test: test that regex inline flags work as intended

This was originally fixed by using non-capturing groups when joining
patterns in crates/core/args.rs, but before that landed, it ended up
getting fixed via a refactor in the course of migrating to regex 1.9.
Namely, it's now fixed by pushing pattern joining down into the regex
layer, so that patterns can be joined in the most effective way
possible.

Still, #2488 contains a useful test, so we bring that in here. The
test actually failed for `rg -e ')('`, since it expected the command to
fail with a syntax error. But my refactor actually causes this command
to succeed. And indeed, #2488 worked around this by special casing a
single pattern. That work-around fixes it for the single pattern case,
but doesn't fix it for the -w or -X or multi-pattern case. So for now,
we're content to leave well enough alone. The only real way to fix this
for real is to parse each regexp individual and verify that each is
valid on its own. It's not clear that doing so is worth it.

Fixes #2480, Closes #2488

CHANGELOG.md

@@ -14,6 +14,8 @@ Bug fixes:
   Disable mmap searching in all non-64-bit environments.
 * [BUG #2236](https://github.com/BurntSushi/ripgrep/issues/2236):
   Fix gitignore parsing bug where a trailing `\/` resulted in an error.
+* [BUG #2480](https://github.com/BurntSushi/ripgrep/issues/2480):
+  Fix bug when using inline regex flags with `-e/--regexp`.
 * [BUG #2523](https://github.com/BurntSushi/ripgrep/issues/2523):
   Make executable searching take `.com` into account on Windows.
 

tests/regression.rs

@@ -1126,3 +1126,37 @@ rgtest!(r2236, |dir: Dir, mut cmd: TestCommand| {
     dir.create("foo/bar", "test\n");
     cmd.args(&["test"]).assert_err();
 });
+
+// See: https://github.com/BurntSushi/ripgrep/issues/2480
+rgtest!(r2480, |dir: Dir, mut cmd: TestCommand| {
+    dir.create("file", "FooBar\n");
+
+    // no regression in empty pattern behavior
+    cmd.args(&["-e", "", "file"]);
+    eqnice!("FooBar\n", cmd.stdout());
+
+    // no regression in single pattern behavior
+    let mut cmd = dir.command();
+    cmd.args(&["-e", ")(", "file"]);
+    eqnice!("FooBar\n", cmd.stdout());
+
+    // no regression in multiple patterns behavior
+    let mut cmd = dir.command();
+    cmd.args(&["--only-matching", "-e", "Foo", "-e", "Bar", "file"]);
+    eqnice!("Foo\nBar\n", cmd.stdout());
+
+    // no regression in capture groups behavior
+    let mut cmd = dir.command();
+    cmd.args(&["-e", "Fo(oB)a(r)", "--replace", "${0}_${1}_${2}${3}", "file"]);
+    eqnice!("FooBar_oB_r\n", cmd.stdout()); // note: ${3} expected to be empty
+
+    // flag does not leak into next pattern on match
+    let mut cmd = dir.command();
+    cmd.args(&["--only-matching", "-e", "(?i)foo", "-e", "bar", "file"]);
+    eqnice!("Foo\n", cmd.stdout());
+
+    // flag does not leak into next pattern on mismatch
+    let mut cmd = dir.command();
+    cmd.args(&["--only-matching", "-e", "(?i)notfoo", "-e", "bar", "file"]);
+    cmd.assert_err();
+});