior.

Added: 
    

Modified: 
    llvm/unittests/Support/RegexTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/unittests/Support/RegexTest.cpp b/llvm/unittests/Support/RegexTest.cpp
index 09f674bb209c07..c6ac42591d1fc7 100644
--- a/llvm/unittests/Support/RegexTest.cpp
+++ b/llvm/unittests/Support/RegexTest.cpp
@@ -60,6 +60,14 @@ TEST_F(RegexTest, Basics) {
   EXPECT_TRUE(r5.match(String));
 }
 
+TEST_F(RegexTest, EmptyPattern) {
+  // The empty pattern doesn't match anything -- not even the empty string.
+  // (This is 
diff erent from some other regex implementations.)
+  Regex r("");
+  EXPECT_FALSE(r.match("123"));
+  EXPECT_FALSE(r.match(""));
+}
+
 TEST_F(RegexTest, Backreferences) {
   Regex r1("([a-z]+)_\\1");
   SmallVector<StringRef, 4> Matches;